Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.638, #2)

Editorial Board (pp. i).

Microfluidic DNA amplification—A review by Yonghao Zhang; Pinar Ozdemir (pp. 115-125).

The application of microfluidic devices for DNA amplification has recently been extensively studied. Here, we review the important development of microfluidic polymerase chain reaction (PCR) devices and discuss the underlying physical principles for the optimal design and operation of the device. In particular, we focus on continuous-flow microfluidic PCR on-chip, which can be readily implemented as an integrated function of a micro-total-analysis system. To overcome sample carryover contamination and surface adsorption associated with microfluidic PCR, microdroplet technology has recently been utilized to perform PCR in droplets, which can eliminate the synthesis of short chimeric products, shorten thermal-cycling time, and offers great potential for single DNA molecule and single-cell amplification. The work on chip-based PCR in droplets is highlighted.

Keywords: PCR; Microfluidics; DNA amplification; Microdroplet technology; Lab-on-a-chip; μTAS

Evaluation of the odd–even effect in limits of detection for electron microprobe analysis of natural minerals by Surendra P. Verma; Kailasa Pandarinath; Fernando Velasco-Tapia; Rodolfo Rodríguez-Ríos (pp. 126-132).

Limit of detection (LOD), being a fundamental quality parameter for analytical techniques, has been recently investigated and a systematic behavior has been observed for most odd–even element pairs for many techniques. However, to the best of our knowledge very few LOD data are available in published literature for electron microprobe analysis; these consist of three papers, two being on rare-earth elements and the third covering a large number of elements of atomic number between 21 and 92. These data confirm the systematic behavior of LODs for many odd–even pairs. To initiate to full this gap, we determined LODs for several major rock-forming chemical elements from Na to Fe with atomic numbers between 11 and 26, during the microprobe analysis of common minerals (olivine, plagioclase, pyroxene, amphibole, quartz, and opaques) in volcanic rocks. The odd–even effect of nuclear stability seems to be present in LOD data for most odd–even pairs investigated. Nevertheless, the experimental strategy concerning the reference materials, calibration procedure, and blank measurements, should be substantially modified to better evaluate the systematic behavior of LOD values in microprobe analysis.

Keywords: Electron microprobe; Detection limit; Odd–even; Minerals

Electrochemical study and flow injection analysis of paracetamol in pharmaceutical formulations based on screen-printed electrodes and carbon nanotubes by Pablo Fanjul-Bolado; Pedro José Lamas-Ardisana; David Hernández-Santos; Agustín Costa-García (pp. 133-138).

Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical–chemical oxidation mechanism of paracetamol at pH 2.0.Quantitative analysis of paracetamol by using its oxidation process (in a Britton–Robinson buffer solution pH 10.0) at +0.20V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5×10⁻⁶M to 1×10⁻³M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1×10⁻⁷M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10⁻⁵M acetaminophen and do not present any memory effect.Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products.

Keywords: Acetaminophen; Electrochemical detection; Screen-printed carbon electrode; Flow injection analysis

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography–fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples by Qiuhua Wu; Yunpeng Li; Chun Wang; Zhimei Liu; Xiaohuan Zang; Xin Zhou; Zhi Wang (pp. 139-145).

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid–liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1molL⁻¹ HCl. Then, the pH of the extract was adjusted to 7.0 with 2molL⁻¹ NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl₃) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5–800ngmL⁻¹ for water sample analysis, and 10–1000ngg⁻¹ for soil samples, respectively. The correlation coefficients ( r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5–1.0ngmL⁻¹ for water samples, and 1.0–1.6ngg⁻¹ for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% ( n=5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20ngmL⁻¹ were 84.0–94.0% and 86.0–92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100ngg⁻¹ varied between 82.0 and 93.4%.

Keywords: Dispersive liquid–liquid microextraction; Benzimidazole fungicides; High performance liquid chromatography; Water samples; Soil samples

Synthesis and application of a highly efficient tetraester calix[4]arene based resin for the removal of Pb²⁺ from aqueous environment by Imam Bakhsh Solangi; Shahabuddin Memon; M.I. Bhanger (pp. 146-153).

