Objective: To develop a urine pretreatment method of Solid Phase Extraction (SPE) for the quantitative determination of a number of aristolochic acids (AAs) and aristololactams (ALs) in rat urine.
Method: The HPLC peak area of AA-I , AA-II, AL-I and AL-II, and other sixteen AAs and ALs was chosen as evaluating index to study the extract results of five Solid Phase Extraction columns (Agilent C18/100 mg, Alltech HG18/100 mg, Alltech C18/100 mg, Alltech C18/300 mg and Agilent Phenyl/200 mg) comparatively. The influences of two washing solvents (water and 1% acetic acid-0.02% triethylamine solution) and seven eluting solvents (ether, acetone, chloroform, ethyl acetate, dichloromethane, methanol and acetonitrile) on extract results of AAs and ALs are comparatively studied with the extracting recoveries of AA-I , AA-II, AL-I and AL-II as indicators. The HPLC peak area of AA-I , AA-II, AL-I and AL-II, and other seven AAs and ALs with good separation being targets, several factors which affect extracting efficiency of analytes, including activating volume, cleansing volume, washing volume and eluting volume, are optimized by orthogonal design experiments with four factors at three levels.
Result: The established method of SPE is as follows: Agilent Phenyl SPE column of 200 mg, activating with 1.0 mL methanol, cleansing with 1 mL water, adding 1.0 mL rat urine sample, washing with 0.8 mL 1% acetic acid 0.02% triethylamine solution, and eluting with 3.0 mL methanol.
Conclusion: The established method of SPE is efficient, selective, simple and fast, and can be used as urine pretreatment method to analyze a variety of aristolochic acids and aristololactams in rat urine.