氢化物发生-原子荧光光谱法测定工业磷酸中的铅

采用盐酸处理工业磷酸试样,用氢化物发生-原子荧光光谱法测定工业磷酸中的铅,对仪器条件、盐酸酸度、预还原剂用量、还原剂用量、共存元素干扰进行了试验,方法的检出限为0．028ug／L,测定精密度0．84％,回收率为98．9％-101．4％。建立的氢化物发生-原子荧光光谱法测定工业磷酸中的铅的分析方法具有操作简单,灵敏度高,重现性好等优点,能满足日常检验的要求。     

微波消解－石墨炉原子吸收法测定鱿鱼中的铅和镉

铅和镉的检测方法归纳起来有原子吸收光谱法、电感耦合等离子体原子发射光谱、质谱法、分光光度法等,本文研究了硝酸－双氧水体系对鱿鱼样品微波消解微波消解石墨炉原子吸收分光光度法测定鱿鱼中的铅和镉的方法,选择正磷酸作为基体改进剂,寒曼扣背景,结果表明本方法简便易操作、精密度好、准确度高。铅和镉的方法检测限为0．017μg／g和0．00055μg／g,铅、镉样品回收率分别在80．0％～98．0％和83．0％～96．1％之间。精密度和重现性均能满足试验要求。     

交流示波极谱滴定法测定电镀液中的微量铅

提出了用交流示波极谱法测定电镀液中的微量铅，并研究了各项试验条件。铅在0．100～10.0mg／mL范围内，标准偏差在0．200％～0．220%之间，相对标准偏差为4．29‰～4．73‰。该法可用于硫酸盐镀锌技术的电镀液中微量铅的分析测定，其加标回收率在98．0％～103％之间，操作简便，测定快速，分析可靠。     

碱熔法消解—火焰原子吸收法测定云南红壤中的铜、铅、锌、镉

采用碱熔法对云南红壤进行消解,再用火焰原子吸收法测定其中铜、铅、锌、镉的含量.结果表明,铜、铅、锌、镉的加标回收率分别为91.32％、93.00％、120.56％、90.80％.该方法操作条件易于控制,精密度高,适用于土壤重金属元素的分析测定.     

碱熔法消解一火焰原子吸收法测定云南红壤中的铜、铅、锌、镉

采用碱熔法对云南红壤进行消解,再用火焰原子吸收法测定其中铜、铅、锌、镉的含量。结果表明,铜、铅、锌、镉的加标回收率分别为91．32％、93．OO％、120．56％、90．80％。该方法操作条件易于控制,精密度高,适用于土壤重金属元素的分析测定。     

石墨炉原子吸收光谱法测定碳纤维中微量元素铅的含量

采用石墨炉原子吸收光谱法,水样处理后加入基体改进剂,测定水中有害元素痕量铅.实验优化了石墨炉原子吸收光谱法的测定条件.重点讨论了铅的灰化温度、原子化温度以及基体改进剂的选用对铅测定结果的影响,结果表明,以磷酸二氢盐、钯盐为基体改进剂可提高灰化温度,消除样品中的钙、镁、钠等复杂基体的干扰,相对标准偏差为2.23％,回收率为94.0％～102.0％,具有良好的精密度和回收率.方法简便快速、结果准确.     

石墨炉原子吸收光谱法测定碳纤维中微量元素铅的含量

采用石墨炉原子吸收光谱法,水样处理后加入基体改进剂,测定水中有害元素痕量铅。实验优化了石墨炉原子吸收光谱法的测定条件。重点讨论了铅的灰化温度、原子化温度以及基体改进剂的选用对铅测定结果的影响,结果表明,以磷酸二氢盐、钯盐为基体改进剂可提高灰化温度,消除样品中的钙、镁、钠等复杂基体的干扰,相对标准偏差为2．23％,回收率为94．0％-102．0％,具有良好的精密度和回收率。方法简便快速、结果准确。     

用催化极谱法测定工业废水中的铅

<正> 铅对人体有害,因此铅离子是工业污水排放的重要控制指标之一。检测铅离子的方法有原子吸收法和双硫腙比色法。前者直接测定工业废水中的铅,灵敏度不高;后者操作步骤繁琐,须使用剧毒试剂氰化钾,污染了环境。用催化极谱法能测定铅近ppb级,而且仪器简单、操作简便、测定快速,但应用于废水中     

氢化物发生-原子荧光光谱法测定碳酸钙中的铅

采用盐酸处理碳酸钙试样,用氢化物发生-原子荧光光谱法测定碳酸钙中的铅,对仪器条件、盐酸酸度、预还原剂用量、还原剂用量、共存元素干扰进行了实验,方法的检出限为0.028 μg/L,测定的相对标准偏差为0.84%,回收率为98.7%～103.9%.建立的氢化物发生-原子荧光光谱法测定碳酸钙中的铅的分析方法具有操作简单、灵敏度高、重现性好等优点,能满足日常检验的要求.     

