Rapid Automated Extraction and Confirmation of Buprenorphine and Norbuprenorphine in Urine by DPX-LC/MS/MS
This study focuses on the rapid cleanup of urine samples (< 500 uL) using disposable pipette extraction (DPX) for high throughput LC/MS/MS screening of buprenorphine (Bup) and main active metabolite norbuprenorphine (Nbup). Using a GERSTEL MultiPurpose autosampler (MPS), DPX extractions of hydrolyzed urine were performed, and analysis results were directly compared to results obtained using the “dilute-and-shoot” (D&S) approach for the same samples. The automated DPX cleanup process significantly reduced matrix effects without compromising the required minimum reportable limits (MRLs), whereas when using the D&S approach, samples had to be diluted by up to a factor 100 to remove such effects, which directly affected the ability to determine Bup and Nbup at the MRLs. Moreover, the addition of valve switching control from MAESTRO software further increased the throughput potential of the solution. The resulting eluents from the automated DPX extractions were injected into an Agilent 6460 LC/MS/MS instrument configured with 2 LC pumps (gradient and re-generative) allowing rapid, just-in-time sample preparation for high throughput screening, averaging a cycle time of 4 min/sample.