Simultaneous identification and quantitative determination of selected aminoglycoside antibiotics by thin-layer chromatography and densitometry.

A TLC-densitometric method has been developed for simultaneous identification and quantitative determination of amikacin, gentamicin, kanamycin, neomycin, netilmicin, and tobramycin. This separation of antibiotics was achieved on silica gel TLC plates without a fluorescent indicator and with methanol-25% ammonia-chloroform (3 + 2 + 1, v/v/v) as the mobile phase. The densitometric measurements were made at 500 nm after detection with a 0.2% ninhydrin solution in ethanol. Under these conditions, good separation of the chosen aminoglycosides was obtained. The method is distinguished by high sensitivity, with the LOD from 0.25 microg for amikacin to 1.00 microg for gentamicin and the LOQ from 0.5 microg for amikacin to 1.65 microg for gentamicin, and a wide linearity range 0.75-6.25 microg/spot for amikacin and netilmicin and 1.5-12.50 microg/spot for other antibiotics. The precision of the determination was very good; RSD varied in the range 0.3-0.6%.