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Analytica Chimica Acta (v.767, #)

Editorial Board (pp. iii).

Conductive polymer-based microextraction methods: A review by Habib Bagheri; Zahra Ayazi; Mehrnoush Naderi (pp. 1-13).

Display Omitted► The structural and electronic properties of conductive polymers are discussed. ► Extraction methodologies based on the use of conductive polymers are described. ► Applicability of conductive polymers are compared with commercial sorbents.Conductive polymers (CPs) are classified as materials which exhibit highly reversible redox behavior and the unusual combined properties of metal and plastics. CPs, due to their multifunctionality, ease of synthesis and their stability, have attracted more attentions in different fields of research, including sample preparation. CPs along with several commercial hydrophilic sorbents, are alternative to the commercially available hydrophobic sorbents which despite their high specific surface areas, have poor interactions and retentions in the extraction of polar compounds. This review covers a general overview regarding the recent progress and new applications of CPs toward their synthesis and use in novel extraction and microextraction techniques including solid phase microextraction (SPME), electrochemically controlled solid-phase microextraction (EC-SPME) and other relevant techniques. Furthermore the contribution of nano-structured CPs in these methodologies is also reviewed.

Keywords: Conductive polymers; Polypyrrole; Polyaniline; Solid phase microextraction; Electrochemically controlled solid-phase microextraction

Total introduction of microsamples in inductively coupled plasma mass spectrometry by high-temperature evaporation chamber with a sheathing gas stream by Marco Grotti; Francisco Ardini; Josè Luis Todolì (pp. 14-20).

Display Omitted► The main features of high-temperature TISIS for use in ICP-MS have been evaluated. ► The sensitivity was 2–8 times higher than that measured for conventional systems. ► Limits of detection were lower for many elements. ► The system was applied to environmental, biological and clinical micro-samples.A systematic study on the high-temperature Torch Integrated Sample Introduction System (TISIS) for use in Inductively Coupled Plasma Mass Spectrometry (ICP-MS) has been performed. The investigation included the optimization of the relevant parameters (chamber temperature, sheathing gas flow rate, nebulizer gas flow rate, sample uptake rate), the evaluation of its performance characteristics (sensitivity, limits of detection, stability, memory effects, use with the dynamic reaction cell) and representative applications to environmental, biological and clinical samples. Under the optimal conditions ( T=150°C; nebulizer gas flow rate of 0.7Lmin⁻¹ along with sheathing gas flow rate of 0.35Lmin⁻¹ and a sample uptake rate of 20μLmin⁻¹), the sensitivity was from 2 to 8 times higher than that measured using a conventional micronebulizer/mini-spray chamber system, due to the enhanced analyte mass transport toward the plasma and the solvent introduction in the vapour form. In addition, for several elements, TISIS provided lower limits of detection than the conventional system, even when the latter worked at 5-fold higher sample uptake rate. Short-term and long-term precision was better than 5%. Spectroscopic interferences arising from common matrices were efficiently removed by the dynamic reaction cell technique. The application of TISIS/ICP-MS to representative certified reference samples (spinach leaves, marine plankton, bone tissue, human blood) proved the suitability of this system for the accurate analysis of limited-size samples.

Keywords: Inductively coupled plasma; Mass spectrometry; Sample introduction; Microsamples

Extent-based kinetic identification using spectroscopic measurements and multivariate calibration by Julien Billeter; Sriniketh Srinivasan; Dominique Bonvin (pp. 21-34).

Display Omitted► Factorization of spectral data in RV- and RMV-forms. ► Prediction of extents of reaction and mass transfer from spectroscopic measurements. ► Reconstruction of all concentrations from the extents. ► Extent-based identification of each rate law independently of other rate processes. ► Illustration using simulated data from homogeneous and gas–liquid reaction systems.Extent-based kinetic identification is a kinetic modeling technique that uses concentration measurements to compute extents and identify reaction kinetics by the integral method of parameter estimation. This article considers the case where spectroscopic data are used together with a calibration model to predict concentrations. The calibration set is assumed to be constructed from reacting data that include pairs of concentration and spectral data. Alternatively, one can use the concentration- and spectral contributions of the reactions and mass transfers, which are obtained by pretreatment in reaction- and mass-transfer-variant form. The extent-based kinetic identification using concentrations predicted from spectroscopic data is illustrated through the simulation of both a homogeneous and a gas–liquid reaction system.

Keywords: Gas–liquid reactions; Reaction kinetics; Extents of reaction; Extents of mass transfer; Multivariate calibration; Spectroscopy

Identification of discriminatory variables in proteomics data analysis by clustering of variables by Sadegh Karimi; Bahram Hemmateenejad (pp. 35-43).

