Analytical Methods (v.5, #4)

Front cover (813-814).

Contents list (815-828).

Analytical monitoring of sodium borohydride by Biljana Šljukić; Diogo M. F. Santos; César A. C. Sequeira; Craig E. Banks (829-839).
Sodium borohydride (NaBH4) determination, both qualitative and quantitative, is of great significance in a plethora of areas. These include NaBH4 for energy systems such as direct borohydride fuel cells and in hydrogen production and storage, as well as use as a reducing agent in organic and inorganic synthesis reactions or in electrodeposition processes. Herein the main methods for NaBH4 monitoring have been summarised and described, including hydrogen evolution, hydride hydrolysis and iodate methods, and different electrochemical and spectroscopic techniques overviewed.

In the present paper, a direct FP assay strategy for the detection of small size molecules on the basis of a noncompetitive FP technique has been proposed by using adenosine as a small molecule object. The detection limit for adenosine is 26 nM. And this assay has a wide dynamic-range of over five orders of magnitude, from 50 nM to 1.0 mM.

In situ detection of γ-hydroxybutyrate and γ-butyrolactone in drinks by secondary electrospray ionization by Christian Berchtold; Stefan Schmid; Lukas Meier; Renato Zenobi (844-850).
γ-Hydroxybutyrate (GHB) and γ-butyrolactone (GBL) are used as “date rape drugs” since they cause catalepsy and memory loss. A new application of secondary electrospray ionization (SESI) mass spectrometry for in situ detection of GHB and GBL in drinks and body fluids is introduced. Different mass spectrometers were compared, including a portable, miniaturized ion trap, a semi mobile bench-top ion trap, and a quadrupole time-of-flight instrument. Direct ionization of GHB and GBL from the headspace of drinks was shown, and the suitability for on-site measurements was tested. Several matrices including various drinks as well as body fluids such as urine and saliva were analyzed. SESI provides a robust, reliable, fast, and efficient ionization method, which is largely independent of the mass spectrometer and the matrix used. The detection limits for GHB and GBL in drinks were found to be always below 0.5 g L−1, which is sufficient to identify them in beverages (a dose of about 2 g L−1 is commonly used). 8 mg L−1 GHB were detectable in urine, which suffices to identify an intoxicated individual. Overall, GHB and GBL can be detected in drinks and small leftovers of drinks as well as in body fluids at concentration levels that are of practical relevance. With a mobile MS instrument, this method could be applied as a diagnostic as well as a preventive on-site method.

Electroanalytical sensing of selenium(iv) utilising screen printed graphite macro electrodes by Athanasios V. Kolliopoulos; Jonathan P. Metters; Craig E. Banks (851-856).
The electroanalytical determination of selenium(iv) via anodic stripping voltammetry is shown to be possible for the first time using screen printed graphite electrodes. The deposition potential and time was optimised allowing a linear range from 10 to 1000 μg L−1 in 0.1 mol L−1 HClO4 to be realised with a limit of detection (3σ) found to correspond to 4.9 μg L−1. Utilising these screen printed graphite electrodes, the detection of selenium(iv) in drinking (tap) water is shown to be feasible allowing a detection limit (3σ) of 19.2 μg L−1 to be realised which is below the levels set by the United States Environmental Protection Agency. Such an approach suggests the possibility of a disposable screening tool for selenium(iv) in drinking water samples.

Trading has impelled the development of analytical procedures for fast identification and counterfeit detection of herbal medicinal products. Panax ginseng has attracted the interest of many people due to its therapeutic properties; thus, in this study a solvent free near-infrared spectroscopic procedure for fingerprinting P. ginseng has been developed using raw materials in order to ensure its quality control. Proper identification of P. ginseng, mixture detection and semi-quantitative determination of binary mixtures have been achieved using chemometrics. Raw near-infrared spectra were normalized and the classification ability of three different pattern recognition procedures was assayed. Soft independent modeling of class analogy (SIMCA), partial least squares discriminant analysis and discriminant analysis reached equal sensitivity value (100%); however, SIMCA obtained the best general classification success rate (95%) and had the higher specificity (100%) and ability to detect debased samples (80%). Moreover, the semi-quantification of mixtures performed with multivariate curve resolution presented a mean percent error of 5.53% and showed that the mixture composition should change in amounts larger than 3.64% in order to retrieve proper results. The overall results suggest that NIR spectroscopy can be used to authenticate P. ginseng.

