Characterization of trace metals in vegetables by graphite furnace atomic absorption spectrometry after closed vessel microwave digestion

A simple and expeditious method for the determination of trace metals (cadmium, chromium, copper, manganese and lead) is proposed. The metals are extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel microwave digestion system for their subsequent detection by graphite furnace atomic absorption spectrometry (GFAAS). The sample preparation procedure facilitates the overall analytical process and enables the construction of calibration curves from inorganic standards. The ensuing method provides good linearity and sensitivity for the five metals, with limits of detection and quantization spanning the ranges 0.05–2.20 and 0.15–7.34 μg/kg, respectively. This sensitivity level is quite appropriate for the intended application. Accuracy was assessed by using a certified reference material (NCS ZC85006 Tomato), for which the proposed method provided amounts of metals consistent with their certified values. The proposed method was applied to tomato, pepper and onion, which are widely consumed in Mediterranean countries.     

GFAAS determination of selenium in infant formulas using a microwave digestion method

A method for determining the selenium content of infant formulas is proposed. It includes wet digestion with nitric acid and hydrogen peroxide in medium pressure teflon bombs in a microwave oven and determination by graphite furnace atomic absorption spectrometry (GFAAS). The absence of interferences is checked. Values obtained for the limit of detection (19.4 ng/g), precision (RSD = 2.2%) and accuracy by analysis of a reference material show that the method is reliable.     

Determination of several elements in duplicate meals from catering establishments using closed vessel microwave digestion with inductively coupled plasma mass spectrometry detection: estimation of daily dietary intake

An estimation of the dietary exposure of French consumers to 21 essential and non-essential mineral elements using duplicate meals (breakfast and lunch) purchased from catering establishments was investigated after digestion by a closed vessel microwave procedure and quantification by ICP-MS. Daily dietary exposure estimates for metals and minerals were compared with the Provisional Tolerable Weekly Intakes (PTWI), the Tolerable Daily Intake (TDI) or the Acceptable Daily Intakes (ADI), as established by the FAO/WHO to estimate the risk of toxicity, and the US Recommended Daily Allowances (US RDA) or the Estimate Safe & Adequate Daily Dietary Intakes (ESADDI). Moreover, comparisons were made with those from previous French studies as well as those from other countries. The estimated mean daily intakes were 11 μg for lithium, 3.42 g for sodium, 192 mg for magnesium, 2.03 mg for aluminium, 3.64 g for potassium, 642 mg for calcium, 154 μg for chromium, 12.3 mg for iron, 2.15 mg for manganese, 4 μg for cobalt, 74 μg for nickel, 925 μg for copper, 10.2 mg for zinc, 147 μg for arsenic, 66 μg for selenium, 112 μg for molybdenum, 3.6 μg for cadmium, 2.32 mg for tin, 3 μg for antimony, 9 μg for mercury and 34 μg for lead. For the non-essential (toxic) elements, aluminium, tin, antimony, cadmium, arsenic, mercury and lead, the daily intake estimates were far below tolerable limits; and similar or somewhat lower than their respective PTWI, ADI, TDI, ESADDI and US RDA for individual minerals and essential trace elements, with good agreement with other country studies. The performance of the multi-elemental ICP-MS technique was also evaluated.     

氧微波低温等离子体用于棉针织物前处理探讨

研究了氧微波低温等离子体去除棉纤维天然杂质的效果,探讨了处理功率、气体压力、时间等参数对棉针织物的去杂效率、强力、漂白白度的影响,并与常规前处理工艺进行了对比.研究表明:以氧微波低温等离子体处理替代传统的棉针织物精练工序后,织物的毛细效应、顶破强力、甘茨白度及染色K/S值等指标可接近或超过常规前处理工艺的水平.     

微波溶样技术在氨基酸分析中的应用初探

建立微波溶样测定氨基酸的方法，缩短氨基酸分析时间，以便快速检测大量样品。通过正交试验设计选择微波溶样的最佳条件是700W，20min，150℃；与常规方法相比，二者标准偏差分别为-3．27％和1．02％。结果显示：微波的功率、温度、时间对测定结果皆有显著性影响。常规方法得出的结果更为可靠，但微波检测在可接受的偏差范围之内大大缩短了分析时间，也不失为快速分析氨基酸的一个好方法。     

微波消解-石墨炉原子吸收分光光度法测定粮食中镉含量

针对粮食中镉含量较低的特点,建立了微波消解-石墨炉原子吸收分光光度法测定粮食中镉含量的方法。试验结果表明,该方法回收率为100%~110%,相对标准偏差为4.7%,定量限为0.41pg。该方法试剂用量少,操作简单、快捷,对于镉含量不高的粮食样品,可以提高其检测的灵敏度和准确度。     

