氢化物发生ICP-AES法测定药用植物中的痕量锗

本文应用氢化物发生ＩＣＰ－ＡＥＳ法研究了药用植物样品中痕量锗的测定方法，系统地研究了ＩＣＰ－ＡＥＳ仪器参数及氢化物发生条件对锗谱线信背比的影响，考察了１３种共存元素的干扰，并比较了植物样品的３种前处理方法。选定Ｈ３ＰＯ４－ＨＮＯ３－Ｈ２Ｏ２消化，在３ｍｏｌ／ＬＨ３ＰＯ４介质中，以１５ｇ／ＬＮａＢＨ４还原，测定药用植物样品中的锗，相对标准偏差≤２．９％，回收率为９４％～１０３％。方法检出限达０．１３μｇ／Ｌ。     

氢化物发生ICP—AES法测定药用植物中的痕量锗

本文应用氢化物发生ＩＣＰ－ＡＥＳ法研究了药用植物样品中痕量锗的测定方法，系统地研究了ＩＣＰ－ＡＥＳ仪器参数及氢化物发生条件对锗谱线信背比的影响，考察了１３种共存元素的干扰，并比较了植物样品的３种前处理方法，选定Ｈ３ＰＯ４－ＨＮＯ３－Ｈ２Ｏ消化，在３ｍｏｌ／ＬＨ３ＰＯ４介质中，以１５ｇ／ＬＮａＢＨ４还原，测定药用植物样品可的锗，相对标准偏差≤２．９％，回收率为９４％～１０３％，方法检出限达０．１３μ     

含氟Y—Ba—Cu—O高温超导体稳定性与结构的研究

应用ＢａＦ２，ＣｕＦ２和ＹＦ３分别部分代换ＢａＯ，ＣｕＯ和Ｙ２Ｏ３制得了一系列带有氟元素的Ｙ－Ｂａ－Ｃｕ－Ｏ高温超导体样品，其中ＢａＦ２代换ＢａＯ的摩尔量可达４５％，样品的零电阻温度为８２．５－９３．５Ｋ。应用ＸＲＤ，ＤＴＡ，ＩＲ和化学方法研究了样品的结构和稳定性。     

石墨炉原子吸收法测定聚苯乙烯泡沫塑料中的汞

本文提出的在聚苯乙烯泡沫塑料中测定汞的方法是将样品溶解在苯中，以Ｎａ２Ｓ２Ｏ３溶液反洗出汞，利用反洗液中Ｎａ２Ｓ２Ｏ３作基体改进剂，石墨炉原子吸收法测定汞，方法简便，快速，特征量为８０ｐｇ／０．００４４Ａ。本法分析样品与冷原子荧光法的结果一致，相对标准偏差≤８％，回收率９２％－１０２％。     

半微分阴极溶出伏安法研究硫离子在银电极上的电化学行为

用半微分阴极溶出伏安法研究硫离子在银电极上的电化学行为。在ＮａＯＨ－ＥＤＴＡ－Ｎａ２ＳＯ３底液中，可消除溶解氧及部分重金属离子Ｃｕ２＋，Ｐｂ２＋，Ｚｎ２＋，Ｃｄ２＋和Ｎｉ２＋的干扰。一些阴离子Ｃｌ－，Ｉ－，ＮＯ－３和ＳＯ２－４不干扰。硫离子浓度在３．１９×１０－６ｍｏｌ／Ｌ至３．１３×１０－５ｍｏｌ／Ｌ范围内与溶出峰高成线性关系。对两种人发样品中硫含量测定的回收率分别为９３．９％和９７．８％。     

Co/γ-Al_2O_3 CATALYSTS FOR NITRIC OXIDE SELECTIVE REDUCTION BY ETHYLENE

采用等量浸渍法制备了Ｃｏ／γＡｌ２Ｏ３催化剂，考察了它们对乙烯选择还原ＮＯ的反应性能，用ＸＲＤ和ＢＥＴ方法表征了催化剂．结果表明，在Ｃｏ／γＡｌ２Ｏ３中存在两种钴相，即Ｃｏ３Ｏ４和ＣｏＡｌ２Ｏ４，前者是Ｃ２Ｈ４的完全氧化活性中心，后者是ＮＯ的选择性还原活性中心．随焙烧温度的提高，Ｃｏ３Ｏ４向ＣｏＡｌ２Ｏ４相的转化是样品对Ｃ２Ｈ４完全氧化活性下降和对ＮＯ选择还原活性升高的主要原因．更高焙烧温度下，样品活性的下降与载体及ＣｏＡｌ２Ｏ４相的烧结有关．     

