Analytical Methods (v.6, #5)
Front cover (1263-1263).
Inside front cover (1264-1264).
Contents list (1265-1278).
A nitrogen factor for Alaska pollack ingredient in fish products by Analytical Methods Committee (1279-1283).
The Analytical Methods Committee has received and approved the following report from the Nitrogen Factors Sub-Committee.
A nitrogen factor for commercial Pangasius (Pangasius hypophthalmus) fillets by Analytical Methods Committee (1284-1287).
The Analytical Methods Committee has received and approved the following report from the Nitrogen Factors Sub-Committee.
Human papilloma virus genotyping by surface-enhanced Raman scattering by Sam Hibbitts; P. Lewis White; Julie Green; Graeme McNay; Duncan Graham; Ross Stevenson (1288-1290).
The first Human Papilloma Virus (HPV) genotyping assay using surface-enhanced Raman scattering (SERS) is reported. Validated PCR primers were used to generate amplification products from plasmids, a control cell line and clinical specimens enabling subsequent identification of specific HPV genotypes using type specific probes across six channels.
A porous layer open tubular monolith on microstructured optical fibre for microextraction and online GC-MS applications by Samuel M. Mugo; Lauren Huybregts; James Mazurok (1291-1295).
A microextraction device comprising a porous layer open tubular (PLOT) polymer housed in a microstructured optical fiber has been shown to be an attractive tool for analyte extraction and coupling to GC-MS as a cost-effective alternative to traditional SPME. This paper details the fabrication of a poly(styrene-co-divinylbenzene) PLOT optical fibre microextraction device and its use in the extraction of polyaromatic hydrocarbons (PAHs) in aqueous solution. Good linear calibrations were obtained with R2 values above 0.970 for five PAHs analyzed, with percent relative standard deviation values of 22.2 to 43.6% for PAH standards with concentrations ranging from 0.1 to 100 ppm. In addition, the robust poly(styrene-co-DVB) PLOT optical fibre porous polymer microextraction (PPME) device appears to retain its effectiveness with repeated use over an extended period of time.
Paper-based standard addition assays by Cory A. Chaplan; Haydn T. Mitchell; Andres W. Martinez (1296-1300).
Standard addition assays conducted on paper-based microfluidic devices are introduced as an alternative to external standards for calibrating quantitative tests. To demonstrate this technique, a colorimetric, paper-based, standard addition assay was optimized for the determination of glucose concentrations in the range of 0 to 5 mM. Comparable results were obtained from the assay via digital image colorimetry under three different lighting conditions.
Non-destructive descriptions of carotenoids in feathers using Raman spectroscopy by Daniel B. Thomas; Kevin J. McGraw; Helen F. James; Odile Madden (1301-1308).
Chemical analyses of pigments in skin, scales, feathers and fur have provided deep insight into the colouration and visual communication strategies of animals. Carotenoid pigments in particular can be important colour signals in birds and other animals. Chromatographic analyses of plumage carotenoids require the destruction of one or more feathers, which has made pigment research on threatened species or museum specimens challenging. Here we show that Raman spectroscopy, coupled with multivariate statistics, can be used to identify the most abundant carotenoid within a single feather barb without sample destruction. Raman spectra from the feathers of 36 avian species were compared to data on pigment presence from high-performance liquid chromatography. Feathers rich with α-doradexanthin, astaxanthin, canary xanthophylls, canthaxanthin, cotingin or lutein were discriminated by subtle shifts in Raman spectral band positions, and by novel bands associated with particular carotenoids. As an example application of this method, we predicted the most abundant carotenoid in the plumage of selected Australian and New Zealand songbirds. α-Doradexanthin is predicted in the plumage of Petroica robins from Australia, whereas Petroica immigrants to New Zealand display a yellow carotenoid that is likely lutein. Raman spectroscopy is useful for non-destructive studies of carotenoids and is well-suited for analysing large ornithological museum collections.
HyLogger™ near-infrared spectral analysis: a non-destructive mineral analysis of Aboriginal Australian objects by Rachel S. Popelka-Filcoff; Alan Mauger; Claire E. Lenehan; Keryn Walshe; Allan Pring (1309-1316).
Cultural heritage materials from Indigenous cultures often use geological raw materials such as natural rock and mineral pigments. For analysis, these complex human-altered materials require high-resolution, non-destructive methods, and in the case of intricate designs, a point-by-point analysis and mapping capability is desirable. The CSIRO Australia HyLogger™ technology has been adapted from mineral exploration and mining applications to the high-resolution non-destructive infrared and visible light spectroscopic mineral analysis of Aboriginal Australian objects. Aboriginal Australian people primarily applied mineral pigments such as hematite and kaolinite to wood, fibre, bark, resin or other organic substrates, making non-destructive in situ scientific analyses of cultural objects challenging. This proof of concept study demonstrated the utility of the near-IR technology for the visual and mineralogical analysis of six Aboriginal Australian objects, of varying size and pigment application, as case studies for the development of methods to identify and differentiate types of mineral pigments regardless of the substrate or binder. While many identified pigments such as hematite and goethite were expected for the red, orange and yellow pigments, HyLogger™ in combination with The Spectral Geologist™ software identified additional mixtures of previously unknown mineral components. White minerals, such as calcite and pyrophyllite, were identified along with kaolinite in mixtures in white pigments on the artefacts. Analyses of individual spectra were used for interpretation of spectral features for specific pigments. Additionally, classes of pigment groups were identified for spectral analysis. This manuscript presents the novel application of the near-IR technology to Australian Aboriginal artefacts for characterisation and high-resolution near-IR spectroscopy of applied mineral pigments. These results challenge and add to prior knowledge about the mineralogical composition of traditional Aboriginal Australian inorganic pigments.
Simple and highly sensitive electrogenerated chemiluminescence adenosine aptasensor formed by adsorbing a ruthenium complex-tagged aptamer on single-walled carbon nanotubes by Zhejian Li; Honglan Qi; Haiying Yang; Qiang Gao; Chengxiao Zhang (1317-1323).
A highly sensitive electrogenerated chemiluminescence (ECL) adenosine aptasensor was designed by simply adsorbing a ruthenium complex-tagged aptamer on single-walled carbon nanotubes (SWNTs). A specific anti-adenosine binding aptamer was used as the recognition molecular element and ruthenium(ii) complex (Ru1) was used as the ECL signal compound. Ru1-tagged aptamer was utilized as an ECL probe and the ECL probe was non-covalently assembled on the surface of the SWNTs to form an ECL probe/SWNTs composite. Analyte adenosine was bound with the aptamer of the ECL probe on the SWNTs so that the ECL probe was moved away or dropped from the SWNTs, resulting in the decrease of ECL signal. The results showed that the decreased ECL intensity was directly related to the logarithm of adenosine concentration in the range from 1.0 × 10−10 M to 5.0 × 10−7 M with a detection limit of 5.0 × 10−11 M. This work demonstrates that the strategy of simply adsorbing ECL probe/SWNTs composites as a biosensing platform is a promising approach to design ECL aptasensors with high sensitivity and selectivity.
Development of a carbon nanotube paste electrode modified with zinc phosphate for captopril determination in pharmaceutical and biological samples by Bruno C. Janegitz; Luiz C. S. Figueiredo-Filho; Fernando Campanhã Vicentini; Maria Fernanda M. Ribeiro; Willian T. Suarez; Orlando Fatibello-Filho; Jonathan P. Metters; Craig E. Banks (1324-1329).
