胶体金修饰电极测定鱼样中组胺的方法研究

基于胶体金修饰的玻碳电极,利用电流～时间曲线法建立了一种简便、灵敏的组胺检测方法。优化了底液的pH值和组胺的电化学测试方法及条件,考察了修饰电极的电化学性能。结果表明,组胺在胶体金修饰电极上的响应电流(-I,μA)与其浓度(c,μmol/L)在0. 1～64μmol/L范围内呈良好的线性关系,检出限为0. 033μmol/L,在带鱼和黄花鱼样品中的加标回收率分别为94. 4%～106%、91. 8%～106%,相对标准偏差分别为3. 2%、2. 5%。该法操作简单、检测速度快、成本低,适用于带鱼和黄花鱼等鱼样中组胺的测定。     

Direct mercury determination in aqueous slurries of environmental and biological samples by cold vapour generation-electrothermal atomic absorption spectrometry

Direct cold vapour generation from aqueous slurries of environmental (marine sediment, soil, coal) and biological (human hair, seafood) samples have been developed using a batch mode generation system coupled with electrothermal atomic absorption spectroscopy. The effects of several variables affecting the cold vapour generation efficiency from solid particles (hydrochloric acid and sodium tetrahydroborate concentrations, argon flow rate, acid solution volume and mean particle size) have been evaluated using a Plackett-Burman experimental design. In addition, variables affecting cold vapour trapping and atomisation efficiency on Ir-treated graphite tubes (trapping and atomisation temperatures and trapping time) have been also investigated. Atomisation and trapping temperatures, trapping time and hydrochloric acid concentration were the significant variables. The 2²+star and 2³+star central composite designs have been used to obtain optimum values of the variables selected. The accuracy of methods have been verified by using several certified reference materials (PACS-1, GBW-07410, NIST-1632c, CRM-397 and DORM-2). A characteristic mass of 390 pg were achieved. The detection limits of methods were in the range of 40-600 ng g⁻¹. A particle size less than 50 μm is adequate to obtain total cold vapour generation of Hg content in the aqueous slurry particles.     

标准物质研制中ICP-AES分析的实验室质量控制

本文从八个方面介绍了标准物质研制中ICP-AES分析的实验室质量控制体系。在此条件下，很好地控制了样品的空白值、精密度和准确度，测定所得数据均被标样研制单位采用。     

光度法测定水样中铝

研究了铝与对乙酰基偶氮胂(ASApA)显色反应,在pH 4.7的HOAc-NaOAc缓冲溶液中,Al3+与ASApA显色形成1:2络合物,最大吸收波长位于612 nm,ε-8.19×103L·mol-1·cm-1,铝量在0～2.8μg·ml-1范围内遵守比耳定律,用于水样中铝的测定,结果满意。     

环境水样及食品中亚硝酸根的分析进展

评述了自1997年至2002年国内外环境水样及食品中亚硝酸根(NO2^-)的分析进展。包括分子光谱法、电化学分析法和色谱分析法，引用文献96篇。     

Evaluation of an on-line coupled continuous flow liquid membrane extraction and precolumn system as trace enrichment technique by liquid chromatographic determination of bisphenol A

An on-line coupled continuous flow liquid membrane extraction (CFLME) and C₁₈ precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l⁻¹ NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C₁₈ precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C₁₈ analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l⁻¹ (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C₁₈ based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples.     

