Automated trichloroacetic acid precipitation method for urine total protein

Urine total protein determination by a trichloroacetic acid (TCA) precipitation method was automated on a Cobas Bio centrifugal analyser. The assay measures the turbidity at 420 nm when a 50 microL sample is mixed with 150 microL of 30 g/L TCA at 25 degrees C. Samples up to 5 g/L can be measured by this method and interference due to pigments and turbidity can be minimised by running a blank with 1.25% hydrochloric acid (HC1) instead of TCA. The standard curve is stable and can be stored in the microcomputer and used again. Within-assay precision (CV) varied from 2 to 4.6% and between-assay precision varied from 1.8 to 5.4%. Analytical recovery ranged from 95 to 106.5% and the results correlated well with those obtained by a manual TCA method (r = 0.98). The method is easy to perform and is considerably faster than the manual procedure, thus saving time and providing a faster turnaround time.