A new method based on the clustering of variables (CLoVA) was proposed for identification of discriminatory variables in proteomic data analysis.Display Omitted► A new method was suggested for identification of discriminatory variables. ► The method works based on the clustering of variables (CLoVA). ► CLoVA was used as an efficient method in proteomics data analysis. ► The method was applied successfully in cancer detection.This article presents a data analysis method for biomarker discovery in proteomics data analysis. In factor analysis-based discriminate models, the latent variables (LV's) are calculated from the response data measured at all employed instrument channels. Since some channels are irrelevant and their responses do not possess useful information, the extracted LV's possess mixed information from both useful and irrelevant channels. In this work, clustering of variables (CLoVA) based on unsupervised pattern recognition is suggested as an efficient method to identify the most informative spectral region and then it is used to construct a more predictive multivariate classification model. In the suggested method, the instrument channels ( m/ z value) are clustered into different clusters via self-organization map. Subsequently, the spectral data of each cluster are separately used as the input variables of classification methods such as partial least square-discriminate analysis (PLS-DA) and extended canonical variate analysis (ECVA). The proposed method is evaluated by the analysis of two experimental data sets (ovarian and prostate cancer data set). It is found that our proposed method is able to detect cancerous from healthy samples with much higher sensitivity and selectivity than conventional PLS-DA and ECVA methods.

Keywords: Classification; Proteomics; Clustering of variables; Cancer; Discriminant analysis; Self-organization map

Multivariate analysis of chromatographic retention data and lipophilicity of phenylacetamide derivatives by Gyöngyi Vastag; Suzana Apostolov; Nada Perišić-Janjić; Borko Matijević (pp. 44-49).

Display Omitted► Chemometric were used for comparing lipophilic parameters of phenylacetamides. ► Nature of substituents affects to lipophilicity of investigated molecules. ► Sum of ranking difference could give similarity between used variables. ► The best variables could be distinguished by using sum of ranking difference. ► Study offers a possibility of significant reduction of experimentally work.One of the most important physicochemical parameters of a molecule that determines its bioactivity is its lipophilicity. Cluster analysis (CA), principal component analysis (PCA), and sum of ranking differences (SRD) were used to compare the lipophilic parameters of twenty phenylacetamide derivatives, obtained experimentally as chromatographic retention data in the presence of different solvents and calculated by different mathematical methods. All the applied methods of multivariate analysis gave approximately similar grouping of the studied lipophilic parameters. In the attempt to group the investigated compounds in respect of their lipophilicity, the obtained results appeared to be dependent on the applied chemometric method. The CA and PCA, grouped the compounds on the basis of the nature of the substituents R₁ and R₂, indicating that they determine to a great extent the lipophilicity of the investigated molecules. Unlike them, the SRD method could not be used to group the studied compounds on the basis of their lipophilic character.

Keywords: Phenylacetamides; Lipophilicity; Cluster analysis; Principal component analysis; Ranking

A sandwich-type DNA biosensor based on electrochemical co-reduction synthesis of graphene-three dimensional nanostructure gold nanocomposite films by Ai-Lin Liu; Guang-Xian Zhong; Jin-Yuan Chen; Shao-Huang Weng; Hong-Nan Huang; Wei Chen; Li-Qing Lin; Yun Lei; Fei-Huan Fu; Zhou-liang Sun; Xin-Hua Lin; Jian-Hua Lin; Shu-Yu Yang (pp. 50-58).

Graphite oxide (GO) Au-nanoparticle graphene capture probe biotinylated target probe avidin-HRP reporter probe.Display Omitted► Graphene-three dimensional nanostructure gold nanocomposite modified GCE is fabricated. ► A “sandwich-type” detection strategy is employed in this electrochemical DNA biosensor. ► The detection limit of the DNA biosensor is 3.4fM. ► The new DNA biosensor exhibited a fast response, high sensitivity and selectivity. ► The new DNA biosensor has been used for an assay of PCR real sample.A novel electrochemical DNA biosensor based on graphene-three dimensional nanostructure gold nanocomposite modified glassy carbon electrode (G-3D Au/GCE) was fabricated for detection of survivin gene which was correlated with osteosarcoma. The G-3D Au film was prepared with one-step electrochemical coreduction with graphite oxide and HAuCl₄ at cathodic potentials. The active surface area of G-3D Au/GCE was 2.629cm², which was about 3.8 times compared to that of a Au-coated GCE under the same experimental conditions, and 8.8 times compared to a planar gold electrode with a similar geometric area. The resultant nanocomposites with high conductivity, electrocatalysis and biocompatibility were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A “sandwich-type” detection strategy was employed in this electrochemical DNA biosensor and the response of this DNA biosensor was measured by CV and amperometric current–time curve detection. Under optimum conditions, there was a good linear relationship between the current signal and the logarithmic function of complementary DNA concentration in a range of 50–5000fM with a detection limit of 3.4fM. This new biosensor exhibited a fast amperometric response, high sensitivity and selectivity and has been used in a polymerase chain reaction assay of real-life sample with a satisfactory result.

