A highly sensitive method for simultaneous determination of ultra trace levels of copper and cadmium in food and water samples with luminol as a chelating agent by adsorptive stripping voltammetry

In the present study a selective method is presented for the simultaneous determination of copper and cadmium in food samples by adsorptive stripping voltammetry. In preliminary studies, it has been proven that the copper and cadmium react with 3-aminophthalhydrazide (luminol), giving rise to the formation of these complexes. These complexes have adsorptive characteristics on hanging mercury drop electrode (HMDE) and can be reduced in a reduction step. In this study the optimum reaction parameters and conditions studies are investigated. The calibration graphs were linear in the concentration range of 0.5–105.0 and 0.8–70.0 ng/ml for copper and cadmium, respectively. The limit of detection of the method was 0.04 ng/ml for Cu²⁺ and 0.02 ng/ml for Cd²⁺. The interference of some common ions was studied and it was concluded that application of this method for the determination of copper (II) and cadmium in food and water samples led to satisfactory results.     

Determination of ultra trace levels of copper in food samples by a highly sensitive adsorptive stripping voltammetric method

A new method is presented, for the determination of copper, based on adsorptive stripping voltammetry of the complex of copper with thiosemicarbazide at a hanging mercury drop electrode (HMDE). The most suitable operating conditions and parameters, such as pH, accumulation potential, deposition time, ligand concentration and scan rate, were selected. The calibration graph for copper (II) was linear over the concentration range 0.01–90.0 ng/ml; the detection limit of the method was 0.007 ng/ml. The interferences of some common ions were studied and the method was found suitable for the determination of copper (II) in rice, tea, tomato, blood and water samples. Moreover, with the use of the proposed method, there is a considerable improvement in the detection limit, the linear dynamic range and the deposition time, compared with the methods other than adsorptive stripping voltammetry for the determination of copper.     

Simultaneous determination of trace amounts of vanadium and molybdenum in water and foodstuff samples using adsorptive cathodic stripping voltammetry

A new procedure is presented for the simultaneous determination of ultra trace amounts of vanadium and molybdenum based on adsorptive cathodic stripping voltammetry (AdCSV). Adsorptive accumulation of the V(V) and/or Mo(VI) with chromoxane cyanine R (CCR) onto a hanging mercury drop electrode, followed by reduction of the adsorbed species using differential pulse voltammetry method. Optimised conditions include a 60 s adsorption period at ?0.10 V, 8.0 μm of CCR in 0.1 m acetate buffer, pH 3.6, and a voltammetric scan using differential pulse mode with 25 mV s^?1 scan rate. Detection limits of 0.1 and 0.08 ng mL^?1 were achieved for V(V) and Mo(VI), respectively, which can be lowered down to 0.06 and 0.04 ng mL^?1 by extending the adsorption time to 180 s. The reduction currents are linear in the range of 0.3–24.0 ng mL^?1 and 0.1–30.0 ng mL^?1 for V(V) and Mo(VI), respectively. The relative standard deviation for ten replicates determination of 4.0 ng mL^?1 V(V) and Mo(VI) were 1.8% and 1.1%, respectively. The proposed method applied for the determination of vanadium and molybdenum in river water, tap water, well water and plant foodstuff such as cucumber, tomato, carrot and tea.     

Ultra trace quantification of chromium(VI) in food and water samples by highly sensitive catalytic adsorptive stripping voltammetry with rubeanic acid

A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of ultra trace levels of chromium(VI) on hanging mercury drop electrode is reported. The method is based on the adsorptive preconcentration of the Cr(III)–dithiooxamide (rubeanic acid) complex and the utilization of the catalytic reaction in the presence of nitrate. At optimized conditions the calibration graph is linear from 0.01 to 6 ng/ml and detection limit is 0.002 ng/ml for accumulation time of 50 s. The interference of some common ions was studied and this method has been applied to the determination of chromium in food and waste water samples with satisfactory results.     

