Abstract des Autors

LC/MS/MS technique has been implemented as routine screening method to analyze corticosteroids, diuretics, beta-blockers, beta-agonists, narcotics, stimulants and other prohibited substances at the National Doping Control Centre, Bangkok, Thailand. Five milliliters urine was consecutively extracted with TBME in basic and acidic condition, respectively. The extracted samples were separated by two different reverse-phase columns (C8 and C18) and then analyzed by LC/MS/MS using switching positive and negative MRM modes. This method reduced reagents, man-power and use of previous GC/MS systems. All prohibited substances could be detected at their MRPL or lower. Two major disadvantages of this method were observed during this period. Some substances showed low extraction recovery and the total run time was more than 23 minutes. It was found that recovery could be increased by adding 3 grams of Na2SO4 to urine in basic condition. The chromatographic gradient program was also modified to reduce retention times and improve peak shapes. This modified LC/MS/MS method was validated for implementation. From one-year experience, the improved method has been demonstrated to be reliable, convenient and cost-effective.