Abstract: Urine pH testing can aid common methods for defeating urine drug test including dilution or adulteration of the sample with bleach, vinegar, Visine, sodium bicarbonate, Drano, soft drinks, or hydrogen peroxide. Urine pH is also an important screening test for the diagnosis of renal disease, respiratory disease, and certain metabolic disorders.
We have developed an assay for the optical measurement of pH in urine samples, which is based on copolymerization of organic conducting polymers such as polyanilines grafted on the surface of polystyrene. They undergo pH-dependent changes in their absorption spectra (maxima between 492 and 560 nm) in the physiological pH range.
Evaluation of the assay performed following National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The method was used to measure 25 urine samples from patients in a methadone treatment program and results were compared with ISE and dye indicator-based pH assays.
Results showed a pH-dependent spectrum chang e that occurred between pH 2 and 12. An external standard curve was used for quantification, which showed a linear range of 4-12 pH value when 510 nm wavelength used on repeated testing. The inter-assay CV for a period of 20 days was 15% for pH equal to or less than 4% and 7% for pH between 4 and 12. The polymeric pH assay showed average 5% higher pH values as compared to ISE results.
The proposed urine pH screening assay is optometric and not based on indicator dye, is rapid, and can easily be reproduced.