Determination of lead and cadmium in food samples by the coprecipitation method

In this study, the coprecipitation method developed using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as coprecipitate carrier was used for the determination of trace lead and cadmium in various food samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was applied for the determination of Pb(II) and Cd(II) in salami, sausage, chicken, anchovy, spinach, cabbage, onion, dill, parsley, lettuce, tea and rice samples. The matrix modifiers were added as 50 μg NH₄H₂PO₄ + 3 μg Mg(NO₃)₂ for both Pb(II) and Cd(II). The signals were measured as peak area. The concentrations of Pb(II) and Cd(II) in the food samples were found to be in the range of 6.63 ng g⁻¹ (anchovy) −3.30 μg g⁻¹ (spinach) and 2.67 ng g⁻¹ (salami) −0.51 μg g⁻¹ (lettuce), respectively.     

Utility of solid phase spectrophotometry for the modified determination of trace amounts of cadmium in food samples

A modified selective, highly sensitive and accurate procedure for the determination of trace amounts of cadmium which reacts with 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (BTAHNA) to give a deep violet complex with high molar absorptivity (7.05 × 10⁶ L mol⁻¹ cm⁻¹, 3.92 × 10⁷ L mol⁻¹ cm⁻¹, 1.78 × 10⁸ L mol⁻¹ cm⁻¹, and 4.10 × 10⁸ L mol⁻¹ cm⁻¹), fixed on a Dowex 1-X8 type anion-exchange resin for 10 mL, 100 mL, 500 mL, and 1000 mL, respectively. Calibration is linear over the range 0.2-3.5 μg L⁻¹ with RSD of ?1.14% (n = 10). The detection and quantification limits were calculated. Increasing the sample volume can enhance the sensitivity. The method has been successfully applied for the determination of Cd(II) in food samples, water samples and some salts samples without interfering effect of various cations and anions.     

Determination of aflatoxins B1 and B2 by adsorptive cathodic stripping voltammetry in groundnut

In this study, adsorptive stripping voltammetry was proposed for determination of aflatoxins B1 (AFB1) and B2 (AFB2) using hanging mercury drop electrode (HMDE) as the working electrode. Both aflatoxins were found to adsorb and undergo irreversible reduction reaction at the working mercury electrode. The experimental conditions were optimised by one-at-a time and experimental design to obtain the best characterised peak in terms of peak height with analytical validation of the method for each aflatoxin. The calibration curves for aflatoxins AFB1 and AFB2 were linear in the ranges of 0.4–40 ng ml⁻¹ and 0.2–70 ng ml⁻¹ with the limit of detections (LOD) 0.15 and 0.10 ng ml⁻¹, respectively. The proposed method was applied for the analysis of aflatoxins in groundnut samples and the results were compared with those obtained by the HPLC technique.     

Kinetic-spectrophotometry method for determination of ultra trace amounts of aluminum in food samples

A simple and sensitive kinetic-spectrophotometry method is developed for the determination of trace amounts of aluminum in food samples based on its catalytic effect on the oxidation of Nile Blue A by potassium bromate in sulfuric acid medium. The absorbance is measured at 595.5 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents, temperature and interferences are also investigated. The calibration curve is linear over the concentration range 0.07–0.9 μg ml⁻¹ of aluminum with good precision and accuracy and the detection limit was down to 0.034 μg ml⁻¹. The relative standard deviation for a standard solution of 0.4 μg ml⁻¹ of aluminum is 1.73% (n = 10). The proposed method proved highly sensitive, selective and relatively rapid for the assay of aluminum at ultra trace level without any pre-concentration and separation step. The method was applied to the determination of aluminum in food samples (rice, tea and potato). The analytical results of the real samples were in good agreement with the standard method.     

方波溶出伏安法同时测定食盐中的痕量铅、镉

在4%的盐酸介质中,应用方波溶出伏安法,在电位-0.508V、-0.712V附近分别产生铅和镉的灵敏溶出峰,方法线性良好,具有简便、快速、灵敏度高的优点,以连续标准加入法定量分析,可适用于食盐中痕量铅、镉的连续分析检测。     

阳极溶出伏安法同时测定高盐调味品中铅镉

采用湿法消解结合阳极溶出伏安法对沾水辣、酱油和鱼露等高盐调味品中铅镉的测定进行了方法研究。探索了仪器条件、电解质及其用量、高盐对铅镉的影响,并对酸类型及酸度的干扰、共存离子干扰进行了实验。铅、镉工作曲线的线性范围分别为2⁵0、1²0μg·L^-1,相关系数分别为0.9999和1.0000,仪器检出限为铅0.043μg·L^-1、镉0.029μg·L^-1,方法检出限为铅2.17μg·kg^-1、镉1.43μg·kg^-1。该方法测定实际样品中铅、镉含量的精密度分别为1.11%⁴.66%、0.69%⁵.34%,加标回收率分别为93.9%¹09.9%、94.7%¹07.5%。结果表明方法简便、灵敏,具有较好的选择性和可靠性。      