We report a novel electrode composite comprising zinc phosphate within a multiwalled carbon nanotube paste electrode matrix which is applied for the detection of trace amounts of captopril (CAP) via square-wave adsorptive anodic stripping voltammetry (SWAdASV); to the best of our knowledge this is the first report on such a composite electrode. Under optimum experimental conditions, the peak current of CAP was found to be linear over the concentration range from 3.7 to 67 μmol L−1 with a limit of detection of 0.1 μmol L−1. The proposed method was applied for the successful determination of CAP in commercial tablet excipients and biological samples using the electroanalytical protocol evaluated against the laboratory standard iodometric procedure. Excellent comparability between the two is found suggesting that the former can replace the latter within laboratory settings or can be applied to in-the-field applications.
High throughput screening of organic residues in archaeological potsherds using direct acidified methanol extraction by Marisol Correa-Ascencio; Richard P. Evershed (1330-1340).
Despite the significant achievements of organic residues analysis of archaeological pottery, the sometimes low lipid recovery and the need to process increasingly large collections of sherds to tackle important archaeological questions require the development of a more efficient and rapid extraction method. In this paper we present a novel methodology for the extraction of absorbed organic residues directly from crushed archaeological ceramic using acidified methanol (H2SO4–MeOH 2% v/v, 70 °C, 1 h). This new protocol was tested by: (i) verifying the recovery of organic residues from previously studied archaeological vessels from different geographical regions, exhibiting a range of different lipid distributions often found in archaeological pottery, and (ii) demonstrating enhanced recovery of organic residues from potsherds that did not yield appreciable lipids when using the widely applied chloroform–methanol extraction. The application of the direct acidified methanol extraction recovers higher concentrations of lipid residues together with simultaneous production of methyl esters of fatty acids, allowing extraction and methylation to be completed in 20% of the time compared to conventional solvent extraction and derivatisation for gas chromatography (GC), gas chromatography mass spectrometry (GC-MS) and gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS).
Simultaneous determination of eighteen perfluorinated compounds in dissolved and particulate phases of wastewater, and in sewage sludge by liquid chromatography-tandem mass spectrometry by Olga S. Arvaniti; Alexandros G. Asimakopoulos; Marilena E. Dasenaki; Elpida I. Ventouri; Athanasios S. Stasinakis; Nikolaos S. Thomaidis (1341-1349).
Perfluorinated compounds (PFCs) are known chemicals that are used in a wide variety of industrial and consumer products, and have been reported to exist in the environment as contaminants. In this study, a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for simultaneous determination of 10 perfluoroalkyl carboxylate acids (PFCAs), 5 perfluoroalkyl sulfonates (PFASs), and 3 perfluoroalkyl sulfonamides (PFSAs) (18 PFCs in total), in dissolved and particulate phases of wastewater (raw and treated), and in dewatered sewage sludge. The target PFCAs were perfluoropentanoic acid (PFPeA; C5), perfluorohexanoic acid (PFHxA; C6), perfluoroheptanoic acid (PFHpA; C7), perfluorooctanoic acid (PFOA; C8), perfluorononanoic acid (PFNA; C9), perfluorodecanoic acid (PFDA; C10), perfluoroundecanoic acid (PFUdA; C11), perfluorododecanoic acid (PFDoA; C12), perfluorotridecanoic acid (PFTrDA; C13), and perfluorotetradecanoic acid (PFTeDA; C14). The target PFASs were potassium perfluorobutanesulfonate (PFBS; C4), sodium perfluorohexanesulfonate (PFHxS; C6), sodium perfluoroheptanesulfonate (PFHpS; C7), sodium perfluorooctanesulfonate (PFOS; C8), and sodium perfluorodecanesulfonate (PFDS; C10), and the target PFSAs were perfluorooctane sulfonamide (PFOSA), N-methylperfluorooctane sulfonamide (N-MeFOSA), and N-ethylperfluorooctane sulfonamide (N-EtFOSA). Wastewater samples were filtered after collection and extracted/purified/pre-concentrated by a solid-phase extraction (SPE) procedure. Particulate matter and sludge samples were extracted by a liquid–solid extraction (LSE) and ultra-sonication procedure, and thereafter purified/preconcentrated by the same SPE procedure that was followed for the dissolved phase of wastewater. The internal standards, perfluoro-n-[1,2,3,4-13C4]octanoic acid (13C4-PFOA), sodium perfluoro-1-[1,2,3,4-13C4]octanesulfonate (13C4-PFOS), and N-methyl-d3-perfluoro-1-octanesulfonamide (2D3-N-MeFOSA) provided adequate compensation for variations in the extraction percentages and instrumental response. The limits of quantification (LOQs) ranged from 0.29 (PFHpS) to 3.0 ng L−1 (PFDoA) for dissolved phase samples, and from 0.15 (PFHpS) to 1.5 ng g−1 dry weight (dw) (PFDoA) for particulate matter and sludge samples. The developed methods were applied successfully to wastewater and sludge samples originated from Athens WWTP. PFC concentrations up to 113 ng L−1 (PFUdA), 33 ng L−1 (PFOA) and 1042 ng g−1 (PFUdA) were determined in influent wastewater, treated wastewater and dewatered sludge, respectively. Analysis of PFCs in the particulate matter of wastewater is needed to avoid underestimation of their concentrations.
Fast fingerprinting of cannabinoid markers by laser desorption ionization using silica plate extraction by M. M. Eiras; D. N. de Oliveira; M. S. Ferreira; M. Benassi; S. O. S. Cazenave; R. R. Catharino (1350-1352).
A fast and reliable technique (STELDI-MS) for Cannabis sativa L. compound determination in extracts emerges as a relevant tool to help increase effectiveness in law enforcement. Cannabis sativa L. samples are extracted in a water–methanol system. Metabolic fingerprinting and structural elucidation are quickly achieved in real samples, with minimal sample preparation.
A highly efficient extraction, separation and detection method for pyrethroids in pork using the interaction between pyrethroids and protein by Zhenbo Liu; Fengyan Jia; Wenwen Wang; Fukai Gao; Peipei Liu; Yongming Liu; Jungang Yin (1353-1358).
In pork samples, the extraction efficiency of pyrethroids was related to the interactions between pyrethroids and proteins. These interactions were explored using the fluorescence quenching method. This showed that the binding interactions between pyrethroids and proteins are strongly hydrophobic. It was found that a slow but full protein denaturation took place in the 80% (volume fraction) isopropanol (IPA) aqueous solution, causing protein unfolding and the release of pyrethroids. Based on this, a highly efficient extraction method for pyrethroids in pork samples is proposed using 80% IPA solution as extraction solvent. A clean-up step using primary secondary amine (PSA) was applied, followed by the final determination by gas chromatography (GC) with an electron capture detector (ECD). The analytical process was validated in the pork sample matrix by analysing spiked blank samples. The mean recoveries of this method were 79.0–90.5% with limits of detection (LOD) between 0.008 and 0.014 μg g−1. This paper proposes a new strategy by full denaturation of protein and releasing of bound drugs to enhance the extraction efficiency of pyrethroids in pork samples.
Characterization of phenolic constituents in Lithocarpus polystachyus by Ya Zhao; Xiong Li; Xing Zeng; Song Huang; Shaozhen Hou; Xiaoping Lai (1359-1363).
