Analysis of estrogens in environmental waters using polymer monolith in-polyether ether ketone tube solid-phase microextraction combined with high-performance liquid chromatography

A simple, rapid and sensitive on-line method for simultaneous determination of four endocrine disruptors (17beta-estradiol, estriol, bisphenol A and 17alpha-ethinylestradiol) in environmental waters was developed by coupling in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). A poly(acrylamide-vinylpyridine-N,N'-methylene bisacrylamide) monolith, synthesized inside a polyether ether ketone (PEEK) tube, was selected as the extraction medium. To achieve optimum extraction performance, several parameters were investigated, including extraction flow-rate, extraction time, and pH value, inorganic salt and organic solvent content of the sample matrix. By simply filtered with nylon membrane filter and adjusting the pH of samples to 6.0 with phosphoric acid, the sample solution then could be directly injected into the device for extraction. Low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method were achieved in the range of 0.006-0.10 ng/mL and 0.02-0.35 ng/mL from spiked lake waters, respectively. The calibration curves of four endocrine disruptors showed good linearity ranging from quantification limits to 50 ng/mL with a linear coefficient R(2) value above 0.9913. Good method reproducibility was also found by intra- and inter-day precisions, yielding the RSDs less than 12 and 9.8%, respectively. Finally, the proposed method was successfully applied to the determination of these compounds in several environmental waters.     

Determination of honokiol and magnolol by micro HPLC with electrochemical detection and its application to the distribution analysis in branches and leaves of Magnolia obovata

A simple and sensitive method has been developed for determining honokiol and magnolol in fresh Magnolia obovata (M. obovata) by micro high-performance liquid chromatography with electrochemical detection (microHPLC-ECD). Chromatography was performed using a Capcell Pak C-18 UG 120 microbore octadecylsilica (ODS) column, methanol-water-phosphoric acid (65 : 35 : 0.5, v/v/v), as a mobile phase and applied potential at +0.8 V vs. Ag/AgCl. Peak heights were found linearly related to the amounts of honokiol and magnolol injected from 0.67 pg to 2.0 ng (r>0.999). The detection limits (S/N=3) were 0.13 pg, respectively. Honokiol and magnolol of 0.27 ng were detected with relative standard deviation (RSD) of 0.73 and 1.17% (n=5), respectively. Honokiol and magnolol in Magnolia Bark of the Japanese Pharmacopoeia were extracted with 70% methanol, diluted with a mobile phase, and injected into the microHPLC-ECD for determination. Recoveries of honokiol and magnolol in Magnolia Bark exceeded 98.7% with RSD, less than 0.93% (n=5). Determination of the distributions of honokiol and magnolol in bark, phloem, wood, leaf blades, and petioles of fresh M. obovata were made using weight samples of 40-238 mg. This method is useful to determine honokiol and magnolol in M. obovata, which is a candidate for crude magnolia bark for traditional Japanese herbal medicines.     

GC-FID/MS method for the impurity profiling of synthetic d-allethrin

A GC/FID/MS method was developed for the identification and quantification of d-allethrin (DA) and its major impurities in commercial samples. Optimisation of the experimental conditions was carried out considering such important requirements as resolution, reproducibility, detection limits of 0.1% (m/m) for the impurities, and short analysis time. Under the optimised final conditions the method was validated for specificity, precision (CV% = 0.133 at 2.10 mg/mL and CV% = 0.035 at 3.00 mg/mL), linearity (0-3.00 microg injected), limits of detection (0.09 ng injected) and quantitation (0.28 ng injected), and robustness. The DA related impurities were identified by using a GC/MS method with ion trap mass detection and also by comparison with synthesised standards. The most abundant impurities were crysolactone, allethrolone, chrysanthemic acid, and chloro-derivatives of DA.     