The present study describes the Pb²⁺ sorption potential of newly synthesized tetraester calix[4]arene (TC4) based resin from aqueous media. The TC4 resin was synthesized through diazotization reaction of TC4 with Amberlite XAD-4 in the presence of sodium nitrite in acidic medium. The TC4 resin was characterized by using different analytical techniques such as FT-IR, elemental analysis and scanning electron microscopy (SEM). The Pb²⁺ removal ability of the resin from the aqueous environment has been evaluated by both batch adsorption as well as column studies. The experiments have been conducted involving the determination of effect of pH, adsorbate concentration, adsorbent dosage, contact time and temperature. Moreover, on the basis of kinetic studies, the pseudo-first-order and pseudo-second-order adsorption kinetics were calculated. The thermodynamic parameters of lead adsorption were also calculated. Equation isotherms such as Langmuir (L), Freundlich (F), and Dubinin–Radushkevich (D–R) were successfully used to model the experimental data. From the D–R isotherm parameters, it was considered that the uptake of Pb²⁺ by TC4 resin is ion exchange mechanism. From the results it has been found that the TC4 resin is a versatile adsorbent for the removal of Pb²⁺ from the aqueous environment. The study also confers its impact on human health, reinstate of polluted sites and other fields of material science.

Keywords: Calix[4]arene; Amberlite resin; Lead(II) adsorption; Solid phase extraction

Multivariate optimization of molecularly imprinted polymer solid-phase extraction applied to parathion determination in different water samples by Taher Alizadeh; Mohammad Reza Ganjali; Parviz Nourozi; Mashaalah Zare (pp. 154-161).

In this work a parathion selective molecularly imprinted polymer was synthesized and applied as a high selective adsorber material for parathion extraction and determination in aqueous samples. The method was based on the sorption of parathion in the MIP according to simple batch procedure, followed by desorption by using methanol and measurement with square wave voltammetry. Plackett–Burman and Box–Behnken designs were used for optimizing the solid-phase extraction, in order to enhance the recovery percent and improve the pre-concentration factor. By using the screening design, the effect of six various factors on the extraction recovery was investigated. These factors were: pH, stirring rate (rpm), sample volume ( V₁), eluent volume ( V₂), organic solvent content of the sample (org%) and extraction time ( t). The response surface design was carried out considering three main factors of ( V₂), ( V₁) and (org%) which were found to be main effects. The mathematical model for the recovery percent was obtained as a function of the mentioned main effects. Finally the main effects were adjusted according to the defined desirability function. It was found that the recovery percents more than 95% could be easily obtained by using the optimized method. By using the experimental conditions, obtained in the optimization step, the method allowed parathion selective determination in the linear dynamic range of 0.20–467.4μgL⁻¹, with detection limit of 49.0ngL⁻¹ and R.S.D. of 5.7% ( n=5). Parathion content of water samples were successfully analyzed when evaluating potentialities of the developed procedure.

Keywords: Multivariate optimization; Parathion; Molecularly imprinted polymer; Water samples

Preparation of alumina-coated magnetite nanoparticle for extraction of trimethoprim from environmental water samples based on mixed hemimicelles solid-phase extraction by Lei Sun; Chuanzhou Zhang; Ligang Chen; Jun Liu; Haiyan Jin; Haoyan Xu; Lan Ding (pp. 162-168).

In this study, a new type of alumina-coated magnetite nanoparticles (Fe₃O₄/Al₂O₃ NPs) modified by the surfactant sodium dodecyl sulfate (SDS) has been successfully synthesized and applied for extraction of trimethoprim (TMP) from environmental water samples based on mixed hemimicelles solid-phase extraction (MHSPE). The coating of alumina on Fe₃O₄ NPs not only avoids the dissolving of Fe₃O₄ NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. Due to the high surface area of these new sorbents and the excellent adsorption capacity after surface modification by SDS, satisfactory concentration factor and extraction recoveries can be produced with only 0.1g Fe₃O₄/Al₂O₃ NPs. Main factors affecting the adsolubilization of TMP such as the amount of SDS, pH value, standing time, desorption solvent and maximal extraction volume were optimized. Under the selected conditions, TMP could be quantitatively extracted. The recoveries of TMP by analyzing the four spiked water samples were between 67 and 86%, and the relative standard deviation (RSD) ranged from 2 to 6%. Detection and quantification limits of the proposed method were 0.09 and 0.24μgL⁻¹, respectively. Concentration factor of 1000 was achieved using this method to extract 500mL of different environmental water samples. Compared with conventional SPE methods, the advantages of this new Fe₃O₄/Al₂O₃ NPs MHSPE method still include easy preparation and regeneration of sorbents, short times of sample pretreatment, high extraction yields, and high breakthrough volumes. It shows great analytical potential in preconcentration of organic compounds from large volume water samples.