Determination of trans-resveratrol in red wine by adsorptive stripping square-wave voltammetry with medium exchange

In the present paper, a method for the determination of trans-resveratrol in red wine samples, by adsorptive stripping square-wave voltammetry (Ad-SSWV) in a glassy carbon electrode, is presented. In 0.10 M perchloric medium, trans-resveratrol experiments an adsorptive–oxidative process, which promotes the appearance of a peak at 0.72 V. Calibration graph have been constructed from 5.0 to 35 ng/mL. Detection limit of 4.2 ng/mL has been calculated, according to Clayton criterion. Extraction of trans-resveratrol from red wine with diethylether and posterior clean-up with C18 cartridges is carried out. Recovery percentages close to 100% have been calculated with different red wine samples. The accumulation of analyte in the electrode is carried out at +0.60 V for 60 s, in the presence of 0.10 M HClO₄ and 10% of ethanol; the measurement stage is performed after a medium exchange, in 0.10 M HClO₄ and 30% of ethanol. The standard addition method was employed for the analysis of real samples, since a matrix effect is observed in red wine extract. The method has been applied to several commercial red wines samples, and the results have been satisfactorily validated by HPLC.     

线扫阳极溶出伏安法测食品包装品和食品容器中Pb、Cd

采用线扫阳极溶出伏安法同时测定食品包装品和食品容器中Pb、Cd,用4%HAc浸泡容器和包装品,在0.70mol/LHAc—0.05mol/LKNO3底液中测定Pb、Cd,Pb、Cd加标回收率为91.0%～109.0%、94.0%～108.3%,测定精密度RSD%分别为0.03%～5.56%、0.26%～4.82%,Pb、Cd的线性范围为:0.05～1.40mg/L。     

Determination of trace aluminum in foods by stripping voltammetry

The study of electrochemical behavior of aluminum–cupferron complex indicated that aluminum and cupferron formed complex in 0.4 mol/L (NH₄)₂SO₄ solution. Accumulation potential of −0.95 V (vs. SCE) was applied, while the solution was stirred for 60 s. The response curve was recorded by scanning the potential to the negative direction and the peak current of −1.18 V (vs. SCE) was recorded. This complex absorbed in hanging mercury drop electrode (HMDE) and create a sensitive peak current. The peak current and concentration of aluminum accorded with linear relationship in the range of 4.0 × 10⁻⁸–2.0 × 10⁻⁹ g/mL. The relative standard deviation (at 10 μg/L) is 3.0% and the detection limit is 8 × 10⁻¹⁰ g/mL. The interference of some common ions was studied. This method has been used to determine trace aluminum in foods and water.     

差分脉冲伏安法检测茶叶中痕量铅的研究

本文旨在建立差分脉冲伏安法快速测定茶叶中的铅元素的方法,利用同位镀汞阳极溶出伏安法对茶叶样品中铅元素的含量进行测定,并对测试条件进行了优化,最终选择了我国四大茶区共29种茶叶作为样品。线性范围为40⁴00μg/L;检测限为:1.2×10^-6g/L;加标回收率为:91.1%¹04.2%;相对标准偏差（n=5）为0.86%;将测定结果与国标法检测结果进行对比,具有良好的线性关系（r=0.9979）。本研究为茶叶中铅的检测开发出了快速、简单、准确的方法,可以用于实际样品的检测。      

阳极溶出伏安法测定饮用水中镉、铅、铜、砷

目的建立阳极溶出伏安法快速测定饮用水中镉、铅、铜、砷含量的检测方法。方法采用微波消解处理水样,以玻碳电极为工作电极,Ag/AgCl电极为参比电极,铂电极为对电极测定其溶出电流,采用外标法定量。结果在浓度为0.1～10μg/L范围内, Cd、Pb、Cu、As线性关系良好,方法检出限为0.00004～0.001 mg/L,加标回收率在98.10%～100.35%间。实际样品测定精密度小于2%。结论该方法稳定、快速、灵敏度高、准确度好,是一种高效的检测痕量重金属离子的方法。     

