In situ preparation of graphitic carbon nitride bonded with cyano groups for enhanced photocatalytic activity

Cyano groups have been successfully introduced on the backbone edge of g-C₃N₄ to fabricate nitrogen defects under mild conditions, which are derived from incomplete polymerization of g-C₃N₄ after BaCO₃ utilization. Characterization results indicate that the interfacial interaction between BaCO₃ and carbon nitride is playing a significant role for introducing cyano groups into g-C₃N₄. Cyano groups working as electron capture centers are proved to change the band gap of carbon nitride, reducing the recombination rate of electron-hole pairs and promoting charge separation. As expected, the hydrogen evolution rate of nitrogen-defect-modified carbon nitride is improved to 71.57 μmol h⁻¹, which is 13.5 times that of pristine C₃N₄. Meanwhile, the degradation efficiency of methyl orange is promoted (5 times that of pristine C₃N₄). This work is the first report on the fabrication of cyano-group-modified carbon nitride with BaCO₃ utilization, and opens a new door for further exploring environmental-friendly carbon nitrides on energy conversion.     

Aroma profile of a red plum purée processed by high hydrostatic pressure and analysed by SPME–GC/MS

The volatile profile of a plum purée processed by high pressure processing (HPP) was evaluated by the method of solid-phase micro-extraction gas chromatography/mass spectrometry (SPME–GC/MS). Two pressure intensity levels and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s). Processed purées were compared to raw purée (unprocessed purée). A total of 40 volatile compounds were identified in the headspace of the plum purée. The major compounds identified were an aldehyde (hexanal) and two alcohols (hexan-1-ol and (Z)-hex-3-en-1-ol). Among the total compounds isolated (40), 23 compounds were significantly influenced by HPP. The modifications of these 23 volatiles represented changes of the 1.8% of the total aroma of the original purée. Results showed that the most intense treatments did not significantly alter the original aroma of plum purée. Therefore, HPP appears to be an alternative technology for the preservation of aromatic compounds of plum purée.Industrial relevanceHigh-pressure processing is one of the most successful technologies to obtain high-quality fruit purées. It is generally recognized that this treatment better preserves the original aroma of fruit. Two levels of pressure intensity and three holding times were applied (400 and 600 MPa for 1, 150 and 300 s) in order to know the effect of the treatments on the original aroma of plum. The combination of pressure and holding time did not affect the original aroma of plum. Results of this paper demonstrated that high-pressure processing preserves plum puree with a fresh-like aroma. On the other hand, a study of storage would be required to assess possible changes in the stability of the plum purée taking into account other parameters such as microbiological stability and inactivation of enzymes.     

Early warning modeling and analysis based on analytic hierarchy process integrated extreme learning machine (AHP-ELM): Application to food safety

Since the actual food safety monitoring data have characteristics of high-dimension, complexity, discreteness and nonlinear properties, it is difficult to accurately predict the risk of actual food inspection process. Therefore, this paper proposes a predictive modeling approach based on analytic hierarchy process (AHP) integrated extreme learning machine (ELM) (AHP-ELM). The proposed approach utilizes the AHP model to obtain the effective process characteristic information (PCIs). Compared with the analytic hierarchy process (AHP) integrated traditional artificial neural network (ANN) approach, the AHP-ELM prediction model is effectively verified by executing a linear comparison between all PCIs and the effective PCIs through daily inspection data source from the supervision and inspection department repository of China quality supervision system. Finally, the PCIs and the prediction value are obtained to provide more reliable food information and identification of potentially emerging food safety issues. The proposed method is applied to the food safety early warning and monitoring system in China. The result shows that the proposed model is effective and feasible in processing the complex food inspection data. Meanwhile, it can help to improve the quality of food products, ensure food safety and reduce the risk of food safety.     

固相萃取-高效液相色谱法测定婴幼儿配方粉中维生素A和维生素E的含量

目的建立固相萃取-高效液相色谱法同时测定婴幼儿配方粉中维生素A和维生素E的含量。方法样品经高温皂化反应后,将皂化液通过EXtrelut NT20固相萃取柱,对目标待测物进行净化,洗脱液经氮气吹干复溶后,过滤膜直接进样,以甲醇作为流动相,通过Zorbax C18色谱柱(4.6 mm×150 mm,5μm)分离,外标法定量。结果维生素A标准溶液在0.5~5.0 mg/L范围内,维生素E标准溶液在5.0~50 mg/L范围内均呈现良好的线性关系,相关系数(r~2)均≥0.999;样品3个水平加标回收率分别为86.0%~104.6%和89.0%~104.0%,相对标准偏差(RSD)均3.0%;检出限分别为1.0和10μg/100 g。结论该方法可用于婴幼儿配方粉中维生素A和维生素E的同时检测,操作简单、快速、准确。     

