HPLC-INTEGRATED SOLID-PHASE EXTRACTION WITH PHOTOCHEMICAL POSTCOLUMN DERIVATIZATION FOR THE DETERMINATION OF OXACILLIN, CLOXACILLIN AND DICLOXACILLIN IN RAW-MILK
A. Ibach et M. Petz, HPLC-INTEGRATED SOLID-PHASE EXTRACTION WITH PHOTOCHEMICAL POSTCOLUMN DERIVATIZATION FOR THE DETERMINATION OF OXACILLIN, CLOXACILLIN AND DICLOXACILLIN IN RAW-MILK, ZEITSCHRIFT FUR LEBENSMITTEL-UNTERSUCHUNG UND-FORSCHUNG A-FOOD RESEARCH AND TECHNOLOGY, 207(2), 1998, pp. 170-173
An automated reversed-phase high-performance liquid chromatography (HP
LC) method with UV detection at 300 nm alter on-line coupled solid-pha
se extraction (SPE) and photochemical post-column derivatization was d
eveloped for the residue analysis of or;acillin, cloxacillin and diclo
xacillin in raw milk. After a centrifugal-ion step for defatting and u
ltrafiltration, a HPLC-integrated SPE using a restricted access sorben
t, is performed. By operating the system in parallel mode, SPE and HPL
C run are performed simultaneously. The procedure allows the analysis
of about 30 samples within 24 h and was used to investigate the milk o
f cows which had been treated with oxacillin. The detection limit was
3 mu g/kg for oxacillin and cloxacillin and 5 mu g/ kg for dicloxacill
in. The recoveries were between 66% and 81% with coefficients of varia
tion between 3.3% and 7,7%. Using an acetonitrile extraction procedure
better recoveries of greater than or equal to 90% were obtained with
fortified samples, but more or less identical results were obtained fo
r the samples with incurred residues after correction for recovery.