The analysis of beta-agonists by packed-column supercritical fluid chromatography with ultra-violet and atmospheric pressure chemical ionisation massspectrometric detection

Packed-column supercritical fluid chromatography (pSFC) using ultra-violet (UV) and atmospheric pressure chemical ionisation (APCI) mass spectrometry (MS) provides a versatile method for the identification and quantification of beta-agonists. We have achieved good separation of clenbuterol, salbutam ol, terbutaline and fenoterol with good resolution and reasonable retention times using a high concentration of methanol modifier in the supercritical CO2, together with small amounts of both acidic (trifluoroacetic acid, TFA A) and basic (triethylamine, TEA, or diethylamine, DEA) additives. APCI-MS gave unambiguous identification of the 4 analytes, and increasing cone volt age provided informative fragmentation patterns. The pSFC-MS technique was shown to be linear (R-2 greater than or equal to 0,996) over the concentrat ion range 1-50 mu g ml(-1). Single ion monitoring (SIM) gave detection limi ts (on-column) of 2.5 ng (clenbuterol), 0.83 ng (terbutaline), 7.6 ng (salb utamol) and 2.7 ng (fenoterol). The pSFC-MS system was shown to be reproduc ible within a day between days, and between restrictors. Analysis of milk s amples 'spiked' with beta-agonists showed that th; matrix caused no interfe rence, with detection limits of approximately 500 mu g l(-1) of beta-agonis ts, More dilute solutions could be analysed by pre-concentration before: th e SFC stage.