Efficient total analyses for bromine type flame retardants by simple NICI-GC/MS by Atsushi Kobayashi; Takuya Kubo; Tomoyuki Sato; Yusuke Kitahara; Shinichiro Amita; Masahiro Mori; Shigeru Suzuki; Koji Otsuka; Ken Hosoya (866-873).
We studied an efficient analytical method for detecting brominated aromatic compounds using negative ion chemical ionization (NICI), with well-known quadruple gas-chromatography mass-spectrometry (GC/MS). We utilized 79 and 35 m/z as monitoring ions of brominated compounds and syringe-spiked PCB#209, thus highly selective and sensitive detection was achieved. With 7.0 m long HP-5 GC column, decabromo-diphenyl ether (DBDE), hexabromobenzene, α-hexabromo cyclododecane (α-HBCD), and tetrabromo bisphenol A were utilized as bromine type flame retardants that are generally consumed in industrial commodities. A shorter column provided more efficient results without degradation of DBDE on GC which are usually observed with longer column (30 m). Also, pseudo environmental water samples can be analyzed without authentic pretreatment procedures. Furthermore, we demonstrated analyses for members regulated by the Restriction of Hazardous Substances. Consequently, the newly developed simple NICI-GC/MS method was effectively worked for screening of flame retardants in a short period of time.

Cellular biomechanical properties including cell elasticity and cell adhesion are regarded as criteria to differentiate cancer cells and normal cells. In this study, the biomechanical properties including the Young's modulus and adhesion force of human lung adenocarcinoma epithelial cell line A549 and non-cancerous human primary small airway epithelial cells (SAECs) were measured by using atomic force microscopy (AFM). It was found that primary SAECs are stiffer and more adhesive than cancerous A549 cells. Upon treatment with anti-cancer drug doxorubicin (DOX) for a short time (4 hours), both biomechanical properties of A549 cells were found to be increased while those of SAECs were decreased, implying that DOX-induced response mechanisms are different between these two types of cells (cancerous vs. primary cells). Using confocal Raman spectroscopy, we measured the changes in (sub)cellular biochemical compositions of both cell types before and after DOX exposure. Our ultimate goal is to find out the potential relationship between the changes in biomechanics and biochemical compositions of lung epithelial cells in response to anti-cancer drugs.

A novel electrochemical pH sensor was fabricated through the use of an anthraquinone–ferrocene (AQ–Fc) complex based on a vertically aligned gold nanowire array electrode (AuNAE). The sensing capability was achieved by monitoring the variation in peak potential of the redox active/pH active anthraquinone moiety with respect to the redox active ferrocene moiety. The pH sensor, based on AQ–Fc/AuNAE, was characterised using scanning electron microscopy (SEM) and cyclic voltammetry (CV). The difference in peak potential of the ferrocene and anthraquinone moieties was measured using square wave voltammetry (SWV) and was found to be linear over the range of pH 2–11, with a sensitivity of 1.38 V pH−1 cm−2 at 25 °C. The electrode was found to respond both in the presence and absence of oxygen, further expanding the potential applications to include de-oxygenated environments. The sensor showed a potential drift of 1.0–3.3% after three hours and 95% of the signal was retained after one week. Such single molecular complex (AQ–Fc) based pH sensors should provide easy manufacturing and long term stability when incorporated into the sensor designs.

A novel detection of nitrite, iodate and bromate based on a luminescent polyoxometalate by Bin Wang; Rui-Qi Meng; Ling-Xiao Xu; Li-Xin Wu; Li-Hua Bi (885-890).
In this paper, we describe a novel detection of nitrite, iodate and bromate in solutions through combining the electrochemistry and the redox reaction accompanying the color change and luminescence switching based on Eu3+-containing tungstogermanate [(CH3)4N]2.5H7.5[Eu(GeW11O39)(H2O)2]2·4.5H2O (Eu-POM) for the first time. Eu-POM was electroreduced to form the reduced Eu-POM accompanied by a color change from colorless to blue and luminescence quenching, while the discoloration and luminescence recovery were observed after the addition of nitrite, iodate and bromate because of the spontaneous redox reactions of nitrite, iodate and bromate with the reduced Eu-POM. Based on this observation, we investigated the changes of absorbances and luminescence intensities of the reduced Eu-POM with the concentrations of nitrite, iodate and bromate and obtained good linear ranges and lower detection limits for the three substances based on S/N = 3. This method successfully combines the electrochromic and luminescent properties of polyoxometalate to develop a novel detection of nitrite, iodate and bromate with good reversibility and high sensitivity as well as a wide linear range. Therefore, such as system shows great potential for the detection of nitrite, iodate and bromate.

Determination of the empirical solvent polarity parameter ET(30) by multivariate image analysis by Fatemeh Shakerizadeh-Shirazi; Bahram Hemmateenejad; Abdol Mohammad Mehranpour (891-896).
The solvent polarity ET(30) scale has found wide-spread applications in studying chemical processes in solvents. This parameter is usually measured by vis spectrophotometric measurements of the long-wavelength intramolecular charge-transfer (CT) absorption band of Reichardt's pyridinium-N-phenolate betaine dye, e.g. the ET(30) dye, dissolved in the solvent or solvent mixture of interest. Recent advances in colorimetric measurements based on digital photo-capturing devices suggest these methods as a simple, cheap and fast alternative to spectrophotometric measurements in some analytical applications. In this work, we studied the feasibility of colorimetric measurements coupled with multivariate data analysis to determine the empirical solvent polarity parameter ET(30). The picture of the ET(30) dye dissolved in different solvents was captured by a digital camera and then color values in the RGB space were analyzed by the principal component analysis (PCA) method. PCA scores of the unfolded image were then used as input of multiple linear regression and an artificial neural network model to predict the ET(30) parameter. The ANN models were optimized to gain a model of lower prediction ability utilizing a cross-validation test. Then, this was used to predict ET(30) values for an external solvent test set. The generated model could explain and predict 99% of the variances in the polarity data and can predict ET(30) values with a root mean square error of 2.25 kcal mol−1 (in the ET(30) scale). The results suggest colorimetric measurements as a useful and practical alternative to the vis spectrophotometric measurements for determination of solvent polarity parameters derived from solvatochromic betaine dyes.

