Specificity of analysis

Analysis of bacterial monomers is performed routinely to detect bacteria at trace levels in environmental samples using GC-MS-MS. PCR is also used routinely by the molecular biology community for detection of clinical infections. MS and MS-MS greatly improve the specificity of analysis of PCR products and provide additional structural information that may be important in apply-... 

THE SPECIFICITY OF ANALYSIS OF PARTICULAR GROUPS OF CHEMICAL AGENTS... 

The probabilistic nature of a confidence interval provides an opportunity to ask and answer questions comparing a sample s mean or variance to either the accepted values for its population or similar values obtained for other samples. For example, confidence intervals can be used to answer questions such as Does a newly developed method for the analysis of cholesterol in blood give results that are significantly different from those obtained when using a standard method or Is there a significant variation in the chemical composition of rainwater collected at different sites downwind from a coalburning utility plant In this section we introduce a general approach to the statistical analysis of data. Specific statistical methods of analysis are covered in Section 4F. 

Before we look more closely at specific gravimetric methods and their applications, let s take a moment to develop a broad survey of gravimetry. Later, as you read through the sections of this chapter discussing different gravimetric methods, this survey will help you focus on their similarities. It is usually easier to understand a new method of analysis when you can see its relationship to other similar methods. 

Time, Cost, and Equipment Automated chemical kinetic methods of analysis provide a rapid means for analyzing samples, with throughputs ranging from several hundred to several thousand determinations per hour. The initial start-up costs, however, may be fairly high because an automated analysis requires a dedicated instrument designed to meet the specific needs of the analysis. When handled manually, chemical kinetic methods can be accomplished using equipment and instrumentation routinely available in most laboratories. Sample throughput, however, is much lower than with automated methods. 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

A detailed kinetic analysis depends on the specifics of the initiation and termination-transfer steps. We shall illustrate only one combination other possibilities are done similarly ... 

The pubHcations detailing standards (5—8) generally include both specifications and methods of analysis for the substances. The estabHshment of standards of quaHty for chemicals of any kind presupposes the abiHty to set numerical limits on physical properties, allowable impurities, and strength, and to provide the test methods by which conformity to the requirements may be demonstrated. Tests are considered appHcable only to the specific requirements for which they were written. Modification of a requirement, especially if the change is toward a higher level of purity, often necessitates revision of the test to ensure the test s vaHdity. 

Specifications and Analysis. Commercial fluorosulfuric acid contains approximately 98% HSO F and approximately 1% H2SO4 and lesser amounts of sulfur trioxide and dioxide. No free HF is present. 

The methods of analysis of the American Oil Chemists Society (AOCS) are the principal procedures followed in the United States and Canada and are official in commercial transactions. When the material is for human consumption or dmg use, it must meet the specifications of the USP (12). Commercial distilled grades of glycerol do not requite purification before analysis by the usual methods. The deterrnination of glycerol content by the periodate method (13), which replaced the acetin and dichromate methods previously used, is more accurate and more specific as well as simpler and more rapid. 

Specifications and Analysis. R%-MaHc acid that is sold in the United States meets the specifications of the Food Chemicals Codex and National Formulary, which are Hsted in Table 5 (40,41). MaHc acid is available in the following U.S. standard sieve sizes ... 

Instmmental methods of analysis provide information about the specific composition and purity of the amines. QuaUtative information about the identity of the product (functional groups present) and quantitative analysis (amount of various components such as nitrile, amide, acid, and deterruination of unsaturation) can be obtained by infrared analysis. Gas chromatography (gc), with a Hquid phase of either Apiezon grease or Carbowax, and high performance Hquid chromatography (hplc), using siHca columns and solvent systems such as isooctane, methyl tert-huty ether, tetrahydrofuran, and methanol, are used for quantitative analysis of fatty amine mixtures. Nuclear magnetic resonance spectroscopy (nmr), both proton ( H) and carbon-13 ( C), which can be used for quaHtative and quantitative analysis, is an important method used to analyze fatty amines (8,81). 

Measurement and specification of nitrates or other nitrogen oxide compounds in sulfuric acid is a complex subject. The difficulty occurs because nitrogen oxides are usually present both as nitrous and nitric compounds, predominantiy in the nitrous form. Hence, analytical procedures specific for nitrates only do not give a complete analysis. 

Descriptions of sulfuric acid analytical procedures not specified by ASTM are available (32,152). Federal specifications also describe the requited method of analysis. Concentrations of 78 wt % and 93 wt % H2SO4 are commonly measured indirectly by determining specific gravity. Higher acid concentrations are normally determined by titration with a base, or by sonic velocity or other physical property for plant control. Sonic velocity has been found to be quite accurate for strength analysis of both filming and nonfuming acid. 

Analysis, Specifications, and Health Factors. Methods of analysis and health aspects are the same as those for dextrose. Specifications for HES are the same as those for com symp. HES is presumed to be GRAS by the EDA (50). Health effects of fmctose are discussed elsewhere (51). 

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