The relation between slope of the endotoxin standard curve and the recovery by the dynamic turbidity method

To study the relation between slope of the endotoxin standard curve and the recovery by the dynamic turbidity method.Methods:Endotoxin standards or samples in different concentrations were reacted with Tachypleus Amebocyte Lysate(TAL)in the BET-32C Bacterial Endotoxin Tester and the slope b_s of the standard curve or the slope b of the dilution curve were calculated by the characteristic reactive time t(0.02)and their con- centrations or dilution multiples.Results:(1)The slope b_s were-0.1646 and-0.2698 for endotoxin standards of 160 EU vial~(-1)and 20 EU vial~(-1),respectively.(2)The judgment equation was b/b_s=[1g(D_(s1)/D_(s2))]/[1g(α)+ 1g(D_(s1)/D_(s2))],while α was the recovery and the D_(s1),D_(s2)were the dilution multiple of endotoxin standards.(3)The slope b_s-were-0.2828,-0.2138 and-0.2898 for 200 EU·vial~(-1)endotoxin standards reacted with TAL with sensitivity of 0.06,0.125,0.5 EU·mL~(-1)respectively from producer A.The slope b_s were-0.2403,-0.2892,- 0.2848 and -0.2896 for 20 EU vial~(-1)endotoxin standards reacted with 0.125 EU mL~(-1)TAL from producer A,B, C and D respectively.(4)The slope b_s were -0.140,-0.150,-0.214 and -0.279 for endotoxin standards of 9000,160,200 and 20 EU vial~(-1)respectively.(5)The b/b_s of water and amphotericin B sample vs 20 E U vial~(-1) were 99.8% and 147%,respectively.Based upon those observations,the endotoxin content of water sample could be determined within the recovery of 50%-200% in the concentration range of 1000 times,and not for amphoteri- tin B sample.Conclusion:The relation between the endotoxin standard curve slope and the recovery is set up and it can be used to judge the endotoxin recovery in samples by the use of the b/b_s ratio.