Keywords: Graphene–gold nanostructure nanocomposites; DNA biosensors; Sandwich-type; Survivin gene; Osteosarcoma

Self-assembled oligo(phenylene ethynylene)s/graphene nanocomposite with improved electrochemical performances for dopamine determination by Jianhui Deng; Meilin Liu; Fanbo Lin; Youyu Zhang; Yang Liu; Shouzhuo Yao (pp. 59-65).

Display Omitted► A novel oligo (phenylene ethynylene)s/graphene nanocomposite (OPE-NH₂/rGO) was synthesized. ► The OPE-NH₂/rGO modified electrode exhibited improved electroactivity to dopamine oxidation. ► The sensor showed good performances for DA detection and can be used for human serum samples.In this work, a novel 1,4-bis (4- aminophenylethynyl)benzene (OPE-NH₂, a symmetric linear conjugated oligo(phenylene ethynylene)s derive) and chemically-reduced graphene oxide (rGO) nanocomposite (OPE-NH₂/rGO) was synthesized by a simple self-assembly method. The OPE-NH₂/rGO nanocomposite was stable and water soluble. The formation of OPE-NH₂/rGO nanocomposite was ascribed to the π–π stacking interaction between the conjugated structure of OPE-NH₂ and rGO as well as the electrostatic force between the amino group of OPE-NH₂ and the carboxyl group on rGO, which was characterized by FT-IR, UV–vis spectra and fluorescence spectra. The OPE-NH₂/rGO nanocomposite exhibited significantly improved electrocatalytic activity to the oxidization of dopamine (DA) than that of rGO or OPE-NH₂. The electrochemical performances of OPE-NH₂/rGO were dependent on the OPE-NH₂ contents, and OPE-NH₂ content of 5wt% exhibited the highest activity. Compared with that of rGO, the nanocomposite presented superior high sensitivity with detection limit of 5nM, excellent selectivity, wide linear range (0.01–60μM) and good stability on the determination of DA. The practical application of the developed OPE-NH₂/rGO nanocomposite modified electrode was successfully demonstrated for DA determination in human serum samples.

Keywords: Oligo(phenylene ethynylene)s; Graphene; Self-assembly; Electroanalysis

Battery-triggered ultrasensitive electrochemiluminescence detection on microfluidic paper-based immunodevice based on dual-signal amplification strategy by Weiping Li; Meng Li; Shenguang Ge; Mei Yan; Jiadong Huang; Jinghua Yu (pp. 66-74).

GCA as immunosensing platform and P-acid/NPS were prepared to immobilize to Ab1 and Ab2 respectively and combine to fabricate to a novel ECL paper-based immunodevice for detecting PSA and CEA.Display Omitted► The as-prepared GCA was employed as immunosensing platform for target capture. ► P-acid/NPS composites were used as signal amplification labels. ► Battery-triggered (constant-potential) ECL detection on this immunodevice. ► The cross-reactivity and cross-talk should be totally eliminated. ► The total immunoassay process could be completed within 15min.Dual-signal amplification strategy for ultrasensitive electrochemiluminescence (ECL) multiplexed immunoassay on microfluidic paper-based analytical devices (μ-PADs) was demonstrated. This dual-signal amplification technique was achieved by employing graphene oxide-chitosan/gold nanoparticles (GCA) immunosensing platform and [4,4′-(2,5-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl) dibenzoic acid] (P-acid) functionalized nanoporous silver (P-acid/NPS) signal amplification label. For further low-cost and disposable applications, battery-triggered constant-potential ECL (+1.0V for P-acid label (vs. Ag/AgCl auxiliary electrode)) was applied on this paper-based immunodevice with the aid of a home-made voltage-tunable power device, allowing the traditional electrochemical workstation to be abandoned. We found that two tumor markers could be sequentially detected in the linear ranges of 0.003–20 and 0.001–10ngmL⁻¹ with the detection limits down to 1.0 and 0.8pgmL⁻¹, respectively, by simply reversing the connection mode on two working electrodes. The results exhibited excellent precision and high sensitivity of such immunoassay, and it also demonstrated that this battery-triggered ECL paper-based immunodevice could provide a rapid, simple and simultaneous multiplex immunoassay with high throughput, low-cost and low detection limits for point-of-care testing.

