发酵液中L-赤藓酮糖的紫外法测定

采用紫外法测定发酵液中的L-赤藓酮糖。以谢里瓦诺夫（Seliwanoff）试剂为显色剂,考察了显色剂用量、反应温度、反应时间和显色稳定时间等因素,确定了优化后的试验条件。紫外法的线性范围为0~1.2 g/L,样品回收率为101.5%~101.9%,测定结果不受发酵液中底物及菌体自溶物影响,具有快速准确的优点。

Experimental study and kinetic analysis of oxidant-free thermal-assisted UV digestion utilizing supported nano-TiO_2 photocatalyst for detection of total phosphorous

A novel thermal-assisted ultra-violet(UV) photocatalysis digestion method for the determination of total phosphorus(TP) in water samples was introduced in this work. The photocatalytic experiments for TP digestion were conducted using a 365 nm wavelength UV light and Ti O2 particles as the photocatalyst. Sodium tripolyphosphate and sodium glycerophosphate were used as the typical components of TP and the digested samples were then determined by spectrophotometry after phosphomolybdenum blue reaction. The effects of operational parameters such as reaction time and temperature were studied for the digestion of TP and the kinetic analysis of two typical components was performed in this paper. The pseudo-first-order rate constants k of two phosphorus compounds at different temperatures were obtained and the Arrhenius equation was employed to explain the effect of temperature on rate constant k. Compared with the conventional thermal digestion method for TP detection, it was found that the temperature was decreased from 120 °C to 60 °C with same conversion rate and time in this thermal-assisted UV digestion method, which enabled the digestion process work at normal pressure. Compared with the individual ultra-violet(UV) photocatalysis process, the digestion time was also decreased from several hours to half an hour using the thermal-assisted UV digestion method. This method will not lead to secondary pollution since no oxidant was needed in the thermal-assisted UV photocatalysis digestion process, which made it more compatible with electrochemical detection of TP.

A derivatization method to improve the assay of salinomycin sodium and its application in the liposomal formulation

Salinomycin sodium（SAL-Na） is a type of antibiotic chemotherapeutic drugs with the potential to treat cancer stem cells. The assay method of SAL-Na included in the pharmacopoeia is a microbiological method, which is not suitable for the rapid detection in daily scientific research. Besides, the assay methods of SAL-Na reported by literature are not suitable for quantification due to the interference of various excipients. Consequently, the deep study on biological mechanism of SAL-Na is hindered by its assay method. In the present study, we aimed to establish an ultraviolet visible（UV-vis） spectrophotometric method to determine the content of SAL-Na in the liposomes. The first approach was a UV spectrophotometry, in which SAL-Na was dissolved in ethanol and then detected at 287 nm. Although the standard curve measured at 287 nm by UV method had good linearity, the quantification limitation was too high to meet the requirement in determining SAL-Na in the liposomes. In addition, the membrane materials in the liposomes severely affected the measurement. The second one was an improved UV-vis spectrophotometry by vanillin derivatization. In this method, SAL-Na was dissolved in 95% ethanol, mixed with vanillin test solution and heated at 72 ℃ for 40 min for derivatization. After cooling down to room temperature, the solution was detected using UV-vis spectrophotometer at 526 nm. This method could be used to accurately determine the content of SAL-Na at lower concentration, and the absorbance value was stable for 5 d at least. Moreover, the membrane materials of the liposomes did not affect the absorbance of SAL-Na at 526 nm. The precision and recovery studies demonstrated that the vanillin derivatization approach was stable and precise in assaying SAL-Na. In conclusion, the UV-vis spectrophotometry by vanillin derivatization could be used for measuring SAL-Na in the liposomes, thereby laying a foundation for deep study of the biological mechanism of SAL-Na in the liposomes.

Simultaneous quantification of lopinavir and ritonavir in human plasma by high performance liquid chromatography coupled with UV detection

High performance liquid chromatography was coupled with UV detection for simultaneous quantification of lopinavir （LPV） and ritonavir （RTV） in human plasma. This assay was sensitive, accurate and simple, and only used 200μL of plasma sample. Samples were liquid-liquid extracted, and diazepam was used as an internal standard. The chromatographic separation was achieved on a C18 reversed-phase analytic column with a mobile phase of acetonitrile-sodium dihydrogen phosphate buffer （10 mmol L-1, pH 4.80） （60：40, v/v）. UV detection was conducted at 205 nm and the column oven was set at 40℃. Calibration curves were constructed between 0,5-20 μg mL-1 for LPV and 0.05-5 μg mL-1 for RTV. The relative standard deviations were 2.16%-3.20% for LPV and 2.12%-2.60% for RTV for intra-day analysis, and 2.34%-4.04% for LPV and 0.31%-4.94% for RTV for inter-day analysis. The accuracy was within 100%＋10%. The mean extraction recoveries were 79.17%, 52.26% and 91.35% for RTV, LPV and diazepam, respectively. This method was successfully applied to human plasma samples from patients orally administered a salvage regimen of lopinavir-ritonavir tablets.