Antimony toxicity occurs either due to occupational exposure or during therapy. There is a growing need for biological monitoring of antimony to provide exposure information to help prevent hazardous exposure. This study presents supercritical carbon dioxide (SC-CO2) extraction as an inherently safe and clean sample treatment method for analyzing trace antimony in spiked human urine. Extraction was performed in the presence of a fluorinated β-diketone chelating agent, thenoyltrifluoroacetone, by unmodified SC-CO2. Quantitative extractions were conducted at 60 °C and 17.2 MPa with 15 min static plus 10 min dynamic extractions. The extracts were subsequently analyzed by graphite furnace atomic absorption spectroscopy with spiking Pd(NO3)2–Mg(NO3)2 matrix modifier. The proposed procedure was successfully applied to determine the concentrations of antimony in spiked urine samples with satisfactory recoveries of 95.6%–102.9% (n = 6) and relative standard deviations <5%. The accuracy of the proposed procedure was also validated by the analysis of the certified reference materials.

Hollow fiber supported liquid membrane (HFSLM) extraction often suffers from matrix effects in extracting weak organic acids in environmental waters, but the reasons for which are unclear. This work systematically studied the influence of dissolved carbon dioxide and carbonate on the HFSLM extraction of analytes in environmental waters, by using triclosan and its two typical degradation products, 2,4-dichlorophenol and 2,4,6-trichlorophenol, as model compounds. HFSLM was conducted by immersing a HFSLM extraction device into a 200 mL water sample modified with 0.01 M HCl and 10% (m/v) NaCl, and shaking at 250 rpm for 90 min. The extraction device was prepared by immobilizing dihexyl ether on the polypropylene hollow fiber membrane wall (60 cm length, 50 μm wall thickness, 280 μm inner diameter), filling the fiber lumen with 0.4 M NaOH as acceptor, and closing the two ends of the fiber with aluminum foil. It was demonstrated that the dissolved carbon dioxide and carbonate present in environmental samples reduces the acceptor pH and thus the recovery of target analytes, and purging the acidified sample with ∼50 mL min−1 N2 for 15 min is a very efficient approach to eliminate this matrix effect. With this purging pretreatment, the recoveries of the analytes in environmental samples increased substantially from below 40% to between 63% and 121%. For the three analytes, the proposed HFSLM method provided enrichment factors in the range of 1090–1322, and detection limits in the range of 0.1–0.2 μg L−1 by coupling with an ultra-performance liquid chromatography-mass spectrometry system.

Improved sensing performance from methionine capped CdTe and CdTe/ZnS quantum dots for the detection of trace amounts of explosive chemicals in liquid media by T. Pazhanivel; D. Nataraj; V. P. Devarajan; V. Mageshwari; K. Senthil; D. Soundararajan (910-916).
Water soluble methionine functionalized CdTe quantum dots (QDs) and CdTe/ZnS core–shell QD samples have been prepared by a reflux condensation method and have been used to detect explosive chemicals, such as dinitrotoluene (DNT), nitrotoluene (NT) and nitrobenzene (NB) in liquid media. Meisenheimer complex formation between the QD surface attached methionine and aromatic explosive molecules has helped to detect them selectively via a fluorescent quenching process. Fluorescence quenching occurred because of the transfer of excited electrons from QD to the explosive molecules. Depending upon the number of nitro groups present on the explosive molecule, the quenching efficiency of different analytes varied. Due to surface passivation and inductive effects, the methionine capped CdTe/ZnS core–shell quantum dot sample resulted in the maximum quenching constant.

In this study, a novel colorimetric method for rapid, sensitive and low-cost detection of glyphosate was developed using cysteamine-stabilized gold nanoparticles (CS-AuNPs). The CS-AuNPs could be aggregated easily in the presence of glyphosate through electrostatic interaction in acidic medium, resulting in a shift in the surface plasmon band and a consequent color change from red to blue (or purple). Therefore, the content of glyphosate could be determined by monitoring with the naked eyes or a UV-Vis spectrophotometer. The detection limit of the present method for glyphosate was 5.88 × 10−8 M, with the linear range of 0.500–7.00 μM. The proposed method is a promising approach for on-site screening of glyphosate content in environmental water samples without using any costly instruments.

