Liquid chromatography with amperometric detection of some sulphonamides and their N4-acetyl-metabolites in serum and urine.
Sulphonamides separated on a C18 LC column were detected at lower levels using amperometric detection at a glassy carbon electrode in comparison with UV detection at 258 nm. Whereas sulphonamides are detectable at a potential of +1.00 V, their N4-acetyl-metabolites required a potential of +1.25 V to be detected after their separation by LC. An interference commonly present in serum and urine, which co-eluted with one of the analytes, was detected at 1.25 V. This was overcome with an appropriate sample preparation in which 150 microliters of serum or 75 microliters of urine were first diluted to 1.5 ml with phosphate buffer (pH 3.0; 0.2 M). A 1.0 ml volume of this solution was then passed through an Extrelut 1 column. The analytes were eluted with dichloromethane, which was evaporated under vacuum, and redissolving the analytes in an appropriate volume of mobile phase, i.e. methanol-phosphate buffer (pH 6.7; 0.067 M) (25:75, v/v). For sulphamethoxazole (SMX) and sulfamethoxypyridazine (SMP) and their N4-acetyl-metabolites the calibration curves were linear between 1.5 x 10(-7) and 8 x 10(-6) M. The recovery ranged between 92.6 and 97.6% in serum and between 80.5 and 99.4% in urine. Detection limits were 10 times lower with amperometric detection than with UV detection. The method has been applied to the quantitation of SMX and SMP and their N4-acetyl-metabolites in serum and urine after their oral administration.
von Baer
D
D
Depto. Análisis Instrumental, Facultad de Farmacia, Universidad de Concepción, Chile.
Momberg
A
A
Carrera
M E
ME
Arriagada
R
R
Smyth
M R
MR
D000107:Acetylation; D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods; D004566:Electrodes; D006801:Humans; D015394:Molecular Structure; D013449:Sulfonamides / Q000032:analysis* / Q000097:blood / Q000652:urine
D013449:Sulfonamides