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离子色谱-电感耦合等离子体质谱法测定乳粉的汞形态

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林立, 王琳琳, 孙海波, 孙继红. 离子色谱-电感耦合等离子体质谱法测定乳粉的汞形态[J]. 岩矿测试, 2014, 33(3): 395-401.
引用本文: 林立, 王琳琳, 孙海波, 孙继红. 离子色谱-电感耦合等离子体质谱法测定乳粉的汞形态[J]. 岩矿测试, 2014, 33(3): 395-401.
shu
LIN Li, WANG Ling-ling, SUN Hai-bo, SUN Ji-hong. Speciation Analysis of Mercury in Milk Powder using Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry Technique[J]. Rock and Mineral Analysis, 2014, 33(3): 395-401.
Citation: LIN Li, WANG Ling-ling, SUN Hai-bo, SUN Ji-hong. Speciation Analysis of Mercury in Milk Powder using Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry Technique[J]. Rock and Mineral Analysis, 2014, 33(3): 395-401.
shu

离子色谱-电感耦合等离子体质谱法测定乳粉的汞形态

  • 1.

    北京工业大学, 北京 100022

  • 2.

    国家食品质量安全监督检验中心, 北京 100094

  • 基金项目: 国家质检总局科技计划项目（2012QK013）; 质检公益性行业科研专项（201210116）
详细信息
    作者简介: 林立, 高级工程师, 博士研究生, 主要从事分析化学的研究.E-mail: linli77422@aliyun.com

  • 中图分类号: TS252.5;O614.243

Speciation Analysis of Mercury in Milk Powder using Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry Technique

  • 1.

    Beijing University of Technology, Beijing 100022, China

  • 2.

    China National Food and Safety Supervision and Inspection Center, Beijing 100094, China

    摘要

  • 对于乳粉的汞形态分析，由于基质的复杂性，有机汞非常容易与样品中蛋白质上的巯基结合，形成稳定的络合物，在前处理过程中须保证各形态提取完全且各形态之间不会发生相互转化，因此样品前处理是汞形态分析的难点；同时乳粉中汞含量极低，对方法检出限提出了更高的要求。本文通过优化样品前处理过程，建立了离子色谱-电感耦合等离子体质谱测定乳粉中三种汞形态（二价汞、甲基汞、乙基汞）的方法。实验采用多种复合酶（蛋白酶、脂肪酶、淀粉酶）对乳粉基质中的蛋白、脂肪、淀粉进行解离，采用L-半胱氨酸-盐酸-甲醇的混合溶液作为提取剂进行超声提取，样品过RP固相萃取小柱去除杂质后用C18色谱柱（5 μm，4.6 mm×150 mm）进行分离，流动相采用10 mmol/L乙酸铵-0.12% L-半胱氨酸-5%甲醇混合溶液进行淋洗，5 min内即可实现三种汞形态的基线分离。二价汞、甲基汞和乙基汞的加标回收率在79.9%~111.2%之间，检出限分别为0.5 μg/kg、0.6 μg/kg、0.9 μg/kg。实际样品分析表明，汞总量很低的乳粉，汞各形态的提取率也能达到70%以上，能够满足检测要求。本方法在样品前处理过程中采用酶解的方式解离复杂基体中的汞形态，提高了提取率至80%以上；仪器分析方面采用甲醇作为增敏剂，提高了检测灵敏度，适用于乳粉样品中痕量汞形态的检测。

    Sample pre-treatment difficulties arise during the analysis for mercury speciation in milk powder due to the complexity of the sample matrix. The organic mercury combines easily with sulfydryl of proteins in the matrix sample, to form a stable complex. Therefore it is very important to ensure that all forms are extracted completely and do not transform during the pre-treatment process. The method with a lower detection limit was necessary because the concentration of mercury was too low. For this purpose, the method for determination of mercury speciation (inorganic mercury, methylmercury, ethylmercury) in milk was established by ion chromatography inductively coupled plasma mass spectrometry with optimized pre-treatment conditions. Protein, fat, and starch in milk powder were dissociated using a variety of composite enzymes (protease, lipase and amylase). The sample was ultrasonically extracted using mixed solution of L-cysteine, hydrochloric acid with methanol and was further purified by RP solid phase column. Mercury speciation was separated by Agilent Eclipse XDB-C18 column (5 μm, 4.6 mm×150 mm).The mobile phase contained 10 mmol/L ammonium acetate, 0.12% L-cysteine, and 5% (m:m) methanol solution. Three kinds of? mercury speciation were baseline separated within 5 min. The spiked recoveries of inorganic mercury, methylmercury and ethylmercury were obtained in the range of 79.9%-111.2%. The instrument detection limits were 0.5 μg/kg, 0.6 μg/kg and 0.9 μg/kg, respectively. The results obtained from actual? sample testing show that the extraction rate of total mercury can reach more than 70% in low concentration mercury milk powder, which meets the test requirements. The extraction rate can reach more than 80% because the composite enzyme was used in this method to dissociate mercury speciation from the complex matrix during sample pre-treatment processing. Methanol was applied as a sensitizer to improve detection sensitivity. A simple, rapid and reliable method was developed for the determination of mercury speciation in milk powder.

