Analytical Methods (v.5, #22)
Front cover (6249-6250).
Contents list (6251-6261).
Fluorescent probes for selective determination of trace level Al3+: recent developments and future prospects by Sudipta Das; Mili Dutta; Debasis Das (6262-6285).
Developments in the field of fluorescent chemosensors for trace level determination of Al3+ have been described. Design, synthesis and applications of Al3+ selective fluorescent sensors have attracted a great deal of attention due to their versatile and emerging biological implications. A systematic description of different fluorescent probes based on their fluorophore skeleton has been made. The sensing mechanism of each fluorescent probe has been briefly discussed. Special emphasis has been given to consideration of the greenness of the methods, particularly, the use of greener solvents like water. The review covers published work on fluorescence sensing of Al3+ worldwide together with our own contribution in this field.
Determination of inorganic arsenic in water by a quartz crystal microbalance by Chengbei Li; Aydan Elçi Başaran; Julian F. Tyson (6286-6291).
A quartz crystal microbalance sensor has been developed for the determination of inorganic arsenic species in water. The gold electrode surface was modified by a self-assembled layer of dithiothreitol, and the frequency change of the modified crystal was proportional to the arsenic concentration from 0 to around 50 μg L−1, a range which spans the current US EPA maximum contaminent level of 10 μg L−1 in drinking water. As dithiothreitol is capable of reducing arsenate to arsenite, the sensor detects both species. The method was applied to the determination of arsenic in spiked rain, tap, pond and bottled water; recoveries not significantly different from 100% were obtained for a number of spike additions of less than 10 μg L−1. Arsenic was only detected in the bottled water sample, at a concentration of 8 μg L−1. This method is simple, fast, and inexpensive compared with other conventional arsenic detection methods, and has the potential to be used in the field.
Advanced statistical analysis and discrimination of gunshot residue implementing combined Raman and FT-IR data by Justin Bueno; Igor K. Lednev (6292-6296).
We report a novel analytical and statistical approach to gunshot residue (GSR) analysis, characterization and discrimination. Spectroscopic data from two complementary techniques (Raman and FT-IR) were combined into a single dataset to improve statistical discrimination of GSR.
Molecularly imprinted polymer-liquid chromatography/fluorescence for the selective clean-up of hydroxylated polycyclic aromatic hydrocarbons in soils by Oriol Baltrons; Montserrat López-Mesas; Cristina Palet; Franck Le Derf; Florence Portet-Koltalo (6297-6305).
Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), a group of metabolites produced during the biodegradation of PAHs by microorganisms, are known to be difficult to analyze from complex environmental or biological matrices. In the field of contaminated soils, where OH-PAHs are less studied, a new method was compared to a common method for the analysis of monohydroxylated PAH metabolites: 2-naphthol, 2-hydroxyfluorene, 9-phenanthrol and 1-hydroxypyrene. After optimizing the microwave assisted extraction (MAE) step, the obtained extracts, containing the OH-PAHs together with the corresponding PAHs, were purified by molecularly imprinted polymers (MIPs). MIPs showed an effective selectivity for the hydroxylated derivatives studied (and not for native PAHs), which allowed their identification and quantification by HPLC/FLD. By this method, good limits of detection (0.003–0.014 μg g−1) and limits of quantification (0.010–0.044 μg g−1) were achieved. On the other hand, following the common method, the sample extract was concentrated by evaporation, silylated, and analyzed by GC/MS. The new method was more sensitive for all OH-PAHs and the analysis showed fewer matrix effects due to the use of MIP clean-up. In the present work the advantages and disadvantages of the new method are shown, as well as the possible application to soil biodegradation studies.
MgF2–Au–MgF2-polydopamine based surface plasmon resonance sensor and its application in biomedical systems by Zhiyi Liu; Qing Peng; Heng Shi; Shuqing Sun; Jun Guo; Xiaoxiao Wang; Le Liu; Yanhong Ji; Jihua Guo; Hui Ma; Yonghong He (6306-6311).
We report a MgF2–Au–MgF2-polydopamine based surface plasmon resonance (SPR) sensor and its biomedical applications. The symmetrical MgF2–Au–MgF2 geometry induced a minimum loss of surface plasmons leading to, so far, the best refractive index resolution of 2.2 × 10−8 refractive index units (RIU) in a glucose solution protocol. Meanwhile, a high detection performance could be maintained in the sensed medium with a refractive index ranging from 1.03 to 1.33 RIU. In order to solve the problem of surface functionalization on MgF2, which was thought to be inert, we managed to form adherent polydopamine films onto the MgF2–Au–MgF2 surface by dopamine self-polymerization, and found that secondary reactions could be used to create a variety of ad-layers for further biological uses. Finally, a model experiment on a chip detecting cellular mediators in human aqueous humor demonstrated the biomedical application of this system.
Equilibrium distribution sampling device for preparation of calibration mixtures for gas chromatography-mass spectrometry by Xiaofeng Xie; Tai V. Truong; Jacolin A. Murray; Jesse A. Contreras; H. Dennis Tolley; Milton L. Lee (6312-6318).
A simple approach for preparing standard mixtures of volatile and semi-volatile organic compounds is reported. When placed in a closed container, standard mixture components partition between a polymeric material such as poly(dimethylsiloxane) (PDMS) and headspace to provide constant vapor concentrations. The granular form of heat-conditioned PDMS provides rapid equilibration with the headspace vapor and serves as a standard reservoir. Solid phase micro extraction (SPME) or gas-tight syringe can be used to deliver sample from the headspace to the analytical instrument. Quantitative calibration can be achieved with either active temperature control or by using a previously constructed look-up table. The effects of PDMS form and temperature on equilibrium distribution, initial equilibrium time, and re-equilibrium time after sampling were investigated. With respect to long term use and stability, analytes introduced onto 2.0 g of PDMS in a 7.4 mL vial were sampled more than 114 times during a test period of 43 days, giving chromatographic peak area %RSD values below 4.5% for all compounds. This device was designed to be solventless, quantitative, reproducible, environmentally friendly, and robust for routine evaluation and calibration of gas chromatography-mass spectrometry (GC-MS) systems.