微波消解在测定食品中微量元素的应用

总结了食品中微量元素测定时常用的样品处理方法,并重点对微波消解食品时样品的取样量、样品预处理的方法、所用溶剂的种类和数量以及加热时间和压力的选择作了阐述,从而为微波消解食品样品提供了操作依据。     

Organic acids,biochemical oxygen demand and chemical oxygen demand in the soluble fraction of piggery slurry

Close, largely linear, relationships were found between volatile fatty acids (VFA) determined by gas chromatography, total organic acids (TOA) determined colorimetrically, biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD) in the soluble fraction of piggery slurries. Samples were taken from untreated and aerobically-treated slurries. All correlations were significant at P=0.001, with values of r ranging between 0.88 for the correlation of VFA and COD, to 0.97 for the correlation of TOA and BOD₅. VFA accounted for up to 69% of BOD₅ and 55% of COD. It is suggested that organic acids could replace soluble BOD₅ in some situations, since the correlations were good. Prediction of COD from organic acids, or BOD₅ from COD, were less accurate, particularly when concentrations were low, since COD contains a biologically inert fraction, which varies with storage. Soluble organic nitrogen was not useful in predicting BOD₅ or COD, correlating only at P=0.02.     

Development of chemical oxygen demand on-line monitoring system based on a photoelectrochemical degradation principle

A simple, rapid, and sensitive on-line chemical oxygen demand (COD) determination method has been proposed and experimentally validated. The method is based on a photoelectrochemical oxidative degradation principle and operates under a continuous flow mode. The method employs a specially designed thin-layer photoelectrochemical cell that incorporates a highly effective nanoparticulate TiO2 photoanode. This approach overcomes many problems associated with the conventional COD determination techniques such as long analysis time, consumption of expensive and toxic reagents, production of secondary toxic waste, and poor reproducibility. The effect of important experimental parameters on the analytical signal generation was systematically investigated, and the optimum conditions were obtained. The method was successfully applied to determine the COD of real samples from various industrial wastewaters. The COD value of real samples determined by this method agreed well with the standard dichromate method. The assay time of 1-5 min/sample can be readily achieved. A practical detection limit of 1 mg L(-1) COD with a linear range of 1-100 mg L(-1) was achieved under the optimum conditions.     

Chemical factors involved in ruminal fiber digestion

In the United States, cattle are commonly fed diets containing cereal grains. The presence of starch and sugars reduces fiber digestion, which may in turn depress intake. In this paper, chemical constraints that may be responsible for the decrease in fiber digestion are explored. A major factor appears to be rumen pH. Moderate depression in pH, to approximately 6.0, results in a small decrease in fiber digestion, but numbers of fibrolytic organisms are usually not affected. Further decreases to 5.5 or 5.0 result in depressed growth rates and decreased fibrolytic microbes, and fiber digestion may be completely inhibited. Proliferation of organisms on readily fermentable carbohydrates may increase the need for total nitrogen as both ammonia and amino acids. The value of amino acids to cellulolytic organisms appears to be primarily as sources of isobutyric, isovaleric, and 2-methylbutyric acids. This reinforces the need to establish dietary requirements for nonprotein nitrogen, degradable protein, and isoacids. Other factors affecting fiber digestion, such as inhibition of cellulytic enzymes and plant concentrations of lignins and phenyl propanoids, are also discussed.     

用溶氧仪代替碘量法测定生化需氧量中的溶解氧

采用溶氧仪代替碘量法测定水质生化需氧量中的溶解氧，讨论了测定中注意事项。经两种方法检测数据对比和标准物质回收试验，表明该测定方法完全能满足日常检测工作需要，既简化了测定程序，又节省了化学试剂。     

微波消化和原子荧光光谱法测定大米中汞

采用微波加热，在高温高压下酸消解样品，运用氢化物原子荧光光谱法测定大米中的汞元素。汞的最低检出限为0．02ng/mL。相对标准偏差为0．37％－2．67％，回收率为93％－104％。     

微波消解石墨炉原子吸收法测定大米中铅镉

采用微波消解—石墨炉原子吸收法对大米中的铅、镉进行了测定,并与常规湿法消解方法进行了比较。利用国家标准物质杨树叶、甘蓝验证了方法的准确度与精密度。结果表明,采用微波消解法,方法准确度为95．0％～105%,精密度为2．8％～8．4%,该方法能够满足食品分析的要求。     