Keywords: Alumina-coated magnetite nanoparticles; Mixed hemimicelles; Solid-phase extraction; Trimethoprim; Environmental water samples

Polyphosphate-doped polypyrrole coated on steel fiber for the solid-phase microextraction of organochlorine pesticides in water by A. Mollahosseini; E. Noroozian (pp. 169-174).

A solid-phase microextraction technique using steel fiber coated with 20μm polypyrrole (Ppy) doped with polyphosphate was developed for the GC determination of a group of organochlorine pesticides (OCPs) in water. The coating was prepared using a three-electrode electrochemical system from a 10% aqueous sodium polyphosphate solution containing 0.05M pyrrole by applying a constant potential of 1.2V for 30min. In order to obtain an adherent, smooth and stable film of polypyrrole, experimental parameters related to the coating process consisting of the type of dopant or counter-ion, deposition potential, concentration of the monomer, concentration of the counter-ion, and deposition time were optimized. The effects of various parameters on the efficiency of SPME process such as extraction time, extraction temperature, ionic strength, desorption time, and desorption temperature were also studied. The coating was highly stable and extremely adherent to the surface of the steel fiber. The method was linear for at least three orders of magnitude with correlation coefficients varying from 0.9818 to 0.9977. The accuracies found through spiking blank samples showed high recoveries between 82 and 110%. Intra- and inter-day precisions of the method were determined from mixed aqueous solutions containing 1.0ngml⁻¹ of each OCP. The intra-day precisions varied from 4.7% for heptachlor to 11.4% for methoxychlor, while the inter-day precisions varied from 6.8% for endosulfan I to 13.0% for p,p′-DDD and o,p-DDD. Limits of detection based on S/N=3 were in the range 0.015–0.66 pgml⁻¹. The proposed method was applied to monitor organochlorine pesticides in some well water samples.

Keywords: Polypyrrole; Polyphosphate; Steel; Electrochemical deposition; Solid-phase microextraction; Organochlorine pesticides

In vitro evaluation of new biocompatible coatings for solid-phase microextraction: Implications for drug analysis and in vivo sampling applications by Dajana Vuckovic; Robert Shirey; Yong Chen; Len Sidisky; Craig Aurand; Katherine Stenerson; Janusz Pawliszyn (pp. 175-185).

A new line of solid-phase microextraction (SPME) coatings suitable for use with liquid chromatography applications was recently developed to address the limitations of the currently available coatings. The proposed coatings were immobilized on the metal fiber core and consisted of a mixture of proprietary biocompatible binder and various types of coated silica (octadecyl, polar embedded and cyano) particles. The aim of this research was to perform in vitro assessment of these new SPME fibers in order to evaluate their suitability for drug analysis and in vivo SPME applications. The main parameters examined were extraction efficiency, solvent resistance, preconditioning, dependence of extraction kinetics on coating thickness, carryover, linear range and inter-fiber reproducibility. The performance of the proposed coatings was compared against commercial Carbowax-TPR (CW-TPR) coating, when applicable. The fibers were evaluated for the extraction of drugs of different classes (carbamazepine, propranolol, pseudoephedrine, ranitidine and diazepam) from plasma and urine. The analyses were performed using liquid chromatography–tandem mass spectrometry. The results show that the fibers perform very well for the extraction of biological fluids with no sample pre-treatment required and can also be used for in vivo sampling applications of flowing blood. A coating thickness of 45μm was found to be a good compromise between extraction capacity and extraction kinetics. Due to the high extraction efficiency of these coatings, pre-equilibrium SPME with very short extraction times (2min) can be employed to increase sample throughput. Inter-fiber reproducibility was ≤11% R.S.D. ( n=10) for model drugs examined in plasma, which is a significant improvement over polypyrrole coatings reported in literature, and permits single fiber use for in vivo applications.