Determination of bile acid profiles in scat samples of wild animals by liquid chromatography-electrospray mass spectrometry by Udaya B. Nasini; Nandan Peddi; Punnamchandar Ramidi; Yashraj Gartia; Anindya Ghosh; Ali U. Shaikh (6319-6324).
A practical and accurate analytical method using liquid chromatography-mass spectrometry (LC-MS) was developed to determine the bile acid profile in the scat samples of various wild animals such as mountain lion, bobcat, coyote, raccoon, fox, etc. Bile acid extraction from the scat sample of the wild animals and its detection using the LC-MS technique are very easy and can be done in a short period of time with good resolution. The bile acid profiles are different in each species and the analytical method is very effective in identifying the wild animals under investigation. The detection limits of all bile acids were very low (∼1.0 ng mL−1) and the analytical method provides excellent reproducibility.
Combination of effective machine learning techniques and chemometric analysis for evaluation of Bupleuri Radix through high-performance thin-layer chromatography by Xiaoping Cheng; Hongmin Cai; Ping He; Yue Zhang; Runtiao Tian (6325-6330).
Chaihu (Bupleuri Radix), the root of Bupleurum chinense and B. scorzonerifolium, is a traditional Chinese herbal medicine authenticated in the Chinese Pharmacopoeia. There are also several variations available from local herbal markets, for example, the roots of B. falcatum, B. bicaule, and B. marginatum var. stenophyllum. In the current study, we collected 64 Chaihu samples, including 33 authenticated samples and 31 commercial samples. Test solutions of all the examples were analysed by high-performance thin-layer chromatography (HPTLC) to assess the principal bio-active components (saikosaponins). The HPTLC fluorescent images acquired were analyzed by sophisticated image processing techniques for comprehensive quantification. High dimensional features for both gray-scale and true color images were constructed for the raw images. Classical classification algorithms, including naive Bayes, Support Vector Machine (SVM), K-nearest neighbors, neural network and logistic, were used to construct prediction models. To gain an insight into the principal components while evaluating the Chaihu sample, feature selection and ensemble feature selection methods were further combined with the classifiers to enhance the discrimination power. Ensemble feature selection was shown to achieve superior performance. Experimental results demonstrated that the roots of Chaihu from different species of the genus Bupleurum could be readily distinguished so that commercial samples could be easily classified.
Marginal Fisher Analysis-based feature extraction for identification of drug and explosive concealed by body packing by Yanling Li; Ping Liu; Haishun Du; Zhu Li; Jinhuai Liu; Daoyang Yu; Minqiang Li (6331-6337).
In the analysis of the energy dispersive X-ray diffraction (EDXRD) spectra of drugs and explosives concealed by body packing (i.e. the internal concealment of illicit drugs), the method of feature extraction based on Marginal Fisher Analysis (MFA) is introduced to resolve the challenge from the data of high dimension, small sample size and poor signal-to-noise ratio. MFA is applied to extract features and makes full use of both the local geometric structure (in the intrinsic graph) and label information (utilized in both graphs) to seek efficient modes of discrimination. Features extracted by principal component analysis (PCA) and PCA plus linear discriminant analysis (LDA) were investigated for comparison with the features extracted by MFA. Further, in order to avoid the influence of classifiers, two kinds of classifiers (K-nearest neighbour and support vector machine) were introduced to classify the samples according to the features. It is shown that the recognition rates obtained by MFA are more accurate (averaged recognition rate > 99.4%) compared with the other candidates. This investigation has demonstrated that MFA is effective in feature extraction for the identification of drugs and explosives concealed by body packing.
Electrooxidation and determination of methacetin (p-acetanisidide) by square wave voltammetry using multiwalled carbon nanotube electrode by Recai İnam; Eda Can; Ersin Demir (6338-6344).
A multiwall carbon nanotube paste electrode (MWCNTPE) was fabricated to investigate the detailed electrochemical behavior of methacetin and achieve its sensitive electroanalytical determination. The sensitive and selective square wave anodic peak seen at +1.06 V was linearly related to methacetin concentration in the range of 0.11 to 22.3 mg L−1 [0.665 to 135 μM]. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.032 mg L−1 [0.193 μM] and 0.11 mg L−1 [0.665 μM], respectively. The percentage recovery of methacetin calculated from natural lake water samples spiked at the 5.0 μg mL−1 [30.3 μM] level was 94.2% with a relative standard deviation of 0.21%. The considerably high recoveries and low standard deviations were evidence for the high accuracy and precision of the recommended method. The recovery of 10.0 μg mL−1 [60.5 μM] methacetin in the presence of the same concentrations of other pesticides such as benzanilide, propanil, tribenuron methyl, rimsulfuron, metsulfuron methyl and chlorsulphuron ranged from 89.2% to 98.3%. The oxidation peak of 10 mg L−1 [65.3 μM] dopamine appeared at +0.740 V(vs. Ag/AgCl) and did not display a significant interfering effect, therefore methacetin and dopamine could be simultaneously determined.
Quantitative investigation on the stacking of metal ions induced by another metal ion based on moving substitution boundary electrophoresis by Jing Lou; Qian Liu; Hou-Yu Wang; Liu-Yin Fan; Shu-Sheng Zhang; Heng Liang; Cheng-Xi Cao (6345-6351).
In this paper, a novel model for the stacking of metal ions via another metal ion was developed based on a dynamic equilibrium system (DES) composed of moving substitution boundary (MSB) and moving chelation boundary (MCB). With Cu2+, Co2+ and EDTA as an example, a substitution reaction took place between Cu2+ and [Co-EDTA]2−, and resulted in the formation of MSB, and Co2+ released from [Co-EDTA]2− reacted with EDTA, which resulted in the formation of MCB and [Co-EDTA]2−, the produced [Co-EDTA]2− reacted again with Cu2+. The reaction between Cu2+, [Co-EDTA]2−, and Co2+, EDTA were repeated. The concentration of Co2+ and [Co-EDTA]2− was stacked accompanying the formation of MSB and MCB until the above two reactions reached equilibrium. Relevant experiments were performed and the results indicated that: (1) Cu2+ can be used for the stacking of Co2+ and higher than 70-fold preconcentration of Co2+ was achieved in capillary electrophoresis (CE); (2) the concentration of Cu2+ had a key role in the stacking of Co2+, a higher Cu2+ concentration resulted in a better focusing efficiency; (3) the initial concentration and zone length (Linitial) of [Co-EDTA]2− were the major factors on enrichment. Furthermore, experiments based on MSB were performed with multi-metal ions (such as Cu2+, Co2+, Ni2+ and Pb2+), which demonstrated the potential application of the MSB-based technique for the separation and stacking of multi-metal ions.
