Extraction of parabens by melamine sponge with determination by high-performance liquid chromatography

In the present study, we propose a novel method for the extraction of parabens in personal care products. A new, simple adsorptive material was obtained by combining metal-organic frameworks and melamine sponges using the adhesive property of polyvinylidene fluoride. This new material, metal-organic frameworks/melamine sponges, was found to be particularly suitable for solid-phase extraction. The structural characteristics of metal-organic frameworks/melamine sponges were first analyzed by scanning electron microscopy. Subsequently, solid-phase extraction was performed on sample solutions, and the extracted substances were then analyzed by high-performance liquid chromatography. Following optimization of important experimental conditions, excellent recovery rates were obtained. Our novel method was then applied to the extraction of four parabens (methylparahydroxybenzoates, ethylparahydroxybenzoates, propylparahydroxybenzoates, and butylparahydroxybenzoates) from real samples. The results yielded limits of detection of 0.26–0.41 ng/mL. The inter- and intra-day recoveries were 104.0–109.7% and 91.2–98.1%, respectively (relative standard deviation, <13.8%).     

贝尔实验室垂直分层空时系统的简化最大似然检测算法

针对贝尔实验室垂直分层空时系统最大似然检测复杂度过高的问题,提出一种简化最大似然算法.该算法利用多维高斯分布逼近干扰加噪声的统计特性,并根据发射天线数和调制阶数来调整待检测发射向量的个数,以减小需搜索的待检测信号向量个数,在复杂度不高的情况下就可达到与最优检测相近的误码性能.仿真结果表明,当发射天线数为4、采用16-QAM调制时,该方案可仅用最大似然算法0.0162倍的复杂度达到与其相近的误码率.     

基于克莱姆—施密特正交化法则的多用户检测器

提出了码分多址（CDMA）系统中一种基于克莱姆-施密特正交化法则的多址干扰抑制算法,不同于传统的多用户检测算法中采用扩频序列对接收信号进行解扩,该算法运用克莱姆-施密特准则递推地完成最优欠妥 扩码的求解,进而对接收信号进行解扩处理,可以实现对多址干扰的完全抑制,性能分析和仿真结果均表明,该算法能有效地抑制CDMA系统中的多址干扰,改善系统的性能。     

基于酸性离子液体填充注射器的泡腾辅助微萃取法测定果汁样品中三嗪类除草剂

开发了一种高效、 环保的基于酸性离子液体填充注射器的泡腾辅助微萃取法, 用于测定果汁样品中三嗪类除草剂. 萃取分散采用酸性离子液体[C₄mim][HSO₄], 它对三嗪类除草剂具有较高的溶解度, 其酸性可与碳酸盐反应产生二氧化碳, 从而加速萃取过程. 该实验的提取和分离步骤在注射器中完成, 整个预处理过程完全不需要任何设备辅助. 对碳酸氢钠用量、 酸性离子液体用量、 盐添加量及洗脱溶剂体积等影响萃取效率的实验条件进行了优化. 在最佳条件下, 三嗪类除草剂浓度在1~200 ng/mL范围内获得了良好的线性关系, 相关系数大于0.9984; 检出限(LOD)和定量限(LOQ)分别为0.06~0.18和0.21~0.61 ng/mL, 日间及日内精密度低于8.3%. 实验结果表明, 该方法可用于果汁样品中三嗪类除草剂的测定.     

Solid-phase microextraction of triazine herbicides via cellulose paper coated with a metal-organic framework of type MIL-101(Cr), and their quantitation by HPLC-MS

Microchimica Acta - A nanostructure was prepared from titania nanoparticles and copper oxide (TiO2NP@CuO) and used to modify a carbon paste electrode (CPE). The modified CPE is shown to enable...     

Fabrication of the Metal-Organic Framework Membrane with Excellent Adsorption Properties for Paraben Based on Micro Fibrillated Cellulose

A kind of novel environmental-friendly composite absorbent material was designed and prepared in this paper. Nanoscale metal-organic frameworks(MOFs) were embedded in the skeleton of cotton micro fibrillated cellulose. By scanning electron microscope(SEM), we observed that a large number of MOFs were attached to the cellulose skeleton. In addition, under the condition of 1800 r/min vortex, the structure of the composite material was stable and was not easily damaged by external forces. The water contact angle test showed that the composite material had excellent hydrophilicity and could be used for the adsorption of pollutants. Then, the material was characterized by energy dispersive X-ray spectroscopy(EDX), X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR) and BET adsorption. Through verification, the material had very stable reusability(n=10). The composite material was applied to the solid phase extraction of water samples, such as rain water, toning water and fruit juice, and was quantitatively analyzed by high performance liquid chromatography(HPLC)-UV. This method was then applied to the extraction of four parabens(methyl-, ethyl-, propyl-, and butyl-paraben) from real samples, yielding limits of detection(LODs) of 0.29-0.58 ng/mL. The linear range was 2-500 ng/mL. The inter-day and intra-day recoveries were 90.7%-106.0% and 87.1%-109.3%, respectively(relative standard deviation<10.8%).     

宽带码分多址系统中的并行干扰抑制技术

研究了宽带码分多址系统中两级并行干扰对消算法（PIC）的性能,并通过基于MATLAB和COSSAP软件平台的系统仿真验证了结论的正确性。研究和仿真结果都表明,PIC算法在大多数情况下对系统的误码性能都有较大程度的改进,在现有技术条件下基本能够保证系统误码性能的稳定性,是一类具有实际应用价值的算法。     

Rapid determination of melamine in milk and milk powder by surface-enhanced Raman spectroscopy and using cyclodextrin-decorated silver nanoparticles

We have synthesized silver nanoparticles (AgNPs) decorated with α-cyclodextrin (CD) by using the traditional silver mirror reaction in the presence of CD. The CD-AgNPs were used as substrate in surface-enhanced Raman spectroscopy (SERS) for determining melamine. The intensity of the Raman band of melamine at 704 cm^?1 was used to determine melamine in milk and milk powder. The use of CD-AgNPs as the SERS substrate rather than classical silver nanoparticles makes the method more sensitive in giving an enhancement by a factor of up to?~?10⁶ in scattering efficiency. The effects of the volume of solutions (of CD-AgNPs, NaCl, NaOH, melamine) and of mixing time were optimized. The standard addition method was employed for quantitative analysis. The correlation coefficient of the calibration plot is 0.9995, and the limit of detection is 3.0 μg L^?1. The method was successfully applied to the determination of melamine in milk and milk powder, with relative standard deviations of <10 % and recoveries between 89 and 104 %.

Selective determination of o-phenylenediamine by surface-enhanced Raman spectroscopy using silver nanoparticles decorated with α-cyclodextrin

Microchimica Acta - We have developed a SERS method for the determination of o-phenylenediamine (OPD) in water. It is based on the chemical cyclization reaction of OPD with nitrite in acidic...     

一种增强型选择放大转发机会协作分集协议

针对协作分集系统中放大转发协议存在的噪声放大问题,提出了一种增强型选择放大转发机会协作分集协议.该协议首先在多个中继中选择最优的中继,然后目的节点对源节点第1步广播的信息做出成功、半成功和失败3种反馈,源节点和最优中继节点根据反馈信息分别采取非协作传输、源节点重传和中继放大转发3种方式,由于加入了源节点重传,因此减少了中继放大转发次数及噪声的放大.理论分析和仿真结果表明,当中断概率为10-3、中继个数为4时,与增强型放大转发机会协作分集协议相比,该协议约有0.4dB的信噪比增益,并且达到了和理想分布式空时码相同的分集-复用折中.