Ultra high performance liquid chromatography (UHPLC) coupled with LTQ Orbitrap mass spectrometry was applied for profiling the phenolic constituents in a water extract of Lithocarpus polystachyus. The constituents were identified by combining their accurate m/z values of [M − H]− ions and MSn spectra, as well as those data provided by literature. Sixty-eight phenolic compounds, including flavonoids, hydroxybenzoic acid, and hydroxycinnamic acid derivatives, were identified or tentatively characterized. Fragmentation behaviours of the flavonoids, especially those of the dihydrochalcone derivatives, were investigated thoroughly. More than half of the phenolic compounds identified had not been reported previously from this plant. Besides, 18 phloretin conjugates were tentatively identified as new compounds. This established UHPLC-PDA/ESI-MSn method is effective for identifying phenolic constituents and could be the basis for the comprehensive quality control of L. polystachyus.
Rapid quantification and comparison of major volatile compounds of ciders from France (Normandy and Brittany) using microextraction by packed sorbent (MEPS) by Waqar Haider; Daniel Barillier; Akhtar Hayat; Jean-Luc Gaillard; Jérôme Ledauphin (1364-1376).
Microextraction by packed sorbent (MEPS) was used for the determination of the volatile composition of 29 French cider samples from two regions: Normandy and Brittany. Extractions using a C18 sorbent were followed by GC-MS analyses for the identification of major volatile organic compounds (VOCs), and GC-FID analyses for the quantification of 19 selected major compounds. The method was found to be rapid and linear up to 300 mg L−1 for all compounds with an average relative standard deviation of 8.5% for tests of repeatability at low concentrations. The limit of detection (LOD) is below 0.1 mg L−1 except for three VOCs which exhibited much higher concentrations in samples. No significant difference in concentrations of higher alcohols were observed in the cider samples from two regions, however their concentrations were higher in hard ciders than sweet ciders. Acetates were found to be present more often in sweet ciders from Normandy than those from Brittany reflecting important differences in the yeasts acting during the fermentation.
Kinetics of hypotonic lysis of human erythrocytes by Lucas Moreira Cunha; Morun Bernardino-Neto; Mario da Silva Garrote-Filho; Carla Braga Avelar; Mariana Vaini de Freitas; Rita de Cássia Mascarenhas Netto; Lara Ferreira Paraiso; Letícia Ramos de Arvelos; Ana Flávia Mayrink Gonçalves-e-Oliveira; Nilson Penha-Silva (1377-1383).
The curve of osmotic stability of erythrocytes is based on the amount of lysis as a function of salt concentration under fixed time incubation and represents an equilibrium situation after a sufficiently long time, although lysis is a rapid process. The curve is valid for the analysis of modulating agents that have influence on this equilibrium, but not for those that have influence on the lysis kinetics. This work has developed experimental conditions to study the hemolysis kinetics based on the interruption of lysis by hypertonicity at predetermined intervals of time. These conditions were used to evaluate the kinetics of hemolysis of 17 volunteers. The lysis curve as a function of time was statistically fitted to a hyperbola, using the analytical routine of the integrated kinetic model of Michaelis–Menten to determine the time required to promote lysis of half of the population of erythrocytes (t1/2) and the maximum absorbance (Amax) reached in the test. The results showed good variance among volunteers. The constant t1/2 was negatively correlated with total and LDL-cholesterol, and Amax, as it was expected, showed significant associations with hematological variables that are under the influence of hemoglobin levels. Stratification of the study population into two age groups (18–30 and 40–90 years old) showed that the t1/2 values were significantly lower in the older population. Although the study population has been small, the study showed that this kinetic approach of the erythrocyte lysis is very promising for analyzing the myriad of variables which have influence on the cell membrane.
A simplified pyrosequencing protocol based on linear-after-the-exponential (LATE)-PCR using whole blood as the starting material directly by Yunlong Liu; Haiping Wu; Hui Ye; Zhiyao Chen; Qingxin Song; Bingjie Zou; Jianzhong Rui; Guohua Zhou (1384-1390).
Pyrosequencing has been one of the most commonly used methods for genotyping; however, generally it needs single-stranded DNA (ssDNA) preparation from PCR amplicons as well as purified genomic DNA extraction from whole blood. To simplify the process of a pyrosequencing protocol, we proposed an improved linear-after-the-exponential (LATE)-PCR by employing whole blood as the starting material. A successful LATE-PCR was achieved by using a common Taq DNA polymerase in high pH buffer (HpH-buffer). As amplicons from LATE-PCR contain a large amount of ssDNA, pyrosequencing can be performed on the amplicons directly. Since DNA extraction and ssDNA preparation are omitted, the labor, cost and cross-contamination risk is decreased compared to conventional pyrosequencing-based genotyping protocols. The results for typing three polymorphisms related to personalized medicine of fluorouracil indicate that the proposed whole-blood LATE-PCR can be well coupled with pyrosequencing, thus becoming a potential tool in personalized medicine.
Development and validation of a microbiological assay by turbidimetry to determine the potency of cefazolin sodium in the lyophilized powder form by Tahisa Marcela Pedroso; Hérida Regina Nunes Salgado (1391-1396).
In many countries, high rates of mortality and morbidity from infectious diseases represent high social and economic costs. Cefazolin sodium is a semi-synthetic β-lactam antimicrobial for parenteral use, belonging to the first-generation cephalosporin's group. Its use in clinical practice stands out for its effectiveness as a therapeutic agent and in surgical prophylaxis, having great importance in the fight against many diseases. This paper reports the development and validation of an efficient, accurate, reproducible, and low cost microbiological assay by a turbidimetric method to quantify cefazolin in the lyophilized powder form. These requirements are essential for the analysis of this cephalosporin in the pharmaceutical industry. The assay is based on the inhibitory effect of cefazolin sodium upon the strain of Staphylococcus aureus ATCC 26923 used as the test microorganism. The method was validated according to the ICH guidelines and the results were treated by analysis of variance (ANOVA), proving to be linear (r2 = 0.9999 for the reference substance and r2 = 0.9995 for the sample), in the selected range from 6 to 11.76 μg mL−1, precise (RSD values < 2.0%), robust and accurate (99.92%). The developed method showed excellent validation results, and the statistical analysis corroborated with its assessment. Furthermore, Student's t-test showed no statistically significant difference between the proposed turbidimetric method and an UV spectrophotometry method previously validated. Thus, the validated method is able to quantify cefazolin sodium in the powder form for injectable solution, while being an economical and rapid alternative for its routine analysis in quality control.
Facile synthesis of hierarchical MCM-41 spheres with an ultrahigh surface area and their application for removal of methylene blue from aqueous solutions by Qishu Qu; Zuli Gu (1397-1403).
Hierarchical mesoporous silica spheres (HS) were prepared by a simple sol–gel method and used for the removal of methylene blue from aqueous solutions. The macrostructure of HS can be tuned simply by adding different amounts of ethanol as a reactant. The prepared HS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption–desorption isotherms, and thermogravimetric analysis. The results showed that HS possessed both macropores and mesopores, with an average diameter of 5.6 μm, a surface area of 2280 m2 g−1, and a pore volume of 1.15 cm3 g−1. The influence of pH, temperature, dosage of adsorbent, and initial methylene blue (MB) concentration on the adsorption behavior were investigated. The experimental results showed that HS exhibited a high adsorption capacity (654.5 mg g−1) and extremely rapid adsorption rate (<2 min) due to their unique hierarchical structure and very high surface area. The kinetic studies showed that the experimental data fitted well to the pseudo-first-order kinetic model. The Langmuir adsorption isotherm model was found to present an accurate description of these adsorption data. The experimental results suggest that HS are potentially useful materials for effective adsorption and removal of methylene blue in aqueous solution.