顺序注射氢化物发生-原子荧光光谱法测定硅铁中的铅

采用HNO3-HF-HClO4消解样品,顺序注射氢化物发生-原子荧光法测定硅铁中的铅。该方法在选定的操作条件下,测定硅铁中铅的回收率为95.0%～106.0%,检出限为0.410 3 ng/mL,相对标准偏差为1%～5%。     

The Determination of n-3 Fatty Acid Levels in Food Products Containing Microencapsulated Fish Oil Using the One-Step Extraction Method. Part 1: Measurement in the Raw Ingredient and in Dry Powdered Foods

An optimized one-step extraction and methylation method (OSE) for the determination of n-3 fatty acid levels in microencapsulated fish oil products has been described. Validation of the method for the food ingredient powder MEG-3^® (a commercial microencapsulated fish oil product manufactured by Ocean Nutrition Canada Ltd, with a gelatin shell matrix) has been demonstrated and compared to a method that combines enzymatic digestion of the shell material, gravimetric determination of released oil payload and an official method of fish oil analysis. Excellent agreement between the two methods was also achieved using a microencapsulated standard of pure ethyl palmitate. The OSE method was applied to an infant formula containing microencapsulated fish oil powder and is shown to be a valid method for such dry powdered foods.     

电导滴定法测定油脂的皂化价

报道用电导滴定法测定油脂皂化价的新方法。该法克服了反滴定法测定色泽较深油脂时,在滴定终点酚酞指示剂色变点不明显的缺点,所得电导滴定曲线线性关系较好,测定结果准确可靠。用于鱼油皂化价测定,其相对标准偏差小于１％。     

原油凝点测定规程差异研究综述

目前进口原油的品种比较复杂,而测定原油凝点的方法可以采用国标法和行标法。但不同的实验方法测定的结果也会不同。通过对影响原油凝点测定的主要影响因素考察、比较两种方法的差异性,分析了影响凝点试验结果产生差异的原因,同时提出提高测定原油凝点准确性的建议。     

Determination of lead in frying oils by direct current plasma atomic emission spectrometry

Two methods for determination of lead in frying oils by direct current plasma-atomic emission spectrometry were investigated. The first method is based on the formation of an oil-water emulsion followed by aspiration of the sample directly into the plasma. The second method involves extraction of lead from oil into an aqueous ethylene diamine tetraacetic acid phase before measurement. The methods were applied to the determination of lead in used frying oil samples collected from different parts of Cairo, Egypt.     

Determination of copper, lead, and nickel in edible oils by plasma and furnace atomic spectroscopies

An atmospheric pressure microwave digestion procedure is described for the determination of copper, lead, and nickel in edible oils. The digestion procedure is compatible with either inductively coupled plasma atomic emission spectrometry (ICP-AES) or graphite furnace atomic absorption spectrometry (GFAAS). Instrument conditions are specified to allow the simultaneous determination of all three metals for each sample introduction. Method detection limits were element-specific but equal to or less than 50 ng/g with ICP-AES and 30 ng/g with GFAAS. Results from spike and recovery experiments at levels of 50, 100, and 200 ng/g are reported for corn and soybean oil. For soybean oil, recoveries at 100 ng/g were 90, 100, and 106%, respectively, for copper, lead, and nickel with ICP-AES, and 89, 106, and 96%, respectively, with GFAAS. Recoveries for corn oil spiked at 100 ng/g were 93, 95, and 103%, respectively, for copper, lead, and nickel with ICP-AES, and 90, 117, and 100%, respectively, with GFAAS. Day-to-day reproducibility was demonstrated by similar method recoveries and reproducibilities in independent analysis of two canola oil sample sets that were spiked at 100 ng/g.     