同位镀铋方波溶出伏安法检测蜂蜜中的痕量铅

目的 采用同位镀铋方波溶出伏安法检测蜂蜜中的痕量铅。 方法 采用铋膜电极替代传统的汞膜电极,并结合方波溶出伏安法和电极同位镀铋膜法,实现对蜂蜜中痕量铅的快速检测。结果 优化了底液, pH, 铋浓度, 沉积电位和沉积时间五项最佳实验条件参数。铅在铋膜电极上可得到灵敏的溶出峰, 其溶出电位为0.580 V。在优化的实验条件下, 该方法检测铅的线性范围为5~100 μg/L(r=0.9965), 检测限低达0.630 μg/L。实验结果与石墨炉原子吸收法结果相比无显著性差异。结论 该研究为蜂蜜等食品中铅的快速、高灵敏检测提供了新的手段。     

Selective cloud point extraction for the determination of cadmium in food samples by flame atomic absorption spectrometry

A new cloud point extraction (CPE) procedure for preconcentration of cadmium prior to the determination by flame atomic absorption spectrometry (FAAS) was developed. The method is based on the fact that cadmium could form hydrophobic ion-associated complex in the presence of iodide and methyl green (MG), and the hydrophobic ion-associated complex could be extracted into surfactant-rich phase. The main factors affecting CPE procedure, such as pH, concentration of KI, MG and surfactant, equilibrium temperature and incubation time, sample volume were investigated. Potential interference from co-existing ions was largely eliminated as most of co-existing ions can not form extractable ion-associated complex with iodide and MG. Under the optimum conditions, the limit of detection (3σ) and limit of quantity (10σ) were 0.90 ng mL⁻¹ and 3.0 ng mL⁻¹ for cadmium, respectively, and relative standard deviation was 4.2% (c = 50 ng mL⁻¹, n = 7). The proposed method was successfully applied to determination of cadmium in the certified reference rice sample (GBW08510) and food samples with satisfactory results.     

氢化物发生-原子荧光光谱法同时测定食品中的镉和锡

为提高食品中镉和锡的检测水平,建立了氢化物发生-原子荧光光谱法同时测定食品中的镉和锡的方法.在最佳实验条件下的检出限:镉0.002 9 ng/ml、锡0.19 ng/ml;线性范围:镉0～2ng/ml,相关系数0.999 8,锡0～100 ng/ml,相关系数0.999 9;在0.5 ng/ml时,镉测定的相对标准偏差为1.5%(RSD),2.5 ng/ml时锡的相对标准偏差为3.1%(RSD);试样加标回收率:镉93.0%～100.5%,锡91.3%～99.2%.该方法具有操作简便、快速、检出限低、灵敏度高、结果准确等优点,适合于各种食品镉、锡的联合测定.     

锑膜修饰电极差分脉冲溶出伏安法测定食品中痕量铅、镉

目的 考察并优化同位镀锑膜电极差分脉冲溶出伏安法测定铅、镉的条件.方法 采用差分脉冲溶出伏安法,以锑膜修饰金电极作为工作电极测定食品中痕量铅、镉离子.结果 铅、镉在锑膜电极上可得到灵敏的溶出峰,铅、镉的溶出电位分别为0.58 V(Epb)和0.81 V(Ecd).当电沉积时间为180 s时,铅、镉的检出限分别为1.95和2.10 μg/L,RSD分别为1.14％和0.95％,铅、镉溶出峰电流同0～100μg/L铅、镉离子呈良好的线性关系(r≥0.997).结论 利用本方法测定了食品样品中铅、镉的含量,并与石墨炉原子吸收分光光度法做了对比,结果令人满意,同时使用锑膜修饰电极可避免使用汞膜电极带来的环境污染.     

线扫阳极溶出伏安法测定茶汤中的Pb、Cu

采用线扫阳极溶出伏安法测定茶叶中的Pb、Cu含量 ,在 0 .3mol/L盐酸底液中 ,Pb、Cu的加标回收率P %分别为93.3%～ 1 0 6 .8%、93.9%～ 1 0 5 .4 % ,测定精密度RSD %分别为 0 .39%～ 2 .1 0 %、0 .33%～ 3.2 0 % ,Pb、Cu的线性范围为 0 .1 0～ 0 .70mg/L。