Di Shao,Shuyun Bi,Rui Zhao,Xiaoyue Sun,Xu Li,Jingfu Yu
Two sensitive surface-enhanced Raman spectroscopy (SERS) analytical methods for dinitolmide and toltrazuril were developed by silver nanoparticles (AgNPs). The dinitolmide and toltrazuril were determined in 0.0565 mol L −1 and 0.0847 mol L −1 NaOH solutions respectively. The enhancement factors (EF) were 1.76 × 10 5 for dinitolmide and 1.27 × 10 5 for toltrazuril. Under optimum conditions, the methods had good linear relationship in the concentration ranges of 0.30–33.30 nmol L −1 for dinitolmide ( I SERS = 1522.52 c + 27,890.46, c :nmol L −1 , R 2 = 0.998) and 0.30–66.70 nmol L −1 for toltrazuril ( I SERS = 1334.29 c + 46,347.83, c :nmol L −1 , R 2 = 0.999). The limits of detection (LOD) (S/N = 3) were 0.915 nmol L −1 for dinitolmide and 1.03 nmol L −1 for toltrazuril. The effects of interferences on the determinations of dinitolmide and toltrazuril were studied. These SERS methods were successfully used to measure the content of dinitolmide and toltrazuril in the duck and chicken samples. The relative standard deviation (RSD) for the detection of dinitolmide and toltrazuril samples could reach 1.45 % ( n = 5). The recoveries were 95.67%–105.39% ( n = 5) and 94.79%–99.44% ( n = 5) for dinitolmide and toltrazuril system respectively.
The purpose of this work is to study the dissolution process of toltrazuril and the influence of the solvent on solubility. In pure solvents, the solubility of toltrazuril increases with the increasing temperature, and the order of solubility data is as follows: ethyl acetate (9.640 × 10–3, 298.15 K) > dichloromethane (6.103 × 10–3, 298.15 K) > toluene (3.132 × 10–3, 298.15 K) > ethanol (1.567 × 10–3, 298.15 K) > isopropyl alcohol (0.9795 × 10–3, 298.15 K) > water (0.01929 × 10–3, 298.15 K), meanwhile in binary mixtures, the solubility increases to a maximum with the increasing temperature and isopropyl alcohol, and then decrease with further increase of cosolvent. However, in the isopropyl alcohol + ethyl acetate mixed solvents, the data increase with the increasing ethyl acetate. Four thermodynamic models are used to discuss the dependence of toltrazuril solubility on temperature and solvent composition. The largest value of relative average deviation and (RAD) and root-mean-square deviation (RMSD) between the calculated and experiment value were no larger than 4.5 × 10–2 and 4.1 × 10–4, respectively. The results indicate that these models were all acceptable to express the dissolution process of toltrazuril in the studied solvents. The method of multiple linear regression analysis (MLRA) involving selected solvent parameters can explain the effect of solvents on solubility of toltrazuril in pure solvents.
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