Colorant testing quantitative analysis

The classical wet-chemical quaUtative identification of chromium is accompHshed by the intense red-violet color that develops when aqueous Cr(VI) reacts with (5)-diphenylcarba2ide under acidic conditions (95). This test is sensitive to 0.003 ppm Cr, and the reagent is also useful for quantitative analysis of trace quantities of Cr (96). Instmmental quaUtative identification is possible using inductively coupled argon plasma—atomic emission spectroscopy... 

Part—I has three chapters that exclusively deal with General Aspects of pharmaceutical analysis. Chapter 1 focuses on the pharmaceutical chemicals and their respective purity and management. Critical information with regard to description of the finished product, sampling procedures, bioavailability, identification tests, physical constants and miscellaneous characteristics, such as ash values, loss on drying, clarity and color of solution, specific tests, limit tests of metallic and non-metallic impurities, limits of moisture content, volatile and non-volatile matter and lastly residue on ignition have also been dealt with. Each section provides adequate procedural details supported by ample typical examples from the Official Compendia. Chapter 2 embraces the theory and technique of quantitative analysis with specific emphasis on volumetric analysis, volumetric apparatus, their specifications, standardization and utility. It also includes biomedical analytical chemistry, colorimetric assays, theory and assay of biochemicals, such as urea, bilirubin, cholesterol and enzymatic assays, such as alkaline phosphatase, lactate dehydrogenase, salient features of radioimmunoassay and automated methods of chemical analysis. Chapter 3 provides special emphasis on errors in pharmaceutical analysis and their statistical validation. The first aspect is related to errors in pharmaceutical analysis and embodies classification of errors, accuracy, precision and makes... 

The enzyme attached to antibody 2 is critical for quantitative analysis. Figure 19-14 shows two ways in which the enzyme can be used. The enzyme can transform a colorless reactant into a colored product. Because one enzyme molecule catalyzes the same reaction many times, many molecules of colored product are created for each analyte molecule. The enzyme thereby amplifies the signal in the chemical analysis. The higher the concentration of analyte in the original unknown, the more enzyme is bound and the greater the extent of the enzyme-catalyzed reaction. Alternatively, the enzyme can convert a nonfluorescent reactant into a fluorescent product. Colorimetric and fluorometric enzyme-linked immunosorbent assays are sensitive to less than a nanogram of analyte. Pregnancy tests are based on the immunoassay of a placental protein in urine. 

The analytical procedure consists of three steps (1) sample extraction, (2) assay, and (3) color formation for visual or spectrophotometric determination of the analyte in the sample. If a semiquantitative or quantitative analysis is desired, the concentration of the analyte can be determined from a calibration curve prepared by plotting absorbance or optical density against concentrations of a series of standards. The principle of immunoassay testing is described below. 

In the field, a quick test for the general level of total phenolics in a plant can be the starting point for a more detailed quantitative analysis of the nature and amounts of specific compounds. Various oxidation-reduction methods have been exploited to analyze total phenolics in plant extracts. Many, but not all, phenols form complexes with ferric chloride (FeCy. Ferric chloride gives a color reaction with phenolic compounds. While the phenolate ion is oxidized, the ferric ions are reduced to the ferrous state. 

Adulteration of fats and oils is an old problem. Many older tests involved determination of physical properties such as refractive index, melting point, and viscosity. However, color tests were later used for this purpose. Thus, Baudonin reaction for sesame oil and the Halpben test for cottonseed oil have been noted. In both cases, a compound characteristic to an oil determines the presence of the oil. However, today such detections and quantitations are carried out with GC and HPLC procedures. Thus, cholesterol and phytosterols may be determined by gas chromatography for fingerprinting purposes however, fatty acid analysis might also be used for higher levels of contamination (31). Detailed discussion of issues related to oil authentication and adulteration has taken place (11). 

Newer methods of chemical analysis led to the isolation of the major alkaloids from crude drug preparations. By 1833, aconitine, atropine, codeine, hyoscyamine, morphine, nicotine, and strychnine had been isolated from plants. Color tests for alkaloids were developed between 1861 and 1882 by 1890 quantitative analysis methods became available. Physiological tests for alkaloids, particularly strychnine, first used in 1856, were employed well into the twentieth century. Tests for alcohol, devised by Lieben (iodoform crystal test, 1870) and others, were later perfected for the quantitative analysis of alcohol in body fluids and tissues. Qualitative tests for carbon monoxide in the blood were developed about this time and in 1880, Fodor developed a palladium chloride reduction method to quantitate carbon monoxide in blood. 

Kaiser test, ninhydrin test, a simple and most frequently used method of on-resin monitoring in SPPS. A positive color reaction, performed with a small aliquot of the resin material, indicates unconverted amino groups. Samples containing <0.5% of unreacted amino groups can usually detected within minutes. A modified version of the Kaiser test allows quantitative analysis [E. Kaiser et al.. Anal. Biochem. 1970, 34, 595 V. K. Sarin et al.. Anal. Biochem. 1981, 117,147]. 

The usual colorimetric assays applied to the normal (5 5) bile acids have not been studied with allo-acids, probably because of the paucity of materials. The Hammersten test has been explored principally by Haslewood (25) who has reported a purple color given by allocholic (19) and cholic acids, their 3.5-isomers (69) and their esters 3a, 7y3,12a-trihydro y-5a-cholanoic acid gives a yellow color (19). Undoubtedly gas-liquid chromatography will play an important role in quantitative analysis of the allo-acids in the future. 

Figure 8.2 Design of protein-embedding barcode is depicted in (a) five thin layers of matrix (the thicker lines) coated with variable concentration of tested protein (thinner lines located above the matrix), (b) A FFPE tissue section of bladder cancer IHC-stained by monoclonal antibody to E-cadherine showing variable intensity of positive staining results which is compared with a protein-embedding bar code as designed in this chapter. Using computer-assisted image analysis with a special software, an automatic quantitative measurement of protein is performed. See color insert.

Analysis. Be can be quantitatively determined by colorimetry down to 40 ppb using eriochrome cyanine R or acetylacetone. The sensitivity may be improved by electrothermal absorption spectroscopy (ETAS) to 1 ppb and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPES) or inductively-coupled plasma mass spectroscopy (ICPMS). A simple spot test for qualitative detection of Be is one with quinalizarin in alcoholic NaOH which can detect 3 ppm. The color is produced by both Be and Mg. If the color persists after the addition of Br2 water. Be is present. If the color is bleached. Mg is indicated. 

Analysis. The green flame color of Ba is an indicator that it may be determined readily by atomic emission or absorption spectroscopy. Ba is quantitatively determined by colorimetry down to 1 ppm using o-cresolphthalein at a pH of 11, by atomic absorption spectroscopy (AA ) to 200 ppb, to 10 ppb by electrothermal absorption spectroscopy (ETA ), and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPE ) and inductively-coupled plasma mass spectroscopy (ICPM ). A spot test for Ba which extends to 30 ppm is provided by a controlled combination of KMn04, H2 04, and H2 03. 

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