食品中微量钒测定方法的研究

本文采用恒温石墨炉原子吸收技术系统地研究比较了普通石墨管、热解涂层石墨管、涂锆热解涂层石墨管测钒的灵敏度差异;考察了热解涂层石墨管测钒时灰化温度,原子化温度及“冷却步骤”(“Cooling down”技术)的使用对灵敏度的影响;试验了常用酸和食品中主要共存物质对钒测定的干扰并初步探讨了硝酸的干扰机理和干扰的消除方法;试验比较了各种样品处理方法,并对微波消化技术进行了详细的实验研究;建立了测定食品中微量钒快速、准确、可靠的分析方法。其样品的最低检出浓度为0.02ppm;平均加标回收率为98.2±6.1％;标准参考样品NBS-SHM1566中钒的测定结果为2.22+0.08ppm(其标定值为2.3+0.1ppm)。     

热解石墨管--电热原子吸收法直接测定植物样品中微量锗

研究了植物样品中微量锗的测定方法，选择了仪器最佳条件；考察了不同基体改进剂对灵敏度的影响，以铅为改进剂，最高允许灰化温度和原子化温度分别为1200和2500℃，方法相对标准偏差为3．11％，利用热解石墨管测定了灵芝标准品和香菇中的锗，结果令人满意。     

密闭消化石墨炉原子吸收法测定食品中的痕量镉

<正> 本文研究了用密闭消化和石墨炉原子吸收法测定食品中镉的最适条件。用O.2—0.5克试样,1毫升浓硝酸,在150℃处理试样成清亮溶液。取20微升试液注入涂锆石墨管中,在450℃灰化,2000℃原子化。测定粮食、鱼干、皮蛋和蜂蜜中痕量镉时硝酸和试样基体不干扰。空白值低,灵敏度和精密度高。回收率为89—109％。涂锆石墨管有较长的使用寿命。     

石墨炉原子吸收法测定食盐中微量钡

石墨炉原子吸收法（ＧＦＡＡＳ）直接测定食盐溶液中微量钡，是采用热解涂层石墨管或浸锆石墨管及Ｖ２Ｏ５、Ｓｉ、ＮＨ４ＮＯ３作复合基体改进剂，既能消除大量基体氯化钠的气相干扰、提高测定钡的灵敏度，又能延长石墨管的使用寿命。在测定０．４１ｎｇＢａ时，相对标准偏差为８％，回收率８９％～１０６％、平均为９８％。     

石墨炉原子吸收法测定罐头食品中的锡

以密闭消解样品,石墨炉原子吸收法测定食品中微量锡。对影响测定灵敏度的条件进行优化,以氯化钯＋硝酸镁为基体改进剂,在灰化温度1000℃,原子化温度1800℃条件下,方法检出限为6.7μg/L,线性范围0.05～0.20mg/L,回收率99.2%～104.4%,相对标准偏差4.3%。本方法具有检出限低、灵敏度高、简便、准确等优点,可满足食品中准确测定较低含量锡的要求。     

石墨炉原子吸收光谱法测定乳制品中铬的含量

本文主要开展了石墨炉原子吸收光谱法测定乳品中铬含量优化条件的研究.通过采用样品处理技术、基体改进剂、平台式横向加热石墨管、交流纵向塞曼效应背景校正技术相结合的技术及通过对仪器测定条件的优化可基本消除样品干扰问题,其测定灵敏度、检出限及精密度大幅提高.     

石墨炉原子吸收法测定食品中的锗含量

本文采用石墨炉原子吸收技术研究了食品中锗的测定方法。采用硝酸钯作为基体改进剂，明显改进了灵敏度。选择带平台热解涂层石墨管，在基体改进剂作用下，使锗的灰化温度提高到１４５０℃，消除了基体干扰。试验了常用无机酸和食品中常见的一些共存物质对锗测定结果的影响。确立了普遍适用的样品前处理方法。本方法所达到的技术指标为：最低检出浓度为０．０４ｍｇ／ｋｇ；平均加标回收率１００．５±６．４％；对几种食品中锗进行重复测定，其变异系数小于１０％。由于缺少含锗标准物质，故本方法不能直接验证，本文一些结果与资料报道￣［１］完全一致，另一些结果与化学法￣［２］结果也很一致。     

石墨炉原子吸收法测定食盐中钡含量

石墨炉原子吸收法测定盐溶液中微量钡,采用基体改进剂,消除基体氯化钠干扰、提高测定钡的灵敏度.该方法的检出限、灵敏度、加标回收率等均能满足分析要求.     