Keywords: Dual-signal amplification; Battery; Electrochemiluminescence; Multiplexed immunoassay; Point-of-care

Development and application of carbon nanotubes assisted electromembrane extraction (CNTs/EME) for the determination of buprenorphine as a model of basic drugs from urine samples by Kobra Sadat Hasheminasab; Ali Reza Fakhari (pp. 75-80).

Display Omitted► Carbon nanotubes assisted electromembrane extraction (CNTs/EME) was developed. ► Carbon nanotubes reinforced hollow fiber was used in this research. ► The CNTs serve as a sorbent and provide an additional pathway for solute transport. ► In comparison with the EME method, this method showed higher extraction efficiency. ► Determination of buprenorphine, a model of basic drugs, in urine samples was performed.In this work carbon nanotubes assisted electromembrane extraction (CNTs/EME) coupled with capillary electrophoresis (CE) and ultraviolet (UV) detection was developed for the determination of buprenorphine as a model of basic drugs from urine samples. Carbon nanotubes reinforced hollow fiber was used in this research. Here the CNTs serve as a sorbent and provide an additional pathway for solute transport. The presence of CNTs in the hollow fiber wall increased the effective surface area and the overall partition coefficient on the membrane; and lead to an enhancement in the analyte transport. For investigating the influence of the presence of CNTs in the SLM on the extraction efficiency, a comparative study was carried out between EME and CNTs/EME methods. Optimization of the variables affecting these methods was carried out in order to achieve the best extraction efficiency. Optimal extractions were accomplished with NPOE as the SLM, with 200V as the driving force, and with pH 2.0 in the donor and pH 1.0 in the acceptor solutions with the whole assembly agitated at 750rpm after 25min and 15min for EME and CNTs/EME, respectively.Under the optimized conditions, in comparison with the conventional EME method, CNTs/EME provided higher extraction efficiencies in shorter time. This method provided lower limit of detection (1ngmL⁻¹), higher preconcentration factor (185) and higher recovery (92). Finally, the applicability of this method was evaluated by the extraction and determination of buprenorphine in patients’ urine samples.

Keywords: Carbon nanotubes assisted electromembrane extraction (CNTs/EME); Buprenorphine; Basic drugs; Capillary electrophoresis; Urine samples

Rapid determination of triclosan in personal care products using new in-tube based ultrasound-assisted salt-induced liquid–liquid microextraction coupled with high performance liquid chromatography-ultraviolet detection by Ming-Jen Chen; Ya-Ting Liu; Chiao-Wen Lin; Vinoth Kumar Ponnusamy; Jen-Fon Jen (pp. 81-87).

Display Omitted► In-tube based salt-induced liquid–liquid ultrasonic microextraction was developed. ► This method is applied for trace analysis of triclosan in personal care products. ► This is an efficient, easy, inexpensive and eco-friendly sample preparation method.This paper describes the development of a novel, simple and efficient in-tube based ultrasound-assisted salt-induced liquid–liquid microextraction (IT-USA-SI-LLME) technique for the rapid determination of triclosan (TCS) in personal care products by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. IT-USA-SI-LLME method is based on the rapid phase separation of water-miscible organic solvent from the aqueous phase in the presence of high concentration of salt (salting-out phenomena) under ultrasonication. In the present work, an indigenously fabricated home-made glass extraction device (8-mL glass tube inbuilt with a self-scaled capillary tip) was utilized as the phase separation device for USA-SI-LLME. After the extraction, the upper extractant layer was narrowed into the self-scaled capillary tip by pushing the plunger plug; thus, the collection and measurement of the upper organic solvent layer was simple and convenient. The effects of various parameters on the extraction efficiency were thoroughly evaluated and optimized. Under optimal conditions, detection was linear in the concentration range of 0.4–100ngmL⁻¹ with correlation coefficient of 0.9968. The limit of detection was 0.09ngmL⁻¹ and the relative standard deviations ranged between 0.8 and 5.3% ( n=5). The applicability of the developed method was demonstrated for the analysis of TCS in different commercial personal care products and the relative recoveries ranged from 90.4 to 98.5%. The present method was proven to be a simple, sensitive, less organic solvent consuming, inexpensive and rapid procedure for analysis of TCS in a variety of commercially available personal care products or cosmetic preparations.

Keywords: In-tube; Ultrasound-assisted; Salt-induced liquid–liquid microextraction; Triclosan; Personal care products; High performance liquid chromatography-ultraviolet detector

A rapid ultrasound-assisted dispersive liquid–liquid microextraction followed by ultra-performance liquid chromatography for the simultaneous determination of seven benzodiazepines in human plasma samples by Purificación Fernández; Cristina González; M. Teresa Pena; Antonia M. Carro; Rosa A. Lorenzo (pp. 88-96).