Electrochemical synthesis and characterization of a new selective chelating agent for Ni(ii) and its environmental analytical application by Mehdi Jalali; Alireza Aliakbar (6352-6359).
This investigation involved electrochemical synthesis of a new Ni(ii) selective chelating agent by electropolymerization of 4-nitrophenol in acetate medium. The prepared polymer was characterized by FT-IR, 1H-NMR, CHNO elemental analysis, GPC, and UV-Vis spectrometry and a suitable chemical structure was suggested. This new ligand was successfully applied in cloud point extraction (CPE) of Ni(ii) before flame atomic absorption spectrometry (FAAS) measurements. The pH and the concentration of the phosphate buffer, chelating agent, surfactant and salt were optimized. In the presence of foreign ions, no significant interferences were observed. Under optimum conditions, the limits of detection (LOD) and quantification (LOQ) were 0.76 and 2.53 ng mL−1, respectively. The mean, preconcentration factor, standard error and RSD for five replicates of 10 ng mL−1 Ni(ii) were calculated to be 9.78 ng mL−1, 29.3, 2.2% and 3.36%, respectively. The method presented good sensitivity and selectivity and was applied for the determination of trace amounts of Ni(ii) in various water and wastewater samples. The results obtained by the proposed method were in good agreement with the results of inductively coupled plasma-optical emission spectrometry (ICP-OES).
Hierarchical Cu–Co–Ni nanostructures electrodeposited on carbon nanofiber modified glassy carbon electrode: application to glucose detection by Hongyu Liu; Xingping Lu; Dejian Xiao; Minxian Zhou; Dujian Xu; Lanlan Sun; Yonghai Song (6360-6367).
Hierarchical Cu–Co–Ni nanostructures (Cu–Co–Ni NSs) attached to carbon nanofibers (CNFs) modified glassy carbon electrode (GCE) was prepared by electrodeposition. Scanning electron microscopy results indicated that many hierarchical Cu–Co–Ni NSs were formed and uniformly dispersed on the CNFs/GCE surface. The electrochemical behavior and electrocatalytic performance of the Cu–Co–Ni NSs/CNFs/GCE towards the oxidation of glucose were evaluated by cyclic voltammograms, chronoamperometry and amperometric methods. The results revealed that Cu–Co–Ni NSs/CNFs/GCE has a good electrocatalytic activity for glucose oxidation and could be used as a nonenzymatic glucose sensor. The sensor showed an acceptable linear range from 0.01 to 4.30 mM with a sensitivity of 104.68 μA mM cm−2, and a detection limit of 3.05 μM (S/N = 3). The good catalytic activity, high sensitivity, good selectivity and stability rendered the Cu–Co–Ni NSs/CNFs/GCE to be a promising electrode for constructing a nonenzymatic glucose sensor.
Chemometric resolution techniques combined with GC-MS to enhance determination of the volatile chemical constituents of bay leaves by M. Asadollahi-Baboli (6368-6375).
The 71 constituents of essential oil (EO) of bay leaves were identified with gas chromatography-mass spectrometry (GC-MS) by applying a similarity search between the obtained mass spectra and database. This number was increased to 131 constituents with the help of different chemometric resolution techniques. Multivariate curve resolution-alternating least squares (MCR-ALS) is used to obtain pure chromatograms and mass spectra for the constituents present in each overlapping/embedded peaks cluster as well as their relative concentrations. Other chemometric methods such as simple to use interactive self-modeling mixture analysis (SIMPLISMA), morphological score (MS) and Fixed Size Moving Window Evolving Factor Analysis (FSMWEFA) were used to determine the number of constituents, pure variables, zero concentration and selective regions. The most important constituents of the Iranian bay leaves are linalool (12.31%), 1,8-cineole (11.38%), α-terpineol acetate (7.71%), eugenol methyl ether (6.87%) and α-phellandrene (4.30%). Despite previous studies, chemometric resolution techniques were implemented as a necessary step for the comprehensive analysis of the volatile constituents of bay leaves.
Co-precipitation assisted cloud point extraction coupled with high performance liquid chromatography for the determination of estrogens in water and cosmetic samples by Xiaohua Xiao; Xiaoguang Chen; Xianfang Xu; Gongke Li (6376-6381).
A rapid and efficient co-precipitation assisted cloud point extraction is proposed for extraction of five estrogens [17β-estradiol (E2), estrone (E1), ethinyl estradiol (EE), diethyl stilbestrol (DES) and dihydro stilbestrol (DHS)] in environmental water and toner samples prior to high performance liquid chromatography analysis. It is based on the combination of co-precipitation with aluminum hydroxide and cloud point extraction with sodium dodecylsulfate to extract the target estrogens. Parameters affecting the extraction of target analytes including the concentration of aluminum hydroxide and sodium dodecylsulfate, extraction time, and blending types were investigated. Under optimum conditions, the enrichment factors were 31.7, 38.5, 28.2, 40.8 and 79.5 for E2, EE, E1, DES and DHS, respectively. A co-precipitation assisted cloud point extraction/high performance liquid chromatography method was developed and the limits of detection (LODs) were in the range of 0.2–0.7 μg L−1. The proposed method was successfully applied for the determination of trace estrogens in environmental water and toner samples, and the recoveries ranging from 77.3 to 104.1% with RSD of 2.0–10.4% were obtained. Moreover, the present method was compared to the previously reported methods and the extraction mechanism was also discussed. The method was rapid, sensitive and suitable for the trace estrogen analysis.
Nondestructive measurement of total volatile basic nitrogen (TVB-N) content in salted pork in jelly using a hyperspectral imaging technique combined with efficient hypercube processing algorithms by Quansheng Chen; Yanhua Zhang; Jiewen Zhao; Zhe Hui (6382-6388).
