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Analytica Chimica Acta (v.601, #1)

Contents (pp. v-vi).

Editorial Board (pp. co1).

Isolation and counting of multiple cell types using an affinity separation device by Kelong Wang; Brandon Cometti; Dimitri Pappas (pp. 1-9).

A simple device for the separation of cells by phenotype is described. Cells are separated/isolated using capture antibodies on a glass chip. Unlike other “sandwich” type assays, the readout is performed without labels using transmission microscopy, simplifying cell enumeration. T and B lymphocytes from cell culture or whole blood were separated using antibodies for the CD4, CD19, and CD71 antigens. The separation slides were found to reproducibly bind cells by antigen expression, allowing for accurate enumeration of mixed cell samples. Inter- and intra-device variability was evaluated, and the issue of nonspecific binding is addressed. We envision that this type of cell separation technique could be used in remote settings, as sample preparation is minimal and the analysis time is rapid (20min from sample acquisition to final readout).

Keywords: Cell sorting; Affinity; Cytometry; Lymphocytes; Cell chromatography

Review: Recent applications of scanning electrochemical microscopy to the study of charge transfer kinetics by Xiaoquan Lu; Qin Wang; Xiuhui Liu (pp. 10-25).

Scanning electrochemical microscopy (SECM) has been proven to be a valuable technique for the quantitative investigation and surface analysis of a wide range of processes that occur at interfaces. In particular, there is a great deal of interest in studying the kinetics of charge transfer characteristics at the solid/liquid and liquid/liquid interface. This overview outlines recent advances and applications of SECM to the investigation of charge transfer reactions at the solid/liquid interface and liquid/liquid interface.

Keywords: Scanning electrochemical microscopy; Ultramicroelectrode; Charge transfer kinetics; Imaging

Cellular separations: A review of new challenges in analytical chemistry by Dimitri Pappas; Kelong Wang (pp. 26-35).

The ability to generate a sample of cells of a given phenotype is a prerequisite for many cellular assays. In response to this growing need, numerous methods for cell separation have been developed in recent years. This Review covers recent progress in the field of cell separations and cell chromatography. Cell separation principles—such as size and affinity capture—are discussed, as well as conventional methods such as fluorescence-activated cell sorting and magnetic sorting. Planar flow cell arrays, dielectrophoresis, field-flow methods, and column separation devices are reviewed, as well as applications of these methods to medicine and biotechnology. Cell attachment and adhesion strategies and a comparison of techniques are also presented.

Keywords: Cell separation; Cell sorting; Cell chromatography; Affinity chromatography; Cytometry

Acidic potassium permanganate as a chemiluminescence reagent—A review by Jacqui L. Adcock; Paul S. Francis; Neil W. Barnett (pp. 36-67).

A critical and comprehensive review of acidic potassium permanganate chemiluminescence is presented. This includes discussion on reaction conditions, the influence of enhancers such as polyphosphates, formaldehyde and sulfite, the relationship between analyte structure and chemiluminescence intensity, and the application of this chemistry to determine a wide variety of compounds, such as pharmaceuticals, biomolecules, antioxidants, illicit drugs, pesticides and pollutants. Previous proposals for the nature of the emitting species are re-evaluated in light of recent evidence.

Keywords: Review; Chemiluminescence; Potassium permanganate

Investigation of retention behaviour of non-steroidal anti-inflammatory drugs in high-performance liquid chromatography by using quantitative structure–retention relationships by Giuseppe Carlucci; Angelo Antonio D’Archivio; Maria Anna Maggi; Pietro Mazzeo; Fabrizio Ruggieri (pp. 68-76).

In this paper, a quantitative structure–retention relationship (QSRR) method is employed to model the retention behaviour in reversed-phase high-performance liquid chromatography of arylpropionic acid derivatives, largely used non-steroidal anti-inflammatory drugs (NSAIDs). Computed molecular descriptors and the organic modifier content in the mobile phase are associated into a comprehensive model to describe the effect of both solute structure and eluent composition on the isocratic retention of these drugs in water-acetonitrile mobile phases. Multilinear regression (MLR) combined with genetic algorithm (GA) variable selection is used to extract from a large set of computed 3D descriptors an optimal subset. Based on GA-MLR analysis, a five-dimensional QSRR model is identified. All the four selected molecular descriptors belong to the category of GEometry, Topology, and Atom-Weights AssemblY (GETAWAY) descriptors. The related multilinear model exhibits a quite good fitting and predictive performance. This model is further improved using an artificial neural network (ANN) learned by error back-propagation. Finally, the ANN-based model displays a remarkably better performance as compared with the MLR counterpart and, based on external validation, is able to predict with good accuracy the behaviour of unknown arylpropionic NSAIDs in the range of mobile phase composition of analytical interest (between 35 and 75% acetonitrile (v/v)).

