Classical analysis, analytical reagents

Despite the tremendous sophistication of pesticide residue and environmental chemical analysis, there remain a number of serious limitations to certain aspects of classical analysis. A number of those limitations can be addressed through the application of immunoassay technology to residue analysis (1-41. Immunoassays rdy on highly specific antibody proteins and relatively simple analytical apparatus to detect and quantify a wide varied of target materials in a broad range of andytical matrices. Since the reagents are specific, immunoassays can generSly be performed with relatively crude sample preparations. Reduced san le preparation, simple... 

Sommer, L., Ackermann, G. and Burns, D.T., Present and Future Status of Organic Analytical Reagents - Part II Inorganic Chemical Analysis Classical Methods, Molecular Spectroscopy (Absorption and Emission) and Solvent Extraction, Pure Appl Chem., 1990, 62, 2323. 

All reagents and solvents that are used to prepare the sample for analysis should be ultrapure to prevent contamination of the sample with impurities. Plastic ware should be avoided since these materials may contain ultratrace elements that can be leached into the analyte solutions. Chemically cleaned glassware is recommended for all sample preparation procedures. Liquid samples can be analyzed directly or after dilution when the concentrations are too high. Remember, all analytical errors are multiplied by dilution factors therefore, using atomic spectroscopy to determine high concentrations of elements may be less accurate than classical gravimetric methods. 

We start with butane-2,3-dione dioxime, more commonly known as dimethylglyoxime (dmg). It is a classic reagent for the analysis of NP, the green aqueous solution of metal ions transforming into a vibrantly red precipitate of Ni(dmg)2 complex it is one of the stars of the show in Ponikvar and Liebman s analytical chemistry chapter in the current volume. Here the stereochemistry is well-established and well-known—both OH groups are found on the same side as their adjacent CH3 group on the butanedione backbone. There have been several measurements of the enthalpy of formation of this species for which we take the one associated with this inorganic analytical chemistry application, i.e. with diverse metal complexes and chelates . 

Immunochemical methods provide a powerful tool in the field of drug residue analysis. The exquisite specificity that can be obtained with immunochemical reagents provides new analytical opportunities that were previously not possible with classic analytical methods and can greatly reduce the amount of sample cleanup required prior to analysis. 

Gravimetric analysis is one of classical analytical methods. It is based on chemical transformation of the sample using excess of a reagent to a substance, which is weighed after processing. The weight of the substance obtained serves as a base for calculation of amount of substance. 

The reflectometer performs the assessment and in some systems it also monitors the reaction. The analyte present in the water of the sample in partnership with the reagents in the test strip, produces the required reaction and the dye or colour is formed that produces a certain reflectance on exposure to radiation. This enables quantitative analysis comparable in precision and accuracy with classical photometry. A special feature of such techniques is that in most cases, undiluted sample material may be used. Also, the range of... 

The classical methods for quantitative analysis of carbohydrates were based mainly on the formation of colored products on treatment of the analytes with strong mineral acids and condensation of the resulting 2-furaldehyde (furfural) derivatives with a suitable chromogenic reagent (usually a phenol or aromatic amine). Examples include the well-known procedmes involving the use of sulfuric acid with phenol, orcinol, cysteine, or anthrone. 

Only limited development of new methodologies has taken place for immunochemical analysis of nucleic acids. Most published methods rely on modifications to classical DNA probe hybridization or immunoassay methods, with considerable blending of the two. For example, some methods employ immobilized oligonucleotide probes to capture the analyte DNA followed by immunoenzymatic detection. Other methods use immunocapture followed by detection with an enzyme-labeled DNA probe. Distinctly new methodologies mostly impact on assay formats (e.g., DNA microarrays and in situ hybridization) and detection reagents (e.g., chemiluminescent enzyme substrates). 

After separation from excess reagent (by liquid-liquid distribution, chromatography, precipitation, etc.), the mass or concentration of this product is determined from activity measurement. The determination is based on a radioactive substance chemically different from the analyte substance (in contrast to isotope dilution analysis) therefore, the chemical reaction is of prime importance. By variation of this key reaction, the principle can be adapted to various procedures. The superiority of radio-reagent methods over classical separation techniques arises from the use of an inactive carrier and the high sensitivity of the activity measurements, which are not subject to interference by the carrier or other substances. 

Other than gravimetric analysis, the other major type of classical wet chemical analysis techniques consists of measuring the volume of a reagent required to react with an analyte. Such a procedure is called titration, which involves the following steps ... 

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