A sensitive and specific enzyme immunoassay for detecting tartrazine in human urinary samples by Yajing Lei; Shujie Zhang; Lizheng Fang; Muhammad Sajid Hamid Akash; Weixing Shi; Kedan Sun; Yingchun Xu; Shuqing Chen (925-930).
Tartrazine is commonly used in foodstuffs, its level is controlled by government, however, it is still used in some food products at levels which are not permitted. We aimed to develop a sensitive and simple method to assess the exposure to tartrazine in pregnant women and the general population in China. A competitive enzyme-linked immunosorbent assay (ELISA) was developed based on polyclonal antibodies for tartrazine. Using this assay, we measured the urinary concentrations of tartrazine in the participants. Under optimal experimental conditions, the standard curve was constructed at concentrations of 0.04–1000 ng mL−1 and the limit of detection (LOD) was set at 0.04 ng mL−1. No cross-reactivity of the antibody was observed with seven other artificial dyes based on this assay. Human blank urine was spiked with tartrazine at concentrations of 0.1, 25, 500 ng mL−1 and analyzed by ELISA, the recoveries of tartrazine were from 99.8% to 106.6% and coefficients of variation were from 3.28% to 14.9%. The study comprised of 351 volunteers (age: 19–69 years), of which 30% were male, 16% were nonpregnant women and 54% were pregnant women. The geometric means for tartrazine in three groups were 2.64, 2.44 and 3.21, respectively. No difference was observed in these groups. The values indicated that both the general population and pregnant women are exposed to tartrazine. Sources of exposure, potential health effects and risk assessment require further investigation.

A simple, reproducible, environmentally friendly cellulose acetate modified glassy carbon electrode was prepared and used for the direct reduction of lindane in aqueous alcoholic medium. This modified electrode offers a high sensing current with a lower reduction potential for lindane. The lowest adsorption of pesticide molecules was observed on the cellulose acetate modified electrode when compared with a bare glassy carbon electrode which enhances the sensitivity of the sensor. This modified electrode is highly stable with respect to time, so that the single electrode can be used for the multiple analysis of the lindane sample. Cyclic voltammetry, differential pulse voltammetry and amperometry were used as the sensing techniques. The reduction potential of lindane on this modified electrode is −1.5 V whereas the reduction potential of nitropesticides is around −0.600 V. This wide difference in reduction potential can be used to estimate lindane even in the presence of nitropesticides by cyclic voltammetry and differential pulse voltammetry. The analytical utility of the proposed method was checked with a commercial lindane lotion and drinking water samples. An amperometric instrument, interfaced with the cellulose acetate modified glassy carbon electrode was designed and tested for the sensing of lindane. The performance of this instrument was assessed.

A novel skeleton weak anion-exchange monolith was prepared by single electron transfer-living radical polymerization (SET-LRP) for high performance liquid chromatography (HPLC). In this study, vinyl ester resin was used as the monomer, ethyleneglycol dimethacrylate as the cross linking agent, carbon tetrachloride as the initiator, ferrous powder as the catalyst, and N,N,N′,N′-tetramethylethylenediamine as the ligand to supply amine-groups. The polymerization conditions were optimized. The characters of the monolith were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy and mercury porosimeter, respectively. Good skeleton structure properties were obtained. Moreover, the prepared monolith was used as HPLC stationary phase to separate immune globulin G (IgG) from human plasma with high efficiency. The influences of buffer concentration and pH of the mobile phase on the separation of IgG were investigated. In addition, the monolith was also used to separate the mixture of beef serum albumin (BSA), IgG and lysozyme (Lys) successfully.

Label-free detection of the foodborne pathogens of Enterobacteriaceae by surface-enhanced Raman spectroscopy by Yunfei Xie; Li Xu; Yiqian Wang; Jingdong Shao; Li Wang; Heya Wang; He Qian; Weirong Yao (946-952).
Label-free and rapid assessment of foodborne pathogenic contamination, which can have significant implications for food safety, is critically important. In this study, seven foodborne bacteria (Salmonella typhimurium ATCC 50013, Salmonella O7HZ10, Shigella boydii CMCC51514, Shigella sonnei CMCC51529, Shigella dysenteriae CMCC51252, Citrobacter freundii ATCC43864, and Enterobacter sakazakii 154) have been examined, which are classified as Enterobacteriaceae according to biological taxonomy. They often have high rates of outbreak. A rapid and sensitive measurement method has been developed based on surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles as SERS substrates. The respective SERS spectra of the pathogens and their reproducibility have been compared. The principal component analysis (PCA) multivariate statistical technique has been employed to analyze the data, and a dendrogram cluster was constructed by hierarchical cluster analysis (HCA). Our results have shown that a rapid, sensitive, label-free identification of the foodborne pathogenic bacteria could be obtained by using gold nanoparticles as effective and stable SERS substrates.