Total volatile basic nitrogen (TVB-N) content is an important index in evaluating the freshness of salted pork in jelly (SPIJ). This work attempted the nondestructive measurement of TVB-N content in the SPIJ using hyperspectral imaging (HSI) with efficient hypercube processing algorithms. Firstly, we developed a VIS-NIR HSI system for data acquisition and extracted the spectra (430–960 nm) from a 3-dimensional hypercube; then selected the efficient spectral intervals using a synergy interval PLS (Si-PLS) algorithm and further selected four dominant waveband images using a genetic algorithm (GA); next we extracted 6 characteristic variables from each dominant waveband image using texture analysis based on statistical feature calculation; finally, principal component analysis (PCA) was implemented on spectral variables and image variables, respectively. A back-propagation artificial neural network (BP-ANN) was used to achieve data fusion and construct a model for TVB-N content prediction. The optimum results were achieved with the root mean square error of prediction (RMSEP) = 6.3435 mg per 100 g and the correlation coefficient (Rp) = 0.8334 in the prediction set. This work demonstrates that HSI with an efficient hypercube processing algorithm has a high potential in nondestructive measurement of TVB-N content in SPIJ.
Simultaneous determination of metolachlor, pendimethalin and oxyfluorfen in bulb vegetables using gas chromatography-tandem mass spectrometry by Xiaohu Wu; Jun Xu; Fengshou Dong; Xingang Liu; Yongquan Zheng (6389-6394).
A sensitive and effective method using the QuEChERS procedure for simultaneous determination of metolachlor, pendimethalin and oxyfluorfen residues in bulb vegetables (garlic, Chinese onion, onion, garlic stem and leek) was developed using GC-MS/MS. Samples were extracted with acetonitrile and cleaned-up with primary secondary amines (PSA). The method showed excellent linearity (R2 > 0.997) for target compounds. The limits of quantitation (LOQ) objective for which the method was satisfactorily validated in five samples matrices was 5 μg kg−1 and the limit of detection (LOD) ranged from 0.5 μg kg−1 to 2.3 μg kg−1. Average recoveries in five bulb vegetables at four levels (0.005, 0.025, 0.1 and 1 mg kg−1) ranged from 77.5% to 114.2% with relative standard deviations (RSDr) from 1.8% to 14.9%. The reproducibility RSDR ranged from 3.9% to 15.0%. This method was successfully applied for the analysis of real samples, confirming the applicability of the method.
Determination of nucleosides and nucleobases in Isatidis Radix by HILIC-UPLC-MS/MS by Yilin Pan; Ping Xue; Xiang Li; Jianwei Chen; Jin Li (6395-6400).
To establish an ultra-high performance liquid chromatography coupled with triple quadrupole mass (HILIC-UPLC-MS/MS) for determination of sixteen nucleosides and nucleobases in Isatidis Radix. Chromatographic separation was carried out on a Acquity UPLC BEH Amide column with gradient elution of acetonitrile (containing 0.1% acetic acid) and water (containing 0.8% acetic acid and 10 mmol L−1 ammonium acetate) at a flow rate of 0.3 mL min−1, the column temperature was set at 35 °C; Waters Xevo™ TQ worked in multiple reaction monitoring mode. Each component were separating in 11 min. All calibration curves were linear (r2 > 0.997) over the tested ranges. The limits of detection of these compounds were 0.02–42.54 ng mL−1. The limits of quantitation of these compounds were 0.05–98.18 ng mL−1. The average recoveries were in the range of 93.81–105.77% with RSD value less than 7.5%. The result showed that almost all of these Isatidis Radix were rich in nucleosides and nucleobases, but their contents were obviously various. The method was simple and fast with high precision, sensitivity and repeatability, which can be used for determination of this type class of nucleosides and nucleobases in other medicinal herbs.
Highly selective fluorogenic anion chemosensors: naked-eye detection of F− and AcO− ions in natural water using a test strip by Moorthy Saravana Kumar; Saravana Loganathan Ashok Kumar; Anandram Sreekanth (6401-6410).
Two new chemosensors S1 and S2 were synthesized and their chromogenic and fluorogenic behavior towards various biologically important anions in a competing solvent DMSO was investigated. Both the sensors portrayed a substantial color change upon addition of F− and AcO− ions and no significant change was observed on addition of other anions such as Cl−, Br−, I−, ClO4− and HSO4−. The binding constant showed that both F− and AcO− anions bind to the sensors in an equal proportion, in which S2 was found to be superior and showed a better binding ability than S1. Job's plots indicated that both sensors formed a (1 : 1) complex (sensor : anion) with F− and AcO− anions. Remarkable fluorescence “turn on” emission behavior was observed with both the sensors when treated with F− and AcO− anions respectively. 1H NMR titration experiments indicated that both S1 and S2 formed a strong hydrogen bond not only with the phenolic-OH but also with the amide-NH of the triazole. We have also demonstrated an easy-to-prepare test strip of S2 to detect F− and AcO− anions even in aqueous medium at a lower limit of about 10 ppm, indicating the potential real-life application of detecting F− and AcO− anions in a natural aqueous environment simply through naked-eye observation.
Validation of a microwave-assisted digestion procedure of pâté samples using diluted HNO3 for Fe and Zn determination by FS FAAS by Silvéria N. P. Souza; Clésia C. Nascentes; Letícia M. Costa (6411-6415).
The efficiency of microwave-assisted acid digestion of pâté samples using diluted nitric acid in different concentrations (3.5, 7.0 and 14 mol L−1) and hydrogen peroxide (30% v/v) was evaluated. Iron and Zn were determined by FS FAAS in colorless solution of pâté samples of chicken, tuna, ham, liver and turkey breast. All acid concentrations were suitable for complete sample matrix destruction and the procedure using 3.5 mol L−1 of nitric acid solution was validated. The figures of merit were evaluated according to the IUPAC and INMETRO guidelines. The standard reference material of bovine liver was evaluated and the results were similar at a 95% confidence level.
