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Analytica Chimica Acta (v.649, #2)

Editorial Board (pp. i).

Application of chemometric assisted dispersive liquid–liquid microextraction to the determination of personal care products in natural waters by Aikaterini N. Panagiotou; Vasilios A. Sakkas; Triantafyllos A. Albanis (pp. 135-140).

A rapid and simple method for the determination of two phthalates and five polycyclic musks in water samples using dispersive liquid–liquid microextraction (DLLME) mated to chemometrics and coupled to GC–MS was developed. Volume of extraction (CCl₄) and disperser solvent (MeOH), pH, ionic strength, extraction time, centrifugation time as well as centrifugation speed were optimized in a 2^7–4 Plackett–Burman design. The obtained significant factors were optimized by using a central composite design (CCD) and the quadratic model between the dependent and the independent variables was built. The optimum experimental conditions of the proposed method were: 250μL carbon tetrachloride, 0.62mL methanol, 7.5min centrifugation time, natural pH containing 0% (w/v) NaCl, while keeping centrifugation speed fixed at 4000rpm.The calculated calibration curves gave high-level linearity for all target analytes with correlation coefficients ranging between 0.9970 and 0.9992. The repeatability and reproducibility of the proposed method, expressed as relative standard deviation, varied between 2.6% to 9.7% and 5.7% to 12.2%, respectively. The obtained LOD values were in the range of 8–63ngL⁻¹.

Keywords: Experimental design; Response surface methodology; Phthalic acid esters; Polycyclic musks

Review of cell and particle trapping in microfluidic systems by J. Nilsson; M. Evander; B. Hammarström; T. Laurell (pp. 141-157).

The ability to obtain ideal conditions for well-defined chemical microenvironments and controlled temporal chemical and/or thermal variations holds promise of high-resolution cell response studies, cell–cell interactions or e.g. proliferation conditions for stem cells. It is a major motivation for the rapid increase of lab-on-a-chip based cell biology research. In view of this, new chip-integrated technologies are at an increasing rate being presented to the research community as potential tools to offer spatial control and manipulation of cells in microfluidic systems. This is becoming a key area of interest in the emerging lab-on-a-chip based cell biology research field. This review focuses on the different technical approaches presented to enable trapping of particles and cells in microfluidic system.

Keywords: Cell handling; Cell trapping; Microfluidics; Lab-on-a-chip

An overview of analytical methodologies for the determination of antibiotics in environmental waters by Marcela Seifrtová; Lucie Nováková; Celeste Lino; Angelina Pena; Petr Solich (pp. 158-179).

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.