Toxic effects of Euphorbia pekinensis Rupr. and development of a validated UPLC/MS/MS method for profiling of urine metabolic changes by P. Y. Hou; K. S. Bi; L. L. Geng; X. Zhao; X. Meng; B. J. Ma; Y. Zeng; X. F. Wang; X. H. Chen (953-960).
This paper was designed to study metabonomics characteristics of the hepatotoxicity and nephrotoxicity induced by JingDaJi (JDJ), a well-known traditional Chinese medicine which has been used for the treatment of scrofula, and as an antivirus and anti-inflammatory medication. Urinary samples from control and JDJ treated groups of rats were analyzed by ultra-performance liquid chromatography/mass spectrometry in positive ionization mode. Hepatic and renal tissues were histopathologically examined to identify specific changes occurring as a result of damage. The results suggested that the ethanol extract of JDJ (EJDJ) was responsible for the hepatotoxicity and nephrotoxicity that occurred following the ingestion of this medicinal herb. Using the principal components analysis, the levels of eight endogenous metabolites including creatinine, phenylacetylglycine, kynurenic acid, phenylalanine, leucine, hippuric acid, xanthurenic acid and 2,8-dihydroxyquinoline were found to be significantly changed in urine from EJDJ treated group. The formation of creatinine, phenylalanine, kynurenic acid, xanthurenic acid, leucine and 2,8-dihydroxyquinoline increased, while the biosynthesis of hippuric acid and phenylacetylglycine decreased.

We identified 6-benzylaminopurine (6-BAP) plant growth regulator using an opto-fluidic ring resonator (OFRR) biosensor and a Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. In this study, the OFRR biosensor with a bulk refractive index sensitivity (BRIS) of 14.5 nm per RIU was fabricated through the optimization process of the OFRR capillary and tapered fiber optic cable. The detection limit of the OFRR biosensor using the 6-BAP standard solution and 6-BAP sample solution extracted from bean sprouts by the QuEChERS method is 0.01 mg kg−1. This result is similar to the experimental results of HPLC and LC-MS/MS. To apply the OFRR biosensor and the QuEChERS method on the spot, improvement in the accuracy of the OFRR biosensor and the recovery of the QuEChERS method is needed.

A simple, accurate and selective LC–MS/MS method using a polarity switch technique was developed and validated for the simultaneous quantification of piperine, cinnamic and gallic acid in rat plasma. Bicalutamide for piperine (positive mode) and furosemide for cinnamic acid and gallic acid (negative mode) were used as internal standards. The precursor and product ions of analytes were monitored using a triple quadrupole mass spectrometer API 4000 Q-Trap instrument, operating in the multiple reaction monitoring mode with polarity switch. The method was validated over the range of ∼5–1000 ng ml−1 for piperine and ∼50–10 000 ng ml−1 for cinnamic acid and gallic acid. Intra- and inter-batch precision of analysis were less than 12.0%. The accuracy determined for these analytes ranged from 93–109%. The recoveries for analytes ranged from 80–90% for spiked plasma samples, and were consistent and reproducible. The validated method was successfully applied for the determination of oral pharmacokinetic parameters of piperine, cinnamic acid and gallic acid in Sprague Dawley rats. A polarity switch method ensured a more comprehensive way to quantify all three analytes simultaneously in a single LC–MS/MS run.

Rapid monitoring and assessment of pollutional load in dairy waste water by Purnima Dhall; Rita Kumar; T. O. Siddiqi; Altaf Ahmed; Anil Kumar (977-981).
In the present scenario, an attempt was made to develop an ideal device (BOD biosensor) with computer-aided software capable of determining the varying BOD load of dairy waste waters and which facilitates instant monitoring. The shelf life of the developed biosensor was more than 400 days. The results of extensive testing of the developed BOD biosensor on dairy waste water over a period of time demonstrate that the BOD values obtained by the device are statistically correlated with conventional BOD values, irrespective of the varying load of waste water (which might occur as a result of different operations in industry). The developed BOD biosensor shows good reproducibility and repeatability over a period of time. Good correlation (r2 = 0.991) was observed between the values obtained from the developed sensor and conventionally estimated values. The repeatability of the measurements with the BOD biosensor dairy industrial waste water samples (inlet and outlet) was within a percentage deviation of ±10%.

In the present work, a new method of chemiluminescence detection coupled with high performance liquid chromatography for three organic acids—tartaric, malic and citric acids is described. The detection is based on the enhancement of the organic acids for the chemiluminescence reaction between cerous sulfate (Ce(SO4)2) and tris (2,2′-bipyridyl)ruthenium(ii) (Ru(bipy)32+). The latter was immobilized on the cationic ion-exchange resin for obtaining high sensitivity and reducing consumption of expensive reagent. Under the optimal conditions, the linear ranges were 7.5 × 10−7 g mL−1 to 7 × 10−6 g mL−1 for tartaric acid, 4.0 × 10−7 g mL−1 to 1.0 × 10−5 g mL−1 for malic acid and 1 × 10−7 g mL−1 to 1.5 × 10−6 g mL−1 for citric acid, and the detection limits were 1.5 × 10−7 g mL−1, 2.0 × 10−7 g mL−1, 4.0 × 10−8 g mL−1 for tartaric, malic and citric acid, respectively. The proposed method had been successfully applied to the determination of three organic acids in fruit juice – with only filtration and dilution steps.

