COMPARATIVE STUDY OF ELISA STOP SOLUTIONS BASED ON MINERAL ACIDS

A comparative study of ELISA stop solutions prepared on the basis of hydrochloric, orthophosphoric and sulfuric acids was performed using a competitive ELISA model for detection of antibodies against bluetongue virus. It was demonstrated that the chemical nature and concentration of the acid significantly affect the optical density of negative (K-) and positive (K+) controls, the time-dependent change of the signal, and the ratio between negative and positive controls. Hydrochloric acid solutions within the range of 0.5-4.0 M provided a high initial signal for K- (approximately 2.0 OD units), limited optical density variation over 30 minutes (3-8%), and the highest control ratio values (50-90). Orthophosphoric acid resulted in an increase of the positive control signal over time, whereas sulfuric acid caused a decrease in both K- and K+ signals, leading to narrowing of the dynamic range. The findings confirm that the selection of the stop solution is a critical factor in ELISA standardization and directly influences the analytical reliability of the diagnostic test system.