Display Omitted► A new method for the determination of benzodiazepines. ► Biological sample, plasma. ► Ultrasound-assisted-dispersive liquid–liquid microextraction. ► Comparative analysis by UPLC-PDA and HPLC-PDA.A simple and efficient ultrasound-assisted dispersive liquid–liquid microextraction (UA-DLLME) method has been developed for the determination of seven benzodiazepines (alprazolam, bromazepam, clonazepam, diazepam, lorazepam, lormetazepam and tetrazepam) in human plasma samples. Chloroform and methanol were used as extractant and disperser solvents, respectively. The influence of several variables (e.g., type and volume of dispersant and extraction solvents, pH, ultrasonic time and ionic strength) was carefully evaluated and optimized, using an asymmetric screening design 3²4²//16. Analysis of extracts was performed by ultra-performance liquid chromatography coupled with photodiode array detection (UPLC-PDA). Under the optimum conditions, two reversed-phases, Shield RP18 and C18 columns were successfully tested, obtaining good linearity in a range of 0.01–5μgmL⁻¹, with correlation coefficients r>0.996. Quantification limits ranged between 4.3–13.2ngmL⁻¹ and 4.0–14.8ngmL⁻¹, were obtained for C18 and Shield RP18 columns, respectively. The optimized method exhibited a good precision level, with relative standard deviation values lower than 8%. The recoveries studied at two spiked levels, ranged from 71 to 102% for all considered compounds. The proposed method was successfully applied to the analysis of seven benzodiazepines in real human plasma samples.

Keywords: Ultrasound-assisted dispersive liquid–liquid microextraction; Ultra-performance liquid chromatography; Benzodiazepines; Plasma

Preparation of hybrid soda-lime/quartz glass chips with wettability-patterned channels for manipulation of flow profiles in droplet-based analytical systems by Zeqing Bai; Qiaohong He; Shanshi Huang; Xianqiao Hu; Hengwu Chen (pp. 97-103).

Smooth flow profile switching of two-phase flows can be realized in the wettability-patterned channels. (a) From the W/O droplet flow to O/W droplet flow; (b) from W/O droplet flow to side-by-side laminar flow; and (c) from O/W droplet flow to side-by-side laminar flow. The two immiscible fluids were n-octanol (transparent) and aqueous dye solution (blue-colored).Display Omitted► Channels were wettability-patterned via UV-lithography of OTS coated in channel. ► Hybrid soda-lime/quartz glass chip facilitated UV degrading in-channel-coated OTS. ► Smooth profile switch of two-phase flows was realized in the patterned channels. ► Partition coefficients of drugs were determined via on-chip solvent extraction.Profile switching of two-phase flows is often required in microfluidic systems. Manipulation of flow profiles can be realized by control of local surface energy of micro channel through wettability-patterning of channel surface. This article presents a facile approach for wettability-patterning of the micro channels of glass chips. Commercially available octadecyltrichlorosilane (OTS) was used to hydrophobilize the channels via the formation of OTS self-assembly monolayer (SAM), and a UV-source that mainly emits deep UV-light of 254 and 185nm was employed to degrade the in-channel formed OTS-SAM. The architecture of soda-lime glass/quartz glass hybrid chip was designed to facilitate the deep UV-light effective degrading the OTS-SAM. The established approach, together with the side-by-side laminar-flow patterning technique, was applied to prepare various finely patterned channel networks for different tasks of flow profile switching. The micro device capable of conducting the profile switch from W/O droplets to two separated continuous phases was demonstrated to perform on-chip quick liquid–liquid extraction for the determination of partition coefficients of pharmaceuticals.

Keywords: In-channel wettability patterning; Glass microfluidic chip; Octadecyltrichlorosilane; Determination of partition coefficients; On-chip liquid–liquid extraction

Synthesis and application of ionic liquid matrices (ILMs) for effective pathogenic bacteria analysis in matrix assisted laser desorption/ionization (MALDI-MS) by Hani Nasser Abdelhamid; Judy Gopal; Hui-Fen Wu (pp. 104-111).

