| 1 Congo Red- Streptomycin systemIn a Britton-Robinson(BR) buffer solution of pH 5.0,congo red(CR) reacted with streptomycin(STP) to form an ion association complex,which can result in the absorbance changed at 497 nm of congo red.In the range of(0.041-2.4)μg-mL-1,there was linearity between the concentration of streptomycin and absorbence of the solution.Based on it,a new spectrophotometry for the determination of streptomycin was proposed.The molar absorptivity was 1.19×105 L·mol-1·cm-1.In this paper optimum reaction conditions and primary chemistry characteristics were discussed.The method has been applied to determination of residual streptomycin in urine with satisfactory results.2 Barium Chloride- Streptomycin systemIn 0.05 mol·mL-1HCl and 2.0 mg·mL-1 Triton X-100 solution,barium chloride reacted with streptomycin to form an barium sulphate nanoparticle,As a result,resonance Rayleigh scattering (RRS) was enhanced greatly and new RRS spectra appeared.The maximum scattering wavelength of RRS was located at 338 nm.The increment of scattering intensity(A/) was directly proportional to the concentration of STP in the ranges of 0.01～4.0μg·mL-1.The method exhibited high sensitivity, and the detection limits(3σ) for STP was 4.8 ng·mL-1.The optimum conditions of the reaction,the influencing factors and the effects of coexisting substances were discussed.A high sensitive,simple and quick method was developed to the determination of residual streptomycin in honey with satisfactory result.3 12-tungstophosphoric Acid- Methylene Blue system In pH 0.65-1.5 NaAc-HCl medium,methylene blue(MB) reacted with 12-tungstophosphoric acid(TPA) by virtue of electrostatic attraction and hydrophobic force to form a 3:2 ion-association complex.As a result,resonance Rayleigh scattering(RRS),second-order scattering(SOS) and frequency doubling scattering(FDS) were enhanced greatly and new RRS,SOS and FDS spectra appeared.The maximum scattering wavelengths of RRS,SOS and FDS were located at 316 nm,647 nm and 311 nm,respectively.The increments of scattering intensity(△I) were directly proportional to the concentration of MB in a certain range.The methods exhibited high sensitivity,and the detection limits(3σ) for MB were 2.3 ng·mL-1(RRS method),5.6 ng·mL-1(SOS method) and 6.4 ng·mL-1(FDS method),respectively.The effects of coexisting substances have been examined,and the results indicated that the methods have good selectivity.Based on the above research,a new spectral method for the determination of trace amounts of MB has been developed.It can be applied to the determination of MB in human serum,and the recovery was between 97.2%and 105.2%.In this work,the optimum conditions of reaction and the influencing factors were investigated.In addition,the reaction mechanism and the reasons for enhancement of resonance light scattering were discussed.4 Sodium Dodeeylbenzenesulfonate-Methylene Blue systemIn 0.05 mol·L-1(pH 1.3)HCl medium,Sodium dodecylbenzenesulfonate(SDBS) reacted with Methylene Blue(MB) to form an ion association complex with the composition ratio of 2:1 by electrostatic interaction and hydrophobicity effect.As a result,the RRS,FDS,and SOS intensities were enhanced greatly.The maximum wavelengths of RRS,SOS and FDS were located at 310 nm, 647 nm and 341 nm,and there was a good linear relationship between the scattering intensity peak current and the concentration of MB a certain concentration range.Therefore,the RRS,SOS and FDS methods for the determination of trace amounts of MB have been developed.The linear ranges and detection limits of MB were(0.004～3.0)μg·mL-1 and 1.2 ng·mL-1 for RRS,(0.008～3.0)μg·mL-1 and 1.4 ng·mL-1 for SOS,(0.006～3.0)μg·mL-1 and 1.7 ng·mL-1 for FDS,respectively.The proposed method applied to the determination of MB in human serum with a satisfactory result,and the recoveries were 94.4-103.7%.
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