Keywords: Solid-phase microextraction; Coatings; Drug analysis; Clinical analysis; Bioanalytical method development

On-chip type cation-exchange chromatography with ferrocene-labeled anti-hemoglobin antibody and electrochemical detector for determination of hemoglobin A_1c level by Tsuyoshi Tanaka; Kojiro Izawa; Mina Okochi; Tae-Kyu Lim; Shugo Watanabe; Manabu Harada; Tadashi Matsunaga (pp. 186-190).

An on-chip type cation-exchange chromatography system with electrochemical detection of HbA_1c, which is one of the most important diabetes marker protein, was developed using ferrocene-conjugated anti-human hemoglobin (Hb) monoclonal antibody (FcAb). The FcAb was used as an electrochemical probe for the detection of each Hb. The system contains syringe pump, on-chip type cation-exchange column consisted of PDMS and cation-exchange resin beads, and a three-electrode flow-cell system. The separation conditions of HbA_1c in blood calibrator samples from other Hbs, e.g. HbA₀, HbA_1a or HbA_1b, were optimized using the on-chip type system. The electrochemical oxidation current from FcAb reacting with each Hb was measured at 350mV (vs. Ag/AgCl). Hbs including HbA_1a and HbA_1b, HbA_1c and HbA₀ fractions were eluted in this order. A linear relationship between HbA_1c levels and electrochemical oxidation currents was obtained in the range from 4.0% to 12.6% HbA_1c. All procedure including antigen–antibody reaction was completed in 15min. Furthermore, a good correlation was obtained between KO500 method (HPLC) and our proposed method. These results indicate that the on-chip type system with electrochemical detection can be applied to a novel POCT device for rapid and precise detection of HbA_1c.

Keywords: Hemoglobin A; _1c; On-chip type cation-exchange chromatography system; Ferrocene-conjugated antibody; Electrochemical detection

Quantification of fructo-oligosaccharides based on the evaluation of oligomer ratios using an artificial neural network by Lucia Onofrejová; Marta Farková; Jan Preisler (pp. 191-197).

The application of an internal standard in quantitative analysis is desirable in order to correct for variations in sample preparation and instrumental response. In mass spectrometry of organic compounds, the internal standard is preferably labelled with a stable isotope, such as¹⁸O,¹⁵N or¹³C. In this study, a method for the quantification of fructo-oligosaccharides using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI TOF MS) was proposed and tested on raftilose, a partially hydrolysed inulin with a degree of polymeration 2–7. A tetraoligosaccharide nystose, which is chemically identical to the raftilose tetramer, was used as an internal standard rather than an isotope-labelled analyte. Two mathematical approaches used for data processing, conventional calculations and artificial neural networks (ANN), were compared. The conventional data processing relies on the assumption that a constant oligomer dispersion profile will change after the addition of the internal standard and some simple numerical calculations. On the other hand, ANN was found to compensate for a non-linear MALDI response and variations in the oligomer dispersion profile with raftilose concentration. As a result, the application of ANN led to lower quantification errors and excellent day-to-day repeatability compared to the conventional data analysis. The developed method is feasible for MS quantification of raftilose in the range of 10–750pg with errors below 7%. The content of raftilose was determined in dietary cream; application can be extended to other similar polymers. It should be stressed that no special optimisation of the MALDI process was carried out. A common MALDI matrix and sample preparation were used and only the basic parameters, such as sampling and laser energy, were optimised prior to quantification.

Keywords: Quantification; Artificial neural networks (ANN); Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI TOF MS); Fructo-oligosaccharides; Internal standard

Extraction and derivatization in single drop coupled to MALDI-FTICR-MS for selective determination of small molecule aldehydes in single puff smoke by Jianping Xie; Jie Yin; Shihao Sun; Fuwei Xie; Xiang Zhang; Yinlong Guo (pp. 198-201).