Derivatisation in gas chromatographic determination of acidic herbicides in aqueous environmental samples

This paper reviews derivatisation processes applied in chromatographic determination of acidic herbicides (with carboxyl and phenol groups), mainly in aqueous environmental samples. The discussion focuses on the basic derivatisation reactions used to convert herbicides to derivatives to make them analysable by gas chromatography, and possibly to reduce detection limits and/or increase extraction recovery from aqueous samples. The reactions are transesterification, esterification, silylation, alkylation, and extractive and pyrolytic alkylation. The reagents used to conduct the reactions are numerous. Diazomethane is a very efficient methylation reagent but explosive and toxic. Methyl iodide also ensures rapid and efficient methylation. Benzyl bromide can be used directly in water but derivatisation yield is low and reproducibility is poor. Butyl chloroformate and dimethyl sulfite can also be used for derivatisation in water, and acetic anhydride can be used for in-situ derivatisation of phenolic herbicides. For increasing selectivity of GC detection pentafluorobenzyl bromide (for ECD) and (2-cyanethyl)dimethyl(diethylamino)silane (for NPD) have been applied. Very characteristic ions are produced in mass spectra if silyl groups are introduced, e.g. by using bis(trimethylsilyl)trifluoroacetamide. Tetramethylammonium, trimethylphenylammonium, tetraalkylammonium, and trimethylsulfonium hydroxides and salts can by used for derivatisation at elevated temperature in the GC injection port. Extractive alkylation is relatively efficient if tetraalkylammonium salts with long chain alkyl groups are used.     

元素周期表实物展窗:元素化学性质的形象化展示

以展示元素单质、化合物和矿物样品为形式制作的元素周期表实物展窗能够形象化地展示各种元素的化学特性。元素周期表实物展窗将实物样品展示度与样品背后的化学内涵相结合,可以展示元素和化学学科的风貌。     

Field‐amplified sample injection combined with capillary electrophoresis for the simultaneous determination of five chlorophenols in water samples

A sensitive method of CZE‐ultraviolet (UV) detection based on the on‐line preconcentration strategy of field‐amplified sample injection (FASI) was developed for the simultaneous determination of five kinds of chlorophenols (CPs) namely 4‐chlorophenol (4‐CP), 2‐chlorophenol (2‐CP), 2,4‐dichlorophenol (2,4‐DCP), 2,4,6‐trichlorophenol (2,4,6‐TCP), and 2,6‐dichlorophenol (2,6‐DCP) in water samples. Several parameters affecting CZE and FASI conditions were systematically investigated. Under the optimal conditions, sensitivity enhancement factors for 4‐CP, 2‐CP, 2,4‐DCP, 2,4,6‐TCP, and 2,6‐DCP were 9, 27, 35, 43, and 43 folds, respectively, compared with the direct CZE, and the baseline separation was achieved within 5 min. Then, the developed FASI‐CZE‐UV method was applied to tap and lake water samples for the five CPs determination. The LODs (S/N = 3) were 0.0018–0.019 µg/mL and 0.0089–0.029 µg/mL in tap water and lake water, respectively. The values of LOQs in tap water (0.006–0.0074 µg/mL) were much lower than the maximum permissible concentrations of 2,4,6‐TCP, 2,4‐DCP, and 2‐CP in drinking water stipulated by World Health Organization (WHO) namely 0.3, 0.04, and 0.01 µg/mL, respectively, and thereby the method was suitable to detect the CPs according to WHO guidelines. Furthermore, the method attained high recoveries in the range of 83.0–119.0% at three spiking levels of five CPs in the two types of water samples, with relative standard deviations of 0.37–8.58%. The developed method was proved to be a simple, sensitive, highly automated, and efficient alternative to CPs determination in real water samples.     

Development and validation of a high-throughput high-performance liquid chromatographic assay for the determination of caffeine in food samples using a monolithic column

The present study reports the development and validation of a high-throughput high-performance liquid chromatographic (HPLC) assay for the determination of caffeine in food samples. The analyte was separated rapidly from sample matrix using a short monolithic column (50 mm × 4.6 mm i.d.). The flow rate was 3.0 mL min⁻¹, while the mobile phase consisted of ACN/water (10:90, v/v). Caffeine was detected directly at 274 nm. Under the optimal HPLC conditions, the sampling rate was 60 h⁻¹. The assay was validated for linearity, LOD and LOQ, precision, selectivity and ruggedness. The case of external calibration versus standard addition for the analysis of real samples was also examined. The proposed assay was applied to the analysis of beverages and coffee samples.