Display Omitted► Prepare and characterize two new series of ionic liquid. ► Apply the two series as matrices for pathogenic bacteria in MALDI. ► Enhance peaks signals and peaks number for MALDI-MS. ► Propose a reasonable mechanism based on physical parameters.Application of two new series of ionic liquid matrices (ILMs) based on the two most predominantly used conventional organic matrices (Sinapinic acid and 2,5-DHB) in conjugation with various bases (aniline (ANI), dimethyl aniline (DMANI), diethylamine (DEA), dicyclohexylamine (DCHA), pyridine (Pyr), 2-picoline(2-P), 3-picoline(3-P)) for bacterial analysis in matrix assisted laser desorption/ionisation mass spectrometry (MALDI-MS) are reported. The results reveal that ionic liquid matrices could significantly enhance the protein signals, reduce spot-to-spot variation and increase spot homogeneity. More importantly, these novel matrices would not produce any interference during MALDI-MS analysis. Among these ILMs, 2,5-DHB/ANI, 2,5-DHB/DMANI and 2,5-DHB/Pyr can be successfully applied to intact bacterial studies compared with other ILMs. Base molecules when added to conventional matrix can promote proton transfer between the bacterial lysate and the matrices. Due to the enhanced proton transfer efficiency by the ionic liquid matrices, almost all the biomolecules of the intact bacterial cells can be ionized and detected in the MALDI-MS. All synthesized ILMs were characterized using ESI (+)/MS and UV-spectroscopy.

Keywords: MALDI; Ionic liquid matrices; Pathogenic bacteria analysis; Electrospray ionization

Determination of dioxin-like polychlorinated biphenyls in 1mL whole blood using programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry by Haitao Shen; Rongfa Guan; Jingguang Li; Lei Zhang; Yiping Ren; Xiaomin Xu; Yang Song; Yunfeng Zhao; Jianlong Han; Yongning Wu (pp. 112-117).

Display Omitted► We developed and validated a PTV-GC–HRMS method to measure low level DL-PCBs. ► Liquid nitrogen was used in PTV external accessory equipment as fast cooling system. ► PTV's high-throughput and HRMS’ high sensitivity and selectivity are well combined.A sensitive method based on programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry (PTV-GC–HRMS) has been developed for the determination of ultra trace levels of dioxin-like polychlorinated biphenyls (DL PCBs) in small amounts of human blood. Blood samples (1mL) were first extracted by column extraction and then purified with column chromatorgraphies. Final extracts (20μL) were introduced to the PTV injector under the solvent vent mode and detected by GC–HRMS (SIM mode). PTV parameters were observed by changing one factor at a time (practical conditions: vent flow: 50mLmin⁻¹, vent pressure: 0kPa and vent time: 0.1min), recoveries of most PCB congeners ranged from 55.1% to 108%, and method detection limits were in the range of 0.11–1.63pgg⁻¹.

Keywords: PTV-GC–HRMS; Blood; Dioxin-like PCBs

High resolution orbitrap mass spectrometry in comparison with tandem mass spectrometry for confirmation of anabolic steroids in meat by Lynn Vanhaecke; Lieven Van Meulebroek; Nathalie De Clercq; Julie Vanden Bussche (pp. 118-127).

Display Omitted► HRMS has great potential in residue analysis of steroids in animal derived matrices. ► HRMS enables untargeted screening strategies for new, initially unknown steroids. ► Good linearity, precision and selectivity were observed upon HRMS analysis. ► Sensitivity of HR-Orbitrap-MS was generally lower compared to QqQ method.A prominent trend which has been observed in recent years in the analysis of veterinary drugs and growth-promoting agents is the shift from target-oriented procedures, mainly based on liquid chromatography coupled to triple-quadrupole mass spectrometry (LC-QqQ-MS), towards accurate mass full scan MS (such as time of flight (ToF) and Fourier Transform (FT) Orbitrap MS). In this study the applicability of high resolution single-stage-Orbitrap-MS for confirmatory analysis of growth-promoting agents in meat was compared to that of a QqQ-MS. Validation according to CD 2002/657/EC demonstrated that steroid analysis based on Orbitrap MS, operating at a resolution of 50,000 FWHM, is indeed capable to compete with QqQ-MS in terms of selectivity/specificity, while providing excellent linearity (for most compounds >0.99) but somewhat inferior sensitivity. Indeed, CC_αs reached from 0.04–0.88μgkg⁻¹ for the 34 anabolic steroids upon MS/MS detection, while upon Orbitrap MS detection a range of 0.07–2.50μgkg⁻¹ was observed. Using QqQ-MS adequate precision was obtained since relative standard deviations, associated with the repeatability and intra-laboratory reproducibility, were below 20%. In the case of Orbitrap MS, for some compounds (i.e. some estrogens) this threshold was exceeded and thus poor precision was observed, which is possibly caused by the lack in sensitivity. Overall, it may be concluded that Orbitrap-MS offers an adequate performance in terms of linearity and precision but lacks in sensitivity for some of the compounds.

Keywords: UHPLC-Orbitrap-HRMS; Anabolic steroids; Validation; CC; _α; CC; _β; CD 2002/657/EC

Amperometric biosensor based on reductive H₂O₂ detection using pentacyanoferrate-bound polymer for creatinine determination by Chi-Hua Nieh; Seiya Tsujimura; Osamu Shirai; Kenji Kano (pp. 128-133).