Determination of cadmium and lead in fresh fish samples by direct sampling electrothermal atomic absorption spectrometry by Ariane V. Zmozinski; Leonardo D. Passos; Isabel C. F. Damin; Maria Aparecida B. Espírito Santo; Maria G. R. Vale; Márcia M. Silva (6416-6424).
The determination of cadmium and lead in fish samples has large analytical interest due to the potential toxicity of these elements. The development of fast and reliable analytical methods is extremely important for an effective control of contamination. In this work, the feasibility of Cd and Pb determination in fresh fish samples using direct sampling by electrothermal atomic absorption spectrometry (DS-ET AAS) was investigated. For optimization of the furnace temperature program, pyrolysis and atomization curves with TORT-2 and DORM-3 certified reference materials were carried out using chemical modifier (0.05% Pd + 0.03% Mg + 0.05% Triton X-100). The figures of merit obtained were: characteristic mass of 1.0 pg and 16 pg and limit of detection (LOD) of 0.2 μg kg−1 and 1.0 μg kg−1 for Cd and Pb, respectively, based on 8 mg of sample mass. The results obtained for certificated references materials were statistically not different from the certified values at 95% confidence level, using the calibration with aqueous standards, showing that this calibration method is suitable for this application. For assessment of the accuracy of the method, fresh fish samples were digested. The results obtained with direct determination of Cd and Pb in fresh fish samples and with microwave assisted acid digestion were statistically accordant. The developed method for analysis of fresh fish samples is accurate, simple, fast and suitable for routine application, avoiding digestion procedures or the drying/lyophilization and grinding procedures, usually used in DS analysis, reducing the preparation time, risk of contamination and costs.
Graphene oxide as a solid sorbent for the preconcentration of cobalt, nickel, copper, zinc and lead prior to determination by energy-dispersive X-ray fluorescence spectrometry by Beata Zawisza; Rafal Sitko; Ewa Malicka; Ewa Talik (6425-6430).
A new method for sample preparation using graphene oxide (GO) as a novel sorbent was developed for the preconcentration of trace amounts of Co(ii), Ni(ii), Cu(ii), Zn(ii) and Pb(ii). The proposed preconcentration procedure is based on dispersive micro-solid phase extraction (DMSPE). It means that GO was dispersed in aqueous samples containing trace elements to be determined. During the stirring of the analyte solution containing the GO suspension, metal ions were sorbed by GO. After the sorption, the solution was filtered under vacuum and GO with the metal ions was collected onto a membrane filter. The obtained samples were analyzed directly by energy-dispersive X-ray fluorescence spectrometry (EDXRF). The parameters affecting the extraction and preconcentration process were optimized. The pH of the analyte solution, the amount of GO, the sample volume, the contact time between analytes and sorbent (stirring time), and the effects of foreign metals are discussed in detail in this paper. The proposed procedure allows us to obtain the detection limits of 0.5, 0.7, 1.5, 1.8 and 1.4 ng mL−1 for Co(ii), Ni(ii), Cu(ii), Zn(ii) and Pb(ii), respectively. The linearity of the method is in the range of 5–100 ng mL−1. The proposed method was successfully applied in the analysis of water. The accuracy of the method was verified using spiked samples and inductively coupled plasma optical emission spectrometry (ICP-OES) as a comparative technique. The recoveries over the range of 94–106% were obtained. This paper shows the great potential of GO as an excellent sorbent in the preconcentration field of analytical chemistry. The proposed method meets green chemistry rules.
Qualitative analysis and quality control of Traditional Chinese Medicine preparation Tanreqing injection by LC-TOF/MS and HPLC-DAD-ELSD by Liang Sun; Hua Wei; Feng Zhang; Shouhong Gao; Qinghua Zeng; Wenquan Lu; Wansheng Chen; Yifeng Chai (6431-6440).
Tanreqing injection, a classical Traditional Chinese Medicine formulation, consists of Radix Scutellariae baicalensis, Fel selenarcti, Cornu naemorhedi, Flos lonicerae and Forsythiae fructus, having a marked curative effect on the diseases of the upper respiratory tract. In order to clarify its chemical profile, a method based on liquid chromatography coupled with time-of-flight mass spectrometry was proposed, and 53 compounds were identified on a formula database of 515 known compounds with the aid of accurate mass measurement for molecular ions and characteristic fragment ions. Using the chemical fingerprints for the purpose of quality control, a high performance liquid chromatography coupled with photodiode array detection and evaporative light scattering detection (HPLC-DAD-ELSD) was developed in this study. The chromatographic fingerprints were evaluated by the dual similarities (S and S′) of an ultra-violet chromatogram, in combination with SE of an ELSD chromatogram, reflecting the complexity of Tanreqing injection with the consideration of both large and small peaks. In addition, the established HPLC-DAD-ELSD method was successfully applied to the quantitative analysis of the five ingredients (chlorogenic acid, caffeic acid, baicalin, ursodeoxycholic acid and chenodeoxycholic acid) and fingerprint analysis in 11 batches of Tanreqing injections. The results obtained in this research will provide the basis for quality control of Tanreqing injections.
A novel microsphere-based fluorescence immunochromatographic assay for monitoring cefalexin residues in plasma, milk, muscle and liver by Sumin Bian; Xiaogang Chu; Yong Jin; Shige Xing; Yue Zhang; Hongbo Hu (6441-6448).
A novel, microsphere-based fluorescence immunochromatographic assay (MFIA), of higher sensitivity and faster detection than the monoclonal-based competitive indirect enzyme-linked immunosorbent assay (ci-ELISA), was developed for the routine surveillance of cefalexin antibiotic residues in plasma, milk, muscle and liver. The cross-reactivities of the fluorescent microsphere–monoclonal antibody (FM–mAb) conjugates to cefaclor, cefadroxil, cefradine and cefixime were 212.7%, 155.6%, 108.1% and 86.6%, respectively. The limits of detection of the proposed MFIA were <0.1 μg L−1 in all the cases, with IC50 values in the range from 0.59 to 0.71 μg L−1. The recoveries were 84.5% to 107.2% with the coefficient of variation less than 6.9% when cefalexin standards were spiked in selected biological matrices. Good correlations among the MFIA, ci-ELISA and ultra performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS) results for blood samples from a cefalexin-injected rabbit were observed. In summary, the entire assay took about 30 min, and was simple, rapid, highly sensitive and cost-effective for both high-throughput screening and individual testing in food quality control.
