What’s the Most Meaningful Standard for Mass Spectrometry: Instrument Detection Limit or Signal-to-Noise Ratio?
When evaluating the performance of mass spectrometers, one needs to consider the best (or most meaningful) figure of merit to use; options include instrument detection limit (IDL) and signal-to-noise ratio (S/N). In the last 15 years, vendor specifications for S/N have increased from 10:1 to greater than 100,000:1. Does that accurately reflect improvements in mass spectrometers? Although there have been many significant changes, the change in S/N specifications has been far greater than the corresponding change in method detection limits (MDL). Under appropriate conditions, S/N is a meaningful standard, but the value of any S/N must be evaluated in context of the chromatography and sample. Factors influencing the validity of vendor S/N specifications are reviewed, and the statistical alternative of IDL is presented as a replacement that is more consistent with regulatory guidelines and a more relevant indicator of instrument performance.