微波消解ICP-OES测定牛蒡茶中的矿质元素

采用HNO3/H2O2微波消解的制样方法,利用全谱直读电感耦合等离子原子发射光谱仪（ICP-OES）对牛蒡茶中的Al、As、Ba、Ca、Cd、Cr、Cu、Fe、K、Mg、Mn、Na、Ni、P、Pb、Sr、Ti、Zn等18种矿质元素进行了测定。结果表明,牛蒡茶中含有人体必需常量元素K、Na、Ca、Mg、P和人体必需微量元素Cu、Fe、Mn、Ni、Ti、Zn,以及人体非必需的微量元素Al、Ba、Sr,而有害元素As、Pb、Cr、Cd均未检出。并建立了一种牛蒡茶中矿质元素的分析测试方法,各元素的回收率均在93.7%¹07%,相对标准偏差在1.31%².31%,检出限低且满足各元素分析要求,此方法具有简捷、快速、准确的特点。      

利用微波消解法快速测定小麦粉中痕量铅、镉的含量

将小麦粉样品用硝酸及过氧化氢消解后,采用微波加热,试液中铅和镉用GF-AAS法测定,并将所得分析结果与常规法相比。结果表明:该方法具有更好的准确度和精密度,且操作更简便、快速,是一种快速检测小麦粉中痕量铅、镉重金属的方法。     

微波消解ICP-OES测定牛蒡茶中的矿质元素

采用HNO3/H2O2微波消解的制样方法,利用全谱直读电感耦合等离子原子发射光谱仪(ICP-OES)对牛蒡茶中的Al、As、Ba、Ca、Cd、Cr、Cu、Fe、K、Mg、Mn、Na、Ni、P、Pb、Sr、Ti、Zn等18种矿质元素进行了测定。结果表明,牛蒡茶中含有人体必需常量元素K、Na、Ca、Mg、P和人体必需微量元素Cu、Fe、Mn、Ni、Ti、Zn,以及人体非必需的微量元素Al、Ba、Sr,而有害元素As、Pb、Cr、Cd均未检出。并建立了一种牛蒡茶中矿质元素的分析测试方法,各元素的回收率均在93.7%~107%,相对标准偏差在1.31%~2.31%,检出限低且满足各元素分析要求,此方法具有简捷、快速、准确的特点。     

Determination of phenolic acids in plant cell walls by microwave digestion

Microwave digestion (750 W for 90 s) with 4 M NaOH was used to release esterified and etherified hydroxycinnamic acids from cell walls of maize (Zea mays L), wheat (Triticum aestivum L), barley (Hordeum vulgare L) and oilseed rape (Brassica napus L) stems. Subtraction of values for saponifiable phenolic acids obtained after treatment with I M NaOH at room temperature from digest results provided a measure of β-ether linked units. These were exclusively (E + Z)-ferulic acid in the cereal straws. Only trace amounts of ether- and ester-linked hydroxycinnamic acids were released from the dicotyledon, ripe straw. Microwave digestion was shown to be an order of magnitude more effective than dioxane-HCl at liberating β-ether bound phenolic acids and as effective, but substantially quicker, than previously described high-temperature alkaline digestions.     

微波消解-ICP-AES法同时测定火腿中多种元素

采用HNO3作消解剂对火腿进行微波消解,利用电感耦合等离子体原子发射光谱法(ICP-AES)同时测定火腿中K、Ca、Na、Mg、Ba、Cu、Fe、Mn、P、Zn、Sr 11种元素的含量.结果表明:各元素的相关系数均在0.999 0～1.000 0之间,除Mn(12.2%)和Cu(10.5%)外,其他元素的精密度均＜10%;国家标准物质玉米(GBW10012)和猪肉(GBW08552)的测定值均在标准值范围内,该方法快速(可在1 min内完成)、准确,能满足火腿中多种元素同时测定的要求.     

微波消解-电感耦合等离子体发射光谱（ICP-AES）法测定螺旋藻中多种微量元素

采用微波消解ICP-AES法对螺旋藻中10种微量元素进行了分析测定。该方法的加标回收率在94.2%～104.8%之间,变异系数（RSD,n=6）在0.95%～4.81%之间,测定结果令人满意。为螺旋藻中微量元素的检测、分析提供了快速、准确的方法。     

微波消解-石墨炉原子吸收法测定卷烟滤棒中的铅含量

为建立检测卷烟滤棒中铅含量的微波消解-石墨炉原子吸收光谱方法,对样品前处理条件和分析测试条件进行了优化,最终确定最优的条件：灰化温度、原子化温度、基体改进剂分别为1000℃,2000℃和1.0 g/L硝酸钯。在优选的实验条件下,方法的检出限为0.084μg/L,相对标准偏差小于3.26%,加标回收率范围在86.3%~99.8%之间。该方法简便、准确、灵敏度高、重复性好、回收率高,适合于卷烟滤棒中铅的测定。