A computational approach to design an electrochemical sensor and determination of acephate in aqueous solution based on a molecularly imprinted poly(o-phenylenediamine) film by Yuqing Duan; Xiaoping Luo; Haihui Zhang; Guibo Sun; Xiaobo Sun; Haile Ma (6449-6456).
A new molecularly imprinted polymer (MIP) electrochemical sensor was prepared by anchoring an imprinted insulating poly(o-phenylenediamine) film on a glassy carbon electrode (GCE) surface for the determination of acephate in aqueous solution. In this protocol, the selection of a functional monomer was performed computationally using the density functional theory method to evaluate the template–monomer interaction energy. The electrochemical properties of the MIP–GCE were characterized by cyclic voltammetry and alternating current impedance. Under optimal experimental conditions, the peak current of the MIP–GCE performed by differential pulse voltammetry was related to the concentration of acephate in the range from 5.0 × 10−7 to 1.0 × 10−4 mol L−1. The detection limit of 1.3 × 10−7 mol L−1 and the limit of quantitation of 4.5 × 1.0−7 mol L−1 were obtained. The prepared MIP–GCE showed high recognition, sensitivity to acephate, and it provides potential for monitoring acephate residues in foods and water samples.
Determining the presence of naphthenic and vegetable oils in paraffin-based lubricant oils using near infrared spectroscopy and support vector machines by Julio Cesar Laurentino Alves; Ronei Jesus Poppi (6457-6464).
The presence of naphthenic base oil and/or vegetable oil in paraffin-based lubricant oils such as automotive engine lubricant oils can severely compromise the lubricant properties and this can cause serious engine damage. A simple and fast method to identify such base stocks in mixture with paraffinic base oil and automotive engine lubricant oil is of great interest for quality monitoring. Near infrared (NIR) spectroscopy combined with chemometric methods has been applied for the development of efficient analytical methods for complex mixtures such as the ones that occur in petroleum derivatives. In this work, we carried out a study to develop classification models using support vector machines (SVM) applied to near infrared (NIR) spectroscopy data to determine the presence of naphthenic oil and/or vegetable oil in paraffin-based oils such as base oil and engine lubricant oil and the results were compared with those obtained with soft independent modeling of class analogy (SIMCA). The use of near infrared (NIR) spectroscopy and SVM provides the greatest results and a fast and simple method that achieves 95% and 100% of right predictions in the validation sample set and 87% and 75% of right predictions in the prediction sample set for the identification of naphthenic base oil, as well as for simultaneous identification of naphthenic base oil and vegetable oil in paraffin-based oils.
Determination of glyphosate and aminomethylphosphonic acid in soybean samples by high performance liquid chromatography using a novel fluorescent labeling reagent by Yaoyao Zhang; Yi Zhang; Qishu Qu; Guoxiu Wang; Chengyin Wang (6465-6472).
A highly sensitive pre-column derivatization HPLC method for simultaneous determination of glyphosate (GLYP) and its major metabolite aminomethylphosphonic acid (AMPA) in soybean samples was developed. The analytes were labeled with a novel fluorescent labeling reagent 3,6-dimethoxy-9-phenyl-9H-carbazole-1-sulfonyl chloride (DPCS-Cl) at 70 °C for 25 min. The optimized concentration of DPCS-Cl was 25 μg mL−1 and the molar ratio of analytes to DPCS-Cl was 1 : 4.2. The derivatives were separated on a reversed-phase column by gradient elution and were monitored with fluorescence detection at 318 nm (excitation) and 440 nm (emission). The method linearity, calculated for GLYP and AMPA, had a correlation coefficient greater than 0.999. The detection limits for GLYP and AMPA were 0.02 ng mL−1 and 0.01 ng mL−1 (S/N = 3), respectively. In addition, a simple sample pretreatment for the soybean samples was developed to extract GLYP and AMPA. The recovery of extraction was more than 95%. Then, this method gave the detection limits of 0.002 mg kg−1 for GLYP and 0.001 mg kg−1 for AMPA in soybean samples. This HPLC method was applied to the determination of glyphosate and AMPA in soybean samples with its merits of simplicity in pretreatment, rapidity in derivatization, stability of the derivatives and high sensitivity.
Determination of Ni, Cr, Cu, Pb and Cd on the Mediterranean endemic plant Posidonia oceanica using the green extraction method “Microwave Assisted Micellar Extraction” and GFAAS by Ana M. Hernández-Martínez; Carolina Padrón-Sanz (6473-6479).
An effort is currently being made to reduce the acid concentrations in traditional methodologies for the analysis of metals based on green chemistry. However, it becomes necessary to develop alternative extraction and analytical environmentally friendly methods that completely avoid the use of acids. In this sense, a Microwave Assisted Micellar Extraction (MAME) method was developed, which employs biodegradable surfactants as extractants. On the other hand, Posidonia oceanica has demonstrated its potential as a bioindicator for metal pollution in the marine environment. Therefore, a new green method has been tested for the extraction of heavy metals (Ni, Cr, Cu, Pb, Cd) from Posidonia oceanica, by using a mixture of biodegradable surfactants: Sodium Dodecyl Sulphate (SDS) and Triton X-100 as extractants and analysis by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The proposed method showed, in general, satisfactory recovery percentages, RSD below 7.29%, and LOD ranging from 0.04 to 0.22 μg g−1. On the other hand, the proposed method was applied to aged Posidonia oceanica as well as different macrophyte samples. The results obtained were compared to those from ISO 11047:1998.
Spectrophotometric determination of trace p-nitrophenol enriched by 1-hydroxy-2-naphthoic acid-modified nanometer TiO2 in water by Xiaofeng Lin; Yiping Chen; Shunxing Li (6480-6485).