准静态扫集胶束电动毛细管色谱法测定扇贝样品中的贝类毒素

采用准静态扫集胶束电动毛细管色谱(MEKC)法测定了扇贝样品中的2种贝类毒素。毛细管内首先充满含十二烷基硫酸钠(SDS)的缓冲溶液,调节缓冲溶液的pH值,使电渗流等于SDS胶束的电泳流速,电动进样时,带正电荷的贝类毒素离子被SDS扫集吸附,由于SDS在毛细管内处于准静止状态,可使进样时间延长至320 s。与常规电动进样MEKC相比,石房蛤毒素和软骨藻酸的检测灵敏度分别提高950和810倍。该方法对石房蛤毒素和软骨藻酸的检出限分别为0.05,0.12 ng/m L。方法可实现对扇贝样品中2种贝类毒素的快速、灵敏检测。     

Determination of Aztreonam by liquid Chromatography with UV and Amperometric Detection

Abstract

A comparative study of UV and amperometric detection of aztreonam after HPLC separation is presented. At pH 2.0 and a detection potential of +1.15 V (vs. Ag/AgCl), the detection limits with amperometric detection are about two times higher (3–5 ng) than those obtained with UV detection (1–3 ng) for aztreonam and its main decomposition products, the E-isomer and open-ring aztreonam. With the advantage of specificity for the aminothiazole group of the aztreonam molecule, amperometry can be used as an alternative or complementary mode to UV detection for the determination of aztreonam in injectable formulations and in human serum.     

Speciation of organomercury compounds by capillary electrophoresis with pre-column derivatization and on-line stacking

A simple capillary electrophoresis method was developed to separate and quantify methylmercury, ethylmercury, and phenylmercury with the enhancement of pre-column derivatization and on-line stacking.     

Simultaneous determination of vanadium and molybdenum as N-benzoyl-N-phenylhydroxamate complexes by combining solvent extraction and liquid chromatography

A normal-phase high-performance liquid chromatographic method for the selective simultaneous determination of vanadium and molybdenum with N-benzoyl-N-phenylhydroxylamine (BPHA) is described. The V(V)-BPHA and Mo(Vl)-BPHA complexes were preconcentrated by solvent extraction into chloroform and injected on to a nitrile-bonded column for chromatography. The mobile phase was a 5.9· 10⁻⁴ M solution of BPHA in chloroform (stabilized with amylene). The detection limits for vanadium and molybdenum were 2.1 and 3.3 ng ml⁻¹, respectively, for an aqueous to organic phase-volume ratio of 20:1. The procedure, applied to the analysis of a synthetic water, showed satisfactory accuracy and precision.     

Simultaneous determination of pantothenic acid and hopantenic acid in biological samples and natural products by gas chromatography-mass fragmentography

A method for the simultaneous determination of pantothenic acid and hopantenic acid in plasma samples was developed using gas chromatography-mass spectrometry with multiple ion detection. Plasma samples were directly purified without deproteinization on an ion-exchange resin, and the eluate was extracted with ethyl acetate under acidic conditions. The organic layer was evaporated to dryness under a stream of nitrogen, and the residue was dissolved in an internal standard solution. Pantothenic and hopantenic acids were converted into their trimethylsilyl derivatives by treating with bis(trimethylsilyl)trifluoroacetamide. Aliquots of this solution were injected into the gas chromatograph-mass spectrometer, which was equipped with a wide-bore fused-silica column (DB-17) and analysed by the multiple ion detection method. The detection limits for pantothenic acid and hopantenic acid in plasma were 1 ng/ml each at a signal-to-noise ratio of 5. This method was applied to a study of the assay of pantothenic acid and hopantenic acid in biological samples and natural products.     

