A. Polettini et al., DEVELOPMENT OF A COUPLED-COLUMN LIQUID-CHROMATOGRAPHIC TANDEM MASS-SPECTROMETRIC METHOD FOR THE DIRECT DETERMINATION OF BETAMETHASONE IN URINE, Journal of chromatography B. Biomedical sciences and applications, 713(2), 1998, pp. 339-352
Citations number
21
Categorie Soggetti
Chemistry Analytical","Biochemical Research Methods
Journal title
Journal of chromatography B. Biomedical sciences and applications
Different hyphenated liquid chromatographic (LC) and mass spectrometri
c (MS) techniques were investigated in,order to set-up a method for th
e fast, direct analysis of betamethasone in hydrolysed and non-hydroly
sed urine using large-volume sample injection. After the optimisation
of the LC parameters using a traditional UV detector and of the thermo
spray and mass spectrometric parameters by flow injection, urine sampl
es (0.5 mi) were submitted to analysis by either LC combined with tand
em mass spectrometry (MS-MS), coupled-column LC (LC-LC) combined with
single quadrupole MS, and LC-LC-MS-MS. Both the three-step configurati
ons (LC-MS-MS and LC-LC-MS) did not provide satisfactory results: loss
of sensitivity was noted in the case of LC-MS-MS (likely due to reduc
ed efficiency in the ionisation of betamethasone in the thermospray ow
ing to the presence of large amounts of matrix interference), while in
the case of LC-LC-MS a high chemical noise resulting in insufficient
selectivity of detection was observed. On the contrary, LC-LC-MS-MS an
alysis proved to meet the demand of high speed of analysis (sample thr
oughput, 4.5 h(-1)), selectivity, and sensitivity (LOQ, 1 ng/ml; LOD,
0.2 ng/ml). Notwithstanding the complex analytical system adopted, the
developed procedure was manageable and very robust, provided that at
the beginning of each analytical session the performance of the system
was controlled by checking the retention time of the analytes on the
first analytical column with UV detection and by optimising vaporiser
temperature of the thermospray by flow injection. (C) 1998 Elsevier Sc
ience B.V. All rights reserved.