Extraction and derivatization in single drop (EDSD) coupled to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) was utilized to determine small molecular aldehydes (SMAs) in single puff smoke. A methanol solution of diphenylamine, 2,5-dihydroxybenzoic acid was used for extraction/derivatization of SMAs and a microdrop of the extraction solution containing the ionic derivatization products of SMAs could be directly deposited in the MALDI target to perform the measurement of SMAs in the cigarette smoke on puff level by MALDI-FTICR-MS. As a result, a consecutive operation of sample pre-treating and MALDI sample plate preparation was achieved. SMAs were derivatized by the reaction with diphenylamine and transformed a stable Schiff base bearing a quaternary ammonium group, and the sensitivity of analysis for SMAs was significantly improved. Good sample homogeneity in in-dot was achieved by adding diphenylamine into the solvent for EDSD and a satisfying repeatability (R.S.D.=7.3% for formaldehyde, n=5) of MALDI-FTICR-MS signals was obtained. This solvent- and reagent-minimized approach with an automatic potential provided a simple, rapid, and accurate procedure for the determination of SMAs in smoke.

Keywords: Extraction and derivatization in single drop; Diphenylamine; Aldehydes; Cigarette smoke; Matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry

The determination for the three genotypes of D16S539 locus based on near-infrared spectroscopy and chemical pattern recognition by Li Ren; Yu-Zhen Gao; Jie-Hong Yin; Wei-Xi Shi; Xiao-Wei Yu; Hong-Ping Xie; Wei-Peng Wang (pp. 202-208).

The paper has established an approach of typing short tandem repeats (STRs) based on the near-infrared spectroscopy (NIRS)–chemical pattern recognition. Taking the three genotypes 9-9, 9-11 and 11-11 of D16S539 locus as example, which have a middle degree of difference, DNA fragments containing the polymorphism sites were amplified by a pair of primers to obtain three genotypes samples; these samples were tested by the NIRS directly; using their spectra as recognition variables, the chemical pattern recognition models of the three genotypes were respectively established by using the principal discriminant variate (PDV) and support vector machine (SVM). The two models have a good fitting ability and strong prediction (i.e. the predicting accuracy was 100%). They are robust for these strong collinear spectra and the small number of the calibration samples. Without any preprocessing for the analyzed samples after PCR, the three genotypes of D16S539 locus could be indirectly determined by using the NIRS-s of the samples with the help of the models. This method is simple, rapid and low cost.

Keywords: Short tandem repeats; Near-infrared spectroscopy; Chemical pattern recognition; Principal discriminant variate; Support vector machine

An optical sensor for the determination of digoxin in serum samples based on a molecularly imprinted polymer membrane by Gema Paniagua González; Pilar Fernández Hernando; J. S. Durand Alegría (pp. 209-212).

This paper reports the synthesis and testing of a molecularly imprinted polymer membrane for digoxin analysis. Digoxin-specific bulk polymer was obtained by the UV initiated co-polymerisation of methacrylic acid and ethylene glycol dimethacrylate in acetonitrile as porogen. After extracting the template analyte, the ground polymer particles were mixed with plasticizer polyvinyl chloride to form a MIP membrane. A reference polymer membrane was prepared from the same mixture of monomers but with no template. The resultant membrane morphologies were examined by scanning electron microscopy. The imprinted membrane was tested as the recognition element in a digoxin-sensitive fluorescence sensor; sensor response was measured using standard solutions of digoxin at concentrations of up to 4×10⁻³mgL⁻¹. The detection limit was 3.17×10⁻⁵mgL⁻¹. Within- and between-day relative standard deviations RSD ( n=5) were in the range 4.5–5.5% and 5.5–6.5% respectively for 0 and 1×10⁻³mgL⁻¹ digoxin concentrations. A selectivity study showed that compounds of similar structure to digoxin did not significantly interfere with detection for interferent concentrations at 10, 30 and 100 times higher than the digoxin concentration. This simply manufactured MIP membrane showed good recognition characteristics, a high affinity for digoxin, and provided satisfactory results in analyses of this analyte in human serum.

Keywords: Molecularly imprinted polymer; Affinity membrane; Digoxin; Organic sample analysis

Application and analysis of structure-switching aptamers for small molecule quantification by Shengnan Xie; S. Patrick Walton / (pp. 213-219).