The method for preconcentration and trace determination of Hg(ii) based on the total fluorescence quenching using a 1,10-phenanthroline (1,10-phen) and dichlorofluorescein (DCF) ternary complex after homogeneous liquid–liquid extraction of the metal complex was developed. Hg(ii) ions were dissolved in acid and the sample was complexed with an excess amount of diethyldithiocarbamate (DDTC). The complex of Hg(ii)–DDTC formed in an aqueous phase and was extracted into a layer of perfluorooctanoic acid dissolved in lithium hydroxide solution, resulting in ∼100 μL of the sediment liquid phase prior to analysis of the ternary complex by spectrofluorophotometry. The optimization conditions were investigated in detail including pH and buffer solution, type of ligand, ionic strength, counter ion and micellar medium. Under the optimized conditions with a preconcentration factor between 15 and 20 using a mixture of 0.2 mol L−1 acetate buffer pH 4.5, 2.5 × 10−3 mol L−1 1,10-phen, 1% (v/v) Triton X-100 and 2.9 × 10−6 mol L−1 DCF in 15 mL final volume, the decrease in fluorescence intensity of the ternary complex was measured against the reagent blank, in the absence of Hg(ii) ions, at the excitation and emission wavelengths of 504.0 and 525.0 nm, respectively. The calibration curve was widely linear over the range of 4.0 μg L−1 to 2.0 mg L−1 with a correlation coefficient greater than 0.997. The method recovery of Hg(ii) was about 76.9 to 98.2% at a concentration of 250 μg L−1. The relative standard deviation (RSD) was below 5.5% with a detection limit of 1.0 μg L−1. The proposed method was successfully applied for the determination of Hg(ii) in drinking water, distilled spirit and fruit wine samples. The results obtained were in agreement with those of FI-HGAAS.

Determination of the mineral composition of Brazilian rice and evaluation using chemometric techniques by Douglas G. da Silva; Ieda S. Scarminio; Daniela S. Anunciação; Anderson S. Souza; Erik G. P. da Silva; Sergio L. C. Ferreira (998-1003).
The mineral composition of Brazilian rice samples was determined and the data obtained were evaluated using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Nineteen commercial rice samples were analyzed, six being brown, seven parboiled and six white. The elements were determined employing inductively coupled plasma optical emission spectrometry (ICP OES), and the accuracy was confirmed using a certified reference material of rice flour. The PCA showed the formation of three clusters: a group with the brown rice samples, other with the parboiled rice samples and another of the white rice samples. PCA also showed that the brown rice samples are richer in minerals than the white and parboiled rice samples. Calcium, sodium, zinc and manganese in white rice samples are higher than in parboiled rice samples, while the parboiled rice has higher contents of iron, magnesium, strontium, potassium and phosphor. HCA also demonstrated formation of three major groups, confirming the results obtained by PCA. Application of HCA in the subgroups of rice samples clearly showed separation of rice brands and also separation between the raw and cooked samples. The mineral composition in the rice samples analyzed agrees with data reported by other authors. This paper revealed that the mineral compositions for white, brown and parboiled rice are significantly different.

The purpose of this research is to develop an UPLC/QTOFMS method for the rapid and simultaneous determination of six estrogens (bis-phenol A, 17α-ethinylestradiol, 17β-estradiol, estrone, dienestrol, estriol) in animal-derived food. The method aimed to be simple to operate with good sensitivity. Sample preparation involved matrix solid-phase dispersion extraction (MSPD) using acetonitrile in C18 and Florisil packings. The pretreatment method of MSPD was optimized to eliminate the complications of the classical pretreatment. Estrogens were qualitatively and quantitatively analyzed using a C18 reversed-phase UPLC/QTOFMS in target MS/MS mode. The six estrogens were successfully separated within 4 minutes with the optimized method of one simple elution with water/acetonitrile 52/48 (v/v). The limits of detection were 0.11–0.81 μg L−1, based on an S/N = 3. The limits of quantification were 0.61–2.20 μg L−1, based on an S/N = 10. The recoveries were determined to be in the range of 59.6–128.5%, with a relative standard deviation (RSD) between 1.2% and 8.0%. Milk and meat samples were analyzed, and the presence of the six estrogens was determined. The detected rate of real samples shows that the high-fat food tends to be the source of estrogens among animal-divided food. An UPLC/QTOFMS method was developed to determine six estrogens in animal-derived food and was successfully applied to real samples, and it showed good sensitivity and simple operation.