Development of a solid-phase extraction method for simultaneous extraction of adipic acid, succinic acid and 1,4-butanediol formed during hydrolysis of poly(butylene adipate) and poly(butylene succinate)

A solid-phase extraction (SPE) method was developed for the simultaneous extraction of dicarboxylic acids and diols formed during hydrolysis of poly(butylene succinate), PBS, and poly(butylene adipate), PBA. Four commercial non-polar SPE columns, three silica based: C8, C18, C18 (EC), and one resin based: ENV+, were tested for the extraction of succinic acid, adipic acid and 1,4-butanediol, the expected final hydrolysis products of PBS and PBA. ENV+ resin was chosen as a solid-phase, because it displayed the best extraction efficiency for 1,4-butanediol and succinic acid. Linear range for the extracted analytes was 1-500 ng/microl for adipic acid and 2-500 ng/microl for 1,4-butanediol and succinic acid. Detection and quantification limits for the analytes were between 1-2 and 2-7 ng/microl, respectively, and relative standard deviations were between 3 and 7%. Good repeatability and low detection limits made the developed SPE method and subsequent gas chromatography-mass spectrometry (GC-MS) analysis a sensitive tool for identification and quantification of hydrolysis products at early stages of degradation.     

Identification and quantification of major species of arsenic in rice

A study was undertaken to develop a method for the chemical speciation of As in rice on the basis of current knowledge in this field for use in preparing a certified reference material (CRM). Samples of the Arborio rice variety were ground to a fine powder, which was extracted under sonication with a water-methanol mixture (1 + 1, v/v). The resulting solutions were injected into a high-performance liquid chromatograph combined on-line with a quadrupole inductively coupled plasma-mass spectrometer. This hyphenated system allowed for the quantification of As species in one analytical step. Four forms of As were detected: inorganic As (III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic As (V) at concentrations of 88.2 +/- 7.1, 50.8 +/- 5.0, 15.2 +/- 1.7, and 51.2 +/- 3.5 ng/g, respectively. The concentration of total As was 211 +/- 7 ng/g. The limits of detection (3sigma criterion) and the quantitation (10sigma criterion) were, respectively, as follows (in ng/g): As (III), 0.095 and 0.320; As (V), 0.082 and 0.273; MMA, 0.110 and 0.367; and DMA, 0.145 and 0.480. Ten hours were needed for the extraction procedure, 6 h for the evaporation, and 30 min for quantification of the analytes. This investigation was performed in the frame of a European Commission Project on the feasibility of CRMs for As and Se species.     

Comparative Study of the Determination of Parabens in Shampoos by Liquid Chromatography with Amperometric and Coulometric Detection

The simultaneous determination of four para‐hydroxybenzoic acid esters (parabens) in shampoos was studied by liquid chromatography (LC) with amperometric (LC‐AD) and coulometric (LC‐CD) detection. The parabens were separated on an ODS C18 reversed column by isocratic elution with a mobile phase based on methanol‐0.1 M acetic acid (60 : 40%, v/v) with 0.02 M NaClO₄ at a flow rate of 0.8 mL min^?1. The limit of detection (S/N>3) for the analytes was in the 15–25 pg (injected mass) range at an applied potential of 1.20 V vs. Ag/AgCl using the LC‐AD and in the 2–3 pg range at a potential of 0.790 V vs. Pd using the LC‐CD. The peak ratio of the internal standard peak (IS: 4‐hydroxybenzoic acid sec‐butyl ester) versus the analyte peak was found to be related to the amount injected from 0.1 ng to 100ng (r=0.996–0.999) with the LC‐AD and from 0.050 ng to 100 ng range (r=0.999–1.000) with the LC‐CD. The relative standard deviation (RSD, n=10) was comprised between 1.8 to 3.5% by LC‐AD ( 5 ng injected) and between 2.0 to 2.4% by LC‐CD (0.5 ng injected). The determination of four most used parabens in ten different shampoos was successfully realized.     

Evaluation of atomic fluorescence spectrometry as a sensitive detection technique for arsenic speciation

The potential of coupling anion-exchange high-performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC–HG–AFS) for arsenic speciation is considered. The effects of hydrochloric acid and sodium tetrahydroborate concentrations on signal-to-background ratio, as well as argon and hydrogen flow rates, were investigated. Detection limits for arsenite, dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate were 0.17, 0.45, 0.30 and 0.38 μg l⁻¹, respectively, using a 20-μl loop. Linearity ranges were 0.1–500 ng for As(III) and MMA (as arsenic), and 0.1–800 ng for DMA and As(V) (as arsenic). Arsenobetaine (AsB) was also determined by introducing an on-line photo-oxidation step after the chromatographic separation. In this case the limits of detection and linear ranges for the different species studied were similar to the values obtained previously for As(V). The technique was tested with a human urine reference material and a volunteer's sample. © 1998 John Wiley & Sons, Ltd.     

