Comparative extraction methods for spectrophotometric analysis of uric acid in avian excreta

Different extraction techniques were compared in uric acid analysis of avian excreta. These include five extraction reagents (0.1 M sodium hydroxide, 0.1 M glycine buffer, 0.068 m lithium carbonate, 0.136 M lithium carbonate and sodium borate buffer, pH 9.1). Each extraction reagent was used with four excreta sample weights (50,100,150 and 200 mg) for four extraction periods (10,20,30 and 40 min) in four extraction volumes (5,10,15 and 20 ml). Extraction with sodium hydroxide gave lower uric acid concentration; however, glycine buffer extraction gave uric acid concentration that was higher (P < 0.05) than extraction with lithium carbonate or sodium borate buffer. Uric acid concentration increased with increase in sample weight and decreased with decrease in reagent volume when extracted with glycine buffer. Filtration of sodium hydroxide and glycine buffer extract with 1-kDa low-binding regenerated-cellulose membrane did not alter uric acid extraction efficiency from avian excreta. Regardless of length of extraction period or volume, the recovery of crystalline uric acid following extraction with lithium carbonate or sodium borate buffer was not different from 100% when 100 mg sample or less was extracted. The optimum extractions condition 25 were 100 mg sample in 10 ml and 50 to 200 mg sample in 15 ml 0.068 M lithium carbonate or sodium borate buffer for 10 min at 99 degrees C.