The clinical interest of LCMSMS in drug quantification

LCMSMS, which is nothing more than HPLC (or UPLC) coupled with tandem mass spectrometry (double mass spectrometry), is about to become the reference method for the majority of clinical biology (notably pharmacology and toxicology) quantification assays. The principle behind mass spectrometry lies on the detection of analytes (following their ionisation) relative to their mass/charge ratio (m/z). The use of two tandem mass spectrometers enables the specificity of this technique to be improved in comparison with the single mass spectrometry detectors. This principle also improves the sensitivity of quantification assays by reducing the background noise and interference.

We observed an improvement for both of these criteria (specificity and sensitivity) once we changed our drug quantification method (amphetamines, cocaine, opiates and cannabinoids) from GCMS to LCMSMS with a gain of at least 10 fold. Furthermore, the system allows us to carry out an integrated solid phase extraction, which is therefore automated and thus leads to better reproducibility with lower volume samples.

Finally, in order to improve our results for quantification assays, and following the conference held by SFTA (Saint Malo, June 2013), we proceeded with pre-analytical changes as of 01 Jan 2014. The samples, which are usually collected in fluoride tubes (or heparin tubes), no longer need to be frozen. They can be transported at fridge temperature. This change was introduced following the significant degradation of the drugs during the defrosting phase. Sodium fluoride preserves the sample better, especially for cocaine assays.