Quantitative analytical computerized instruments

Qualitative chemistry is an area of chemistry concerned with identifying substances. In Activity 9.1 you will perform a qualitative analysis to detect the presence of certain ions that, in turn, may reveal an art forgery. The ions could come from paints that were not available at the time of the artwork. In this qualitative analysis, metal ions (cations) and nonmetal ions (anions) are reacted with solvents and with each other. Then the cations and anions present are identified by the products produced. In addition, flame tests and pH determinations are used to identify ions. Qualitative analysis is an engaging opportunity for you to develop experience with chemical change and review solubility principles. Nowadays, however, most of the time a chemist analyzes a substance to detect ion content using quantitative analytical computerized instruments. 

Analysis procedures can be additionally classified into procedures that involve physical properties, wet chemical analysis procedures, and instrumental chemical analysis procedures. Analysis using physical properties involves no chemical reactions and at times relatively simple devices (although possibly computerized) to facilitate the measurement. Physical properties are especially useful for identification, but may also be useful for quantitative analysis in cases where the value of a property, such as specific gravity or refractive index (Chapter 15), varies with the quantity of an analyte in a mixture. 

Increased sophistication of chemical instrumentation and computerized data acquisition have quantitatively and qualitatively changed analytical chemistry. Chemists measure more variables and perform more experiments in less time than feasible just a few years ago. Without a concomitant enhancement of interpretive skills the newfound data affluence may be a curse and not a blessing. 

This change reflects a growing awareness that chemical interactions between chemical species are important in complex chemical systems. Increased reliance on multi-elemental analysis reflects the ease with which such analyses can be performed. Recent advances in electronics, chemical instrumentation, and computerized data acquisition have quantitatively and qualitatively changed analytical chemistry. Chemists measure more variables and perform more experiments in less time than feasible just a few years ago. In spite of our recently acquired data affluence, many complex problems remain unsolved. The enhanced insight that additional dataware to provide has failed to materialize. In some cases, more data cloud the issue rather than clarify it. Acquiring massive quantities of data is ineffective until interpretations are made and incorporated into a mechanistic description of the system. 

In a modern laboratory, automated computer software for data acquisition and processing performs most of data reduction. Raw data for organic compound and trace element analyses comprise standardized calibration and quantitation reports from various instruments, mass spectra, and chromatograms. Laboratory data reduction for these instrumental analytical methods is computerized. Contrary to instrumental analyses, most general chemistry analyses and sample preparation methods are not sufficiently automated, and their data are recorded and reduced manually in laboratory notebooks and bench sheets. The SOP for every analytical method performed by the laboratory should contain a section that details calculations used in the method s data reduction. 

Modem computerized analytical instruments have quantitative analysis programs that allow the analyst to specify the calibration standard concentrations, select the curve-fitting mode, and calculate the results of the samples from the calibration curve equation. Many of these programs will remn outher standards and samples automatically, flag suspect data, compute precision and recovery of spikes, track reference standards for quahty control, and perform many other functions that used to be done manually by the analyst. 

Presenting nearly 50% new and revised material, this thoroughly updated edition incorporates the latest advances in instrumentation, computerization, calibration, and method development in NIR spectroscopy. The book underscores current trends in sample preparation, calibration transfer, process control, data analysis, and commercial NIR instrumentation. New chapters highlight novel applications including the analysis of agro-forestry products, polymers, blood, and control serum. They also cover NIR spectra, process analytical technologies (PAT), quantitative and qualitative analyses for nutraceuticals, NIR photography uses in medicine, and counterfeit detection methods for various applications. 

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