毛细管电泳对微生物代谢中硫酸根和硫代硫酸根的分离与测定

建立了微生物代谢中硫酸根和硫代硫酸根的毛细管电泳分析方法．在选定实验条件下，各种阴离子（Ｓ２Ｏ２－３、ＳＯ２－４、ＣＩ－、ＮＯ－３、ＰＯ３－４）在４ ｍｉｎ内达到完全分离，其中 Ｓ２Ｏ２－３和ＳＯ２－４迁移时间的相对标准偏差小于１％，峰面积的相对标准偏差小于５％．测定了４种菌株分别在两种培养基中的Ｓ２Ｏ２－３和ＳＯ２－４浓度随培养时间的变化．结果表明，其中一菌株在ＳＫ基中对Ｓ２Ｏ２－３有明显的氧化作用．     

小麦根系中有机酸的离子色谱法分析研究

研究了离子交换和离子排斥法用于小麦根系中有机酸分析的色谱条件,首次建立了植物报系中有机酸的高子色谱分析方法。分别用Ｎａ＿２ＣＯ＿３／ＮａＨＣＯ＿３,Ｎａ＿２ＣＯ＿３／ＮａＯＨ和ＨＣｌ作离子交换和离子排斥分高的流动相,选用化学抑制型电导检测器。对样品中柠檬酸、苹果酸、丁二酸、反丁烯二酸、乙酸、草酸的检测限为Ｏ１～０．５μｇ／ｍＬ,相对标准偏差为１．７８％～２．９７％,样品加标回收率为１００±１０％。     

含氟Y－Ba－Cu－O高温超导体稳定性与结构的研究

应用ＢａＦ２、ＣｕＦ２和ＹＦ３分别部分代换ＢａＯ、ＣｕＯ和Ｙ２Ｏ３制得了一系列带有氟元素的Ｙ－Ｂａ－Ｃｕ－Ｏ高温超导体样品，其中ＢａＦ２代换ＢａＯ的摩尔量可达４５％，样品的零电阻温度为８２．５～９３．５Ｋ。应用ＸＲＤ、ＤＴＡ、ＩＲ和化学方法研究了样品的结构和稳定性。初步实验结果表明，氟元素只有少量进入超导相，但含氟的Ｙ－Ｂａ－Ｃｕ－Ｏ超导体在水蒸气和二氧化碳中的稳定性则大大提高。     

S_2OF_(10)气体标准样品制备方法和测定方法研究

提出了一系列的安全、方便、可靠、在线和可连续操作的热解吸／色谱分析柱制备Ｓ２ＯＦ１０纯品、指数稀释法配制Ｓ２ＯＦ１０标准样品、应用定量校正系数测定样品中痕量Ｓ２ＯＦ１０的方法和技术。分别采用气相色谱、红外光谱、气相色谱／质谱等方法对色谱制备的Ｓ２ＯＦ１０纯品进行了纯度分析和测定。配制Ｓ２ＯＦ１０标准气体的体积分数范围为８．０×１０－７～２．６×１０－４。气相色谱测定Ｓ２ＯＦ１０的定量校正系数为０．１９７,测定方法的相对误差范围为１．８％～２０％。     

电热原子吸收法直接测定牛奶样中痕量的铅和镉

采用石墨炉原子吸收法，直接测定了牛奶与奶粉中痕量Pb与Cd．发现食品加工过程中荐在着重金属的污染．     

Radioimmunoassay of PCBs in Milk and Blood

A radioimmunoassay was developed capable of determining Aroclor 1260 in milk at levels of from 20 to 80 ppb and in blood from 2 to 16 ppb. The values obtained by radioimmunoassay correlate well with those determined by gas-liquid chromatography (r² = 0.96 for milk and 0.99 for blood) but were lower. Antiserum was produced in rabbits and was specific for 2, 2′, 4, 4′, 5, 5′-hexachlorobiphenyl. It cross-reacted with congeners and isomers in Aroclor 1254 and 1260 to the extent that a 20% decrease in binding was observed with 0.1 ng of either mixture. The method requires preliminary cleanup of the extract on alumina and utilizes 25 % dimethyl sulfoxide in the assay medium to promote solubilization of the substrates.     

Determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in Milk, Cheese and Chocolate

 Combined analytical procedures consisting of wet digestion step followed by instrumental determination – differential pulse cathodic stripping voltammetry (DPCSV) or electrothermal atomic absorption spectrometry (ETAAS) – as well as a direct analysis method – slurry sampling ETAAS – for the determination of Cd, Co, Cr, Cu, Fe, Ni and Pb in milk, cheese and chocolate are described and compared. Wet digestion using a mixture of HNO₃-HClO₄-H₂O₂ is proposed for complete matrix decomposition prior to trace analyte determinati on by DPCSV or ETAAS. A mixture of HNO₃-H₂O₂ is used for slurry preparation. Optimal instrumental parameters for trace analyte measurements are presented. The reliability of the procedures has been verified by analyzing standard reference materials. Results obtained are in good agreement with the certified values and the relative standard deviations (for these results) are in the range 5–10% for wet digestion DPCSV or ETAAS and 3–9% for slurry sampling ETAAS in the range of 2 μgċg⁻¹ (Cd) to 12 μgċg⁻¹ (Fe). Received August 24, 1999. Revision January 20, 2000.     

