Three determination methods in enzyme-linked immunosorbent assay, namely optical absorption, fluorescent and chemiluminescent immunoassay, were established for quantitation of biotoxins protein ricin in various matrices. The detection conditions were systematically optimized. The results showed the best signal-to-noise (SNR) could be obtained for CLIA when dilution factor was 1 :8000; and the chemiluminescence signal was stable at around 3 minutes after horseradish peroxidase reacted with its substrate. Whereafter, the three methods were compared for determination of ricin under individually optimized conditions. The comparative results indicated that chemiluminescent immunoassay could provide wider linear range (from 0. 02 mu g/L to 5. 5 mu g/L with correlation coefficient of 0. 999), higher sensitivity ( limit of detection was 0. 005 mu g/L), and could be adopted as a simple, rapid and robust approach. The CLIA method was applied to measure the spiked ricin in water, carbonated beverage, milk powder, coffee and human serum samples. The limits of detection grid the recoveries were from 0. 005 to 0. 08 mu g/L and from 89. 6% to 108. 8%, respectively. The method was quite suitable for quantitative determination of trace amounts of ricin in contaminated or poisoned samples.