High-performance liquid chromatography of azobenzene derivatives with spectrophotometric and electrochemical detection

The chromatographic behaviour of azobenzene and fourteen of its derivatives was studied by reversed-phase high-performance liquid chromatography with a C18 stationary phase. The optimal composition of the mobile phase is 9:1 methanol-0.01 M aqueous sodium dihydrogen phosphate which is 0.0002 M in ethylenediaminetetraacetic acid, with a pH of 4.5. The solutes can be detected spectrophotometrically, voltammetrically or polarographically. Spectrophotometric measurement in the visible range is more sensitive than in the UV range (detection limits of 0.04-0.1 ng at 410 nm compared with 0.3-0.5 ng at 265 nm). Voltammetric detection is highly sensitive for hydroxy and amino derivatives [detection limits 0.02-0.09 ng at +0.8 V (Ag-AgCl)], whereas for other substances the detection limits are a few nanograms. Polarographic detection is the least sensitive [detection limits 4-8 ng at -0.6 V (Ag-AgCl)]. All the calibration graphs exhibit good linearity, but spectrophotometric detection yields a wider linear dynamic range. Voltammetric detection is more precise at low solute concentrations (relative standard deviations of the peak heights 0.5-1.0% and 1.0-1.5% for voltammetric and spectrophotometric detection, respectively, with amounts of solute from 1 to 10 ng).     

Copper(II) Ion‐Selective Electrodes Based on Dithiosalicylic and Thiosalicylic Acids

Potentiometric carbon paste electrodes for copper(II) based on dithiosalicylic and thiosalicylic acids are described. The sensor based on dithiosalicylic acid (DTS) exhibits a linear response with a nearly Nernstian slope of 27.7 mV per decade, whereas the electrode based on thiosalicylic acid (TS) shows a super‐Nernstian slope. The limits of detection for the DTS sensor and the TS sensor are 10^?7.9and 10^?6.3 M for copper(II) activity, respectively. Selectivity coefficients are tabulated, and the influence of the pH on the response of these ISEs is studied. The DTS electrode is successfully used for potentiometric titration of humic acids with copper in order to get more information about complexing properties of these acids.     

Analysis of erythromycin in biological fluids by high-performance liquid chromatography with electrochemical detection

A simple and sensitive high-performance liquid chromatographic assay was developed for the quantitative determination of major erythromycin components and their potential metabolites or degradation products in plasma and urine. An ether extract of alkalized plasma sample was chromatographed on a reversed-phase column and the components in the column effluent were monitored by an electrochemical detector. The recovery of the drug from extraction was virtually 100%. The detection limits for erythromycin A in plasma were 5-10 ng/ml and 30 ng/ml using 1 and 0.2 ml of sample, respectively. For urine samples, a simple one-step deproteinization with two volumes of acetonitrile was satisfactory for analysis. The method has been evaluated in plasma and urine from dogs receiving oral or intravenous erythromycin A. The standard curves for potential metabolites or degradation products were not constructed due to the lack of sufficient samples.     

Determination of chlorophenoxy acid herbicides by capillary electrophoresis with integrated potential gradient detection

This report describes separation and detection of chlorophenoxy acid herbicides spiked in drinking water by the technique combining solid-phase extraction, field-amplified sample stacking, capillary electrophoresis, and potential gradient detection. The herbicide solution (400 mL) was concentrated to 0.1 mL by the solid-phase extraction procedure. The buffer containing 3 mM ammonia and 0.3 mM hydroxypropyl-beta-cyclodextrin was adjusted to pH 9.0 with ammonia. The sample solution was injected into the capillary to 30% of the whole length, and -9 kV and 9 kV were employed for field-amplified sample stacking and separation, respectively. The herbicides were baseline separated and the detection limits with the above combined techniques were in the range of 1-4 x 10(-2) ng/mL.     