Fabrication of multi-walled carbon nanotubes/oxide reinforced hollow fibers by sol-gel technique for rapid determination of metronidazole in milk by Jia Li; Yan-Bin Wang; Lan Wu; Ke-Yao Li; Wei Feng (1404-1411).
Three types of multi-walled carbon nanotubes (MWCNTs)/oxide reinforced hollow fibers, i.e. MWCNTs/SiO2, MWCNTs/TiO2, MWCNTs/ZrO2, based on sol–gel techniques were fabricated, compared and applied to extract metronidazole in milk samples by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The factors influencing the extraction and desorption process were optimized, and the adsorption mechanism of MWCNTs/SiO2 reinforced hollow fibers was briefly discussed. MWCNTs/SiO2 reinforced hollow fiber might be selective to some organic compounds due to specific and non-specific adsorption of MWCNTs and SiO2 nanoparticles. It was found that the method provided linear range from 0.01–1000 mg L−1 (R = 0.9985), low detection limit of 0.01 mg L−1, preferable recoveries (69–96%) at three different concentrations. The obtained results demonstrated that MWCNTs/SiO2 hollow fiber solid phase microextraction could become a potential tool for quality control to monitor the amount of metronidazole residues in milk products.
Classification of rapeseed colors using Fourier transform mid-infrared photoacoustic spectroscopy by Yuzhen Lu; Changwen Du; Changbing Yu; Jianmin Zhou (1412-1417).
Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) combined with multivariate discriminant analysis was employed to classify colors of rapeseeds. A total of 129 rapeseed varieties representing three colors (black, reddish and mottled-yellow) were scanned in the range of 500–4000 cm−1. A Savitzky–Golay algorithm was used for the spectral pretreatment. Principal components analysis (PCA) gave an overview of sample distribution in the score space of principal components. The whole sample set was divided into calibration and prediction sets, according to the Kennard–Stone algorithm. Classification models were developed using linear discriminant analysis combined with principal components analysis (PCA-LDA), partial least square discriminant analysis (PLS-DA), and support vector machine (SVM). Results showed that the best accuracy was achieved by the SVM model, with the overall error rates (ERs) of 1.1% and 2.5%, in calibration and prediction sets, respectively. Besides, the PLS-DA model performed slightly better than the PCA-LDA model. This work had demonstrated the good potential of FTIR-PAS to classify rapeseed colors.
Au nanoparticle grafted thiol modified magnetic nanoparticle solid phase extraction coupled with high performance liquid chromatography for determination of steroid hormones in human plasma and urine by Asadollah Beiraghi; Kamyar Pourghazi; Mitra Amoli-Diva (1418-1426).
A new, simple, rapid and sensitive preconcentration method was developed for separation of two neutral steroids (progesterone and testosterone) through an off-line extraction/preconcentration procedure using Au nanoparticles grafted on a 3-(trimethoxysilyl)-1-propanethiol modified magnetic nanoparticle adsorbent prior to their determination by HPLC-UV. The preconcentration step was optimized by a comprehensive study on the main factors affecting the extraction/preconcentration efficiency of the steroids such as pH value, amount of surfactant, amount of magnetic adsorbent, sample volume, desorption conditions and ionic strength. The validity of the method was investigated and good analytical performance was obtained including a wide dynamic range of 0.1–200 ng mL−1, low detection limits of 0.05 and 0.07 ng mL−1, and good precision (as RSD%) lower than 3.90 and 4.19% for progesterone and testosterone, respectively. The method was applied to determine the steroidal hormones in human plasma and urine samples. The levels were found to be 0.8 and 9.2 ng mL−1 for progesterone and 7.9 and 97.5 ng mL−1 for testosterone in plasma and urine samples, respectively, which are within the normal range reported in the literature.
Preconcentration and determination of pesticides with graphene-modified polymer monolith combined with high performance liquid chromatography by Ruifang Qi; Haochen Jiang; Shuxia Liu; Qiong Jia (1427-1434).
In this study, a graphene-modified poly(butyl methacrylate–ethylene dimethacrylate) monolithic column was successfully utilized for purification and enrichment of four pesticides (fludioxonil, cyprodinil, flusilazole, and triflumizole) in fruit and vegetable samples. Several experimental parameters affecting the extraction efficiency were investigated, such as sample pH, sample flow rate, sample volume, salt concentration, eluent type, and eluent flow rate. Combined with HPLC analysis under the optimized conditions, good linearities were obtained for all targets with R2 values greater than 0.9965. The limits of detection (S/N = 3) for four pesticides were found to be in the range of 0.93–3.0 μg kg−1. The intra-day and inter-day relative standard deviations, ranging from 3.4% to 6.2%, were within an acceptable scope. Compared with direct HPLC analysis and preconcentration with unmodified poly(butyl methacrylate–ethylene dimethacrylate) monolith, the incorporation of graphene into the monolith increased the enrichment capacity for the analytes. The developed method was successfully applied to the determination of pesticides in fruit and vegetable samples (apple, grape, orange, tomato, cucumber, rape). The recoveries of four pesticides at different spiked levels in the samples were in the range of 70.2–95.0% with the relative standard deviations less than 6.4%.
A novel method for cetylpyridinium bromide determination in aqueous solution based on fluorescence quenching of dye by Fengting Huang; Xiangfeng Guo; Lihua Jia; Rui Yang (1435-1441).
A new, highly selective and sensitive fluorescent detection method was developed for determining quaternary pyridinium salts cationic surfactant in an aqueous solution of polyoxyethylene-23-lauryl ether (Brij 35). The method was based on the emission of a fluorescent dye, disodium-4,4′-bis-(4-anilino-6-morpholino-s-triazin-2-ylamino)-2,2′-stilbenedisulfonate (CXT), was quenched by cetylpyridinium bromide (CPB). The fluorescence intensity of CXT showed distinct changes towards CPB with excellent selectivity and sensitivity among a series of common surfactants at the optimum pH 8.0. Furthermore, the fluorescence of the CXT/CPB complex is not affected by other common surfactants and most anions commonly associated with the quaternary pyridinium salt cationic surfactant in environmental samples. Also, the fluorescent intensity of CXT (5.0 μM) shows a linear response toward the concentration of CPB from 0 to 20 μM (R2 = 0.9956) and the detection limit was calculated to be 65 nM. The method is found to be precisely applicable to the analysis of CPB in real environmental samples.
Interaction of quercetin with aqueous CdSe/ZnS quantum dots and the possible fluorescence probes for flavonoids by Wei-Ping Hu; Guo-Dong Cao; Wei Dong; Huai-Bin Shen; Xiu-Hua Liu; Lin-Song Li (1442-1447).
Based on the quenching of the fluorescence intensity of quantum dots, the interaction of CdSe/ZnS quantum dots with four flavonoid compounds, including quercetin, rutin, luteolin, and 5,7,3′,4′-tetrahydroxy-flavanone, and their mechanism were studied. A fluorescence method with a detection limit of 0.14 mg L−1 for the determination of quercetin at concentrations between 0.576 and 184 mg L−1 was proposed according to its quenching effect on the QDs. The quercetin samples were determined by this method with satisfactory results. The study indicated that CdSe/ZnS QDs could be a potential excellent fluorescence probe to detect flavonoids.
Macroporous ordered silica foam for glucose oxidase immobilisation and direct electrochemical biosensing by Xiaodong Cao; Yuxue Sun; Yongkang Ye; Ying Li; Xiaoguang Ge (1448-1454).
