Sample preparation colorants

Colorless phosphate ester surfactants were also prepared by treating P4O,0 with an organic OH-containing compound in the presence of a phosphinic acid color inhibitor, e.g., bis(hydroxymethyl)phosphinic acid color inhibitor. Thus, 558 parts dodecanol containing 2.4 parts of phosphinic acid color inhibitor was treated with 142 parts P4O10 at 100-135°C. The phosphate ester surfactant had a VCS color value of 1, whereas a sample prepared without the color inhibitor had a VCS color value of 5. Twenty-eight similar surfactants were prepared using various alcohols and alcohol-alkylene oxide condensates [22]. 

Sample preparation in case of sampling this is a critical step because undesired reactions easily occur at this step (e.g., color decay due to light or oxygen) resulting in um-eliable data. 

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

FIGURE 4 Effect of sample preparation on the fragmentation of an rMAb observed in (A) SDS-PAGE and (B) CE-SDS with LIF detection. SDS-PAGE lanes (Lane I) molecular weight standards bovine serum albumin at (Lane 2) 8 ng and (Lane 3) 2 ng (Lane 4) rMAb control after alkylation with (Lane 5) iodoacetic acid and (Lane 6) iodoacetamide. (See color plate 4.)... 

Flow injection analysis is based on the injection of a liquid sample into a continuously flowing liquid carrier stream, where it is usually made to react to give reaction products that may be detected. FIA offers the possibility in an on-line manifold of sample handling including separation, preconcentration, masking and color reaction, and even microwave dissolution, all of which can be readily automated. The most common advantages of FIA include reduced manpower cost of laboratory operations, increased sample throughput, improved precision of results, reduced sample volumes, and the elimination of many interferences. Fully automated flow injection analysers are based on spectrophotometric detection but are readily adapted as sample preparation units for atomic spectrometric techniques. Flow injection as a sample introduction technique has been discussed previously, whereas here its full potential is briefly surveyed. In addition to a few books on FIA [168,169], several critical reviews of FIA methods for FAAS, GF AAS, and ICP-AES methods have been published [170,171]. 

The solution to the problem was discovered when a titrated sample (clear solution) was left on the bench and, after a period, it started changing back to a faint yellow color. We hypothesized that air oxidation may have caused that effect and, consequently, air may have interfered with analysis. Standard samples prepared and purposely delayed during the analysis showed that end-point volumes were larger, indicating that some of the iodide ions turned into free-iodine by air oxidation which, in turn, required more thiosulfate for titration and, therefore, larger end-point volume. The following chemical equations obtained from the literature 8) show what happens before, during, and after titration. The reaction of a chlorinated isocyanuric acid compound with potassium iodide in acidic pH is ... 

In this chapter we describe characteristic validation procedures of the Heavy Metals Limit Test in the Japanese Pharmacopoeia (JP) [1]. Although an equivalent test is commonly listed in both the United States Pharmacopoeia and the European Pharmacopoeia, there are differences in the color reagents and conditions of sample preparation of the JP procedure. Heavy metals are defined in the JP as poisonous metallic impurities such as Pb, Bi, Cu, Cd, Sn, and Hg that form colored colloidal precipitates with sodium sulfide TS in a slightly acidic solution of pH 3 to 4. The level is expressed as the equivalent quantity of lead. 

The purpose of this section is to provide a review of HPLC methods available for the determination of synthetic colors in foods, including sample preparation, separation techniques, and detection systems. 

Sample preparation for color analysis will depend on the type of food sample. Liquid samples such as beverages can be filtered through a 0.45 /rm pore membrane filter and injected directly in the HPLC. Carbonated beverages are degassed. Beverages containing suspended solids are filtered or centrifuged to eliminate suspended solids (143,156,160). 

P Ashkenazi, C Yarnitzky, M Cais. Determination of synthetic food colors by means of a novel sample preparation system. Anal Chim Acta 248 289-299, 1991. 

Triacetin intended for use in the manuf of US smokeless propellants shall comply with the requirements of Spec JAN-T-301, as detd by the following tests a.)Color Prepare the standard by adding 0.5 ml of 0.1N iodine soln 100 ml w and visually compare the color in 25 ml Nessler tube with that of sample. The color of sample shall be no darker than that of standard... 

The instruments discussed earlier are the primary ones used in toxicant analysis, but an enormous number of analytical techniques are used in the field. Many of the instruments are expensive (e.g., Raman spectrometers, X-ray emission spectrometers) and few laboratories possess them. Many other instruments are available, however, such as the specific-ion electrode, which is both sensitive and portable. Specific-ion electrodes have many other advantages in that sample color, suspended matter, turbidity, and viscosity do not interfere with analysis therefore many of the sample preparation steps are not required. Some of the species that can be detected at ppb levels are ammonia,... 

In the case of off-line sample preparation methods, clean up is required in samples having colors and other interfering impurities. Biological and environmental samples contain thousands of other substances as impurities and these were extracted along with the analytes of interest. Due to the similar properties of the co-extractives, they usually interfere in the analyses of the... 

Color Strength, Hue, Chroma [20, p. 99-105], The coloring properties of a dye are assessed by preparing a dyed test sample whose color is evaluated. This must, in principle, always be done by the human eye because color perception, being a subjective sense impression, is not accessible to direct measurement. However, with the aid of colorimetry this visual perception can be represented more or less closely by measurable quantities. Since colorimetry is an objective method and is therefore more accurate and reproducible than subjective visual assessment, it is veiy widely used today. Color is a three-dimensional quantity and must therefore be expressed by a set of three numbers (color coordinates). In practice, these are typically the values of color strength, hue, and chroma. 

Dong H, Kemptner J, Marchetti-Deschmann M, Kubicek C, Allmaier G (2009) Development of a MALDI two-layer volume sample preparation technique for analysis of colored conidia spores of Fusarium by MALDI linear TOF mass spectrometry. Anal Bioanal Chem 395 1373-1383. doi 10.1007/s00216-009-3067-3... 

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