Online Sfesfc for the Analysis of Antibiotics

Online supercritical fluid extraction (SFE)-SFC can be used for the analysis of antibiotics in complex samples, resulting in time savings and less exposure to organic solvents. Multidimensional systems take advantage of two orthogonal separation techniques with complementary characteristics, for example one extraction and one chromatographic step, where the first step is aimed at producing a clean and undiluted sample containing the compounds of interest, and the second step provides a high resolution separation of the target analytes.

The main advantages of these online systems is that a fast and automatic sample preparation reduces or avoids the errors of the manual steps. Also, solvent consumption is less, which reduces toxic hazards and disposal costs. As is often the case in chromatogra-phy, the largest source of error in the quantitative analysis of antibiotics and the most time-consuming steps occur in the sample preparation and extraction stages.

Supercritical fluid techniques have a number of advantages for use in multidimensional chromatographic

Figure 2 Chromatogram obtained from SFC of a mixture of sulfonamides with UV (wavelength 270 nm). Peak identification: A, sulfadoxine; B, sulfamethazine; C, sulfamerazine; D, sulfa-dimethoxine; E, sulfadiazine; F, sulfaquinoxaline; G, sulfachlor-pyridazine; H, sulfathiazole. Chromatographic conditions: column packed with 5 ^m particle amino-bonded Spherisorb (100 x 4.6 mm i.d.), column temperature 90°C, CO2 flow rate of 4mL min~1, pressure 361 bar. Mobile phase was CO2 modified initially with 15% methanol and after 4 min with 25% methanol. Reproduced with permission from Perkins JR, Games DE, Startin JR and Gilbert JJ (1991) Analysis of sulfonamides using supercritical fluid chromatography and supercritical fluid chromatogra-phy-mass spectrometry. Journal ofChromatography 540: 239.

Figure 2 Chromatogram obtained from SFC of a mixture of sulfonamides with UV (wavelength 270 nm). Peak identification: A, sulfadoxine; B, sulfamethazine; C, sulfamerazine; D, sulfa-dimethoxine; E, sulfadiazine; F, sulfaquinoxaline; G, sulfachlor-pyridazine; H, sulfathiazole. Chromatographic conditions: column packed with 5 ^m particle amino-bonded Spherisorb (100 x 4.6 mm i.d.), column temperature 90°C, CO2 flow rate of 4mL min~1, pressure 361 bar. Mobile phase was CO2 modified initially with 15% methanol and after 4 min with 25% methanol. Reproduced with permission from Perkins JR, Games DE, Startin JR and Gilbert JJ (1991) Analysis of sulfonamides using supercritical fluid chromatography and supercritical fluid chromatogra-phy-mass spectrometry. Journal ofChromatography 540: 239.

systems. The commonest multidimensional system, LC-GC, is limited to the determination of thermally stable and volatile solutes, while SFC can substitute the first fractionation step, as well as the second step of high resolution chromatography. In the case of SFE-SFC, the transfer is performed without changes in the mobile phase, which minimizes losses of analytes and reduces technical complexity

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