Keywords: Quantitative structure–retention relationships; Artificial neural network; Reversed-phase high-performance liquid chromatography; Non-steroidal anti-inflammatory drugs; Chromatographic optimisation

Infrared spectroscopy and outer product analysis for quantification of fat, nitrogen, and moisture of cocoa powder by Anežka Veselá; António S. Barros; Andriy Synytsya; Ivonne Delgadillo; Jana Čopíková; Manuel A. Coimbra (pp. 77-86).

The combination of the near infrared (NIR) and Fourier-transform infrared (FTIR) absorbance spectra (1100–2500nm and 4000–600cm⁻¹) of 100 cocoa powder samples was used to build calibration models for the determination of the content of fat, nitrogen, and moisture. The samples that comprised the dataset had an average composition of 13.51% of fat, 3.77% nitrogen, and 3.98% moisture. The fat content ranged from 2.42 to 22.00%, the nitrogen from 0.88 to 4.48%, and moisture from 1.60 to 7.80%. For NIR, the relative root mean square error of cross-validation (RMSECV) was 7.0% ( R²=0.96) for fat, 1.7% ( R²=0.98) for nitrogen, and 5.2% ( R²=0.94) for moisture. For FTIR, the relative RMSECV was 10.4% ( R²=0.94) for fat and 3.9% ( R²=0.95) for nitrogen. However, for moisture, it was not possible to build a calibration model with suitable predictability. The combination of the NIR and FTIR domains (data fusion) by outer product analysis PLS1 allowed to predict these parameters and to characterise frequencies in one domain based on the information of the other domain. This work allows to conclude that the second derivative of NIR is the recommended procedure to quantify fat, nitrogen, and moisture content in cocoa powders by infrared spectroscopy.

Keywords: Cocoa powder; Infrared spectroscopy; Near infrared; Fourier-transform infrared; Fat; Nitrogen; Moisture; Outer product-principal component transform-partial least squares regression

Improving the chemiluminescence-based determination of sulphide in complex environmental samples by using a new, automated multi-syringe flow injection analysis system coupled to a gas diffusion unit by Fernando Maya; José Manuel Estela; Víctor Cerdà (pp. 87-94).

A new, completely automated multi-syringe flow injection analysis (MSFIA) system coupled to a gas diffusion unit (GDU) was used for the chemiluminescence (CL)-based determination of sulphide ion in various types of environmental matrices with a high sensitivity and selectivity, and the need for no manual sample pretreatment. Sulphide ions are transferred as H₂S from the donor channel of the GDU to its acceptor channel (AC) through a hydrophobic membrane inserted between the two streams. The solution held in AC replaces the initial sample matrix, which may contain a wide variety of interferents, with one suitable for the CL determination of the analyte. Once sulphide ions have been isolated from the sample matrix, they are determined by their catalytic action on the luminol/H₂O₂ chemiluminescent reaction system. The influence of various chemical and hydrodynamic variables is discussed and the performance of the proposed system compared with that of existing flow systems for the same purpose. Under the operating conditions used, the proposed method features a linear working range of 0.02–2mgL⁻¹, a limit of detection (3 σ_blank) of 0.003mgL⁻¹, a throughput of 20samplesh⁻¹ and a coefficient of variation of 2.4% ( n=10) for a 1mgL⁻¹ sulphide concentration. The method was used to determine sulphide in leachates and various types of water samples.

Keywords: Multi-syringe flow injection analysis; Gas diffusion; Chemiluminescence detection; Luminol; Sulphide; Environmental samples

The determination of hydrogen peroxide generated from cigarette smoke with an ultrasensitive and highly selective chemiluminescence method by Yufei Hu; Zhujun Zhang; Chunyan Yang (pp. 95-100).