Polypyrrole nanotubes–polyaniline composite for DNA detection using methylene blue as intercalator by S. Radhakrishnan; C. Sumathi; V. Dharuman; J. Wilson (1010-1015).
Electrochemically active nanostructured polypyrrole (PPy) coated with polyaniline (PANi) was deposited on an electrode followed by gluteraldehyde (GA) attachment for grafting 5′-amine modified single strand DNA (ssDNA) to form PPy–PANi–GA–ssDNA and DNA hybridization in phosphate buffered solution. Differential pulse voltammetry (DPV) was used to monitor the hybridization events with methylene blue as the electrochemical indicator. The exhibited sensitivity and selectivity was attributed to the nanotube structure of PPy–PANi and the conductivity obtained was 472 times greater than that for the conventional PPy–PANi composite. The biosensor was characterized by cyclic voltammetry, electrochemical impedance , FT-IR, DPV and scanning electron microscopy. This sensor showed good stability, selectivity and higher sensitivity than the multi-walled carbon nanotubes (MWCNT)/Ag nanoparticles (NPs) and PPy/MWCNT/AuNPs composites reported previously. The dynamic range observed was 1 × 10−9 to 1 × 10−13 M, with a lower detection limit of 50 fM.

Development of an HPLC–MS/MS method for the simultaneous analysis of six kinds of parabens in food by Shurui Cao; Zhiyong Liu; Lei Zhang; Cunxian Xi; Xianliang Li; Guomin Wang; Ruo Yuan; Zhaode Mu (1016-1023).
Parabens (the esters of 4-hydroxybenzoic acid) are widely used as preservatives in thousands of foods, cosmetics and pharmaceutical products. A high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method was developed and validated for the quantification of six kinds of parabens in food. The method was shown to be quantitative for the methyl, ethyl, propyl, butyl, isopropyl and isobutyl esters of 4-hydroxybenzoic acid. Samples were extracted by acetonitrile and cleaned up by solid phase extraction columns of LC-C18. Analysis was carried out by HPLC–MS/MS in a 15 min run time using atmospheric pressure electrospray ionisation in the negative mode (ESI−) and multiple reaction monitoring (MRM) scanning. The calibration curve was linear over a range of 10–1000 μg L−1 for parabens, and the limit of quantification (LOQ) was 10 μg L−1. The recovery of the method was 84.5–108.8% and values for intraday and interday precision were between 1.16 and 9.21%. The method was successfully applied in the determination of parabens in food samples.

An electrochemical biosensor has been fabricated for catechin detection using the nanoparticle–polymer composite as a matrix. The composite has been electrochemically synthesized and tyrosinase enzyme was entrapped during polymerization of the composite material. The composite has been characterized for its morphology, optical, structural, and electrochemical behavior. Studies revealed that the presence of gold nanoparticles (AuNPs) in the polymer matrix resulted in an increase in conductivity, enhanced current intensity and diffusion coefficient. The AuNPs–PPy composite provided large surface area for enzyme immobilization and facilitated electron transfer, evident from almost 10% enhancement in biosensor response in the presence of nanoparticles (NPs). For catechin detection, the biosensor showed well defined redox peaks at 0.24 V/0.14 V for the redox reaction of the hydroxyl group present in the catechol moiety of the catechin and a weak oxidation peak at 0.62 V corresponding to the oxidation of the hydroxyl group present in the central ring of catechin. The linearity was achieved from 1 × 10−9 M to 1 × 10−8 M, with a sensitivity of 6.8 × 10−5 A M−1. The limit of detection (3 × SD/sensitivity) and Km value are 1.2 × 10−9 M and 4.5 × 10−9 M respectively. The response time of the biosensor was about 10–12 s with an optimum pH at 7.0. The biosensor has been tested for catechin detection in water and apple juices and the response was within 10% error.

In this work, a simultaneous ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction (IL-based MADLLME) method was developed for the determination of plasticizers in water using high-performance liquid chromatography (HPLC) with ultraviolet detection. Several parameters affecting the extraction efficiency, such as type and volume of ionic liquid and disperser solvent, microwave time and temperature, were investigated by single factor experiments. Then, the microwave irradiation time and temperature, and the volumes of extraction and disperser solvents were optimized using response surface methodology (RSM). The optimal values were determined to be within an extraction volume of 110 μL, a dispersive solvent volume of 0.26 mL, and a microwave irradiation temperature and time of 60 °C and 2 min, respectively. The calibration curves were linear in the range of 23–230 μg L−1 for dimethyl phthalate (DMP), 23.8–238 μg L−1 for diethyl phthalate (DEP), 16.5–165 μg L−1 for benzylbutyl phthalate (BBP), 19.5–195 μg L−1 for dibutyl phthalate (DBP), and 18.6–186 μg L−1 for diethylhexyl phthalate (DEHP). Under the optimum conditions, the limits of detection (LODs) of these plasticizers were in the range of 0.71–1.94 μg L−1. Validation of the methodology was carried out by the method of standard addition at two concentration levels for three water samples. The recoveries of the analytes were in the range of 85.2–103.3%, with the relative standard deviations (RSDs, n = 6) ≤ 5.9%. The results show that IL-based MADLLME is a suitable method for the determination of these five plasticizers in water.

