Abstract: OBJECTIVE： To investigate detection methods of trace amounts of bacterial endotoxins in drugs using horseshoe crab reagents，and to reduce use of horseshoe crab resources. METHODS： Using trace amounts of horseshoe crab reagents produced by two different manufacturers，A and B，and using 25 μL of horseshoe crab reagent as the reaction system，the micro dynamic colorimetric method was validated，and the variety applicability was studied. The results were compared with those of constant 100 μL of horseshoe crab reagent detection. In addition，the micro gel method was used to compare the test results of the limulus reagent from two manufacturers A and B with the constant and micro limulus reagent，using 50 μL limulus reagent as the reaction system. RESULTS： The recovery rates of the trace dynamic colorimetric method using the trace horseshoe crab reagent from manufacturer B at concentration points of 0.316 and 0.0316 EU/mL were 82% and 72%，respectively，which were relatively low. In different 6-day standard curves，the negative control time was greater than the reaction time at the lowest point of the standard curve. After double logarithmic transformation，linear regression was performed using the least squares method to calculate the correlation coefficient |r|≥0.980. The results of micro gel method and micro test from the two manufacturers A and B were basically consistent. CONCLUSION： The method of detecting bacterial endotoxins with trace horseshoe crab reagent is basically feasible.

Key words: bacterial endotoxins, horseshoe crab reagent, microcalorimetry, micro dynamic colorimetric method, micro gel method