Keywords: Abbreviations; AcAc; acetic acid; ACN; acetonitrile; AmAc; ammonium acetate; APCI; atmospheric pressure chemical ionization; AZI; azithromycin; CF; concentration factor; CIN; cinoxacin; CIPRO; ciprofloxacin; CLAR; clarithromycin; CLIN; clindamycin; CTC; chlortetracycline; CZE; capillary zone electrophoresis; DAD; diode-array detector; DAN; danofloxacin; DEME; demeclocycline; DIF; difloxacin; DOXY; doxycycline; ENO; enoxacin; ENRO; enrofloxacin; ERY; erythromycin; ESI; electrospray ionization; FAc; formic acid; FD; fluorescence detection; FLE; fleroxacin; FLU; flumequine; FQs; fluoroquinolone antibiotics; GAT; gatifloxacin; HPLC; high-performance liquid chromatography; IS; internal standard; LC; liquid chromatography; LEV; levofloxacin; LLE; liquid–liquid extraction; LOD; limit of detection; LOME; lomefloxacin; LOQ; limit of quantification; MAR; marbofloxacin; MCX; mixed-cation exchange; MECLO; meclocycline; MeOH; methanol; MINO; minocycline; MLs; macrolide antibiotics; MOXI; moxifloxacin; MS; mass spectrometry; MS/MS; tandem mass spectrometry; NAL; nalidixic acid; NOR; norfloxacin; OFLO; ofloxacin; OXO; oxolinic acid; OXY; oxytetracycline; PEFLO; pefloxacin; PIP; pipemidic acid; Qs; quinolone antibiotics; RIA; radioimmunoassay; ROXI; roxithromycin; SAD; sulfanilamide; SARA; sarafloxacin; SAs; sulfonamide antibiotics; SAX; strong-anion exchange; SCP; sulfachloropyridazine; SCT; sulfacetamide; SDM; sulfadimidine; SDT; sulfadimethoxine; SDX; sulfadoxine; SDZ; sulfadiazine; SGN; sulfaguanidine; SIM; selected ion monitoring; SM; sulfameter; SMD; sulfamethoxydiazine; SML; sulfamoxole; SMM; sulfamonomethoxine; SMO; sulfamethoxine; SMP; sulfamethoxypyrazine; SMR; sulfamerazine; SMT; sulfamethizole; SMX; sulfamethoxazole; SMZ; sulfamethazine; SNT; sulfanitran; SPAR; sparfloxacin; SPE; solid-phase extraction; SPIR; spiramycin; SPME; solid-phase microextraction; SPY; sulfapyridine; SQX; sulfaquinoxaline; SRM; selected reaction monitoring; SSM; sulfisomidin; SSX; sulfisoxazole; SSZ; sulfasalazine; STZ; sulfathiazole; TCs; tetracycline antibiotics; TET; tetracycline; TLS; tylosin; TMP; trimethoprim; TOS; tosufloxacin; UHPLC; ultra-high-performance liquid chromatography; UV; ultraviolet; VAN; vancomycin; WCX; weak-cation exchange; WWTPs; wastewater treatment plantsFluoroquinolone antibiotics; Tetracycline antibiotics; Sulfonamide antibiotics; Macrolide antibiotics; Wastewaters; Liquid chromatography–tandem mass spectrometry; SPE

Microfluidics with MALDI analysis for proteomics—A review by Jeonghoon Lee; Steven A. Soper; Kermit K. Murray (pp. 180-190).

Various microfluidic devices have been developed for proteomic analyses and many of these have been designed specifically for mass spectrometry detection. In this review, we present an overview of chip fabrication, microfluidic components, and the interfacing of these devices to matrix-assisted laser desorption ionization (MALDI) mass spectrometry. These devices can be directly coupled to the mass spectrometer for on-line analysis in real-time, or samples can be analyzed on-chip or deposited onto targets for off-line readout. Several approaches for combining microfluidic devices with analytical functions such as sample cleanup, digestion, and separations with MALDI mass spectrometry are discussed.

Keywords: Microfluidics; Proteomics; MALDI; Microchip analytical procedure

Speciation of antimony in airborne particulate matter using ultrasound probe fast extraction and analysis by HPLC-HG-AFS by A. Bellido-Martín; J.L. Gómez-Ariza; P. Smichowsky; D. Sánchez-Rodas (pp. 191-195).

A fast extraction procedure has been developed for Sb(III) and Sb(V) oxoanions speciation in airborne particulate matter samples. Different extraction media (diammonium tartrate, hidroxilammonium clorhidrate, citric acid+ascorbic acid, phosphoric acid and citrate solutions) were tried, with assistance of an ultrasonic probe. The operation power and time of extraction were also optimized. The higher extraction recoveries were obtained with a 100mmolL⁻¹ hidroxilammonium clorhidrate aqueous solution assisted by the ultrasound probe operated at 50W during 3min. The extracts were analyzed by HPLC-HG-AFS. The chromatographic separation of Sb(III) and Sb(V) was also optimized using diammonium tartrate and phthalic acid as mobile phases. The separation of both Sb species was performed in less than 3min under isocratic conditions, using a 200mmolL⁻¹ diammonium tartrate solution. The proposed extraction procedure and the HPLC-HG-AFS instrumental coupling have been successfully applied to airborne particulate matter samples, with high Sb content, collected in heavy traffic streets from Buenos Aires (Argentina). The results showed the presence of both Sb species at similar concentrations in the ngm⁻³ level. The extraction yield was higher than 90% for all the analyzed samples.

