LC-MS(/MS) Analysis of Psychotropic Drugs

Therapeutic drug monitoring of psychotropic drugs has an established place in psychiatry. The laboratory that is performing these analyses has to cope with the special clinical situation of psychiatric patients, e.g. fast turn-around times, high quality of the results, patients taking different drugs at the same time. From the technological point of view a very specific and also sensitive method is needed to manage the above-mentioned demands. In the last few years HPLC connected to mass spectrometry has been introduced in the specialized clinical laboratory. This new technology features a very high specificity and a high sensitivity. This leads to shorter times of analyses for each sample that allows a higher throughput of samples and reduces the turn-around-times. Possible interferences of co-administrated drugs are reduced and low limits of quantification are achieved. Tandem mass spectrometry may even increase the specificity and sensitivity of this analytical technique. There are two different principles of the ionisation process, electrospray ionisation and atmospheric pressure ionisation, each having its special applications. Whereas atmospheric pressure ionisation has a wider range of linearity, electrospray ionisation is milder and allows also the detection of instable compounds. HPLC connected to mass spectrometry in addition permits multicomponent analyses enabling the determination of different drugs in a single run. With these techniques also compounds formerly known as difficult to be analysed (e.g. fluphenazine, penfluridol and olanzapine) may be determined with a high precision and accuracy.