毛细管电泳在线化学发光分离及检测铬（Ⅲ）与钒（Ⅴ）

基于在碱性介质中 Cr( )和 V( )对鲁米诺和过氧化氢的催化化学发光反应 ,研究了毛细管电泳在线化学发光分离和检测 Cr( )和 V( )。方法简便、快速、灵敏、进样量少。 Cr( )和 V( )的检出限分别为 7.8× 1 0 - 8mol/L和 5.0× 1 0 - 6mol/L ,线性范围分别是 32～ 80 ng/m L和 0 .55～ 3.0μg/m L     

Practical considerations in the gas chromatography/combustion/isotope ratio monitoring mass spectrometry of 13C-enriched compounds: detection limits and carryover effects

This paper describes a methodological investigation of the use of gas chromatography/combustion/isotope ratio monitoring mass spectrometry (GC/C/IRMS) for the compound-specific stable isotope analysis of 13C-enriched compounds. Analysis of two 13C-enriched fatty acid methyl esters, possessing delta13C values of approximately 500 per thousand, at a range of concentrations, demonstrated that detectable responses, i.e. chromatographic peaks, could be observed in the 45/44 output even when the compound was present in such low abundance that no peak was observed in the m/z 44 ion chromatogram. A limit of detection, defined as the point at which the signal-to-background ratio was equal to 3, was calculated for two compounds and for both ion chromatograms. The limit of detection in the 45/44 chromatogram was found to be ca. 30 pg injected for methyl 13C-hexadecanoate and ca. 20 pg injected for methyl 13C-octadecanoate, whilst, in the m/z 44 ion chromatogram, detection limits were approximately 180 and approximately 200 pg, respectively. The delta13C value recorded for the analytes was found to be both inaccurate and imprecise below 5 ng of each component injected, although this would not represent a significant drawback in qualitative tracer-type experiments. In a further study of co-injected mixtures of labelled (approximately 500 per thousand) and unlabelled (natural abundance, -20 to -30 per thousand ) fatty acid methyl esters a significant within-run carryover effect was observed, where the isotope values recorded for compounds eluting immediately after enriched components were significantly affected. Whilst this would not affect qualitative results, quantitative data for mixtures containing enriched compounds should be considered with caution. The standards employed in this investigation were enriched to approximately 500 per thousand in 13C; however, these effects would probably be accentuated at higher levels of labelling and with other elements. The limit of detection work demonstrated the potential of GC/C/IRMS as a highly sensitive and selective detector with many possible applications.     

Determination of hydralazine and metabolites in urine by liquid chromatography with electrochemical detection

The cyclic voltammetric behavior of hydralazine and its primary metabolites, the pyruvate and acetone hydrazones, was examined in the positive potential range at both conventional and electrochemically pretreated glassy carbon electrodes. The enhanced oxidations observed at the treated surface were used as the basis of amperometric electrochemical detection of the compounds following reversed-phase liquid chromatography. The detection limits so obtained at +0.75 V vs. Ag/AgCl (1, 3, and 5 ng injected, respectively) were comparable to those previously reported for absorption and fluorescence detection approaches employing derivatization/preconcentration procedures. For liquid chromatography with electrochemical detection, however, direct quantitation of all three species in urine samples was readily accomplished without any chemical derivatization or sample treatment operations other than particulate filtration.     

Arsenic speciation by ion-exchange separation and graphite-furnace atomic-absorption spectrophotometry

As(III), As(V), monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA) were determined by graphite-furnace atomic-absorption spectrophotometry after separation of the species by ion-exchange chromatography. The detection limits (ng/ml) were DMA 0.02, MMA 2.0, As(V) 0.4 and total arsenic 4.0. As(III) was determined by difference. This system gave better detection limits and/or shorter analysis times than previously reported systems.