Fish oil sensory properties can be predicted using key oxidative volatiles

The high level of PUFA in fish oil, primarily eicosapentaenoic acid (EPA) and DHA result in rapid oxidation of the oil. Current methods used to assess oxidation have little correlation with sensory properties of fish oils. Here we describe an alternative method using solid phase microextraction (SPME) combined with GC‐MS to monitor volatile oxidation products. Stepwise discriminant function analysis (DFA) was used to classify oils characterized as acceptable or unacceptable based on sensory analysis; a cross‐validated success rate of 100% was achieved with the function. The classification function was also successfully validated with tasted samples that were not used to create the method. A total of 14 variables, primarily aldehydes and ketones, were identified as significant discriminators in the classification function. This method will be useful as a quality control method for fish oil manufacturers. Practical applications: This paper describes an analytical method that can be used by fish oil manufacturers for quality control purposes. Solid phase microextraction and GC‐MS were used to monitor volatile oxidation products in fish oil. These data, combined with results of analyses by a sensory panel, were used to create a function that classified fish oil samples as acceptable or unacceptable. The volatile oxidation products used to in the function were primarily aldehydes and ketones. This method can be used by fish oil manufacturers as an alternative to expensive sensory panels.     

A Convenient Method for the Accurate Determination of Phosphorous in Fish Oils

The phosphorous content of fish oil was determined by acid hydrolysis for 168 h (one week) in 2 M hydrochloric acid at 120°C in glass tubes, followed by filtration and molybdenum blue colour development in an aliquot of the filtrate. The method is regarded as a convenient routine laboratory procedure, and the results obtained by the method are in good agreement with those obtained with the ashing procedure of the American Oil Chemists' Society. The determination has been satisfactorily applied to the analysis of many South African fish oils.     

A simple and quick determination of aldehydes in autoxidized vegetable and fish oils

A simple and quick method for the quantitative determination of aldehydes in oxidized oils was established. The analysis was based on the reaction of N,N-dimethyl-p-phenylenediamine (DPPD) with aldehydes in the presence of acetic acid. Reaction products were determined by visible absorption at wavelengths of 400, 460 and 500 nm. The errors of the DPPD method in the analyses of total aldehydes in authentic mixtures of various aldehydes were less than 5%, and this method could be used successfully to determine aldehyde contents in oxidized vegetable and fish oils. The reaction time of the DPPD method (10 min at 30°C) is much shorter than that of the conventional method that uses 2,4-dinitrophenylhydrazine as a reagent (30 min at 60°C). The simplicity of the procedure enables a quick determination of aldehyde contents in oxidized oil samples.     

Determination of Furan Fatty Acids in Food Samples

Furan fatty acids (F-acids) are valuable bioactive compounds found at low concentrations in food. A method for the quantitative determination of saturated F-acids in food is reported. The sample preparation is based on accelerated solvent extraction, transesterification into methyl esters and silver ion chromatography (20% AgNO₃ in silica, 1% deactivated) of the resulting methyl esters. There then follows determination of the enriched F-acid methyl (or ethyl) esters by GC/EI-MS in the selected ion monitoring (SIM) mode. The 9-(3-methyl-5-pentylfuran-2-yl)-nonanoic acid ethyl ester (9M5-EE) was used as an internal standard for recovery checks. The limit of detection was 11 pg, and the recovery rate of the silver ion chromatography was 85% (n = 5). Further F-acid standards were used for evaluation of individual SIM-responses. Application of the method to various biological samples gave the following results: champignons (n = 2) contained 1.7 or 2.5 mg/100 g dry weight F-acids, while fish oil capsules (n = 5) contained between 18 and 234 mg/100 g oil F-acids distributed over up to seven F-acids. The concentrations and patterns were different to fresh fish. Accordingly, fish oil supplements seem to be a minor source for F-acids compared to (fresh) fish. Organic butter samples (n = 4) contained about twice the amount of F-acids when compared with conventional butter (n = 5).     

Effect of ingredients on oxidative stability of fish oil‐enriched drinking yoghurt

The oxidative stabilities of fish oil‐enriched milk and fish oil‐enriched drinking yoghurt were compared by following the development of lipid oxidation in plain milk, plain yoghurt and yoghurt to which ingredients present in drinking yoghurt were added one by one. All samples were enriched with 1 wt‐% fish oil. After 3 weeks of storage, development of peroxide values, volatile secondary oxidation products and fishy off‐flavors were much more pronounced in the milk compared to any of the yoghurt samples, irrespective of any added ingredients used to prepare flavored drinking yoghurt. Thus, pectin, citric acid or glucono‐delta‐lactone did not affect the oxidative stability of fish oil‐enriched yoghurt emulsions. Furthermore, the fruit preparation and added sugar did not lead to increased antioxidative activity. It is concluded that yoghurt as the dairy component in the fish oil‐enriched emulsion was responsible for the remarkably high oxidative stability and was able to protect the n‐3 PUFA against oxidative deterioration. It should be considered that this strong antioxidative effect of yoghurt might mask potential antioxidative effects of the other ingredients in the drinking yoghurt.