The detection mechanism of creatinine biosensor. CNH: creatinine amidohydrolase, CRH: creatine amidohydrolase, SOD: sarcosine oxidase, POD: peroxidase. The hollow arrows and the cross symbol indicate the extremely low reactivity of PVI[Fe(CN)₅] against SOD.Display Omitted► PVI[Fe(CN)₅] has a low reactivity against sarcosine oxidase (SOD). ► PVI[Fe(CN)₅] is suitable as a mediator for the SOD/peroxidase sensing system. ► The catalytic effects of mediator are related to the hydrophilic/phobic properties. ► The proposed biosensing method is applicable for urine creatinine determination.Pentacyanoferrate-bound poly(1-vinylimidazole) (PVI[Fe(CN)₅]) was selected as a mediator for amperometric creatinine determination based on the reductive H₂O₂ detection. Creatinine amidohydrolase (CNH), creatine amidohydrolase (CRH), sarcosine oxidase (SOD), peroxidase (POD), and PVI[Fe(CN)₅] were crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) on a glassy carbon (GC) electrode for a creatinine biosensor fabrication. Reduction current was monitored at −0.1V in the presence of creatinine and O₂. It is revealed that PVI[Fe(CN)₅] is suitable as a mediator for a bioelectrocatalytic reaction of POD, since PVI[Fe(CN)₅] neither reacts with reactants nor works as an electron acceptor of SOD. The amounts of PVI[Fe(CN)₅], PEGDGE, and enzymes were optimized toward creatinine detection. Nafion as a protecting film successfully prevented the enzyme layer from interferences. The detection limit and linear range in creatinine determination were 12μM and 12–500μM ( R²=0.993), respectively, and the sensitivity was 11mAcm⁻²M⁻¹, which is applicable for urine creatinine tests. The results of the creatinine determination for four urine samples measured with this proposed method were compared with Jaffe method, and a good correlation was obtained between the results.

Keywords: Pentacyanoferrate-bound poly(1-vinylimidazole); Creatinine amidohydrolase; Reductive H; ₂; O; ₂; detection; Peroxidase; Nafion; Urine creatinine test

An improved method for ratiometric fluorescence detection of pH and Cd²⁺ using fluorescein isothiocyanate–quantum dots conjugates by Rijun Gui; Xueqin An; Wenxue Huang (pp. 134-140).

Display Omitted► Dual-functional quantum dots were used for ratiometric fluorescence detection of pH and Cd²⁺. ► Limit of detection for Cd²⁺ was 12nM. ► Experimental results confirmed high selectivity of this sensor. ► Perfect analytical performance was achieved in real samples.In this study, thioglycolic acid capped-CdTe quantum dots (QDs) were modified by polyethylenimine (PEI), and then combined with fluorescein isothiocyanate (FITC) to fabricate FITC–CdTe conjugates. The self-assembly of FITC, CdTe and PEI was ascribed to electrostatic interactions in aqueous solution. The resulting conjugates were developed toward two routes. In route one, ratiometric photoluminescence (PL) intensity of conjugates ( I_FITC/ I_QDs) was almost linear toward pH from 5.3 to 8.7, and a ratiometric PL sensor of pH was favorable obtained. In route two, firstly added S²⁻ induced remarkable quenching of QDs PL peak (at the “OFF” state), which was restored due to following addition of Cd²⁺ (at the “ON” state). In the conjugates, successive introduction of S²⁻ and Cd²⁺ hardly influenced on FITC PL peaks. According to this PL “OFF-ON” mode, a ratiometric PL method for the detection of Cd²⁺ was achieved. Experimental results confirmed that the I_FITC/ I_QDs exhibited near linear proportion toward Cd²⁺ concentration in the range from 0.1 to 15μM, and the limit of detection was 12nM. Interferential experiments adequately testified that the proposed sensors of pH and Cd²⁺ were practicable in real samples and complex systems. In comparison with conventional analytical techniques, the ratiometric PL method was simple, rapid, economic and highly selective.

Keywords: Quantum dots; Fluorescein isothiocyanate; Ratiometric sensor; Fluorescence

Investigation on the application of titania nanorod arrays to the determination of chemical oxygen demand by Chao Wang; Jiancheng Wu; Peifang Wang; Yanhui Ao; Jun Hou; Jin Qian (pp. 141-147).

