In 0.1 mol/L HCl medium, 12-tungstophosphoric(TP) acid reacted with matrine(Mat) and oxymatrine(Oxy) to form an ion-association complex. As a result, the new spectra of resonance Rayleigh scattering(RRS), second-order scattering(SOS) and frequency doubling scattering(FDS) appeared and their intensities were enhanced greatly. The maximum scattering wavelengths of RRS, SOS and FDS were located at 370, 670 and 390 nm, respectively. The in-crements of scattering intensity were directly proportional to the concentration of Mat and Oxy in a certain range. Based on this, the method for the determination of matrine and oxymatrine has been established. It has been applied to the determination of matrine and oxymatrine in samples of Radix sophorae flavescentis with satisfactory result. The reaction mechanism and reasons of RRS enhancement were discussed.
In a pH 4.2-6.0 HAc-NaAc buffer medium,the resonance Rayleigh scattering intensities of separate basic triphenylmethane dyes,such as methyl violet (MV),ethyl violet (EV),crystal violet (CV),methyl green (MeG),iodine green (IG),malachite green (MG),light green (LG),and tungstate ion solution,are very weak,but when these cationic dyes react with the tungstate ion (WO 42-) to form ion-association complexes,their RRS are enhanced sharply and new RRS spectra appear.The reaction products of methyl violet,ethyl violet,and crystal violet with WO 42-have similar spectral characteristics and there are two strong RRS peaks at 330 nm and 560 nm.The reaction products of methyl green,iodine green,malachite green,light green with WO 42-have similar spectral characteristics and there are three RRS peaks at about 335 nm,450 nm and 580 nm.The sensitivities of seven kinds of reaction products show a sequence of malachite green>light green>crystal violet>ethyl violet>methyl green>iodine green>methyl violet.The linear ranges and detection limits of the above seven systems are 0.06-2.78 μg mL-1 and 18.1 ng mL-1 (MG),0.08-4.83 μg mL-1 and 22.6 ng mL-1 (BG),0.10-4.90 μg mL-1 and 31.4 ng mL-1 (CV),0.14-2.95 μg mL-1 and 40.5 ng mL-1 (EV),0.17-3.70 μg mL-1 and 50.2 ng mL-1 (MeG),0.22-5.70 μg mL-1 and 67.1 ng mL-1 (IG),and 0.25-7.30 μg mL-1 and 76.3 ng mL-1 (MV).A sensitive,simple and fast RRS method for the determination of basic triphenylmethane dyes using the tungstate ion as the probe has been developed.The method is applicable to the determination of malachite green residues in fish flesh.
YU LiHong,LIU ZhongFang,HU XiaoLi,KONG Ling & LIU ShaoPu School of Chemistry and Chemical Engineering
In a pH=0.65―1.5 NaAc-HCl medium, methylene blue(MB) reacts with 12-tungstophosphoric acid (TPA) by virtue of electrostatic attraction and hydrophobic force to form a 3:2 ion-association complex. As a result, the intensities of resonance Rayleigh scattering(RRS), second-order scattering(SOS) and frequency doubling scatte- ring(FDS) are enhanced greatly. The maximum scattering wavelengths of RRS, SOS and FDS are located at 316, 647 and 311 nm. The increments of scattering intensity(△I) are directly proportional to the concentration of MB in a certain range. The methods exhibited high sensitivity, and the detection limits(3s) for MB are 2.3 ng/mL(RRS method), 5.6 ng/mL(SOS method) and 6.4 ng/mL(FDS method), respectively. The effects of coexisting substances have been examined, and the results indicate that the methods have good selectivity. Based on the above researches, 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 recoveries are 97.5%―105.0%. The results are in good agreement with those obtained by the pharmacopoeia method. In this work, the optimum conditions of the reaction and the influencing factors were investigated. In addition, the reaction mechanism and the reasons of the enhancement of resonance light scattering were discussed.
HU Xlao-liLIU SaLIU Shao-puLIU Zhong-fangSONG Yan-qi