皮蛋中铅的电热原子吸收测定

<正> 铅是食品中的有害元素之一,故常用食品对铅的含量都有一定的卫生标准。对于含铅量为1μg/g左右的皮蛋或其他食品处理0.5克试样,可以用灵敏度高的石墨炉原子吸收测定。但用普遍石墨管测定时,重现性差,且由于基体干扰,常需在测定前萃取分离或采用标准加入法。前者手续较烦,后者测量误差较大。我们用压力消化法处理试样,用锆盐溶液处理石墨管和用磷酸作基体改进剂消除基体干扰,方法简单且结果的重现性好。     

直接进样-石墨炉原子吸收光谱法测定白酒中的镉

建立直接进样-石墨炉原子吸收光谱法测定白酒中镉的方法,研究不同基体改进剂对吸光度的影响,选择磷酸二氢铵作为测定镉的基体改进剂,进一步研究了磷酸二氢铵溶液的质量浓度、灰化温度、原子化温度对吸光度的影响.结果表明,在单因素试验的基础上,通过正交试验确定的最佳测定条件为:磷酸二氢铵溶液的质量浓度为4.0 mg/mL、灰化温度900℃、原子化温度2100℃.在此条件下,测定白酒中镉的质量浓度为0.210 ng/mL,精密度为3.91％,检出限为0.32 ng/mL,加标平均回收率为96.3％,相对标准偏差为2.61％.直接进样-石墨炉原子吸收光谱法测定白酒中镉,该方法快速、准确、无污染,具有较高的实用价值.     

Calibration and evaluation of nitric acid and ammonia permeation tubes by UV optical absorption

An ultraviolet (UV) optical absorption system has been developed for absolute calibrations of nitric acid (HNO3) and ammonia (NH3) permeation tube emission rates. Using this technique, dilute mixtures containing NH3 or HNO3, both of which interact strongly with many surfaces, are accurately measured at levels below a part per million by volume. This compact and portable instrument operates continuously and autonomously to rapidly (<1 h) quantify the emission of trace gases from permeation devices that are commonly used to calibrate air-monitoring instruments. The output from several HNO3 and NH3 permeation tubes, with emission rates that ranged between 13 and 150 ng/min, was examined as a function of temperature, pressure, and carrier gas flow. Absorptions of 0.015% can be detected which allows a precision (3sigma) of +/-1 ng/min for the HNO3 and NH3 permeation tubes studied here. The accuracy of the measurements, which relies on published UV absorption cross sections, is estimated to be +/-10%. Measurements of permeation tube emission rates using ion chromatography analysis are made to further assess measurement accuracy. The output from the HNO3 and NH3 permeation tubes examined here was stable over the study period, which ranged between 3 months and 1 year for each permeation tube.     

Changes in the cadmium content of rice during the milling process

Milled rice and bran were prepared from brown rice (Oryza sativa japonica) using a commercial scale rice-mill to investigate the changes in cadmium (Cd) content caused by the milling process. Rice sample solution was prepared by microwave digestion using HNO3 and HF, then analyzed by ICP-MS. Cd was measured at m/z 114 in interference correction with MoO and Sn. The digestion method was validated with 4 kinds of certified reference material of "rice flour". We found that the Cd content was reduced only slightly by the milling process. When the Cd concentration of brown rice was regarded as 100, the relative content of the milled rice was 97 (average of 6 samples). In addition, the reduction of the Cd content was only slight when milled rice was processed to "wash-free" rice. The relative Cd content of the bran was 139 when that of brown rice was regarded as 100. These results support the hypothesis that the Cd content is not greatly decreased by the milling process.     