The figure shows the correlation between the experimental COD values by the titania nanorod array sensors and standard COD values (dichromate method). The correlation was satisfactory with correlation coefficient ( R) 0.9801, demonstrating the results obtained by our method were in good agreement with the standard method.Display Omitted► TiO₂ nanorod arrays were used for the determination of COD value for the first time. ► Obtained values correlated with conventional (i.e., dichromate) COD determination method. ► Described sensor shows long term stability and environmental friendly.In the present paper, the TiO₂ nanorod arrays electrode was developed as a sensor for the determination of chemical oxygen demand (COD) based on a photoelectrochemical degradation principle. Effects of common parameters, such as applied potential, light intensity and pH on its analytical performance were investigated. Under the optimized conditions, the nanorod arrays electrode was successfully applied in the COD determination for both synthetic and real samples. In the COD determination, the proposed method can achieve a practical detection limit of 18.3mgL⁻¹ and a linear range of 20–280mgL⁻¹. Furthermore, the results obtained by the proposed method were well correlated with those obtained using the conventional (i.e., dichromate) COD determination method. The main advantages of this COD determination method were its simplicity, long term stability and environmental friendly (corrosive and toxic reagents not consumed). This work would open a new application area (COD determination) of the TiO₂ nanorod arrays.

Keywords: Chemical oxygen demand; Determination; Titania nanorod arrays; Photoelectrochemical

Simultaneous determination of fangchinoline and tetrandrine in Stephania tetrandra S. Moore by using 1-alkyl-3-methylimidazolium-based ionic liquids as the RP-HPLC mobile phase additives by Yan Tang; Ailing Sun; Renmin Liu; Yongqing Zhang (pp. 148-154).

Display Omitted► ILs is used as the mobile phase additives to determine fangchinoline and tetrandrine. ► Effects of alkylgroup, counterion, concentrations of IL and pH were investigated. ► The mechanism of the separation with ILs as the mobile phase additives was discussed.A reversed phase high performance liquid chromatography (RP-HPLC) method for simultaneous determination of fangchinoline (FAN) and tetrandrine (TET) in Stephania tetrandra S. Moore was established by using 1-hexyl-3-methylimidazolium tetrafluoroborate as the mobile phase additives in this paper. Four types of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) were used as additives of the mobile phase to separate FAN and TET by RP-HPLC. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of IL and the pH of the mobile phase, which influenced the chromatographic behaviors of FAN and TET, were investigated in detail. The linearity, sensitivity, accuracy and repeatability of the proposed method were also investigated. The probable mechanism of the separation with ILs as the mobile phase additives was explored and discussed.

Keywords: Ionic liquids; Mobile phase additives; Stephania tetrandra S. Moore; Reversed phase high performance liquid chromatography

Molecularly imprinted nano particles combined with miniaturized homogenous liquid–liquid extraction for the selective extraction of loratadine in plasma and urine samples followed by high performance liquid chromatography-photo diode array detection by H. Ebrahimzadeh; K. Molaei; A.A. Asgharinezhad; N. Shekari; Z. Dehghani (pp. 155-162).

Display Omitted► Synthesis of MIP as a selective sorbent for extraction of loratadine. ► For first time MISPE combined with MHLLE was applied to preconcentrate loratadine. ► Very high selectivity and affinity to LOT Grafting with lack of matrix effect. ► The method is applicable for clinical and chemical laboratories.In this work a molecularly imprinted polymer was developed as a selective sorbent for extraction of loratadine (as a model) in complex matrices followed by miniaturized homogeneous liquid–liquid extraction (MHLLE) for the first time. The molecularly imprinted polymer (MIP) which is based on loratadine as the template was synthesized successfully by precipitation polymerization and was used as a selective sorbent. This technique was applied for preconcentration, sample preparation, and determination of loratadine using high performance liquid chromatography-photo diode array detection (HPLC-PDA). Optimization of various parameters affecting molecular imprinted solid phase extraction (MISPE), such as pH of adsorption, composition and volume of eluent, adsorption and desorption times were investigated. Besides, in the subsequent stage (MHLLE) the type and volume of extraction solvent, sodium hydroxide amount, surfactant concentration, and extraction time were investigated and optimized. Under the optimal condition, maximum enrichment capacity and Langmuir constant were 91mgg⁻¹ and 0.014Lmg⁻¹, respectively. Furthermore, enrichment factor and extraction recovery of MIP-MHLLE method were 30 and 90%, respectively. The LOD of the proposed method was 0.2μgL⁻¹ and a linear dynamic range of 1–1000μgL⁻¹ was obtained with correlation coefficient of greater than 0.998. The present method was applied for extraction and determination of loratadine in plasma and urine samples in μgL⁻¹ levels and satisfactory results were achieved (RSD <8% based on three replicate measurements).

Keywords: Molecularly imprinted polymer nanoparticles; Miniaturized homogenous liquid–liquid extraction; Precipitation polymerization; Loratadine

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Analytica Chimica Acta (v.767, #)

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Analytica Chimica Acta (v.767, #)