Optimal Parameters for the GC/MS Quantitation of Barbiturates in Urine at Lower Concentration Levels

This study is placed on evaluating optimal factors for the quantitative determination of barbiturates in urine at lower concentration levels. An automatically well-established solid phase extraction (SPE)is used for the urine samples, and then the extract is methylated prior to the GC/MS measurement steps. The optimization of GC/MS quantitative effectiveness is evaluated based on four specific parameters including the use of different internal standards (ISs), the added magnitude of ISs, reconstitute volume, and temperature programming conditions. The resulting data indicate the following conditions can be recommended for the routine quantitation: the added magnitude of 50 ng/mL IS, and 90μL reconstitution volume and 20℃ ramp rate in temperature programming conditions. The quantitation using all evaluated conditions results in the following observations: 10 ng/mL LOD and 40 ng/mL LOQ for butalbital, 20 ng/mL LOD and 80 ng/mL LOQ for amobarbital, 20 ng/mL LOD and 20 ng/mL LOQ for pentobarbital, 10 ng/mL LOD and 20 ng/mL LOQ for secobarbital, 20 ng/mL LOD and 40 ng/mL LOQ for phenobarbital.