Chemistry
Chemical Analysis
Chemical analysis involves the techniques and methods used to identify and quantify the components of a substance. It encompasses a wide range of analytical techniques such as spectroscopy, chromatography, and mass spectrometry. The goal of chemical analysis is to understand the composition and properties of substances, which is essential for various scientific and industrial applications.
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eBook - ePub- John Kenkel(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
Analytical Chemistry for Technicians, Lewis Publishers, Chelsea, MI, 1988. With permission.)1.3 TERMINOLOGY
The basic terminology associated with analytical chemistry and analytical laboratory work is important and may be foreign to persons who have not been associated with such laboratory work in preparation for their jobs. We thus present a small glossary of terms in this section. Other important terms specific to particular analyses are given elsewhere in this book and can be found in the index.Chemical Analysis This is the determination of the chemical composition or chemical makeup of a material sample. Qualitative Analysis The determination of what substances are present in a material sample, usually without the need or desire to determine quantity of these substances. Quantitative Analysis The determination of how much of a specified substance is present in a material sample.Quantitation This is the determination of quantity, as in the quantitative analysis above. Quantification This is another word for quantitation. Quantitative Transfer A transfer of a chemical or solution from one container to another, making sure that every trace of this chemical is in fact transferred. Analyte This is the substance being analyzed for in an analytical procedure. This can be an element, a compound, or an ion. Assay This is another word for Chemical Analysis. 1.4 FUNDAMENTALS OF MEASUREMENT
In the analytical chemistry laboratory, many measurements are made, and the accuracy of these measurements obviously is a very important consideration. Different measuring devices give us different degrees of accuracy. A measurement of 0.1427 g is more accurate than a measurement of 0.14 g simply because it contains more digits. The former (0.1427 g) was made on an analytical balance, while the latter was make on an ordinary balance. A measurement recorded in a notebook should always reflect the accuracy of the measuring device. It does not make sense to use a very accurate measuring device and then record a number that is less accurate. For example, suppose a weight on an analytical balance was found to be 0.14g. It would be a mistake to record the weight as 0.14 g, even if you know personally that the weight is 0.14 g. Presumably, there are other people in the laboratory using the notebook, and your entry will be construed as to contain only two digits. The following example further illustrates this point.
eBook - ePub- Yves Mouton(Author)
- 2013(Publication Date)
- Wiley-ISTE(Publisher)
Generally speaking, the methods for material characterization should be considered as a whole, where each element must find its place: chemical methods as well as mechanical or rheological tests. It is not always necessary to fully analyze a product to characterize it in the context of its utilization. In some cases, bitumen for example, it is even preferable to abandon classic analysis in the strict sense of the term and resort to typical global methods — chemical, physical or rheological — as long as these are based on proven reasoning and designing.6.1. Chemical Analysis of formulated products
What is generally known as chemical “analysis” of a formulated product in the civil engineering field is nothing but, in most cases, the characterization of a material or product by chemical methods in order to answer one of the following questions:– to which chemical family does the major constituent of this product belong?; – how can a digital imprint of this product be established to check its delivery subsequently?; – how can a sample be verified to show that it contains the necessary strength of the active ingredient for obtaining the expected performance?; – how can it be verified whether a material is changing or not during the course of a given test?The most commonly adopted methods to deal with these problems are infrared spectrometry for identifying the chemical family, supported by chromatographic methods if the products are very complex, and functional assays for quantitative determinations. To this list we may add thermogravimetric methods, which are particularly interesting for the characterization of polymers. However, bituminous materials are to be treated in an original manner: Chemical Analysis plays an important role, but for example is not the most appropriate answer to the second question above. It pales in comparison with physico-mechanical tests (essentially rheological testing) which treats the sample in a global manner and completes the information with data yielded from research. It is for this reason that this subject has been amply developed in Chapter 2 (section 2.2 ).6.2. Infrared spectrometry
