PDF《火焰原子吸收》

Cu: N9300183;

Mn: N9303783;

Ni: N9300177;

Zn: N9300178). 工作曲线是在50毫升 独立的锥形的聚丙烯瓶 (序列号 B0193234) 中经系 列容积比稀释制备而成. 在进行样品分析之前, 每个单 独的金属离子所做的标准曲线都包括四个点 (三个标 准点和一个空白点) , 其标准曲线相关系数 (r2 ) 均达到 0.999以上 (附录1-第7-8页) . ASTM? 1型水 (Millipore? 过滤系统过滤, 美国密理博公司? , 比尔里卡, 马萨诸 塞州) , 使用0.2%的硝酸 (Tamapure? , 多摩化学制剂 公司, 日本) 酸化, 同时也用于标准空白和所有稀释 液. NIST? 1568a 有证参考物: 大米粉中的痕量金属, 用于验证方法. 每个元素的质量控制检查标准均配制 成曲线中间点的浓度. 三个牌子的粉状香料和草药样品 (香菜粉, 姜粉和黑胡椒粉) 均购于印度的超市用于实 验分析. 准确称取0.5克左右的样品或标准参考物质, 每个均称取两份, 作为平行样. 将称取的样品转移至消 解罐中, 消解罐为聚丙烯材质, 消解后的样品用0.2% 的HNO3 稀释定容至25mL的聚丙烯管中. 实验中使用的 所有的样品管清洗干净后用10% (体积比) 的HNO3 浸 泡至少24小时, 使用前再用去离子水充分冲洗.

2 A microwave sample preparation system was used for the digestion of spice samples and the certified reference material (CRM). This is an industrial-type microwave oven which is equipped with various accessories to optimize the sample digestion. The samples were digested using

100 mL high- pressure vessels made of PTFE. The sample digestion was performed in accordance with the program given in Table

2 (Page 3), as per U.S. Environmental Protection Agency (EPA) Method 3052. Standards, Samples and Certified Reference Material Preparation Single-element PerkinElmer Pure Calibration Standards for atomic spectroscopy were used as the stock standards for preparing the working standards (Part Nos. Co: N9303766;

Cu: N9300183;

Mn: N9303783;

Ni: N9300177;

Zn: N9300178). Working standards were prepared by serial volume/volume (v/v) dilution in

50 mL conical free-standing polypropylene vials (Part No. B0193234). Four-point calibration curves (three standards and one blank) were constructed for each individual metal ion and their calibration curve correlation coefficients (r2 ) were better than 0.999 before the start of the sample analysis (Appendix I C Page 5). ASTM? Type I water (Millipore? Corporation, Billerica, Massachusetts, U.S.) acidified with 0.2% nitric acid (Tamapure? ,TAMA Chemicals, Japan) was used as the calibration blank and for all dilutions. NIST? 1568a CRM for Trace Metals in Rice Flour was used to validate the method. Quality control (QC) check standards were prepared at the calibration curve midpoint for each individual element. Three branded powdered spice and herb samples available in India (coriander powder, ginger powder, and black pepper powder) were bought from a supermarket to be analyzed. Approximately 0.5 g of each sample or CRM was accurately weighed in duplicate, then transferred to a digestion vessel. The digested samples were brought up to

25 mL in poly- propylene vials with 0.2% HNO3. All sample vessels were cleaned by soaking with 10% v/v HNO3 for at least

24 hours and rinsed abundantly in de-ionized water before use. There is an increasing need to monitor the essential element levels in food samples at ever decreasing concentrations. For this purpose, very sensitive, yet rapid and inexpensive methods are necessary. The quantification of trace metals in food samples has routinely been carried out by inductively coupled plasma optical emission spectroscopy (ICP-OES),4 inductively coupled plasma mass spectrometry (ICP-MS),5,6 graphite furnace atomic absorption spectrophotometry (GFAAS)7 and flame atomic absorption spectrophotometry (FAAS).8,9,10 Compared with other techniques, FAAS has the characteristics of good precision and simplicity with lower cost and minimum operator proficiency. The objective of this work is two-fold: (1) to accurately analyze, using FAA........