Preconcentration and determination of polybrominated diphenyl ethers in environmental water samples by solid-phase microextraction with Fe3O4-coated bamboo charcoal fibers prior to gas chromatography–mass spectrometry

In this paper, bamboo charcoals were modified using Fe₃O₄ nanosheets for the first time. The composites, as a novel solid-phase microextraction (SPME) fiber coating, were used for the extraction of seven polybrominated diphenyl ethers (PBDEs) in environmental water samples. The extraction factors (stirring rate, extraction time, and ionic strength) and desorption factors (desorption time and desorption temperature) of the fibers were systematically investigated and optimized. Under optimum conditions, the linear range was 1–1000 ng L⁻¹. Based on the ratio of chromatographic signal to base line noise (S N⁻¹ = 3), the limits of detection (LODs) can reach 0.25–0.62 ng L⁻¹. The novel method was successful in the analysis of PBDEs in real environmental water samples. The results indicate that bamboo charcoal/Fe₃O₄ as an SPME coating material coupled with gas chromatography–negative chemical ionization-mass spectrometry is an excellent method for the routine analysis of PBDEs at trace levels in environmental water samples.     

Silica Gel Catalysed Rearrangement of α-Epoxyketones to 1,2-Diketones

A convenient and simple method for the preparation of diphenylpropane-1,2-diones is described. The process involves rearrangement of α-epoxyketones on silica gel; an unusual migration of a proton instead of the more common benzoyl migration.     

发光二极管用于活性炭负载光催化剂反应器中挥发性有机化合物的降解

The applicability of ultraviolet-light emitting diodes(LEDs)as a light source for photocatalysis using granular activated charcoal (GAC)impregnated with transition metal-enhanced photocatalysts for the control of volatile organic compounds(VOCs)was investigated. Two target compounds(toluene and methyl mercaptan)were selected to evaluate the removal activities of the TiO2/GAC composites.The photocatalysts were prepared by a sol-gel method.Methyl trimethoxy silane was added as a precursor sol solution to bind...     

基于XY双变量特征提取策略的秸秆炭热值LIBS定量分析

农业生物质能已逐步成为我国现代工业主要清洁能源之一。利用激光诱导击穿光谱（LIBS）技术实现秸秆炭热值（CV）精准预测。针对传统X自变量特征提取方法在LIBS定量分析秸秆炭CV过程中缺陷问题,提出了一种XY双变量特征提取法。研究首先分析了秸秆炭CV与各元素含量之间相关性,选取与CV相关性极显著（p<0.01）的Y型特征变量,其主要获取了以炭单质、芳香环和羧基等形式存在的C,O,H和Na元素的分析线展宽波段;同时通过筛选偏最小二乘回归（PLSR）模型回归系数阈值获取与CV相关的X型特征变量,当阈值为4×10-5时模型交互验证均方根误差（RMSECV）降至最低值,其所对应的变量主要为参与农作物生理生长的Ca,Cr,Mg和K元素的分析线光谱线。基于所提取XY双特征变量构建遗传算法优化及自适应增强的人工神经网络（GA-BP-Adaboost）模型,当变异概率、交叉概率和相对误差率（RE）分别设为0.1,0.95和0.01时,最优模型预测平均相对误差（AREP）和预测相对标准误差（RSDP）分别为2.39%和2.97%,相比于XY-PLSR模型效果分别较低了0.82%和0.91%。结果表明：XY双变量特征提取法结合GA-BP-Adaboost模型可以为生物质炭在工业使用过程中CV精确定量预测分析提供方法依据。     

刚竹毒蛾危害下的毛竹叶片光谱特征波长研究

旨在获取刚竹毒蛾危害下的毛竹叶片光谱特征波长,以助于该虫害的有效、准确识别。将于福建省顺昌县实测的105条高光谱数据随机划分为实验组(71条)和验证组(34条)。基于实验组数据,利用单因素方差分析获取健康、轻度危害、中度危害、重度危害等虫害等级间具有极显著差异的波长;结合常用遥感卫星的波段设置对上述波长进行筛选,采用欧式距离、相关系数及光谱角匹配等3种方法判定其虫害判别能力,获取特征波长,并引入验证组样本对其予以验证。结果表明：(1)受害叶片的光谱反射率明显低于健康叶片,虫害等级越高,其反射率越低;(2)受害叶片的光谱特征变化较大,随着虫害等级的上升,其光谱曲线中的“绿峰”及“红谷”趋于消失,“红边”斜率逐渐减小;(3)确定原始光谱703.43~898.56 nm及一阶微分光谱497.68~540.72,554.53~585.25和596.24~618.23 nm为刚竹毒蛾危害下的毛竹叶片光谱特征波长,其对该虫害具有较强的判别能力。该研究从叶片尺度剖析了寄主对刚竹毒蛾的响应机理,是“地-天”耦合的理论基础,可为虫害遥感监测技术体系的建立提供重要依据。