高效离子色谱法同时测定婴幼儿配方奶粉中单糖及功能性低聚糖的研究

目的 建立高效阴离子交换色谱-脉冲安培检测同时测定婴幼儿配方奶粉中4种单糖和9种功能性低聚糖的方法 .方法 样品经提取、乙酸沉淀蛋白、净化处理后,外标法定量.淋洗液为乙酸钠和氢氧化钠,流速0.4 ml/min,梯度洗脱,洗脱时间50 min.采用高效阴离子交换色谱,色谱柱为CarboPacTM PA20(3 mm×15...     

电感耦合等离子体质谱法同时测定化妆品中的铅、汞、砷和镉

建立了电感耦合等离子体质谱法(ICP-MS)同时测定化妆品中铅、汞、砷和镉含量的方法。样品经密闭微波消解后,以铟作为内标物质,用ICP-MS同时测定铅、汞、砷和镉的含量,并将该方法和国家法定方法的检测结果进行比较。结果表明,4种元素标准曲线的线性关系良好,r值均为0.999 7,检出限为0.006~0.1μg·L-1,重复性实验(n=6)的RSD为0.65%~4.82%,回收率为94.1%~108.6%。方法学比较表明该方法和国家法定方法的测定结果基本一致。     

烘焙纸中残留甲苯向食品模拟物中迁移分析

目的 研究烘焙纸中残留甲苯向食品中的迁移规律,并考察烘焙纸微观结构变化对迁移的影响。方法 采用气相色谱-串联三重四级杆质谱(GC-MS/MS)法,研究在不同烘焙温度、时间、纸张定量、甲苯初始浓度、微波加热等条件下,残留甲苯向橄榄油和改性聚苯醚(Tenax-TA)中的迁移规律,通过扫描电镜等技术手段,考察迁移前后烘焙纸微观结构的变化。结果 烘焙温度越高,甲苯迁移率越大;迁移率随迁移时间的延长而升高,但超过40 min后,甲苯向Tenax-TA中的迁移率出现明显下降趋势;纸张定量越大,迁移率越低;初始浓度对迁移率的影响不显著;微波功率越高,迁移率越大。随着微波时间的延长,迁移率呈先升高后降低的现象。扫描电镜结果表明,经过高温烘焙后,纸张纤维孔隙的尺寸及数量有所增加。结论 烘焙纸中残留甲苯在一定条件下向食品模拟物中发生迁移,纸张内部纤维结构的变化使甲苯分子更容易穿过孔隙进入食品中,加速了迁移的发生。     

固相萃取-高效液相色谱-紫外检测法测定蔬菜中阿维菌素的残留量

目的建立固相萃取—高效液相色谱法-紫外检测法测定蔬菜中阿维菌素残留量的方法。方法选取本地区市售的6种蔬菜样品,经乙酸乙酯提取,经固相萃取柱净化后用甲醇定容。在C_(18)色谱柱上进行分离,以甲醇-水(9:1,体积比)为流动相,流速1.0 mL/min,检测波长为245 nm。结果在0.05～1.00μg/mL浓度范围内,方法线性关系良好,r~2值为0.9999,定量限为0.01 mg/kg。平均回收率为94.0%～98.0%,相对标准偏差不超过6%(n=6)。结论本方法前处理过程简便高效,样品检出限低,灵敏度较高,适用于蔬菜中阿维菌素残留量的检测。     

荧光分光光度法测定营养素补充剂中硫胺素含量的测量不确定度评定

参照GB/T 5009.84-2003《食品中硫胺素（维生素B1）的测定》测定营养液补充剂中硫胺素的含量。通过对测定过程中的不确定度来源进行分析,评定出各不确定度分量,最后计算出合成标准不确定度和扩展不确定度,结果表明：试样中硫胺素含量为0.49 mg/100 g,扩展不确定度为0.052 mg/100 g。不确定度分量结果显示,标准曲线拟合产生的不确定度在不确定度合成中贡献最大,因此在营养素补充剂中硫胺素进行测定时,应对标准曲线的拟合过程加强控制,确保结果的准确性。