Determination of fosfomycin in pus by capillary zone electrophoresis.
A method is described for the determination of fosfomycin in pus by capillary zone electrophoresis with reversed electroosmotic flow, and indirect UV absorbance detection. Sample pre-treatment is limited to removal of proteins and cell debris by adding the double volume of methanol, followed by vortexing for few seconds, and centrifugation at 15,000 x g for 2 min. The supernatant is directly injected into the instrument. Fosfomycin is separated from sample constituents with a background electrolyte at pH 7.25 (25 mM benzoate buffer with 0.5 mM hexadecyltrimethylammonium bromide added, adjusted to pH with tris(hydroxymethyl)-aminomethane (TRIS)). Separation is carried out in a capillary with 50 microm I.D., 64.5 cm total length, 56.0 cm to the detector, at 25 degrees C with -25 kV voltage applied. Due to the low absorbance of the analyte, indirect UV detection was performed at 254 nm using a bubble cell capillary. Sample was injected by pressure (450 mbar s). Repeatability for fosfomycin in spiked pus (from 8 or 10 consecutive injections of three different series at concentrations of 100 microg/mL of the antibiotic) was between 2.4 and 8.2% relative standard deviation (RSD). Accuracy (expressed as recovery of fosfomycin determined by three independent analysis at 10, 100 and 300 microg/mL fosfomycin added to plain pus) was between 75 and 102%. Intermediate reproducibility (n = 9 at three different days) was between 2 and 12% RSD. Limit of detection and limit of quantitation were 4.5 and 15 microg/mL, respectively. The concentration of fosfomycin in pus of patients treated with the antibiotic ranged up to 240 microg/mL. The concentration of other anionic pus constituents identified beside chloride (acetate, succinate, lactate, phosphate) ranged between 20 and 7800 microg/mL.
Petsch
Martina
M
Institute of Analytical Chemistry, University of Vienna, Währinger Strasse 38, A-1090 Vienna, Austria.
Mayer-Helm
Bernhard X
BX
Sauermann
Robert
R
Joukhadar
Christian
C
Kenndler
Ernst
E
D000038:Abscess / Q000473:pathology; D000900:Anti-Bacterial Agents / Q000032:analysis*; D001826:Body Fluids / Q000737:chemistry*; D019075:Electrophoresis, Capillary / Q000379:methods*; D005578:Fosfomycin / Q000032:analysis*; D006801:Humans; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013492:Suppuration
D000900:Anti-Bacterial Agents; D005578:Fosfomycin