LC-MS/MS bioanalytical challenge: ultra-high sensitivity assays

The challenges of developing and running low pg/ml LC-MS/MS bioanalytical assays in a regulated laboratory are reviewed. The practical problems encountered in implementing ultrasensitive assays are less in reaching a suitable sensitivity on the instrument than in implementing procedures to control losses and contamination, eliminate matrix interferences and ensure assay robustness so that the assay can be validated to industry standards. Solutions to these problems can be found in each of the three facets of the bioanalytical assay: the sample preparation, the chromatographic separation and the mass spectrometric detection. The key to developing an ultrasensitive assay is to optimize each of these elements. Progress in MS instrumentation has been essential in our ability to reach the low pg/ml limits.