Keywords: Antimony; Speciation; Airborne; Particulate matter; Ultrasound probe; High Performance Liquid Chromatography-Hydride Generation-Atomic Fluorescence Spectrometry

High-sensitivity determination of lead and cadmium based on the Nafion-graphene composite film by Jing Li; Shaojun Guo; Yueming Zhai; Erkang Wang (pp. 196-201).

Graphene nanosheets, dispersed in Nafion (Nafion-G) solution, were used in combination with in situ plated bismuth film electrode for fabricating the enhanced electrochemical sensing platform to determine the lead (Pb²⁺) and cadmium (Cd²⁺) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the composite film modified glassy carbon electrode were investigated. It is found that the prepared Nafion-G composite film not only exhibited improved sensitivity for the metal ion detections, but also alleviated the interferences due to the synergistic effect of graphene nanosheets and Nafion. The linear calibration curves ranged from 0.5μgL⁻¹ to 50μgL⁻¹ for Pb²⁺ and 1.5μgL⁻¹ to 30μgL⁻¹ for Cd²⁺, respectively. The detection limits (S/N=3) were estimated to be around 0.02μgL⁻¹ for Pb²⁺ and Cd²⁺. The practical application of the proposed method was verified in the water sample determination.

Keywords: Nafion-graphene; Nanosheets; Lead; Cadmium; Bismuth

A new sample preparation method compatible with capillary electrophoresis and laser-induced fluorescence for improving detection of low levels of β-lactoglobulin in infant foods by Cristina Pelaez-Lorenzo; Jose Carlos Diez-Masa; Isabel Vasallo; Mercedes de Frutos (pp. 202-210).

β-Lactoglobulin (βLG) is the main allergenic protein in cow's milk and can cause allergy even when present at very low concentration. The aim of this work is to develop an innovative sample preparation method fully compatible with capillary electrophoresis and laser-induced fluorescence detection for improving the sensitivity when analyzing βLG. Different types of baby food were on purpose contaminated with diverse dairy desserts and submitted to thermal treatment to simulate potential contamination at production. Sample preparation prior to CE analysis was performed by the classical extraction method and by the innovative one, and the results were compared. Analysis was performed by capillary electrophoresis with laser-induced fluorescence detection. The innovative method permitted to detect contaminations as low as 1 part of yoghurt in 10000 parts of baby food.

Keywords: Capillary electrophoresis; Laser-induced fluorescence detection; Extraction method; β-Lactoglobulin; Allergen; Baby food

A novel microextraction technique based on 1-hexylpyridinium hexafluorophosphate ionic liquid for the preconcentration of zinc in water and milk samples by H. Abdolmohammad-Zadeh; G.H. Sadeghi (pp. 211-217).

A simple dispersive liquid–liquid microextraction methodology based on the application of 1-hexylpyridinium hexafluorophosphate [HPy][PF₆] ionic liquid (IL) as an extractant solvent was proposed for the preconcentration of trace levels of zinc as a prior step to determination by flame atomic absorption spectrometry (FAAS). Zinc was complexed with 8-hydroxyquinoline (oxine) and extracted into ionic liquid. Some effective factors that influence the microextraction efficiency such as pH, oxine concentration, amount of IL, ionic strength, temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3s) and the enhancement factor were 0.22μgL⁻¹ and 71, respectively. The relative standard deviation (RSD) for six replicate determinations of 13μgL⁻¹ Zn was 1.92%. In order to validate the developed method, a certified reference material (NIST SRM 1549) was analyzed and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the trace determination of zinc in water and milk samples.

Keywords: Microextraction; Ionic liquid; Preconcentration; Zinc; Water; Milk

Determination of organochlorine pesticides in water samples by dispersive liquid–liquid microextraction coupled to gas chromatography–mass spectrometry by Carol Cortada; Lorena Vidal; Raul Pastor; Noemi Santiago; Antonio Canals (pp. 218-221).

