Selective determination of tobramycin in the presence of streptomycin through the visible light effect on surface plasmon resonance of gold nanoparticles

Tobramycin (TBR) is an antibiotic of the aminoglycoside class used for the treatment of bacterial infections. A careful study was made aiming to find conditions for the determination of TBR in the presence of streptomycin (STP) as well as in the presence of components used in ophthalmic solutions by taking advantage of the effect of the surface plasmon resonance of gold nanoparticles (AuNPs). The proposed modified Turkevich method for AuNPs synthesis as well as the stabilization of the aqueous dispersion under specific experimental conditions allowed a linear analytical response that did not require rationing of signal values to correct for linearity. The analytical curves, constructed by measuring transmitted light either at 529 nm or at 681 nm, covered three decades of concentration (from 4.0 × 10− 9 to 1.6 × 10− 7 mol L− 1). In this concentration range, STP does not interact with the monosodium citrate capped AuNPs probe. The limit of detection for TBR was 3.8 × 10− 9 mol L− 1. The method was applied in ophthalmic solutions and in simulated samples containing STP. The results produced recoveries compatible to the ones achieved using a chromatographic method based on chemical derivatization. No significant interference was imposed by substances presents in ophthalmic solutions in their characteristic concentrations. Studies in saliva from volunteers under the treatment with TBR were made.