Monitoring hydrogen peroxide (H₂O₂) in aqueous cigarette smoke condensate (CSC) is helpful for interpreting the relationship between cigarette smoke and oxidative stress, inflammation and disease. It is also significative for elucidating the pathogenic effects of CSC. In this paper, a novel flow-injection chemiluminescence (FI-CL) method was well established for determination of H₂O₂ in the complex sample CSC which did not need pretreatment. The sensitive and selective method is based on the CL reaction of luminol with low concentration (10⁻⁷molL⁻¹) and H₂O₂ at low concentration level (<10⁻⁸molL⁻¹) in an alkaline medium catalyzed by a complex K₅[Cu(HIO₆)₂] (DPC), which has proved no interference of other metal ions or horseradish peroxidase (HRP). The proposed method had been used to determine trace amount of H₂O₂ with a limit of detection (3 σ) of 4.1×10⁻¹¹molL⁻¹, which enables minimal amount of sample for analysis. A satisfactory result has been gained for the determination of H₂O₂ in CSC sample by use of the proposed method. The concentration of H₂O₂ in two reference cigarette (84cm, Longfeng) smoke condensate have been determined at 4–6μmolL⁻¹ level.

Keywords: Hydrogen peroxide; Chemiluminescence; K; ₅; [Cu(HIO; ₆; ); ₂; ]; Cigarette smoke condensate

Resonance Rayleigh scattering spectra for studying the interaction of anthracycline antineoplastic antibiotics with some anionic surfactants and their analytical applications by Shaopu Liu; Fen Wang; Zhongfang Liu; Xiaoli Hu; Aoer Yi; Hui Duan (pp. 101-107).

In pH 5.8 acidic medium, the anionic surfactants such as sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) or sodium dodecyl sulfonate (SLS) can react with anthracycline antibiotics such as epirubicin (EPI), daunorubicin (DNR) or mitoxantrone (MXT) to form ion-association complexes, which lead to a great enhancement of resonance Rayleigh scattering (RRS) intensity and appearances of new RRS spectra. The maximum RRS peaks are situated at 313nm for SDS–DNR and SDS–EPI system, 296nm for SDS–MXT system. The linear ranges and detection limits for EPI, DNR and MXT are 0.26–20.0, 0.25–20.0, 0.14–10.0 and 0.074, 0.078, 0.042μgmL⁻¹, respectively. In this paper, the characteristics of the absorption, fluorescence and RRS spectra of the reaction products are studied as well as the optimum reaction conditions and analytical chemistry properties. A sensitive, simple and rapid RRS method for the determination of anthracycline anticancer antibiotics has been developed.

Keywords: Anthracycline antibiotics; Anionic surfactants; Resonance Rayleigh scattering

Naked eye sensor on polyvinyl chloride platform of chromo-ionophore molecular assemblies: A smart way for the colorimetric sensing of toxic metal ions by Deivasigamani Prabhakaran; Hiroshi Nanjo; Hideyuki Matsunaga (pp. 108-117).

We demonstrate the possibility of fabricating a simple, naked eye colorimetric sensor miniature, using chromo-ionophore molecular assemblies anchored on polyvinyl chloride (PVC) surface. The ion-sensing probe (4- n-dodecyl-6-(2-thiazolylazo)-resorcinol) provides a better efficiency with PVC platform in developing a series of colour transitions, while targeting trace levels of Cd²⁺, Pb²⁺ and Hg²⁺. The physical properties of the film sensor are controlled by measuring the probe isotherm plot. The surface morphology and molecular composition of the solid-state optical sensor are characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The changes in sensor's optical intensity and its response time for the target analytes are followed by absorption spectroscopy. High speed of response ( t≤5min) and confidence in determination of analytes from chemically complex matrices has been achieved, using simulated synthetic mixtures and spiked real environmental samples, with a relative standard deviation of <3.9%. The proposed method offers consistent data reproducibility and reliability, with a detection limit of 0.031, 0.025 and 0.034μM, for Cd²⁺, Pb²⁺ and Hg²⁺ ions, respectively. The sensor strips are reversible and reusable without any change in the sensing efficiency, up to four cycles. The signal response observed with the proposed method is consistent between sensors, and also are stable over time.

Keywords: Optical sensor; Langmuir–Blodgett film; Toxicity; Environmental analysis; Pollutants; Colorimetry

Liquid chromatographic analysis of phosphoamino acids at femtomole level using chemical derivatization with N-hydroxysuccinimidyl fluorescein- O-acetate by Ying-Hua Deng; Rong-Jun Li; Hua-Shan Zhang; Xiao-Lan Du; Hong Wang (pp. 118-124).