We have applied macroporous-ordered silica-foam (MOSF) for glucose oxidase (GOx) immobilisation and for glucose biosensing. Due to the favorable properties of MOSF, the immobilised GOx retained good bioactivity, resulting in good performance in direct electrochemistry and electrocatalysis. A glucose biosensor based on a poly(diallyldimethyl-ammonium chloride) (PDDA)/GOx–MOSF/modified glassy carbon electrode allowed the detection of glucose with high sensitivity (2.336 μA mM−1 cm−2), a linear range from 50 to 1950 μM, and LOD (glucose) = 4.2 μM (S/N = 3). The biosensor displayed good sensitivity, stability, selectivity, and reproducibility of fabrication, making MOSF a promising material for construction of redox mediator-free enzyme biosensors based on direct electrochemistry of an immobilised enzyme.
Electron capture detection of oxybutynin in plasma: precolumn derivatization approach and application to a pharmacokinetic study by Achyut Khire; Pradeep Vavia (1455-1461).
Oxybutynin is an antimuscarinic agent used for the treatment of an overactive bladder. Because of its poor chromophore, it is difficult to determine oxybutynin by HPLC-UV analysis The difficulty increases when the analysis involves a complex biological matrix like plasma. Precolumn derivatization with trifluoroacetic anhydride followed by GC separation and ECD was used to solve this problem. The developed GC-ECD method had good linearity in the concentration range 2–20 ng ml−1 with a correlation coefficient of 0.9959. The accuracy and sensitivity for the determination of the halogenated derivative by this method was better than that for GC–MS. NMR and mass spectroscopy data confirmed the derivatization reaction. The developed GC-ECD method was used to study the pharmacokinetic parameters of an oxybutynin transdermal patch (36 mg/39 cm2) and oxybutynin gel (10% w/w). The Cmax, Tmax and AUC0–96 values for the oxybutynin transdermal patch and oxybutynin gel were equivalent.
Simple hollow fiber liquid membrane based pre-concentration of silver for atomic absorption spectrometry by José Antonio López-López; Jan Ake Jönsson; Manuel García-Vargas; Carlos Moreno (1462-1467).
Silver pollution has gained attention in the last few years because silver is being massively used as a bactericide in self-care, medical and textile products. Difficulties of Ag determination are associated with the very low concentrations in which it is normally found (ng L−1) and the nature of the sample matrix. Standard methods such as liquid–liquid extraction (LLE) are regularly used. Alternatively, liquid phase micro-extraction (LPME) appears to be an environmentally friendly tool for sample treatment that offers higher pre-concentration factors. This allows the determination of ultra-trace levels of silver using standard instrumental techniques such as atomic absorption spectrometry. In this work, a hollow fiber LPME is proposed. Silver pre-concentration has been conducted using tri-isobutylphosphine sulphide (TIBPS) as a carrier from the sample to an acceptor solution through a solvent placed in the fiber pores. Accurel-PP 50/280 fibers with an internal volume of 20 μL were used for 50 mL samples. After optimization, 0.1 M KNO3 in the sample, 0.1 M TIBPS in dihexyl ether as the organic phase and 1 M Na2S2O3 in the acceptor solution were established. The system offers enrichment factors of 1053 times, a limit of detection of 1.16 ng L−1. This method improves the limit of detection of the most recent liquid micro-extraction methods for silver pre-concentration coupled with GFAAS, being in this case comparable to ICP-MS detection based techniques.
Development of a sensitive assay for SERCA activity using FRET detection of ADP by Meng Jing; Raffaello Verardi; Gianluigi Veglia; Michael T. Bowser (1468-1474).
Various isoforms of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) regulate Ca2+ homeostatic balance in both the heart (SERCA2a) and skeletal muscle (SERCA1a). Ca2+ plays a key role in these tissues as an intracellular signal that controls contractility. Due to its key role in the contractility cycle, SERCA is emerging as a promising pharmacological target to modulate heart muscle function. SERCA function is regulated by its endogenous inhibitor phospholamban (PLN). Upon binding, PLN decreases SERCA's apparent affinity for Ca2+. Therefore, the interaction between PLN and SERCA has an important role in determining both physiological and pathological conditions. Quantifying the inhibitory potency of PLN is of great importance in understanding the pathophysiology of heart muscle. Traditionally, SERCA activity assays have been performed using a PK/LDH-coupled enzyme reaction, which suffers from limited sensitivity. We have developed a new SERCA activity assay based on the direct detection of the product ADP via time resolved FRET (TR-FRET). Under optimized conditions, our assay reduced the amount of SERCA required to perform the assay 1000-fold. Inter-day reproducibility was shown to be excellent for SERCA preparations in either detergent (C12E8) or reconstituted lipids. The inhibitory effect of PLN on SERCA measured under the low-concentration conditions of our assay allowed us to more accurately investigate the binding between PLN and SERCA. Significant inhibitory effects of PLN were observed even at mid-nanomolar concentrations, significantly lower than previous Kd estimates for the SERCA–PLN complex.
A high-performance liquid chromatography method with pre-column derivatization for the simultaneous determination of reduced glutathione, carnosine and taurine by Maria A. Khalikova; Dalibor Satinsky; Petr Solich; Alexandr A. Zinchenko; Elena T. Zhilyakova; Oleg O. Novikov (1475-1481).
A new gradient reversed-phase HPLC method with pre-column derivatization was developed and validated for simultaneous determination of reduced glutathione, carnosine and taurine in new pharmaceutical eye drops. Chromatographic separation was achieved with a fused core analytical column Supelco Ascentis Express C18 (100 mm × 4.6 mm, 2.7 μm). A 30 mM triethylamine in acetonitrile with 30 mM triethylamine aqueous solution (pH 2.5, adjusted with glacial acetic acid) was used in a gradient elution mode at a flow rate of 0.8 mL min−1. The column temperature was maintained at 30 °C, the injection volume of the derivatized sample was 5 μL and the detection wavelength was 375 nm. The tested validation parameters included system suitability, accuracy, precision, linearity, LOD, LOQ and sample solution stability. The standard calibration curves showed good linearity with correlation coefficients r > 0.997 for all compounds. The mean percentage recoveries obtained for reduced glutathione, carnosine and taurine were 99.61, 99.38 and 99.43%, respectively. Precision was <2% for retention times and peak areas. The applicability of this method was demonstrated by the analysis of a multicomponent eye drop formulation containing reduced glutathione, carnosine and taurine.
A simple method for benzoyl chloride derivatization of biogenic amines for high performance liquid chromatography by Fereydoon Aflaki; Vanik Ghoulipour; Nader Saemian; Maryam Salahinejad (1482-1487).
A simple, economical and reproducible benzoylation procedure was developed for the derivatization of biogenic amines (BAs) prior to high-performance liquid chromatography determination. The significant factors affecting biogenic amine benzoylation yield were optimized by central composite design. The derivatized BAs were extracted from basic aqueous solutions by 2-undecanol for direct HPLC injection. The obtained optimal conditions significantly decreased reagent consumption, uncertainty and time of analysis. The optimized method was used for further determination of BAs in real samples of non-alcoholic beers. The method showed good linearity (correlation coefficients > 0.997) and good recoveries (from 87.3 to 96.3%). The repeatability and reproducibility of the method were >4.6% and >6.7% respectively. Moreover, the detection limits of BAs were calculated between 0.02 and 0.09 μg ml−1 in non-alcoholic beers samples.
Characterisation of colourants on illuminated manuscripts by portable fibre optic UV-visible-NIR reflectance spectrophotometry by Maurizio Aceto; Angelo Agostino; Gaia Fenoglio; Ambra Idone; Monica Gulmini; Marcello Picollo; Paola Ricciardi; John K. Delaney (1488-1500).
