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1 Chapter 12 The Analysis of Real Sample (31-34).

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1 1 Chapter 12 The Analysis of Real Sample (31-34)

2 2  Quantitative analysis steps  1.Selecting a method 方法选择  2.Sampling 取样  3.Preparing a laboratory 实验室样品制备  4.defining replicate samples 确定重复测定 次数  5.preparing solutions of the samples 溶样  6.eliminating interferences 排除干扰  7.completing the analysis 分析  8.computing the results and estimating their reliability 结果计算及数据评价

3 3  Real samples are far more complex than those that you encounter in the instructional laboratory. 实际样品测定复杂性  31A Choice of method for the analysis of real samples  The choice of a method for the analysis of a complex substance requires good judgment and a sound knowledge of the advantages and limitations of the various analytical available. 为复杂物质选择分析方法需要很 多相关知识。

4 4  31A-1 Definition of the problem  确定需要解决的问题  Concentration of species 形态浓度  Accuracy 准确性  Other components 共存组成  Properties of sample 样品性质  The number of samples 样品数量

5 5  31A-2 Investigation of the literature  文献调研  The technology for computer-based scientific information retrieval provides an efficient means for surveying the analytical literature. 计算机查询文献。  The various analytical journals may be consulted. Monographs on methods for completing the analysis are valuable in deciding among several possible techniques.  各种分析杂志及专著可提供技术指导。

6 6  31A-3 Choosing or devising a method 选择或设计方法  decide upon the route to be followed in the laboratory.  Simple or complex 简单还是复杂  The number of samples 样品数量  Error and interferences 误差与干扰  It is to be hoped that one or more tentative methods worth testing will have been located. 最好试验几种方案

7 7  31A-4 Testing the procedure  方法检验  The analysis of standard sample  标准样分析  Analysis by other method  其它分析方法比较  Standard addition to the sample  标准加入法  31B The accuracy obtained in the analysis of complex materials  Table

8 8  Preparing Samples for Analysis  样品制备  32A Sample 取样  32A -1The effects of sampling uncertainties  s  2 =s s 2 +s m 2  s s sampling process error  s m method error

9 9  Decomposing and dissolving the sample  样品分解  33A sources of errors in decomposition and dissolution  样品分解中误差  Incomplete dissolution of the analyte  溶解 不完全  Losses of the analyte by volatilization  蒸发损失  Introduction of analyte as a solvent contaminant  溶剂影响  Introduction of contaminants from reaction of solvent with vessel walls.  器皿污染

10 10  33B Decomposing samples by inorganic acid in open vessels  HCl,HNO 3,H 2 SO 4,HClO 4,HF  Oxidizing mixture  33C Microwave decompositions


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