Application of chemometric modelling appealing to the second order advantage to solve interference problems in wastewater analysis

GOICOECHEA, HÉCTOR C; MARTINEZ GALERA, MARIA; GIL GARCÍA, MARIA; SANTIAGO VALVERDE, ROSARIO; MERCEDES DE ZAN,; JULIA CULZONI,

Belgrado

Congreso; 2nd EMCO workshop on Emerging Contaminants inj wastewaters: Monitoring Tools and Treatment Technologies; 2007

EMCO

Second-order multivariate analysis is gaining widespread acceptance by the analytical community, a fact that can be appreciated from a survey of literature in relevant analytical, chemometrics and applied journals. This is due to the variety of second-order instrumental data which are being produced by modern instruments, and also to their attractive properties from an analytical point of view. On the other hand, the interest rises due to the development of recent algorithms which make the resolution of difficult tasks possible, with applications including environmental, biological and food analyses, among others. It is important to remark that a reasonable selection of data and algorithms may allow for quantitation of analytes even in the presence of unexpected sample constituents, a property known as the second-order advantage.[1] This avoids the major drawback of lower-order analytical methods, namely the requirement of a large diverse calibration set, a practical benefit which can hardly be overstated. HPLC-DAD data constitute an interesting example of second order data, with a high potential for solving interference problems in environmental analysis: i.e. the compounds of interest can be conveniently separated by using the chromatographic technique, but the problem of unexpected substances in the sample causing interferences can be solved by application of a suitable algorithm. In this context, a new powerful algorithm was tested [unfolded-partial least squares followed by residual bilinearization (U-PLS/RBL)[2]] and compared with a well known established method [multivariate curve resolution-alternating least squares (MCR-ALS)[3]] forthe simultaneous determination of eight tetracyclines (tetracycline, oxytetracycline, meclcycline, minocycline, metacycline, chlortetracycline, demeclocycline and doxycycline) in wastewaters by HPLC-DAD. Tetracyclines were preconcentrated using OASIS MAX C18 cartridges and then separated on a Thermo AQUASIL C18 (150x4.6 mm, 5 μm) column with an oxalic acid-methanol-acetonitrile mobile phase using a gradient program for 20 min. The whole method was validated with respect to linearity, precision, detection and quantification limits and accuracy. The results show that the eight tetracycline antibiotics can be successfully determined in wastewaters, the drawbacks due to matrix interferences being adequately handled and overcome by using U-PSL/RBL. Quantification limits were approximately 0.2 ng mL-1,relative standard deviation was lower than 10% and recoveries ranged from 60.9 to 99.0%. [1]         K. S. Booksh, B.R. Kowalski, Anal. Chem. 66 (1994) 782A-791A. [2]         A. C. Olivieri, J. Chemometrics 19 (2005) 253-265 [3]        A. DeJuan, E. Casassas, R. Tauler, in R. A. Myers (Ed.), Encyclopedia of Analytical.Chemistry, Vol. 11, Wiley, Chichester, 2002, pp. 9800-9837.