Phosphotungstic acid methods

Chickens maintained in the dark for 2 days were exposed to 1000 lux previous subcutaneous injection of 6-3h glucosamine while others remained in the dark. For the experiments with chickens with one eye occluded, they had one eye covered with black tape while the other eye was exposed to light, previous injection of the radiochemical. Retinal gangliosides were obtained by the TCA-PTA (trichloroacetic acid - phosphotungstic acid) method (Maccioni et al., 1974). Statistical analysis as in Table 1. Values for retinas in light were considered 100%. 

In biological materials, various nonspecific precipitants have been used in the gravimetric deterrnination of choline, including potassium triiodide, platinum chloride, gold chloride, and phosphotungstic acid (28). Choline may also be determined spectrophotometricaHy and by microbiological, enzymatic, and physiological assay methods. 

For light microscopic examination, liver tissue was fixed in 10 % buffered formalin, embedded in paraffin, sectioned and stained with hematoxylin and eosin. In some cases, preparations were stained with PTAH (phosphotungstic acid-haematoxylin), by the Van Gieson method and the PAS (periodic acid-Schiff)... 

The standard method used to prepare these AHC s was by anchoring a preformed complex onto an alumina support which had been treated with a heteropoly acid such as phosphotungstic acid (PTA). Alternately, the AHC can be prepared by treating an anchored Rh(COD)2 precursor with an appropriate ligand (8). We report here the use of AHC s which have been prepared by this... 

Lowry method uses a combination of the Biuret copper-based reagent and the Folin-Ciocalteau reagent, which contains phosphomolybdic-phosphotungstic acid. Reagents react with protein, yielding a blue colour that displays an absorbance maximum at 750 nm... 

Only in a few cases has this compound been isolated from the products of hydrolysis of proteins, since its separation is extremely laborious. It can only be effected after all the other amino acids have been removed by crystallisation and by the ester method, and after the diamino acids have been precipitated by phosphotungstic acid. From the last mother-liquors it is obtained by crystallisation, and is best identified in the form of its /8-naphthalene sulpho-derivative. 

The separation and estimation of the three compounds—arginine, histidine, lysine—is carried out by the method described by Kossel and Kutscher in 1900, which was slightly modified in 1903 by Kossel and Patten. It is based upon the earlier work of Drechsel, Hedin and Kossel, and depends upon the precipitation of arginine and histidine as their silver salts, and of lysine by phosphotungstic acid, and then by picric acid. 

The separation and estimation of the two main groups of amino acids can be carried out in one experiment, instead of separately as described. The protein is hydrolysed by sulphuric acid, the tyrosine, cystine and diaminotrioxydodecanic acid are removed by crystallisation, and the diamino acids are precipitated by phosphotungstic acid. From this precipitate they are obtained by decomposition with baryta, and they are then separated by means of their silver compounds by Kossel, Kustcher and Patten s method. The filtrate from the phosphotungstic acid precipitate is freed from the excess of phosphotungstic acid by means of baryta, and the solution is treated by Fischer s ester method for the monoamino acids. 

Bahbouh et al. used a conductimetric method for the analysis of dipyridamole [21], Ground tablets containing the drug were dissolved in 100 mL of 67% ethanol, and a portion was transferred to a titration cell equipped with a conductivity cell. The sample solution was diluted to 50 mL with water and titrated with 5 mM phosphotungstic acid. After each addition of titrant, conductivity measurements were recorded after a 2 min interval and plotted against the amount of titrant added. The end point was determined at the curve break. Results obtained by this method were in good agreement with those obtained by the official pharmacopoeial methods. 

The differences reflected in the two methods indicate the presence of amphoteric asphaltene compounds, an observation that is at odds with that reported by Sternberg et al. (7) for asphaltenes from the Synthoil process. The bases isolated by this ion exchange method correspond closely in amount to those isolated by the phosphotungstic acid scheme. 

The two predominant analyses of uric acid are the phosphotungstic acid (PTA) method and the uricase method. In the PTA method, urate reduces PTA to form a blue product. In the uricase analysis method, urate is oxidized by uricase oxidoreductase. 

Phosphotungstic acid and magnesium were used as precipitant. CHOD-PAP method for the determination of HDL-cholesterol. 

Phosphotungstic acid (PTA), uricase, and HPLC-based methods have been described for measuring uric acid. ... 

Enzymatic methods generally offer greater specificity over conventional non-enzymatic colorimetric methods for the measurement of uric acid. Even so, methods that depend upon the use of oxidizing agents—such as phosphotungstic acid to oxidize uric acid to allantoin and carbon dioxide, and the resulting reduction of... 

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