A panel of 136 ESI+/ESI- therapeutic drugs; drugs of abuse and their metabolites; and biomarkers of alcohol consumption were analyzed using a Force Biphenyl analytical column equipped with a guard column and an online filter. Mobile phase A consisted of 0.1% formic acid in water, mobile phase B consisted of 0.1% formic acid in methanol, the temperature was 30°C, and the ESI+ isobars utilized gradient conditions with a 10 minute cycle time. Urine samples underwent glucuronide hydrolysis. Barbiturates, THCA-A, and THC-COOH were analyzed in ESI- and had a total run time of 5 minutes. They were spiked into urine and diluted at a 1:10 ratio with water. Finally, alcohol metabolites were monitored in ESI- with a 5 minute analysis time. Samples were prepared by diluting with water at a 1:10 ratio and injecting 10 μL.
The Biphenyl stationary phase showed an improved resolution of isobars thanks to its unique selectivity due to the pi-pi interactions that occur between the phase and most drugs and drug metabolites. A demonstration of this powerful selectivity is exemplified for seven isobaric compounds sharing the m/z 286 (morphine, hydromorphone, norcodeine, norhydrocodone, 7-aminoclonazepam, pentazocine, and asenapine), which are all baseline resolved. The problematic urinary interferences in alcohol metabolites analysis were resolved without the use of buffer or additional mobile phases. The ESI- panel with barbiturates achieved partial resolution of amobarbital and pentobarbital, which may eliminate the need for confirmatory testing.
This work demonstrates that one LC-MS/MS setup is possible for the analysis of multiple panels, which simplifies testing procedures, saves time, and ultimately reduces costs.