Phosphorylation of amino acid residues in proteins plays a major role in biological systems. In this paper, a reversed-phase high performance liquid chromatographic (HPLC) method based on chemical derivatization has been described for the separation and quantification of phosphoamino acids at femtomole level, using fluorimetric detection (FLD). The protocol involved pre-column derivatization of phosphoamino acids with N-hydroxysuccinimidyl fluorescein- O-acetate (SIFA) and subsequent separation on ZORBAX Eclipse XDB-C8 column. Several experimental factors that influenced derivatization and separation were carefully investigated. The derivatization was performed at 40°C for 40min in borate buffer (pH 8.5). Under the optimum conditions, phosphoserine (P-Ser), phosphothreonine (P-Thr) and phosphotyrosine (P-Tyr) were satisfactorily separated in 8min. The detection limits (signal-to-noise ratio=3) for the phosphoamino acids could reach 10–20fmol, which was the lowest value reported for HPLC methods and comparable to those obtained by capillary electrophoresis with laser-induced fluorescence (CE-LIF) detection methods. The proposed method has been validated and used to characterize the phosphoamino acids in the hydrolyzed phosphorylated protein samples. The results clearly demonstrated the potential of this technique to study phosphoamino acids as well as provided a new analytical methodology that should be applicable to the study of phosphorylation of protein in biological system.

Keywords: Phosphoamino acids; Derivatization; N; -Hydroxysuccinimidyl fluorescein-; O; -acetate; High performance liquid chromatography

Determination of alkali and alkaline earth elements along with nitrogen in uranium based nuclear fuel materials by ion chromatography (IC) by Poonam Verma; Karanam L. Ramakumar (pp. 125-129).

An accurate and sensitive ion chromatographic (IC) method with suppressed conductivity detection is described for determination of traces of Na, K, Mg and Ca along with nitrogen in uranium based materials. The method involves matrix separation after sample dissolution by hydrolyzing and filtering off the polyvalent cations. Transition elements interfering in the determination of Ca were removed by cation exchange cartridge containing iminodiacetate resin. Detection limits were between 2 and 6μgL⁻¹ and overall precision were better than ±5%. Recovery of spiked cations was in range from 96% to 104%. Results obtained were in good agreement with other methods.

Keywords: Uranium based nuclear samples; Ion chromatography; Alkali and alkaline earth elements; Interferences; Iminodiacetate resin

Chiral selectors for enantioresolution and quantitation of the antidepressant drug fluoxetine in pharmaceutical formulations by¹⁹F NMR spectroscopic method by Mojtaba Shamsipur; Leila Shafiee Dastjerdi; Soheila Haghgoo; Dominique Armspach; Dominique Matt; Hassan Y. Aboul-Enein (pp. 130-138).

¹⁹F NMR spectroscopy was applied to the quantitative determination of fluoxetine enantiomers using different chiral recognition agents in pharmaceutical formulations. Several parameters affecting the enantioresolution including the type and concentration of chiral selector, concentration of fluoxetine and temperature were studied. The chiral selectors investigated are the cyclic oligosaccharides α-, β- and γ-cyclodextrin and a diamino derivative of methylated α-cyclodextrin (DAM-α-CD), linear polysaccharides (maltodextrin with dextrose equivalents of 4.0–7.0, 13.0–17.0 and 16.5–19.5) and the macrocyclic antibiotic vancomycin. Among the chiral selectors used, DAM-α-CD turned out to give the best resolution of the¹⁹F NMR signals of ( R)- and ( S)-fluoxetine. The calibration curve was linear for ( R)- and ( S)-fluoxetine over the range 0.10–1.35mgmL⁻¹, the detection limits (S/N=3) being 5.9 and 7.5μgmL⁻¹ for the pure solutions of ( R)- and ( S)-fluoxetine, respectively. The recovery studies performed on pharmaceutical samples ranged from about 90 to 110% with relative standard deviations of <8%. The results showed that the proposed method is rapid, precise and accurate. Applying statistical Student's t-test revealed insignificant difference between the real and measured contents at the 95% confidence level.

Keywords: Fluoxetine; ¹⁹; F nuclear magnetic resonance analyses; Enantioseparation; Chiral selectors; Pharmaceutical formulations

Erratum to “Voltammetric characterization of metal sulfide particles and nanoparticles in model solutions and natural waters” [Anal. Chim. Acta 594 (2007) 44–51] by Elvira Bura-Nakić; Damir Krznarić; Darija Jurašin; George R. Helz; Irena Ciglenečki (pp. 139-139).

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Analytica Chimica Acta (v.601, #1)