The energy of combustion of crystalline 3,4,5-trimethoxybenzoic acid in oxygen at T=298.15 K was determined to be -4795.91.3 kJ mol-1 using combustion calorimetry. The derived standard molar enthalpies of formation of 3,4,5-trimethoxybenzoic acid in crystalline
and gaseous states at T=298.15 K, ΔfHmΘ (cr) and ΔfHmΘ (g), were -852.91.9 and -721.72.0 kJ mol-1, respectively. The reliability of the results obtained was commented upon and compared with literature values.
Authors:L. Zhou, J. Xu, L. Luan, J. Ma, Y. Gong, D. Qin, and C. Pan
Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and l-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.
Authors:K. M. Qin, Y. Shi, Q. B. Fang, H. Cai, G. M. Yang, and B. C. Cai
Baihe Zhimu Tang (BZT) is a widely used traditional Chinese medicinal formula for the treatment of various diseases; however, its active components have remained unknown. In this study, high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) methods were developed for the analysis of metabolic components of BZT. The HPLC experiments used a reversed-phase Shim-Pack VP-ODS C18 column with the column temperature at 35°C and a mobile phase system consisting of aqueous formic acid (0.05%, υ/υ) and acetonitrile using a gradient elution at the flow rate of 0.2 mL/min−1. The ESI-MS was operated with a single-quadrupole mass spectrometer in both negative and positive ion modes. After oral administration of extraction of BZT, the rat's plasma, urine, and feces were also analyzed; 37 metabolic components including 23 original components and 14 transformative components of BZT were detected. The analysis of metabolic components in BZT by HPLC-ESI-MS methods could be a useful means of identifying the multi-components of BZT and understanding their possible metabolic mechanism of action in the body. The results also narrow the range of active compounds to be found in BZT, and pave the way for further pharmacology and active mechanism research.