The use of ultraviolet and visible diffuse reflectance spectrophotometry as a preliminary technique in the investigation of illuminated manuscripts is discussed. Because ancient manuscripts are amongst the most fragile and precious artworks, characterisation of the materials used in their decoration should be performed using non-invasive analytical methods. Ultraviolet and visible reflectance spectrophotometry with optical fibres (FORS) allows non-invasive identification of several colourants used by ancient illuminators, causing no damage or mechanical stress to the artworks subjected to analysis. Identification is usually based on the comparison of analytical data with a spectral database built from painted areas on parchment, created by preparing paints according to ancient recipes as described in medieval technical treatises. Such database and the spectral features of the colourants analysed are discussed, along with the benefits of extending the spectral range of analysis into the shortwave infrared (to 2500 nm). FORS can be best appreciated as a rapid preliminary tool that offers an overview on the main colourants employed and guides the selection of painted areas of manuscripts on which more selective techniques, such as X-ray fluorescence or Raman spectroscopy, can be employed for a more complete and accurate identification.
Identification of materials' binding peptide sequences guided by a MALDI-ToF MS depletion assay by Sascha Steckbeck; Julian Schneider; Linda Wittig; Klaus Rischka; Ingo Grunwald; Lucio Colombi Ciacchi (1501-1509).
We introduce a novel technique for an initial identification of peptide sequences that specifically bind to material surfaces based on the matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-ToF MS) depletion method. The technique relies upon time-resolved, sensitive measurements of the MALDI-ToF MS peak signals acquired from a solution containing several peptides placed in contact with an inorganic surface, in our case amorphous SiO2. Large errors intrinsic in the MALDI-ToF MS spectral analysis and uncertainties arising from the adsorption behaviour of peptide mixtures limit the predictive power of the method. However, when combined with other characterisation and modelling techniques, such as High-Performance Liquid Chromatography (HPLC), Atomic Force Microscopy (AFM), Quartz Crystal Microbalance with Dissipation (QCM-D) and Molecular Dynamics (MD), it can be used as a guide to identify novel material-binding peptide sequences, such as TPGSR for SiO2. The strategy presented in this work may have an impact on the design and synthesis of novel hybrid biomaterials based on the biomolecular recognition of inorganic surfaces.
Preparation of sorbent based on porous monolith incorporated with graphene oxide nanosheets for stir cake sorptive extraction of strongly polar aromatic amines by Xiaojia Huang; Yong Zhang; Dongxing Yuan (1510-1516).
In this study, poly(ethylene glycol dimethacrylate/graphene oxide) (EDMA/GO) monolith was prepared by one-step in situ polymerization. The porous monolith was used for the first time as the sorbent of stir cake sorptive extraction (SCSE) for the preconcentration of strongly polar aromatic amines (AAs) from water samples. The effect of the content of EDMA and GO in the monolith on the extraction efficiencies was investigated in detail. The sorbent was characterized by elemental analysis, transmission electron microscopy, scanning electron microscopy and infrared spectroscopy. Analysis of polar AAs in environmental water samples by a combination of poly(EDMA/GO)-SCSE and HPLC with diode-array detection was selected as a paradigm for the practical application of the new sorbent. Under the optimal conditions, the limits of detection (S/N = 3.0) of the developed method for AAs ranged from 0.04 to 0.19 μg L−1. Good reproducibility of the method was obtained as intra- and inter-day precisions, the relative standard deviations (RSDs) were less than 4.0%. Finally, the proposed method was successfully applied to the determination of trace AAs in environmental water samples. The recoveries of AAs spiked in different matrices ranged from 74.2% to 105%, and RSDs of repeatability ranged from 1.6% to 9.6%.
A turn-on fluorescein spirolactam derivative as a high selective fluorescence probe for detection of silver ion(i) in water by Dong-Sheng Lin; Jia-Ping Lai; Hui Sun; Zhou Yang; Yue Zuo (1517-1522).
In this paper, a fluorescein spirolactam derivative, ((E)-3′,6′-dihydroxy-2-((thiazol-2-ylmethylene)aminospiro[isoindoline-1,9′-xanthen]-3-one) (HTMIX), was synthesized and used as a turn-on fluorescence probe for the detection of silver ion in aqueous solution. The binding mechanism of HTMIX to Ag+ was evaluated using the Hildebrand–Benesi equation based on a 1 : 1 binding model with R = 0.9993. And the influence of sixteen common metal ions on the fluorescence intensities of HTMIX–Ag+ solution was investigated in detail. The results show that HTMIX exhibited high selectivity towards Ag+ in a 20% ethanol solution. The obtained fluorescence probe was used for the quantitative determination of Ag+ with a good linear range from 0.1 μM to 10 μM (R = 0.9969) and a satisfactory detection limit of 0.08 μM. In addition, the present probe has been further used for the detection of Ag+ in tap water, river water and lake water. And the accuracy of the results obtained by the proposed method was in good agreement with that obtained by flame atomic absorption spectrometry.
Direct determination of ampicillin and amoxicillin residues in food samples after aqueous SDS extraction by micellar liquid chromatography with UV detection by Fawzia A. Ibrahim; Jenny Jeehan M. Nasr (1523-1529).
A simple, sensitive and rapid micellar HPLC method was optimized and validated for the analysis of amoxicillin and ampicillin residues in food samples. Analytical separation was performed in less than 7 min using a RP C18 column with UV detection at 220 nm and a micellar solution of 0.05 M sodium dodecyl sulphate, 5% 1-propanol and 0.3% triethylamine in 0.02 M phosphoric acid buffered at pH 5 as the mobile phase. The flow rate was 1 mL min−1 and the effluent was monitored at 220 nm. The micellar method was successfully applied to quantitatively determine amoxicillin and ampicillin residues in spiked chicken muscles, chicken liver, bovine muscles, liver, kidney and eggs. The method was fully validated in accordance with ICH guidelines. Linearity was in the range 0.4–20 μg mL−1 for each drug and the percentage recoveries of both drugs ranged from 95.5 to 102.3% for amoxicillin and 95.6 to 101.7% for ampicillin. High extraction efficiency of amoxicillin and ampicillin was obtained without matrix interference in the extraction process and in the subsequent chromatographic determination. An aqueous solution of SDS surfactant only was used in extraction. No organic solvent was used during the pretreatment step. Hence, it is considered an interesting technique for “green” chemistry.
Simultaneous analysis of isoniazid and rifampicin by high-performance liquid chromatography with gradient elution and wall-jet/thin-layer electrochemical detection by Hongling Yan; Yaping Zhou; Qingji Xie; Yi Zhang; Pei Zhang; Hualing Xiao; Wen Wang; Shuozhuo Yao (1530-1537).
High-performance liquid chromatography (HPLC) with gradient elution was coupled to a glassy carbon electrode (GCE)-based wall-jet/thin-layer electrochemical detector (ECD) for the simultaneous analysis of isoniazid (isonicotinyl hydrazide, INH) and rifampicin (RIF). The simultaneous HPLC-ECD analysis of INH and RIF was performed using a reversed phase C18 column (150 mm × 4.6 mm, 5 µm) using a gradient elution program at a flow rate of 1.0 mL min−1, and an HPLC-Ultraviolet (UV) detector at a wavelength of 268 nm and the HPLC-ECD at a working potential of 0.9 V vs. SCE were used. Linear calibration plots for INH and RIF were obtained in the range of 0.01–100 µM for INH and RIF. Our wall-jet/thin-layer ECD gave limits of detection (LODs) of 0.3 and 0.5 nM (S/N = 3) for INH and RIF, respectively, which are lower than those obtained with the UV detector and a commercial ECD. Our method was successfully applied for the simultaneous determination of INH and RIF in an antitubercolosis drug and urine substrate samples.