Using a flow-batch analyzer for photometric determination of Fe(iii) in edible and lubricating oils without external pretreatment by Inakã S. Barreto; Marcelo B. Lima; Stéfani Iury E. Andrade; Mário César U. Araújo; Luciano F. Almeida (1040-1045).
In this study a flow-batch analyzer (FBA) was utilized and its feasibility was demonstrated for the determination of Fe(iii) in edible and lubricating oils without external pretreatment. The FBA method uses the reaction of this ion with thiocyanate in organic medium. The formed red complex was monitored by employing a light emitting diode (LED, λmax = 520 nm) and a phototransistor linked to the mixing chamber by optical fibers. All standard solutions were prepared in-line and all analytical processes were carried out by simply changing the operational parameters in FBA control software. Comparing with the reference method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. The relative standard deviation, analytical frequency and limit of detection were estimated for both viscous matrices (edible and lubricating oils) at <2.1% (n = 3), about 95 h−1, and 0.004 mg kg−1, respectively. The recovery study shows results between 97.8% and 103.6% for both matrices. The FBA method showed better analytical features when compared with previous automatic flow methods. Thus, the FBA is potentially useful as an alternative for the determination of other ions in similar samples or in other viscous matrices without external pretreatment.

A novel magnetic adsorbent, magnetic microsphere functionalized with Cyanex272, has been successfully synthesized via a chemical bonding alkylation method. A flow injection on-line preconcentration, with a micro-column packed with the as-synthesized magnetic adsorbent, coupled with UV-Vis spectrophotometric method was developed for the determination of phenol at a wavelength of 270 nm. Various experimental parameters were optimized as follows: eluent (methanol), sample flow rate (1.4 mL min−1), sample volume (1.4 mL), sample pH (5.0), and eluent flow rate (2.2 mL min−1). Under the optimum conditions, the intra-day and inter-day relative standard deviations were 1.37% and 2.69% (n = 5), respectively. The proposed method has been successfully applied to the determination of phenol in phenol ear drops, compound borax solution, and phenol ointment samples and the accuracy was assessed through recovery experiments.

An ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of thiodicarb and its main metabolite (methomyl and methomyl-oxime) residues in cotton leaves and cotton seeds. The mass spectrometer was operated in multiple reaction monitoring mode with positive electrospray ionization. The samples were extracted by acetonitrile, the extract was cleaned up by Pesti-Carb/NH2 solid phase extraction column, then separated by reversed phase liquid chromatography, and determined by UPLC-MS/MS. It showed that the recoveries ranged from 67.5% to 109.2% at spiked levels of 0.01–0.1 mg kg−1, while the relative standard deviation was 2.8% to 9.1%. The limit of the detection was 0.2–1.3 μg kg−1, and the limit of quantification was 0.9–4.0 μg kg−1.

Combining enzymatic 18O-labeling and 2-D LC-MS/MS for a study of protein interactions in primary T cells by Diana Lang; Sabine Anker; Benno Kuropka; Eberhard Krause (1058-1061).
Affinity-MS experiments with primary cells require alternative proteomic approaches, as the widely used metabolic labeling method SILAC is impracticable. We now describe a novel application of a recently developed 2-D LC-MS/MS approach for identification of phosphorylation-dependent protein interactions in human primary T cells. Using this approach, we identified a set of Tyr 595-phosphorylated ADAP interaction partners which belong to the larger TCR proximal signaling complex. The results show that a combination of two-dimensional RP–RP LC-MS/MS and 18O-labeling is a powerful means for peptide-based affinity MS experiments.

Dictamni Cortex (Baixianpi) is a commonly used medicinal herb in traditional Chinese medicines (TCMs), possessing various bioactivities. Quinoline alkaloids are regarded as one of the main active components in this herb. In the present study, a more convenient, specific and accurate analytical method using 1H NMR has been developed for the quantitative determination of dictamnine, one of the main active quinoline alkaloids in Dictamni Cortex. In a less crowded region δ 8.0–8.5, the signal of H-5 of dictamnine was well separated from other signals in chloroform-d1. The quantity of dictamnine was calculated by means of the integral value of H-5 of dictamnine to that of the known amount of internal standard, pyrazine. This assay was precise and reproducible, with RSDs less than 3%. The recovery results of dictamnine were observed between 92.10 and 108.10% and the limit of detection (LOD) and limit of quantitation (LOQ) were 3.3 μg ml−1 and 13.2 μg ml−1, respectively. This newly developed method was proven to be highly accurate, precise and robust, for the determination of dictamnine in Dictamni Cortex. The results obtained from 1H NMR method were also compared with those from conventional HPLC method, and no remarkable difference was found between these two methods.

Ion selective electrodes are not suitable for measurements of silver ion concentrations in alkaline carbonate media by Jonas Hedberg; Troy A. Lowe; Susanna Wold; Inger Odnevall Wallinder (1068-1070).
An ion selective electrode (ISE) for determination of the labile silver ion concentration in carbonate containing solutions of pH 10 was seen to give incorrect results due to shifts in the Ag|Ag+ equilibrium. This drawback was not the case for the differential pulse anodic stripping voltammetry (DPASV) method.

Back cover (1071-1072).