A new colorimetric method for the estimation of resorcinol

A new, rapid, simple, and sensitive colorimetric method for the estimation of resorcinol in microgram amounts is described.     

Evaluation of a colorimetric method for vitamin A estimation

A simple colorimetric procedure for plasma vitamin A is evaluated, which does not require sophisticated or expensive equipment. Vitamin A values obtained with 30 human plasma samples and 11 liver samples obtained from lactating rabbits, using a colorimetric procedure based on Carr-Price reaction with ferric chloride and acetyl chloride were compared with those obtained with spectrophotometric and spectrofluorimetric micro methods. With widely varying plasma samples, the values showed a high degree correlation and good agreement. The intraassay variation was 3% which is in the acceptable range. The plasma samples could be analysed within 4 weeks and the reagents, were found to be stable, unlike some batches of trifluoro acetic acid (TFA).     

A short-duration colorimetric method based on phenol-sulfuric acid reaction for the estimation of glucosylhemoglobin

Hemolysates were treated with HCl (0.18 m)-acetone solution to remove heme and the globin precipitated was washed with acetone. It was dissolved in 1 ml of 0.05 m Tris-HCl, pH 7.0, subjected to heat treatment for 10 min at 100°C to remove traces of acetone, and treated with 0.05 ml of 80% phenol and 3 ml of H₂SO₄. The color was measured at 480 nm. Glucosylhemoglobin values in control subjects and diabetics were respectively 0.286 ± 0.051 and 0.513 ± 0.081 mole hexose/mole hemoglobin. The increase in diabetics was highly significant (P < 0.001). A good correlation (r = 0.85) between fasting blood sugar values and glucosylhemoglobin level was observed. When globin solution was subjected to 4 hr hydrolysis with HCl-oxalic acid (2 and 1 mole/liter) solution prior to phenol-sulfuric acid reaction, estimated glucosylhemoglobin values increased to 0.720 ± 0.083 in control subjects and 1.036 ± 0.115 in diabetics. The possible reasons for this increase are discussed.     

Non-specificity of a colorimetric method for the estimation of N-acetyl-D-glucosamine.

The colorimetric method of Reissig et al. for the estimation of N-acetylamino sugars, is often used as a specific method for the quantification of the N-acetyl-D-glucosamine. Although this assay is more sensitive to the monomer, it recognizes all soluble N-acetyl-D-glucosamine oligomers. This result is very important because this method is extensively used in biology for the estimation of chitinolytic activity.