Coupling neutral desorption sampling to dielectric barrier discharge ionization mass spectrometry for direct oil analysis by Yafei Zhou; Zhongchen Wu; Cao Li; Nannan Wang; Xinglei Zhang; Huanwen Chen; Saijin Xiao (1538-1544).
Rapid analysis of viscous oil samples is of great interest in food science and the food industry. Herein, neutral desorption sampling in conjunction with dielectric barrier discharge ionization mass spectrometry (ND-DBDI-MS) has been established for the fast and accurate identification of various hogwash oil (HHO) and edible oil samples under ambient conditions. Mass spectra in the negative ion detection mode were recorded in the mass range of m/z 50–500 Da, and characteristic substances responsible for the classification were identified using MS/MS experiments. Particularly, free fatty acids (e.g., oleic acid, linoleic acid, palmitic acid, etc.), typical representatives of oil quality, were successfully measured and used as decisive markers to differentiate HHO from qualified edible oil samples with the help of principal component analysis (PCA). Methodological reproducibility was characterized in terms of statistical method such as cluster analysis (CA). The experimental results show that ND-DBDI-MS is an important tool for the rapid analysis of highly complex viscous samples such as oil samples, with potential applications in food safety analysis.
Determination of benzo(a)pyrene and aflatoxins (B1, B2, G1, G2) in vegetable oil by GPC-HPLC-FLD by Hao Wang; Li Zhao; HongMei Yang; QiLei Guo; HaiLiang Shi; HongYan Pan; LiPing Zhao; Cong Qian (1545-1549).
This study develops a gel permeation chromatography-high performance liquid chromatography-fluorescence detection (GPC-HPLC-FLD) method for determination of benzo(a)pyrene and aflatoxins (B1, B2, G1, G2) in vegetable oil. In the method, sample is extracted with ethyl acetate/cyclohexane (1 : 1, v/v), and cleaned up with the GPC. The separation of target compounds is performed on a Extend C18 column (4.6 × 250 mm, 5 μm) at 25 °C with methanol and 10 mmol L−1 ammonium acetate solution as mobile phase with gradient elution at a flow rate of 1.0 mL min−1. The injection volume was 10 μL, detection wavelengths were set at 360 nm (λex) and 440 nm (λem) at 0–23 min, and 380 nm (λex) and 408 nm (λem) at 23–35 min using FLD. The detection limits of benzo(a)pyrene and aflatoxins (B1, B2, G1, G2) were 0.5, 1.0, 1.0, 1.0 and 1.0 μg kg−1, respectively. The linear detection ranges of benzo(a)pyrene and aflatoxins (B1, B2, G1, G2) are 0.5–25.0 μg kg−1, 1.0–30.0 μg kg−1, 1.0–10.0 μg kg−1, 1.0–30.0 μg kg−1, 1.0–10.0 μg kg−1 with correlation coefficients (R2) of 0.9998, 0.9999, 0.9997, 0.9998, 0.9996, respectively. Recovery rates in vegetable oil spiked with target compounds are in the range of 82.6–101.6%, with the relative standard deviation of 4.85–9.84%. The real sample tests show that this simple and accurate method can be used for determination of benzo(a)pyrene and aflatoxins (B1, B2, G1, G2) in vegetable oil.
Metal organic framework-derived anthill-like Cu@carbon nanocomposites for nonenzymatic glucose sensor by Changting Wei; Xia Li; Fugang Xu; Hongliang Tan; Zhuang Li; Lanlan Sun; Yonghai Song (1550-1557).
A novel nonenzymatic glucose sensor was constructed based on anthill-like Cu@carbon nanocomposites which were derived from a Cu-based metal organic framework by a simple thermolysis method. The final nanocomposites were characterized by scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction and electrochemical techniques. The results showed that the derived nanocomposites maintained the morphology of the original materials upon thermolysis, while the produced Cu nanoclusters were embedded in three-dimensional carbon frameworks and presented an anthill-like structure. Since the final products gave a sufficiently large specific surface area, good catalytic activity towards the oxidation of glucose and appropriate pores for electrolyte transfer, the resultant glucose sensor based on the anthill-like Cu@carbon nanocomposites showed a wide linear range of 0.2–8.0 mM and a low detection limit of 29.8 μM. The low cost, simple preparation and good catalytic activity of anthill-like Cu@carbon nanocomposites render them promising candidates as electrode materials for the construction of novel nonenzymatic sensors.
Induction of an electrochemiluminescence sensor for DNA detection of Clostridium perfringens based on rolling circle amplification by Dongneng Jiang; Fei Liu; Chang Liu; Linlin Liu; Yi Li; Xiaoyun Pu (1558-1562).
Clostridium perfringens is one of the predominant pathogens causing infectious diseases. This work describes the application of a rolling circle amplification (RCA) based electrochemiluminescence sensor for detection of C. perfringens. Firstly, the target DNA is captured by the probes on the pretreated electrode. Subsequently, RCA reaction is executed isothermally. The products of RCA are incubated with hemin, resulting in the decrease of the ECL emission, which is related to the quantity of the target DNA. The ECL-sensor provides the capability of discriminating the target DNA from non-target sequences even with only one base difference, suggesting an advantageous selectivity. Meanwhile, the lowest concentration of the target DNA is 10−15 M, showing satisfactory sensitivity. Therefore, this strategy combines amplification ability of RCA and high sensitivity of ECL, and enables a low fM detection of C. perfringens without the bacterial culture.
Pharmacokinetic study of liquiritin in rat serum using molecularly imprinted solid-phase extraction combined with RP-HPLC by Huang Yang; Li Kang; Shao Hui Kai; Liu Sheng Quan; Xiang Fei Jun (1563-1568).
A method using molecularly imprinted solid-phase extraction combined with RP-HPLC-UV was developed for determination of liquiritin (LQR) in rat plasma after oral administration of Compound Liquorice Tablets (CLTs). To this end, molecularly imprinted polymers were prepared by in situ polymerization, using LQR as the template, acrylamide as the functional monomer, and ethylene glycol dimethacrylate as the crosslinker, whose solid-phase extraction properties for liquiritin were evaluated by HPLC-UV. The enrichment and extraction recovery were investigated in the study after the extraction procedure was optimized. The recovery was larger than 85.0% and the RSD was less than 10.0%. The calibration curve was expressed as y = 16 004x− 1.864 (r = 0.996) with a linear range of 0.007–1.683 μg mL−1. Besides, the Tmax was 0.5 h for liquiritin and the Cmax was 0.8 μg mL−1 after oral administration of compound liquorice tablets. In addition, the pharmacokinetic parameters were calculated using a two-compartment model. The results indicated that the monolithic polymer pipette presented a good extraction efficiency for liquiritin. At the same time, the results indicated that the index components could basically reveal the pharmacokinetic behavior. This study was aimed to explore an approach that could be applied to promulgate the pharmacokinetics and provide more information for clinical applications.
Aptamer-based spectrophotometric detection of kanamycin in milk by Nandi Zhou; Juan Zhang; Yaping Tian (1569-1574).
