Blanc J A, Manneh V A, Ernst R, Berger D E, de Keczer S A, Chase C, Centofanti J M, DeLizza A J
Development Department, Syva Co., San Jose, CA 95161-9013.
Clin Chem. 1993 Aug;39(8):1705-12.
The major metabolite of cannabis found in urine, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (delta 9-THC), is the compound most often used to calibrate cannabinoid immunoassays. The hydrophobic delta 9-THC molecule is known to adsorb to solid surfaces. This loss of analyte from calibrator solutions can lead to inaccuracy in the analytical system. Because the calibrators remain stable when not used, analyte loss is most probably caused by handling techniques. In an effort to develop an effective means of overcoming adsorption losses, we quantified cannabinoid loss from calibrators during the testing process. In studying handling of these solutions, we found noticeable, significant losses attributable to both the kind of pipette used for transfer and the contact surface-to-volume ratio of calibrator solution in the analyzer cup. Losses were quantified by immunoassay and by radioactive tracer. We suggest handling techniques that can minimize adsorption of delta 9-THC to surfaces. Using the appropriate pipette and maintaining a minimum surface-to-volume ratio in the analyzer cup effectively reduces analyte loss.
尿液中发现的大麻主要代谢物11-去甲-δ9-四氢大麻酚-9-羧酸（δ9-THC）是最常用于校准大麻素免疫分析的化合物。已知疏水性的δ9-THC分子会吸附到固体表面。校准溶液中分析物的这种损失会导致分析系统不准确。由于校准物在未使用时保持稳定，分析物损失很可能是由处理技术引起的。为了开发一种有效克服吸附损失的方法，我们在测试过程中对校准物中的大麻素损失进行了量化。在研究这些溶液的处理过程中，我们发现，用于转移的移液器类型以及分析仪杯中校准溶液的接触表面积与体积比都会导致明显且显著的损失。通过免疫分析和放射性示踪剂对损失进行了量化。我们建议采用能够将δ9-THC对表面的吸附降至最低的处理技术。使用合适的移液器并在分析仪杯中保持最小的表面积与体积比可有效减少分析物损失。
