Development and validation of a sensitive and fast solid-phase spectrophotometric procedure for phenol determination...

A very sensitive, simple, and fast solid-phase spectrophotometric procedure for the determination of phenol using the p-nitrobenzenediazonium reagent (DAR reagent) was developed. This procedure is based on the simultaneous concentration of the orange product on a Dowex 1-X2 anion exchanger within 15 min, and a direct absorbance measurement of the sorbed species at both 530 nm (the absorption maximum of the phenol-DAR in the resin phase) and 700 nm (the range where only the resin absorbs light). Quality control and evaluation of the analytical parameters was carried out using a comprehensive prevalidation strategy. The linearity of the method was confirmed within an analyte working range from 0.01 to 0.10 µmol (0.2 to 2.0 nmol mL(-1)). The precision ranged from ±1.17 to ±9.61%; the accuracy ranged from -17.50 to +17.81%. The evaluated limiting values were L(D) = 0.0013 µmol and L(Q) = 0.0082 µmol. The DAR-SPS method was successfully applied to the determination of phenol in a pharmaceutical sample of salicylic acid (98.0-100.0%) and vaccines (98.0-103.4%).