A rapid and simple dispersive liquid–liquid microextraction (DLLME) has been developed to preconcentrate eighteen organochlorine pesticides (OCPs) from water samples prior to analysis by gas chromatography–mass spectrometry (GC–MS). The studied variables were extraction solvent type and volume, disperser solvent type and volume, aqueous sample volume and temperature. The optimum experimental conditions of the proposed DLLME method were: a mixture of 10μL tetrachloroethylene (extraction solvent) and 1mL acetone (disperser solvent) exposed for 30s to 10mL of the aqueous sample at room temperature (20°C). Centrifugation of cloudy solution was carried out at 2300rpm for 3min to allow phases separation. Finally, 2μL of extractant was recovered and injected into the GC–MS instrument. Under the optimum conditions, the enrichment factors ranged between 46 and 316. The calculated calibration curves gave a high-level linearity for all target analytes with correlation coefficients ranging between 0.9967 and 0.9999. The repeatability of the proposed method, expressed as relative standard deviation, varied between 5% and 15% ( n=8), and the detection limits were in the range of 1–25ngL⁻¹. The LOD values obtained are able to detect these OCPs in aqueous matrices as required by EPA methods 525.2 and 625. Analysis of spiked real water samples revealed that the matrix had no effect on extraction for river, surface and tap waters; however, urban wastewater sample shown a little effect for five out of eighteen analytes.

Keywords: Organochlorine pesticides; Dispersive liquid–liquid microextraction; Sample preparation; Water samples analysis

Improved derivatization technique for gas chromatography–mass spectrometry determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2( 5H)-furanone in drinking water by Cariton Kubwabo; Brian Stewart; Suzanne A. Gauthier; Barbara R. Gauthier (pp. 222-229).

The quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2( 5H)-furanone (Mutagen X or MX) in drinking water is difficult due to the low concentration of MX in drinking water, its high sensitivity to pH change, and matrix effects that interfere with the derivatization and analysis. Typically, the quantification of MX involves derivatization by methylation. We present a one-step derivatization procedure for MX using N-methyl-bis-trifluoroacetamide (MBTFA) and analysis by ion trap GC/MS/MS. The new method resulted in a significant reduction in analysis time, and improved detection limits. The abundant and selective ions in the mass spectrum of the trifluoroacylated MX (trifluoroacetic acid-4-chloro-3-dichloromethyl-5-oxo-2-hydro-furan-2-yl ester) allowed for a clear identification and quantification of the compound, with a method detection limit of 7.7ngL⁻¹, and a limit of quantitation of 24.4ngL⁻¹. The trifluoroacylated MX was shown to be stable for 30 days in an excess of the derivatization reagent. The new method was applied for the determination of MX in several drinking water samples, with a concentration range from not-detected to 517ngL⁻¹; these values are comparable to those obtained in previous studies. The development of this new simplified analytical method for MX is an important step forward in the field of disinfection by-product (DBP) research, particularly in light of the recent scientific recognition of halogenated furanones as emerging drinking water contaminants. Increased analytical ability may well be a decisive factor in the monitoring of these disinfection by-products.

Keywords: Mutagen X; N; -methyl-bis-trifluoroacetamide; Drinking water; Solid phase extraction; Derivatization; Tandem mass spectrometry

A new matrix for analyzing low molecular mass compounds and its application for determination of carcinogenic areca alkaloids by matrix-assisted laser desorption ionization time-of-flight mass spectrometry by Chia-Hsien Feng; Chi-Yu Lu (pp. 230-235).

Arecoline is the main alkaloid present in the areca nut (or betel nut) and it has central nervous system effects. Its pharmacological activities induce the constriction of the bronchial smooth muscles, and stimulation of the lacrimal and intestinal glands. Chewing areca nut is harmful to health because this habit may increase the risk of the development of oral cancer. In this study, a fast method was provided for the determination of areca alkaloids by matrix-assisted laser desorption ionization (MALDI) mass spectrometer with a time-of-flight (TOF) analyzer. Traditionally the MALDI-TOF method was not suitable for the analysis of small molecular weight ( m/ z<600) compounds because of the high background of the matrix. In this study, a new matrix was utilized to decrease the background interference effectively. After simple sample preparation, 1μL sample supernatant was mixed with 1μL matrix and then deposited on the target plate. This new matrix was also used to test the MALDI imaging experiment. Application of this MALDI-TOF method for trace analysis of arecoline by this new matrix in human plasma at sub μM level proved workable.

