ICP-AES法测定蔬菜、水果中锌含量的不确定度评定

不确定度[1-3]在我国各行业的应用发展不均衡,在蔬菜、水果检测方法的评定方面鲜有报道。ICP作为一种灵敏度高、快速、高效的检测手段在食品、环保及其它领域得到了广泛的应用,其检测结果不确定度的评定较为重要。本文以ICP法测定番茄中的锌为例,对ICP法测定蔬菜、水果中重金属     

蔬菜中阔草清等8种农药残留量的高效液相色谱-质谱分析

建立了固相萃取-高效液相色谱-电喷雾质谱法同时测定蔬菜中的阔草清、西玛津、硫双威、绿麦隆、扑草净、仲丁威、马拉硫磷和二嗪农等8种农药的分析方法.蔬菜用乙腈超声波提取,经过ODS-C18固相萃取小柱富集纯化.采用C18柱分离,以体积分数0.03%甲酸乙腈-体积分数0.03%甲酸水溶液为流动相,线性梯度洗脱,以保留时间和质荷比对分离出的组分进行定性,用峰面积进行定量.结果表明,8种农药的质量浓度与其峰面积在一定的范围内呈良好的线性关系,检出限为0.1～5.0 μg/L,相关系数为0.9939～0.9998,样品的加标平均回收率为83%～106%,相对标准偏差为3.1%～9.8%.方法适用于蔬菜中阔草清等8种农药残留量的分析.     

Validation of a Gas Chromatographic–Tandem Mass Spectrometric Method for Analysis of Pesticide Residues in Six Food Commodities. Selection of a Reference Matrix for Calibration

A gas chromatographic–tandem mass spectrometric (GC–MS–MS) method for analysis of 30 multi-class pesticide residues in four vegetables (cucumber, marrow, pepper, and eggplant) and two fruits (melon and watermelon) has been developed and validated. The performance characteristics linearity, detection limit (LOD), quantification limit (LOQ), precision, and recovery were studied. The effect of the matrix on the calibration step was studied by comparing calibration curves and recoveries for each food commodity. Two different food commodities, cucumber and watermelon, were selected as potential reference matrixes for the target vegetables and fruits, respectively.     

高效液相色谱法测定蔬菜和水果中吡虫啉农药残留量

采用高效液相色谱法测定了蔬菜和水果中吡虫啉残留量的分析方法,优化了样品前处理方法及HPLC分离测定条件。样品采用饱和氯化钠浸泡,乙腈/二氯甲烷(16/2)(V/V)萃取,正己烷去杂质。结果表明:在优化条件下,本法测定吡虫啉的线性范围为0.05~5.0μg/mL,检出限为0.05μg/mL,平均加标回收率为86.0%,其线性方程为y=93.478x-0.3104,r=0.9999。该方法具有操作简便,干扰小,灵敏度高等特点,可满足蔬菜和水果中吡虫啉残留检测的要求。     

Application of coupled-column liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection to the determination of pyrethroid insecticides in vegetable samples

This study reports the first application of coupled-column liquid chromatography–photochemically induced fluorimetry–fluorescence detection (LC-LC-PIF-FD), demonstrating its potential for the quantitative and selective detection of seven pyrethroids in vegetable samples such as cucumber, green bean, tomato and aubergine. An internal surface reversed-phase (ISRP) column coupled to a C₁₈ column for analyte clean-up and determination were used, respectively. In comparison with a C₁₈ column, the ISRP substantially improved the separation between analytes and interferences from the vegetable matrix. The limits of detection ranged from 0.01 to 0.22 g kg^–1 in the vegetable samples (equivalent to 0.01 and 0.13 g L^–1 in the extract injected), and limits of determination ranged from 0.56 to 8.33 g kg^–1 in the vegetable samples (equivalent to 0.34 and 5.00 g L^–1 in the extract injected). Samples were extracted into dichloromethane to yield mean recoveries at two levels of concentration between 72.8 and 110.0% in all cases. Relative standard deviations were lower than 11%.     

