Influence of on and other modifying factors on the distribution behavior of 4-quinolones to solid phases and humic acids studied by "negligible-depletion" SPME-HPLC

Flumequine, oxolinic acid, and sarafloxacin are 4-quinolone antimiciobials that are used in fish farming. The objective of this investigation was to s tudy the influence of pH on the distribution behavior between buffer soluti ons and Aldrich humic acids (DOC) of these compounds. Negligible-depletion solid-phase microextraction coupled to highperformance liquid chromatograph y (nd-SPME-HPLC) was used to quantify the free concentration of the antimic robials. It was shown that the distribution of the antimicrobials between b uffer and the SPME fiber could be described as a function of pH and ionizat ion constants. Distribution coefficients between buffer and DDC(D-DOC)were established. It was not possible to describe this distribution using pH and ionization constants. The magnitude of the D-DOC values (10(3.4)-10(5.2)) was found in the same range as for highly hydrophobic chemicals despite the low hydrophobicity of the F-quinolones (K-OW < 10(1.7)).