Keywords: Carcinogenic; Alkaloid; Arecoline; Areca nut; Small molecular weight; Matrix-assisted laser desorption ionization Imaging

Molecularly imprinted conducting polymer based electrochemical sensor for detection of atrazine by Elodie Pardieu; Helene Cheap; Christophe Vedrine; Mathieu Lazerges; Youssef Lattach; Francis Garnier; Samy Remita; Christine Pernelle (pp. 236-245).

An original electrochemical sensor based on molecularly imprinted conducting polymer (MICP) is developed, which enables the recognition of a small pesticide target molecule, atrazine. The conjugated MICP, poly(3,4-ethylenedioxythiophene-co-thiophene-acetic acid), has been electrochemically synthesized onto a platinum electrode following two steps: (i) polymerization of comonomers in the presence of atrazine, already associated to the acetic acid substituent through hydrogen bonding, and (ii) removal of atrazine from the resulting polymer, which leaves the acetic acid substituents open for association with atrazine. The obtained sensing MICP is highly specific towards newly added atrazine and the recognition can be quantitatively analyzed by the variation of the cyclic voltammogram of MICP. The developed sensor shows remarkable properties: selectivity towards triazinic family, large range of detection (10⁻⁹molL⁻¹ to 1.5×10⁻²molL⁻¹ in atrazine) and low detection threshold (10⁻⁷molL⁻¹).

Keywords: Electrochemical sensors; Molecularly imprinted polymers; Conducting polymers; Atrazine

Enzyme assays with boronic acid appended bipyridinium salts by Boaz Vilozny; Alexander Schiller; Ritchie A. Wessling; Bakthan Singaram (pp. 246-251).

In-vitro fluorescent enzyme assays have been developed for sucrose phosphorylase (SPO) and phosphoglucomutase (PGM). These assays make use of a selective carbohydrate sensing system that detects the unlabeled enzymatic products fructose and glucose-6-phosphate. The system comprises 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt as the reporter unit and boronic acid appended viologens as selective receptors with working ranges from 70μM to 1.0mM for fructose (SPO) and 190μM to 2.0mM for glucose-6-phosphate (PGM). The change in fluorescence can be converted into product concentration, allowing initial reaction velocities and Michaelis–Menten kinetics to be calculated. The assays are also carried out in multiwell plate formats, making them suitable for high-throughput screening of enzyme inhibitors. Rapid PGM inhibition screening is demonstrated with EDTA and LiCl. The PGM assay can also be used for enzyme quantification with a detection limit of 50ngmL⁻¹.

Keywords: Boronic acid; Saccharide; Enzyme assay; Fluorescence; Viologen

1-(2-Formamidoethyl)-3-phenylurea functionalized activated carbon for selective solid-phase extraction and preconcentration of metal ions by Zhifeng Tu; Qun He; Xijun Chang; Zheng Hu; Ru Gao; Lina Zhang; Zhenhua Li (pp. 252-257).

A novel method that utilizes 1-(2-formamidoethyl)-3-phenylurea-modified activated carbon (AC-1-(2-formamidoethyl)-3-phenylurea) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace levels of Cr(III), Cu(II), Fe(III) and Pb(II) were optimized using batch and column procedures in detail. The optimum pH value for the separation of metal ions simultaneously on the new sorbent was 4. And the adsorbed metal ions could be completely eluted by using 2.0mL 2.0molL⁻¹ HCl solution. Common coexisting ions did not interfere with the separation and determination of target metal ions. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.8, 39.9, 77.8 and 17.3mgg⁻¹ for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The detection limits of the method were found to be 0.15, 0.41, 0.27 and 0.36ngmL⁻¹ for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The relative standard deviation (RSD) of the method was lower than 4.0% ( n=8). The method was successfully applied for the preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) in natural and certified samples with satisfactory results.

Keywords: Activated carbon; 1-(2-Formamidoethyl)-3-phenylurea; Metal ions; Solid-phase extraction; Inductively coupled plasma atomic emission spectrometry

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Analytica Chimica Acta (v.649, #2)