Flow-injection chemiluminescence determination of ascorbic acid by use of the cerium(IV)-Rhodamine B system

A highly sensitive flow-injection (FI) method with chemiluminescence (CL) detection is used for the determination of l-ascorbic acid. The method is based on the CL reaction of Rhodamine B with cerium(IV) in sulfuric acid media. l-Ascorbic acid is suggested to be a catalyst utilized in the energy-transferred excitation process. The proposed procedure allows quantitation of l-ascorbic acid in the range 3.8×10⁻¹³ to 1.0×10⁻¹⁰ mol l⁻¹ with a correlation coefficient of 0.9998 (n=5) and relative standard deviation (R.S.D.) of 0.92% (n=11) at 1.0×10⁻¹¹ mol l⁻¹. The detection limit (3×blank) was 1.0×10⁻¹³ mol l⁻¹. The method is successfully used to determine l-ascorbic acid in fresh vegetables. The possible mechanism of the chemiluminescence in the system is discussed.     

Rapid multiresidue screening method for organophosphate pesticides in vegetables

Summary A rapid and efficient multiresidue extraction procedure using ethyl acetate and sodium sulfate has been applied to the analysis of diazinon, methamidophos, chlorpyrifos, malathion, parathion, parathion-methyl, dimethoate and monocrotophos residues in many different kinds of vegetables. No cleanup step was required Concentrated extracts were analysed by gas chromatography with flame photometric detection in phosphorus mode. Recovery studies were performed in six kinds of matrices at two fortification levels. Recoveries were in the range 80–115%. The limit of quantification of the analytical method has been estimated as 0.01 ppm for diazinon, methamidophos and malathion, 0.03 ppm for chlorpyrifos, parathion, parathion-methyl and dimethoate and 0.1 ppm for monocrotophos. Experiments showed that potentially it should be possible to develop a rapid and universally applicable method for organophosphate pesticide residues in different matrices.     

Multicomponent determination of pesticides in vegetables by gas chromatography with mass spectrometric detection and multivariate calibration

Three multivariate calibration methods, partial least squares (PLS-1 and PLS-2) and principal component regression (PCR), were applied for the first time to the simultaneous determination of a mixture of six pesticides in vegetables samples by gas chromatography with mass spectrometric detection (GC-MS). PLS-1 method showed better prediction ability than PLS-2 and PCR methods. The GC-MS chromatograms obtained of vegetable samples spiked with the target pesticides were used to build the calibration matrix. The PLS-1 models were evaluated by predicting the concentrations of independent test samples. Also, the proposed models were successfully applied for the determination of these pesticides in vegetable samples after an extraction step with dichloromethane. By using the first derivative signals in PLS-1 models, simultaneous determination of the compounds was not improved.     

离子色谱法测定蔬菜中硝酸盐

应用离子色谱法代替原用的镉还原法(即国标法)测定了蔬菜中硝酸根。离子色谱法的应用使测定的选择性、准确性、精密度和速度得到改善。蔬菜样品经捣碎,用自制的活性碳柱脱色和用微孔膜过滤等步骤的预处理后所得溶液即可进行离子色谱测定。所用色谱柱为IonpacAS14A-3C阴离子分离柱,淋洗液为Na2CO3和NaHCO3的混合溶液,洗出液中的NO3-经转化为游离酸(HNO3)后用电导检出器测定其导电率。在量程为30μS和进样液(50μL)中NO3-浓度在1.0~32.5 mg.L-1的范围内,NO3-离子峰高的积分值与进样液中NO3-浓度之间呈线性关系。用含不同浓度NO3-离子的3种蔬菜按方法测定以检验其精密度,所求得RSD值(n=6)在0.7%~5.6%之间。经检验,方法的测定结果与镉还原法的结果之间无显著差异。