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  • 图 1  超声时间对提取率的影响

    Figure 1. 

    下载: 全尺寸图片 幻灯片

    图 2  甲醇对汞检测灵敏度的影响

    Figure 2. 

    下载: 全尺寸图片 幻灯片

    图 3  IC-ICP-MS联机检测汞的各种形态的分离色谱图(浓度以汞计均为10 μg/L)

    Figure 3. 

    下载: 全尺寸图片 幻灯片

    图 4  乳粉样品中汞形态的色谱分离图

    Figure 4. 

    下载: 全尺寸图片 幻灯片

    表 1  ICP-MS仪器工作条件

    Table 1.  Working parameters of the ICP-MS instrument

    工作参数设定条件工作参数设定条件
    功率1500 W采样深度9.5 mm
    载气(Ar)流量0.60~1.20 L/min采集质量数202Hg
    辅助气(Ar)
    流量    		与载气流量的总和
    保持在1.0~1.2
    L/min之间    		矩管石英一体化，
    2.5 mm中心通道
    进样管内径< 0.2 mm灵敏度> 300 Mcps/(μg/g)
    采样锥铂锥积分时间0.5 s
    下载: 导出CSV

    表 2  不同提取液对汞形态的回收率

    Table 2.  The recovery rate of Hg speciation by different extraction systems

    汞形态回收率(%)
    体系①：0.12% L-半胱氨酸溶液+0.1%盐酸+0.1%硫代硫酸钠溶液+5%甲醇体系②：0.12% L-半胱氨酸溶液+0.1 mol/L盐酸+5%甲醇体系③：50 mmol/L氢氧化钠碱性溶液+5%甲醇
    二价汞12.198.555.3
    甲基汞100.4102.344.9
    乙基汞97.680.639.4
    下载: 导出CSV

    表 3  线性方程、线性范围和仪器检出限

    Table 3.  Linear equations, linear range and the detection limit of the instrument

    汞形态线性方程相关系数
    (r2)    		线性范围
    (μg/L)    		仪器检出限
    (μg/L)
    二价汞y =20512x-1268.71.00000.5~20.00.01
    甲基汞y =14778x-586.90.99980.5~20.00.012
    乙基汞y =13671x-258.40.99930.5~20.00.018
    下载: 导出CSV

    表 4  方法加标回收率和精密度

    Table 4.  Recovery and precision tests of the method

    物质名称加标溶液1
    (2 μg/L)    		加标溶液2
    (10 μg/L)    		加标溶液3
    (20 μg/L)
    平均
    回收率
    (%)    		RSD
    (%)    		平均
    回收率
    (%)    		RSD
    (%)    		平均
    回收率
    (%)    		RSD
    (%)
    二价汞105.62.191.63.195.22.1
    甲基汞95.61.797.52.2111.22.0
    乙基汞79.92.884.73.287.33.2
    下载: 导出CSV

    表 5  乳粉中汞的形态分析

    Table 5.  Analytical results of mercury speciation in milk powder

    样品名称测汞仪测定的
    总汞含量
    (mg/kg)    		汞形态的测定值(mg/kg)汞形态的
    提取率
    (%)
    二价汞甲基汞
    (以汞计)    		乙基汞
    (以汞计)
    乳粉10.3520.3170.028未检出98.0
    乳粉20.1520.1320.015未检出96.7
    乳粉30.0360.034未检出未检出94.4
    乳粉40.0190.0110.003未检出73.6
    乳粉50.0250.021未检出未检出84.0
    鱼肉标准物质
    (GBW 10029)    		0.86
    (标准值0.85)    		未检出0.85
    (标准值0.84)    		未检出98.8
    下载: 导出CSV
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出版历程
收稿日期:  2013-11-02
录用日期:  2013-11-29
刊出日期:  2014-03-25

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