Kinetics of the Reaction of Pyrogallol Red, a Polyphenolic Dye, with Nitrous Acid: Role of ŸNO and ŸNO2

In the present work we studied the reaction under gastric conditions of pyrogallol red (PGR), a polyphenolic dye, with nitrous acid (HONO). PGR has been used as a model polyphenol due to its strong UV-visible absorption and its high reactivity towards reactive species (radicals and non-radicals, RS). The reaction was followed by UV-visible spectroscopy and high performance liquid chromatography (HPLC). A clear decrease of the PGR absorbance at 465 nm was observed, evidencing an efficient bleaching of PGR by HONO. In the initial stages of the reaction, each HONO molecule nearly consumed 2.6 PGR molecules while, at long reaction times, ca. 7.0 dye molecules were consumed per each reacted HONO. This result is interpreted in terms of HONO recycling. During the PGR-HONO reaction, nitric oxide was generated in the micromolar range. In addition, the rate of PGR consumption induced by HONO was almost totally abated by argon bubbling, emphasising the role that critical volatile intermediates, such as •NO and/or nitrogen dioxide (•NO₂), play in the bleaching of this phenolic compound.

Measurement of the albumin content of urinary protein using dipsticks

An albumin selective urine strip based on bis (3',3''-diiodo-4', 4''-dihydroxy-5',5''-dinitrophenyl)-3,4,5,6-tetrabromo sulfonphthalein dye (DIDNTB) dye was examined in populations with clinical proteinuria. The relationship of albumin to the sum concentration of all protein in urine was found to vary widely even though the albumin concentration generally increased with the total protein concentration. The albumin reagent strips correlated well with immuno-nephrometric assays for albumin on specimens from hypertensives, diabetics, and renal disease which tended to have albumin contents of >/= 50.0%. High proteinuria concentrations of > 250 mg/l, with low albumin contents of </= 30%, occurred more frequently in cases of cancer, infection, and myeloma. The albumin strip read higher than the immuno assay in samples with high proteinuria and low albuminuria. The albumin strip was also less affected by albumin fragmentation than by the immunological assay. Overall, the albumin strip gave a lower risk of false negatives than a protein strip based on tetrabromophenol blue (TBPB) dye and was more sensitive to disease condition. The protein strip was not sensitive to low levels of albumin and the agreement between TBPB dye strip and the quantitative analysis was not as affected by the albumin content.