Modern tools for the analysis of cellular function aim for the quantitative measurement of all members of a given class of biological molecules. Of the analyte classes, nucleic acid measurements are typically the most tractable, both on an individual analyte basis and in parallel. Thus, tools are being sought to enable measurement of other cellular molecules using nucleic acid biosensors. Of the variety of potential nucleic acid biosensor strategies, structure-switching aptamers (SSAs) present a unique opportunity to couple sensing and readout of the target molecule. However, little has been characterized about the parameters that determine the fidelity of the signal from SSA biosensors. In this study, a small molecule biosensor based on a SSA was engineered to detect the model small molecule, theophylline, in solution. Quantitative theophylline detection over nearly three orders-of-magnitude was achieved by scintillation counting and quantitative PCR. Further analysis showed that the biosensor fidelity is primarily controlled by the relative stability of the two conformations of the SSA.

Keywords: Aptamer; Structure switching; Theophylline; Biosensor design; Molecular barcode; Affinity

Capillary electrophoresis–electrochemiluminescent detection of N, N-dimethyl ethanolamine and its application in impurity profiling and stability investigation of meclophenoxate by Zhifeng Fu; Lin Wang; Yonghong Wang (pp. 220-224).

Numerous drugs are carboxylic acid derivatives containing amino group, and hydrolysis reaction of these agents often generates toxic amines. Thus, the detection of amine impurity is of great importance in drug quality control of these amino group-containing ester and amide. A capillary electrophoresis method coupled with end-column electrochemiluminescent detection based on tris(2,2′-bipyridyl)ruthenium(II) system was proposed for the analysis of N, N-dimethyl ethanolamine (DMEA, the degradation product of meclophenoxate) in the presence of its precursor. Baseline separation of DMEA and meclophenoxate can be easily achieved under the selected conditions. DMEA can be assayed within 3min over the concentration range of 5.0×10⁻⁸ to 3.0×10⁻⁶molL⁻¹ with a detection limit of 2.0×10⁻⁸molL⁻¹ at the signal-to-noise ratio of 3. The relative standard deviations of the signal intensity and the migration time were less than 5.3 and 2.5% for a standard sample containing 1.0×10⁻⁷molL⁻¹ DMEA ( n=5), respectively. The presented method has been successfully applied for the profiling of DMEA resulting from the hydrolysis of meclophenoxate in commercial formulations. A primary stability investigation of meclophenoxate in aqueous solution was also carried out at different temperatures, and the results showed that the degradation of meclophenoxate accelerated at the higher temperature.

Keywords: Capillary electrophoresis; Electrochemiluminescence; N; ,; N; -Dimethyl ethanolamine; Meclophenoxate; Impurity profiling; Stability investigation

The effect of the copper(II) salt anion in the Chiral Ligand-Exchange Chromatography of amino acids by Benedetto Natalini; Roccaldo Sardella; Giovanni Carbone; Antonio Macchiarulo; Roberto Pellicciari (pp. 225-233).

Due to the strong involvement in numerous biochemical processes, the separation and resolution of amino acids is a continuously challenging task. Among the experimental parameters affecting the performances in a Chiral Ligand-Exchange Chromatography (CLEC) environment, the effect of the copper(II) salt counter-ion has received very limited attention. Aimed at evaluating the Cu(II) counter-ion effect upon the overall chromatographic performances when the S-trityl-( R)-cysteine is adopted as the chiral selector for the coated stationary phase, a number of both organic (acetate, formate, trifluoromethane-sulfonate) and inorganic (bromide, chloride, nitrate, perchlorate, sulfate) salts has been engaged for the enantiomer separation of a selected set of aliphatic (Allo-Ile, Ile, Leu, Nor-Leu, Nor-Val, Val) and aromatic (AIDA, ATIDA, His, Phe, Phg, Tyr) amino acids. By varying the physico-chemical nature of the Cu(II) anion, a pronounced impact upon the resolution factor ( R_S) has been observed. Even if to a lesser extent, the enantioseparation factor values ( α) underwent variation, as well. A molecular modelling investigation has also been carried out as a rationalization attempt of the observed chromatographic outcomes.

Keywords: Chiral Ligand-Exchange Chromatography; Chiral coated phase; Copper(II) counter-ion; Enantiomer separation; Molecular descriptors

Sections

Personal tools

Analytica Chimica Acta (v.638, #2)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.638, #2)