微波消解-原子吸收法快速测定莼菜中铜、锌的含量

应用微波消解制备系统,对莼菜湿样中铜、锌元素进行了微波消解研究,并采用原子吸收法测定其元素的含量。通过L9(34)正交设计,讨论了HNO3/H2O2比、固液比、消解时间、微波功率对微波消解结果的影响。最佳的消解条件为:HNO3/H2O2(V/V)=1:1,固液比(g/ml)=1:12,消解时间为6min,微波功率为700W。在最佳微波消解条件下,进行了精密度实验、回收率实验和金属离子干扰实验。结果表明,所得铜的回收率在97.60%～102.80%之间,RSD为4.61%;锌的回收率在98.40%～101.80%之间,RSD为6.19%。微波消解法处理莼菜湿样,具有快速、简便、节约试剂、消解完全等特点,测定结果的精密度、准确度令人满意。     

Radiochemical investigations on the decomposition of (mono) methyl-mercury by means of acid with regard to the determination of total mercury in fish (author's transl)]

Considerable amonts of mercury in fish muscle tissue are organically bound i.e. appear as (mono)methylmercury-compounds. In order to make mercury of organic origin available for the determination of total mercury by the "cold vapour atomic absorption method", a splitting of the carbon-mercury bond by means of suitable chemical treatment must be maintained beforehand. The main subject of this article are investigations with special regard to the behaviour of (mono)methylmercurychloride during different wet digestion methods. The procedures under study involve wet digestion under reflux with HNO3, with mixtures of HNO3 and HC10(4) and HNO3 and H2SO4, as well as wet digestion with HNO3 in a closed system (pressure decomposition). The course of the decomposition of (mono)methylmercury dependent on time, temperature and concentration of reagents are discussed in detail. All experiments were controlled by measurement of the radioactivity of Hg-203 which had been added in the chemical form of CH3-Hg-Cl. From the analytical results obtained two methods of sample preparation have been derived that permit a reliable determination of total mercury in fish.     

氢化物发生-原子吸收流动注射分析测定鸡蛋中的硒时四种湿法消化方法比较

<正> 硒是人体内必需的元素,它对预防癌症、心血管病、早衰、胃病等有明显疗效,但食入过量的硒则对人体有害。对食物含硒量的测定已成为食品分析中常见的分析项目。近来报道了氢化物发生一原子吸收流动注射分析测定环境样品中痕量硒的方法。本文作者将上述体系和技术用于鲜鸡蛋中硒的测定,对测定前的四种不同湿法消煮进行了比较。     

微波消化微量滴定法测定牛乳中的钙含量

应用微波消化及微量滴定技术,对牛乳中的钙含量进行测定。结果表明：用5mL 浓HNO3、3mL H2O2的混合液对10.00mL 样品进行消化,加入0.4mL 三乙醇胺消除Al3+、Fe3+ 对钙离子测定的影响,取得了较好的测定效果。伊利纯牛奶和高钙奶的EDTA 标准液消耗体积平均值分别为1.616、1.450mL,RSD 分别为0.16% 和0.32%,7 次测定的回收率为98%～101.5%。与传统的消化方法及常量滴定法相比,该法具有简单、快速、节省试剂、环境污染小等优点。     

微波消解-石墨炉原子吸收法测定果汁中铅和镉

应用具有温度传感器附件的Ethos1型微波消解仪处理果汁样品,并采用石墨炉原子吸收法对其中铅、镉含量进行测定。对消解试剂和微波消解条件进行了筛选和优化,研究了石墨炉原子吸收的测定条件。研究表明,以HNO3-H2O2(7∶1,V/V)作为微波消解试剂,180℃,1 200W,消解8min最佳。在基体改进剂NH4H2PO4存在下,可有效地消除基体的影响,建立了微波溶样原子吸收光谱法测定果汁中Pb、Cd的方法,其Pb和Cd的检测限分别为6.0μg/L和1.0μg/L。将该法应用于果汁样品中Pb、Cd的测定,结果令人满意,RSD小于5.0%,Pb回收率为78.7%～102.4%,Cd回收率为97.8%～108.7%。通过试验,提出在微波消解前,在电热消解仪上进行预消解(140℃,20min),增大了称样量,显著降低了方法的检出限。微波消解法处理果汁样品,具有快速、简便、节约试剂、消解完全等特点,测定结果的精密度、准确度令人满意。     

FAAS测定侗家奇液酒中13种微量元素

将火焰原子吸收光谱法(FAAS)技术应用于保健酒中微量无机元素的分析,测定了侗家奇液酒中13种微量元素。结果表明,侗家奇液酒含有丰富的微量元素K、Ca、Zn、Fe、Mn、Mg、Mo、Sr、Li、Rb和Se,重金属元素Cu、Pb含量比较低。在选定实验条件下,样品中各元素互不干扰,样品用3 mL/L硝酸稀释后直接进样测定,所测元素回收率为98.1%～103.9%,精密度RSD为0.02%～4.8%。方法简便、快速、安全、可信。