Abstract: bjective To establish effective methods for detecting hazardous substances in dialyzers. Method  The industry-standard of hemolysis test and reducing substance assay were optimized: ①the contact time between hollow fibers and red blood cells was prolonged and a dynamic, back-and-forth sliding motion of the fibers in the erythrocyte suspension was introduced; ②the entire dialyzer was exhaustively extracted and, after extraction, fully obtain all the extraction solutions to determine the total amount of reducing substances in the device. The hemolysis rate and reducing substance content of 16 batches of dialyzers were tested by both the standard and optimized protocols; results were compared. After further refinement, the optimized methods were applied to 28 additional  batches of dialyzers to determine hemolysis rate and total reducing substances and to analyze their correlation. In addition, relevant studies on the wavelength band of the maximum absorption peak of the dialyzer extract and the appropriateness of the current extract-collection protocol in biological experiments were also conducted.  Result  The optimized hemolysis test (t=-5.987, P＜ 0.001) and reducing substance content (t=-4.601, P ＜0.001) assay demonstrated higher sensitivity than the standard protocols. With the standard methods, hemolysis rate and reducing substance content levels of the 16 batches of dialyzers were uniformly low; with the optimized methods, hemolysis rate ranged from 0.5 % to 12.2 %, and total reducing substances from 3.8 mL to 90.4 mL. For the 28 batches of dialyzers, hemolysis rate correlated positively with total reducing substances (r=0.478, P=0.013); when total reducing substances exceeded 30 mL, hemolysis rate was ≥5 %. The dialyzer extract showed maximum UV absorbance at 200 nm. After obtaining extract liquid in the common way, a substantial volume of fluid remained inside the hollow fibers.   Conclusion  ①The optimized methods for the reducing substances content and hemolysis rate are effective for quantifying hazardous components. Controlling the total amount of reducing substances can, to a certain extent, achieve the goal of limiting the content of hazardous substances.  ② Industry standard YY0053 needs to be revised: the reducing substance assay and hemolysis rate test should be tightened according to the optimized protocols mentioned in our study. the UV absorbance wavelength should be corrected; and the      extraction procedure for biological tests should specify complete removal of residual fluid from the dialyzer using repeated vacuumassisted aspiration.

Key words: Dialyzer, Reducing substance, Hemolysis rate, UV absorption, Preparation of extracts for biological tests