PubMed · 4156571
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G S Riley. 1974. Characterization of phenobarbitone samples.. https://doi.org/10.1111/j.2042-7158.1974.tb09209.x
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The physical compatibility of fluorouracil mixed with leucovorin calcium or levoleucovorin calcium, undiluted and modestly diluted with 5% dextrose injection, was evaluated. Fluorouracil 50 mg/mL was combined in duplicate with leucovorin or levoleucovorin 20 mg/mL (as the calcium salt) in 250-mL polyvinyl chloride (PVC) portable-pump reservoirs in six volume ratios, either undiluted or diluted with 5% dextrose injection (to a final volume 25% greater than the drug volume). Duplicate reservoirs of each combination were stored for seven days at 4, 23, or 32 degrees C. Samples were evaluated visually with a high-intensity monodirectional light beam to observe development of particulates. Turbidimetry and light-obscuration particle counting and sizing also were used to evaluate compatibility. Small amounts of tiny crystalline particles developed in most of the combinations, usually by four days. In some cases, the particles could be seen in normal diffuse room light. Particle content was greater with higher leucovorin concentrations and over longer storage periods. Storage temperature did not play a consistent role in particle development. Fluorouracil and leucovorin calcium or levoleucovorin calcium were not compatible when stored in PVC reservoirs at 4, 23, or 32 degrees C.
Many proteins derived from the latex of Hevea brasiliensis that remain soluble in trichloroacetic acid (TCA) can be precipitated by phosphotungstic acid (PTA). A combination of 5% TCA and 0.2% PTA precipitates a wide range of proteins effectively even when they are present in low concentrations (below 1 microgram ml-1). In addition to its protein purification function, acid precipitation also increases the sensitivity of the subsequent protein assay by allowing the test sample to be concentrated. Another advantage of protein precipitation by TCA and PTA is that very small amounts of protein (of the order of 10 micrograms) can be repeatably recovered without the use of precipitate-bulking agents such as sodium deoxycholate. This general procedure of protein purification and concentration is simple and rapid, but the use of PTA may not be fully compatible with the Bradford protein assay. A modified Lowry microassay is described which enables about 3 micrograms ml-1 to be quantitated at the photometric absorbance of 0.05. When used in conjunction with protein concentration by precipitating with TCA/PTA, approximately 0.4 microgram ml-1 protein present in 6 ml of solution can be assayed.
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