What is the confirmatory method for measuring drugs of abuse using the mass-to-charge ratio?

The confirmatory method for measuring drugs of abuse that utilizes the mass-to-charge ratio is gas chromatography with mass spectrometry (GC-MS). This technique effectively identifies and quantifies substances based on their mass and charge after separation using gas chromatography.

GC-MS is highly valued in toxicology for several reasons. First, it provides definitive identification of compounds due to the unique mass spectrometry signatures of different drugs. When a sample is introduced, it is vaporized and carried through the column of the gas chromatograph, where it is separated based on its chemical properties. Once separated, the compounds enter the mass spectrometer, which determines their mass-to-charge ratio. This allows for precise identification, making it a powerful tool for confirming the presence of specific drugs of abuse in biological samples.

In contrast, other methods listed, such as thin layer chromatography, isoelectric focusing, and serum protein electrophoresis, serve different purposes. Thin layer chromatography is primarily used for screening and not definitive identification. Isoelectric focusing and serum protein electrophoresis are techniques used for protein analysis and do not directly measure drugs of abuse. Therefore, while they may have their own applications, they do not match the specificity and confirmatory capabilities of GC-MS in the context of drug testing.