Micellar electrokinetic chromatographic method for the determination of letrozole, citalopram and their metabolites in human urine.

A new micellar electrokinetic chromatographic method has been developed to analyse human urine samples containing a combination of a drug used for the treatment of breast cancer (letrozole), an antidepressant (citalopram) and their main metabolites. Best results were obtained by using 15 mM borate buffer (pH 9.2) containing 20 mM sodium dodecyl sulphate and 12% (v/v) 2-propanol as the background electrolyte. The separation was performed through a fused silica capillary at 40 degrees C with the application of 6s (3.45 kPa) of hydrodynamic injection and 30 kV of separation voltage. Detection wavelength was 240 nm. Under these conditions, the migration times for all the studied compounds were ranged between 3.0 and 8.0 min. Linearity ranges were determined as 0.4-5.0 microg/mL for all the compounds. Detection limits between 12.5 and 25 ng/mL were determined in urine samples. According to the validation study, the developed method has been proven to be accurate, precise, sensitive, specific, rugged and robust. This method has been used to determine letrozole, citalopram and their metabolites in human urine at clinical levels. Prior to determination, the samples are purified and enriched by means of an extraction-preconcentration step with a preconditioned C(18) cartridge and by eluting the compounds with methanol. The developed method was applied to the determination of these analytes in three urine samples from patients undergoing treatment with letrozole or citalopram.

Micellar electrokinetic chromatographic study of the separation of an aromatase inhibitor and a tryciclic antidepressant in the breast cancer treatment.

Micellar electrokinetic chromatography (MEKC) was investigated for the simultaneous determination of letrozole, imipramine and their metabolites in human urine samples over a concentration range of therapeutic interest. Experimental parameters such as pH of the running electrolyte, sodium dodecylsulphate (SDS) concentration, borate concentration, voltage, etc were investigated. Under optimal conditions of 25 mM SDS, 15 mM borate buffer (pH 9.2), 15% 2-propanol, as background electrolyte; 28 kV and 40 degrees C, as voltage and cartridge temperature, respectively; resolution between the peaks was greater than 1.7. Before the determination, a solid phase extraction (SPE) procedure with a C(18) cartridge was optimized. Good linearity, accuracy, precision, robustness and ruggedness were achieved and detection limits of 12.5 ng/mL for letrozole and its metabolite and 37.5 ng/mL, were obtained for imipramine and their metabolites. Real determinations of these analytes in two patient urines were carried out. Sensitivity achieved in this method is sufficient to perform kinetic studies in humans.