- Debasis Bagchi, Sreejayan Nair(Authors)
- 2016(Publication Date)
- Academic Press(Publisher)
Gravimetry is one of the basic methods of studying the composition of raw materials, which deals with the quantitative determination of an analyte based on the mass of the solid components in a sample. These methods have a significantly limited usage due to their nonspecificity. However, they are considered decisive in defining several qualitative indices of the raw material, such as the amount of moisture and certain solid components (depending on the sample preparation).Refractometry is based on the measurement of the refractive index of the substance, that is, the ratio of the speed of light in a vacuum to its speed in a substance. This speed is related to the temperature, composition, concentration, and purity of the substance. The index of refraction depends on the density of a liquid and thus on the concentration of the solute in the solution. Measurements are usually made at 20°C using the sodium D-line as the light source.There are four widely used spectroscopic techniques: UV-Vis spectrophotometry, infrared spectroscopy (IRS), nuclear magnetic resonance (NMR) spectroscopy, and atomic adsorption spectroscopy. The basic principle of all spectroscopic methods is in the measuring of the difference between the properties of light (in IR, Vis, UV range, etc.) before and after its contact with the testing sample. UV-Vis spectroscopy is one of the most inexpensive and simple methods that are accepted in analytical chemistry and might be used in the majority of analytical laboratories.Mass spectrometry is a method based on ion formation from compounds followed by the steps of their separation and detection. The result of this procedure is the information of the mass-to-charge ratio (m /z ) and an abundance of individual ions formed during the analysis. This allows for qualitative and quantitative characterization of the composition of the sample.The aforementioned methods might be used directly or as part of more complicated chromatographic techniques.Chromatography is a process based on the multiple repetitions of absorption and desorption of a sample while moving in a stream of a mobile phase (eluent) along a stationary phase (sorbent). Separation of the complex mixtures by chromatographic methods is based on the different affinity of the components to the eluent and sorbent. During the chromatography, the eluent containing the sample is moving through the stationary phase. Normally the stationary phase is a material with a developed surface, and the mobile phase is a flow of gas or liquid that is filtered through a sorbent bed.
- Hildegarde Heymann, Susan E. Ebeler(Authors)
- 2016(Publication Date)
- Academic Press(Publisher)
4Uses of chemical testing in the alcoholic beverage industry
Abstract
In this chapter, we discuss the various uses and purposes of chemical testing from the raw material to final products. For the various purposes, we provide examples of analytes that may be measured or monitored. Each type of alcoholic beverage may have different analyses that can or should be performed, however, with the use of a process analytical chart, the analyst can determine the critical points during processing where analytical information can be used to inform the decision-making process.Keywords
ingredients production processes storage chemical stability product consistency legal compliance flavor process analytical chartsIn this chapter4.1 Introduction4.2 Confirm composition of starting materials or ingredients4.3 Monitor production processes4.4 Monitor and ensure stability during storage (chemical and microbial)4.5 Consistency and quality assurance/quality control4.6 Ensure compliance with tax, legal, and safety regulations4.7 Flavor and off-flavor assessment4.8 Developing process analytical charts4.9 ConclusionsReferences4.1. Introduction
Chemical analyses in the alcoholic beverage industry provide a fundamental basis for many of the day-to-day decisions made by winemakers, brewers, and distillery managers. Frequently, sensory assessment on a formal or informal basis can inform production decisions, however, Chemical Analysis can also be crucial for preventing and solving problems in a timely manner and for ensuring consistent and stable products. Further, many chemical analyses are required for tax or legal purposes. The choice of the analytical procedures will depend on the uses of the analytical information, as well as the desired turnaround times for the information and the performance measures of the available methods.In this chapter we will review some of the basic uses and purposes of chemical testing for the alcoholic beverage industry. The focus here is on analytes that exemplify specific purposes; the analyses discussed are not meant to provide a comprehensive listing of all analytes that are routinely measured in alcoholic beverages. In subsequent chapters we will focus on some of the common analytes measured, the methodologies for their analysis, and the performance measures required for a variety of purposes.
