Study on repeatability of the determination of temozolomide by micellar electrokinetic capillary chromatography using internal standards

This paper demonstrates the study of the use of single or multiple (2-4) internal standards for the improvement of the repeatability of the micellar electrokinetic capillary chromatographic measurements of temozolomide in model solution and in serum. The dimethylformamide, dimethylsulfoxide, paracetamol and benzyl alcohol were selected as internal standards. The best precision data (RSD less than 0.036%) of the migration times could be reached with two internal standards applying weighted correction according to the distance of the internal standards from the analyte. We also investigated the effects of the use of new capillaries, buffer renewal and postcondition procedures on the repeatability.