The surface of nanometer TiO2 was simply and quickly modified by chemical adsorption with 1-hydroxy-2-naphthoic acid (HNA), which can strengthen the affinity between TiO2 and p-nitrophenol (p-NP). A novel method for preconcentration of p-NP with HNA-modified nanometer TiO2 (HNA–TiO2) and determination by spectrophotometry has been developed. Under the optimum adsorption conditions, the best adsorption ratio of p-NP was greater than 98.0% at pH 0.3 after only stirring for 15 min, and the adsorptive capacity of HNA–TiO2 for p-NP was greater than 25.0 μg mg−1. The adsorbed p-NP could be eluted by 5 mL 2.0 mol L−1 NaOH and the elution percentage was greater than 92.0%. This method gave a concentration enrichment factor of 50 for a 250 mL sample, the detection limit (3σ, n = 11) was reduced to 25.4 μg L−1, the relative standard deviation was 3.10%. This simple and fast method was successfully applied to the determination of p-NP in industrial wastewaters and natural waters, so the interference from the matrix and similar organic pollutants (benzoate and phenol) could be avoided. Analytical recoveries of p-NP added to samples ranged from 93.5% to 104.1%.
Solid-phase extraction based on polyethyleneimine-modified eggshell membrane coupled with FAAS for the selective determination of trace copper(ii) ions in environmental and food samples by Xue Zou; Yuming Huang (6486-6493).
Polyethyleneimine (PEI) can selectively capture trace-level free copper ions (Cu2+), from which the true toxic effects of copper originate. Thus, PEI-functionalized eggshell membrane (ESM) may serve as a green, economical, easily available, and selective solid phase extraction (SPE) adsorbent material for Cu2+ enrichment. In this paper, the potential of the PEI-functionalized ESM (PEI–ESM) as a biosorbent for the selective solid phase extraction and preconcentration of trace Cu2+ in environmental water samples and food samples in combination with flame atomic absorption spectrometry (FAAS) was investigated. After modification, the dynamic uptake capacity of PEI–ESM increased by about 20-fold compared with ESM. Various factors affecting Cu2+ extraction by SPE were investigated. Under the optimal conditions, Cu2+ could be easily extracted by the PEI–ESM packed cartridge. The favorable limit of detection (LOD) for Cu(ii) was 0.15 μg L−1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 2.0% for 50 μg L−1 Cu(ii) (n = 11). The reproducibility among columns was satisfactory (RSD among the columns is less than 5%). Stability testing demonstrated that the PEI–ESM maintained over 92.0% recovery for Cu(ii) even after a run of 45 adsorption and desorption cycles, showing its operational stability. The proposed method has been applied successfully to the analysis of copper in environmental water samples and food samples, which demonstrated that PEI–ESM could be an excellent SPE adsorbent for copper pretreatment and enrichment from real water samples and food samples.
Analysis of rosuvastatin stress degradation behavior using liquid chromatography coupled to ultraviolet detection and electrospray ionization mass spectrometry by Alaa Khedr; Fathalla Belal; Fawzia Ibrahim; Tarek Elawady (6494-6502).
A validated sensitive stability-indicating LC-UV-ESI-MS method was established to analyze rosuvastatin calcium (ROS) and its potential degradation products (DPs). ROS was subjected to different stress conditions recommended by ICH guidelines including photolytic, oxidative, thermal, acidic and basic hydrolysis. Successful separation of the drug from its DPs was achieved on a Zorbax Eclipse Plus C18 column (4.6 × 100 mm, 3.5 μm) using acetonitrile : 0.1% formic acid in water (40 : 60, v/v) as the mobile phase. The flow rate was 0.5 mL min−1 and the sample was detected simultaneously using a UV detector at 242 nm and an ESI-MS detector. ROS was found to be sensitive to photolysis and acidic hydrolysis and slightly affected by oxidation and heat. The proposed chemical structures of the DPs were characterized by studying their fragmentation patterns using ion trap-MS. DPs having different molecular masses including 481, 497, 479, 463 and 513 were produced under different stress conditions. A major DP released upon oxidation was proposed to be rosuvastatin-N-oxide. The ESI-MS response factors of potential DPs were concluded by a simple statistical procedure. Validation parameters including linearity, accuracy, precision, robustness, and specificity were evaluated. The limit of detection (LOD) and limit of quantification (LOQ) were 15 and 50 pg μL−1 for MS detection and were 1 and 2.5 ng μL−1 for UV detection, respectively. The relative standard deviation values of intraday and interday precision were not more than 1.92% and 1.81%, respectively. The proposed method was successfully applied on ROS tablets concerning drug assay and purity testing.
Multi-family methodologies for the analysis of veterinary pharmaceutical compounds in sediment and sludge samples: comparison among extraction techniques by Pedro N. Carvalho; António Pirra; M. Clara P. Basto; C. Marisa R. Almeida (6503-6510).
Veterinary drugs are still poorly studied in terms of pathways, release rates and effects on the environment. So, it is necessary to determine their levels in sewage sludge and soil/sediments affected by wastewaters. However, published methodologies deal usually with compounds from only a few classes. In addition, there is a lack of comparisons among the different extraction technologies used. A multi-family methodology for the simultaneous determination of minocycline, oxytetracycline, tetracycline (tetracyclines), enrofloxacin (fluoroquinolone) and ceftiofur (cephalosporin) in sludge and sediment was pursued. Three extraction techniques were compared, vortex agitation, ultrasonic extraction (USE) and microwave assisted extraction. Introduction of solid-phase extraction (SPE) for sample clean-up and pre-concentration was also evaluated. The complex matrix of solid samples posed specific problems, implying the need for individualized approaches for sediments and sludge. For sediments, USE sequential extraction (2 cycles) with methanol–acetone was chosen. LODs, when using SPE, ranged from 0.009 to 0.02 μg g−1. For sludge, samples were sequentially extracted three times by USE with methanol–formic acid. The SPE allowed lowering the limits 10 times ranging from 0.08 to 0.3 μg g−1 for LODs. The method yielded good selectivity and acceptable recovery results. The present methodology resulted in suitable multi-family approaches, less common than the majority of similar processes published.
Photodegradation kinetics of lodenafil carbonate, structure elucidation of two major degradation products using UPLC-MS/MS and in vitro cytotoxicity by Cristiane Franco Codevilla; Alini Dall Cortivo Lange; Juliana Maria de Mello Andrade; Jéferson Segalin; Pedro Eduardo Fröehlich; Ana Maria Bergold (6511-6516).