Rapid Determination of Lactulose in Milk Using Seliwanoff's Reaction

ABSTRACT

A rapid method based on Seliwanoff's reaction to distinguish between UHT and sterilised milk was proposed. Lactulose was determined directly in milk with no treatment. Analysis of raw milk and its carbohydrates showed that the only interference was the relatively high concentration of lactose, which imposes the lower limit of detection. Small variations of lactulose (9mg dL^?) during heat treatment could be observed when the absorbance was measured against pretreated milk (blank). This method showed a linear range between 17–170mg dL^? and a detection limit lower than that of the official HPLC method. This novel procedure was compared with a commercially available enzymatic method and the results obtained correlated well.     

A Potentiometric Method for Determination of Oxidized Ketone Bodies in Milk

Following the decarboxylation of acetoacetic acid by heating and the separation of acetone from milk matrix by steam distillation, acetone was allowed to react with bromine in the presence of nitric acid, causing the formation of bromoacetone and bromide; the latter was then quantified by means of a suitable ion-selective electrode applying the calibration principle. Based on checking reproducibility and on comparative analyses performed by a widely accepted photometric method, the potentiometric method developed was found to be adequate for the determination of the oxidized ketone bodies.     

高效液相色谱法测定乳及乳制品中硫苯唑残留量

建立了高效液相色谱测定乳及乳制品中硫苯唑残留量的检验方法,用氢氧化钾皂化试样中脂肪,用乙酸乙酯提取硫苯唑,在45℃以下浓缩近干,定容至1.0 mL.在高效液相色谱测定中用ODS C18柱为固定相,甲醇和水(70+30)混合溶液作为流动相.在保留时间为4.43 min时用二极管阵列检测器检测硫苯唑的色谱峰,外标法定量.检出限(3S/N)为0.02 mg·kg-1,回收率在94.5%～98.6%之间,相对标准偏差(n=10)在1.3%～4.2%之间.     

牛奶的保鲜

本文介绍了牛奶的保鲜方法,说明了牛奶致腐的原因,概述了因微生物的作用所导致的牛奶中乳糖、蛋白质和脂肪3种主要成分的变化,并简单介绍了这些变化的反应机理。     

Simple and Rapid Method for Determination of Selenium in Breast Milk by HG-AFS

A digestion procedure using H₂SO₄/HNO₃/H₂O₂ was found to be effective for destruction of human milk samples. In conjunction with a sensitive hydride generation atomic fluorescence spectrometry detection system, it is suitable for determination of selenium in those samples where the available mass of breast milk and the low selenium concentration are limiting factors. Only 1g of milk sample is needed. The procedure is simple, rapid and of low contamination potential since it is performed in the same Teflon tube from weighing to measurement. The digestion of 20 samples is completed in three hours. The detection limit is 0.25±0.04ngg^–1 of a measured solution of sample or 2.5ngg^–1 of milk. The relative uncertainty is 10% (coverage factor of 2.3, 95% probability). Because of these advantages the method is particularly suitable for epidemiological studies. The mean concentration of selenium in 62 samples of human milk from lactating women residing in the North East of Italy was 12±3ngg^–1, which is in the range of reference data.     

An On—line Galvanic Cell Generated Electrochemiluminescence and Flow Injection Determination of Calcium in Milk and Vegetable

An on-line Ag/Al galvanic cell is investigated and employed to generate electrochemiluminescence(ECL).The potential of the galvanic cell could be adjusted by varying the components of flow reagent.The cell performed perfect capability of supplying a stable potential for ECL generation.Based on the weak ECL of calcein blue could be greatly sensitized by the presence of calcium in alkaline solution,calcium contents in milk samples and in cabbage were assayed and the results were compared with those from ICP-AES method.     

The Determination of Iodine in Milk and Milk Chocolate by Anion HPLC

Abstract

An HPLC method is described for the extraction and analysis of iodine as iodide in milk, cocoa beans and milk chocolate. Prior to analysis samples are finely ground if necessary and combusted in a modified Shoeninger flask. The liberated halide is absorbed in a basic reducing medium which is concentrated and brought to volume with distilled water prior. HPLC analysis used an 8 mm 5μ C₁₈ cartridge in a RCM-100 with detection of the iodide ion at 226 nm. The mobile phase consisted of an ion-pairing agent, buffer and acetonitrile. The method is accurate and precise showing reasonable agreement with a National Bureau of Standards spray dried milk sample.