Aminoglycoside antibiotics are widely used drugs. The residual antibiotics in animal-derived food are proven to be harmful to human health and therefore should be strictly controlled in the food industry. A spectrophotometric method based on a kanamycin-specific aptamer and gold nanoparticles (AuNPs) was developed for the quantitative detection of kanamycin. Two types of functionalized AuNPs were synthesized by self-assembly of thiol-modified single-stranded DNAs (ssDNAs), which were complementary to the 5′ terminal and 3′ terminal sequences of the kanamycin aptamer. As the kanamycin aptamer is mixed with these AuNPs, the AuNPs aggregate due to the hybridization of the aptamer with the complementary ssDNAs on the surface of AuNPs. However, when different concentrations of kanamycin are present, it can bind with the aptamer specifically and competitively, which leads to the disaggregation of the AuNPs aggregate, and a change in the UV-visible absorption spectrum of AuNPs. The absorbance at 527 nm is utilized to detect the concentration of kanamycin. The detection range of this method is 1–500 nM, with a detection limit of 1 nM. The developed method was then successfully employed to detect kanamycin in milk samples, and a similar response range and detection limit were obtained.
Development and validation of an HPLC-UV method for quantifying nevirapine and its main phase I metabolites in human blood by Aline T. Marinho; Ana L. A. Godinho; David A. Novais; Alexandra M. M. Antunes; M. Matilde Marques; Teresa Ramos; Clara G. Dias; Emília C. Monteiro; Sofia A. Pereira (1575-1580).
Nevirapine (NVP) is a widely used drug for the treatment of HIV-infection, which is associated with severe toxic events dependent on its biotransformation. Thus, the availability of analytical methods for the biomonitoring of NVP and its main metabolites is of utmost importance. In this paper we report the development and validation of a reversed phase HPLC-UV method for the quantification of NVP and its main phase I metabolites in human plasma. The method was validated over a range of 10–2500 ng mL−1 for the phase I metabolites of NVP and 10–10 000 ng mL−1 for NVP. The coefficients of variation (CV) of the average back-calculated concentrations were lower than 9% and the LLOQ was 10 ng mL−1 for each analyte. The accuracy and precision of the method were acceptable. There was no significant interference from plasma components or from other typically co-administered antiretroviral drugs and the mean recovery was 94%. This method represents an inexpensive, sensitive, accurate and precise alternative to mass spectrometry-based biomonitoring of NVP.
On-line solid-phase extraction coupled liquid chromatography-ESI-ion trap-mass spectrometry for analysis of abamectin and ivermectin residues in milk by Cheanyeh Cheng; Liang-Chun Liu (1581-1589).
A solid-phase extraction column was on-line coupled to a liquid chromatography electrospray ionization ion-trap tandem mass spectrometer to perform on-line sample pretreatment and simultaneous analysis of abamectin and ivermectin residues in milk samples. Multiple-reaction monitoring of secondary mass spectrometry in the positive mode was used to detect both abamectin and ivermectin. The matrix-fortified external standard calibration curves of the secondary mass spectrometry in the concentration range of 0–15 ng mL−1 for abamectin and ivermectin shows good linearity. The limit of the detection/quantification (LOD/LOQ) for abamectin and ivermectin was 0.67/2.23 ng mL−1 and 0.63/2.11 ng mL−1, respectively. Quantification of five different brands of milk samples by the standard addition method with the assistance of the statistical t-test indicates that two brands of milk samples do contain trace amounts of abamectin and ivermectin. Abamectin and ivermectin are not detected in the other three brands of milk samples. The accuracy of the two brands of milk samples for abamection and ivermectin was 82–88% and the precision was 4.8–9.7%. The running time for one sample was 10 min.
An imprinted electrochemical sensor for bisphenol A determination based on electrodeposition of a graphene and Ag nanoparticle modified carbon electrode by Rong Cai; Wei Rao; Zhaohui Zhang; Fang Long; Yuli Yin (1590-1597).
In this study, a highly sensitive and selective imprinted electrochemical sensor based on a Ag nanoparticle and graphene modified carbon electrode with covalent anchoring and electrochemical reduction was prepared for the determination of bisphenol A (BPA) in aqueous solution. The imprinted film was fabricated by electrodepositing pyrrole in the presence of BPA onto the graphene and Ag nanoparticle modified electrode surface. The morphologies of the electrodes were characterized by scanning electron microscopy. The electrochemical performance of the imprinted electrochemical sensor was investigated by cyclic voltammetry and differential pulse voltammetry techniques in detail. The response currents of the imprinted electrochemical sensor exhibit a linear relationship toward the negative logarithm of the concentrations of BPA ranging from 1.0 × 10−11 to 1.0 × 10−8 mol L−1. The detection limit of the imprinted electrochemical sensor toward BPA is calculated to be 3.2 × 10−12 mol L−1 (S/N = 3). The imprinted electrochemical sensor was successfully applied to detect BPA in real plastic samples with good recoveries ranging from 93.3–103.0%.
Facile functionalization of Ag@SiO2 core–shell metal enhanced fluorescence nanoparticles for cell labeling by Meicong Dong; Yu Tian; Dimitri Pappas (1598-1602).
We describe a versatile approach for functionalizing core–shell Ag@SiO2 nanoparticles for live-cell imaging. The approach uses physical adsorption and does not need covalent linkage to synthesize antibody-based labels. The surface orientation is not controlled in this approach, but the signal enhancement is strong and consistent. Antibodies were then attached using a non-covalent process that takes advantage of biotin–avidin affinity. Metal-enhanced nanoparticles doped with rhodamine B were used as the luminescent reporter. The enhancement of rhodamine B was between 2.7 and 6.8 times. We demonstrated labeling of CD19+ Ramos B lymphocytes and CD4+ HuT 78 T lymphocytes using anti-CD19 and anti-CD4 nanocomposite labels, respectively. This physical adsorption process can accommodate a variety of fluorophore types, and has broad potential in bioanalytical and biosensing applications.
HPLC/ICPMS with effluent diversion for robust and time-efficient determination of selenium metabolites in human urine by Sabine Kokarnig; Nina Kroepfl; Doris Kuehnelt; Kevin A. Francesconi (1603-1607).
Reversed-phase high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (RP-HPLC/ICPMS) is widely applied for the determination of major urinary selenium metabolites such as selenosugars. Urine often also contains small amounts of non-polar Se species like dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe). Although these compounds are not significant quantitatively, they present considerable analytical problems because of their enhanced signals and long retention on reversed-phase columns. The use of solvent gradients to reduce the retention times of DMSe and DMDSe is usually hampered by the intolerance of ICPMS towards high loads of organic solvent. We report a simple instrumental set-up that allows application of a methanol gradient program without compromising ICPMS detection. High loads of organic solvents were prevented from reaching the ICPMS system by using a 6-port valve between the HPLC column and the ICPMS system. The combination of this experimental set-up and the developed methanol gradient provided separation of the main urinary selenium metabolites, three selenosugars and TMSe, within 7 min, and elution of non-polar selenium species DMSe and DMDSe and re-equilibration was completed within 15 minutes. The introduction of 1% CO2 in argon into the nebuliser gas flow significantly improved the stability of the system. Stability over 12 hours of measurement time tested by repeated injection (40 times) of a urine sample spiked with 3 selenosugars and TMSe gave variations in retention times of ≤0.5% and in ICPMS signal response of ≤2% for all four species. The method can be used to determine the main urinary selenium metabolites in the presence of non-polar selenium species within an overall analysis time, including re-equilibration, of 15 minutes instead of two hours for isocratic elution, offering great advantages for the analysis of large numbers of samples.
Back matter (1609-1610).