Solving matrix-effects exploiting the second order advantage in the resolution and determination of eight tetracycline antibiotics in effluent wastewater by modelling liquid chromatography data with multivariate curve resolution-alternating least squares

M.M. DE ZAN; M.D. GIL GARCÍA; M.J. CULZONI; G.G. SIANO; H.C. GOICOECHEA; M. MARTÍNEZ GALERA

JOURNAL OF CHROMATOGRAPHY - A

Elsevier

Año: 2008 vol. 1179 p. 106 - 114

0021-9673

The effect of piecewise direct standardization (PDS) and baseline correction approaches was evaluated in the performance of multivariate curveresolution (MCR-ALS) algorithm for the resolution of three-way data sets from liquid chromatography with diode-array detection (LC-DAD). First,eight tetracyclines (tetracycline, oxytetracycline, chlorotetracycline, demeclocycline, methacycline, doxycycline, meclocycline and minocycline)were isolated from 250mLeffluentwastewater samples by solid-phase extraction (SPE) with OasisMAX500 mg/6mLcartridges and then separatedon an Aquasil C18 150mm×4.6mm (5m particle size) column by LC and detected by DAD. Previous experiments, carried out with Milli-Qwater samples, showed a considerable loss of the most polar analytes (minocycline, oxitetracycline and tetracycline) due to breakthrough. PDS wasapplied to overcome this important drawback. Conversion of chromatograms obtained from standards prepared in solventwas performed obtaining ahigh correlation with those corresponding to the real situation (r2 = 0.98). Although the enrichment and clean-up steps were carefully optimized, thesample matrix caused a large baseline drift, and also additive interferences were present at the retention times of the analytes. These problems weresolved with the baseline correction method proposed by Eilers. MCR-ALSwas applied to the corrected and uncorrected three-way data sets to obtainspectral and chromatographic profiles of each tetracycline, as well as those corresponding to the co-eluting interferences. The complexity of thecalibration model built from uncorrected data sets was higher, as expected, and the quality of the spectral and chromatographic profiles was worse.