Spectrophotometric Determination of Neomycin and Gentamycin with La La-Trypan

In the medium of pH 3.0～6.5, La(Ⅲ) and trypan red(TR) can react neomycin sulfate(NEO) or gentamycin sulfate(GEN) to form three ingredient red ion association complexes . The maximum absorption wavelengths are at 388 nm. Their molar absorptivities (e) are 4.86×10~(4)(NEO) and 2.10×10~(4)(GEN) L·mol~(-1)·cm~(-1), respectively. The maximum negative absorption wavelengths are located at 432 nm(NEO) and 428 nm(GEN). Their molar absorptivities(e) are 1.38×10~(4)(NEO) and 1.19×10~(4)(GEN) L·mol~(-1)·cm~(-1), respectively. When the dual-wavelengths overlapping absorption spectrometry is used to determine the concentrations of aminoglycoside antibiotics, their molar absorptivities e are (6.24)×10~(4)(NEO) and 3.28×10~(4)(GEN) L·mol~(-1)·cm~(-1), respectively. The optimum reaction conditions and the chief properties of analytical chemistry are studied. The method has been applied to the determination of the content of the commercial neomycin and gentamycin antibiotics with satisfactory results.