The photostability of lodenafil carbonate was studied and some degradation products were observed. A stability-indicating liquid chromatography method for the determination of lodenafil carbonate was used to determine the kinetics of photodegradation. The identification of two major photodegradation products was performed by an isocratic ultra performance liquid chromatography-tandem mass spectrometry method (UPLC-MS/MS). UPLC-MS/MS was carried out on a Waters® Acquity Ultra Performance LC system coupled to a Micromass® Quadrupole Time of Flight tandem mass spectrometer equipped with an electrospray ionization interface in positive ion mode. The column applied was Acquity UPLC® BEH C18; the mobile phase consisted of a mixture of methanol–formic acid 0.1% pH 4.0 (55 : 45, v/v) at a flow-rate of 0.4 mL min−1 and UV detection at 290 nm. The photodegradation of lodenafil carbonate followed first-order reaction kinetics and the kinetic parameters of degradation rate constant and t90% were calculated. Under photodegradation conditions, ion products were detected at m/z 393 (DP-1) and at m/z 377 (DP-2). The product DP-1 is 4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo [4,3-d]pyrimidin-5-yl)-benzenesulfonic acid and DP-2 probably is 4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo [4,3-d]pyrimidin-5-yl) benzenesulfinic acid. The degraded samples of lodenafil carbonate were also evaluated in order to determine the in vitro cytotoxicity against mononuclear cells.
A horizontally oriented setup for liquid–liquid–liquid microextraction of estrogens by Habib Bagheri; Hossein Maleki; Ali Es'haghi (6517-6522).
A horizontally oriented liquid–liquid–liquid microextraction (HOLLLME) setup was developed and applied for the isolation of two major estrogens from aquatic media. In contrast to the conventional procedure, in this setup the extracting microdrop was suspended from a horizontally positioned needle in order to provide much higher stability to the extracting phase. The developed HOLLLME approach was applied to isolate two major selected estrogens from aquatic media followed by high performance liquid chromatography-ultraviolet (HPLC-UV) determination. Estrogens were, initially, extracted from water samples into hexane and subsequently, the back extraction stage was performed with 6 μL of sodium hydroxide solution suspended from a horizontally fixed GC microsyringe tip. Important parameters influencing the extraction process were optimized and an extraction time of 25 min, back extraction time of 5 min, temperature of 35 °C, pH of 6 for a donor phase, dropsize of 6 μL and organic phase volume of 300 μL were achieved as optimum values. The enrichment factors of 111 for estrone and 80 for estriol were obtained at 1 mg L−1 concentration. The calibration curves showed linearity in the range of 10–500 μg L−1 with coefficients of determination higher than 0.99. The limits of detection and quantification were 3 and 10 μg L−1, respectively. Under optimized conditions, the relative standard deviation percent (RSD%) values were found to be from 6.8 to 13.0. Two typical surface water samples were used to assay the validation of the developed method.
Fabrication of an efficient polyaniline–polyphenol oxidase based biosensor for catechol by Venkatesan Sethuraman; Perumal Muthuraja; Paramasivam Manisankar (6523-6530).
Amperometric polymerization of aniline was carried out in the presence of TritonX-100. Entrapment of tyrosinase (polyphenol oxidase, PPO) onto polyaniline in the presence of TritonX-100 with glutaraldehyde as a cross-linking agent results in a biosensor for polyphenols. Catechol is taken as a model compound. Cyclic voltammetric studies reveal the electroactivity of catechol on the developed biosensor. HR-SEM shows the surface morphology of polyaniline prepared in the presence of TritonX-100 (PANI(T)) and polyphenol oxidase entrapped polyaniline in the presence of TritonX-100 (PANI(T)–PPO). The optimum reaction conditions to construct the polyaniline, tyrosinase based catechol biosensor are studied. The linear concentration range is from 5 × 10−7 to 1.65 × 10−4 mol dm−3, with a Michealis–Menten constant Km = 85.44 μmol dm−3 and an activation energy of 41.74 kJ mol−1. It retains 65% of the original activity after 25 days, which is much higher than that of other biosensors. With a lower quantity of enzyme loading, better response, sensitivity, shelf life and higher stability are observed. The developed biosensor was used to quantify catechol in green tea samples and the results were compared with those from HPLC.
Preparation of a new electrochemical biosensor for single base mismatch detection in DNA by Nasrin Moradi; Mir Fazlollah Mousavi; Masoud Ayatollahi Mehrgardi; Abolhassan Noori (6531-6538).
In this study, a sandwich-type electrochemical DNA hybridization biosensor for the detection of single base mismatches (SBMs) has been described. 2,5-Dihydroxybenzoic acid (DHBA) is employed as a new redox probe in this study. For construction of the biosensor, thiolated capture DNA is self-assembled on a gold electrode surface and hybridized with one region of a target DNA sequence. Subsequently, a signaling amino-labeled probe DNA is hybridized to a second region of the target DNA to complete the DNA double-helix self-assembled monolayer (SAM). Finally DHBA is covalently attached to the signaling probe DNA using the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHS) cross-linking reaction. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are employed to characterize the modification steps. The electrochemical signal of DHBA was followed for studying different types of mismatches (GA, GT, TT, CA), both near the electrode surface (N-type) and far from it (F-type). The presence of a SBM leads to a considerable decrease in the electrochemical signal of DHBA compared to that of complementary DNA (cDNA), which makes the detection of mismatches (including thermodynamically stable GA mismatches) possible. The redox signal of DHBA was compared with that of methylene blue (MB) as a well-known and standard redox reporter in DNA biosensors. The results showed that for an N-type SBM, which is located between the electrode and the site of intercalation, the redox signal of MB switches off, whereas for an F-type SBM, which is located above the site of intercalation, electrons flow from the Au electrode to the intercalated MB, and hence the biosensor could not distinguish the presence and absence of an SBM. The proposed biosensor is straightforward with no need for target labeling, and is sensitive enough to detect SBMs independent of their position in DNA double helix.
Back cover (6539-6540).