人工神经网络应用于光谱分析同时测定增效联磺片三组分含量

应用人工神经网络原理，采用误差反向传播方法，对紫外吸收光谱重叠的增效联磺片中的三个组分含量不经分离可同时进行测定。磺胺嘧啶（ＳＤ）、磺胺甲恶唑（ＳＭＰ）、甲氧苄胺嘧啶（ＴＭＰ）的平均回收率分别为１０３．１％、９８．２１％、９８．７６％。探讨了人工神经网络中网络参数对分析结果的影响。     

薄层扫描法测定增效联磺片中磺胺嘧啶的含量

本文采用岛津ＣＳ－９３０型薄层扫描仪，以紫外反射吸收方式灵敏快速地测定了增效联磺片中磺胺嘧啶的含量。λｓ＝２７０ｎｍ，散射参数Ｓｘ＝３，薄层厚度０．３ｍｍ；展开剂为氯仿：乙醇：庚烷（１：１：１），平均回收率为９８．０１％，检出限为０．０５μｇ。     

光化学—荧光分析法研究——Ⅳ.磺胺嘧啶的光化学-荧光测定法

本文利用光化学反应,采用荧光检测手段,建立了磺胺嘧啶的光化学-荧光分析法。该法的线性范围为0.02～3.2μg/ml,检测限为0.02μg/ml,0.8μg/ml磺胺嘧啶标样的测定的相对标准偏差为2.6％(n=12)。该法用于磺胺嘧啶的测定,结果满意,回收率为92.8～106.9％,平均回收率98.8％(n=6)。该法操作简便、快速,容易实现在线分析。应用质谱、红外光谱、纸色谱、薄层色谱以及同步扫描荧光光谱等手段,对该光化反应过程进行了初步探讨,提出了一种可能的光化反应机制。     

紫外导数光谱法测定增效联磺制剂中三组分含量

作者建立了同时测定联磺制剂中磺胺嘧啶（ＳＤ） ,磺胺甲基异嚙唑（ＳＭＺ） 和甲氧苄氨嘧啶（ＴＭＰ） 三组分含量的导数紫外分光光度法。其回收率为９８．２％ ～９９ ．６ ％ ,变异系数为０．２６ ～０．９６ ％ 。     

可变误差多面体法同时测定复方新诺明中二组分的含量

以可变误差多面体法处理多波长吸光光度数据同时测定了复方新诺明制剂模样和五个批号实际样品中磺胺甲恶唑（ＳＭＺ）,甲氧苯氨嘧啶（ＴＭＰ）的含量,１１份模拟样中ＳＭＺ、ＴＭＰ的回收率分别为９９．８％和１００．３％,复方新诺明片和注射液的测定结果与药典方法一致。     

薄层色谱法检测磺胺二甲基嘧啶中杂质

建立限量检测磺胺二甲基嘧啶中杂质的方法.用薄层色谱法,使用两种展开剂系统分步同向展开对样品中的杂质进行检测.本法能简便有效地检测出磺胺二甲基嘧啶中各种可能杂质.     

快速溶剂萃取–高效液相色谱法测定禽蛋中磺胺嘧啶

建立快速溶剂萃取–高效液相色谱法测定禽蛋中磺胺嘧啶残留的方法。用单因素和正交试验对禽蛋中磺胺嘧啶的萃取条件进行优化,确定了最佳萃取条件:以甲醇为萃取剂,在130℃循环萃取4次,冲洗体积分数为80%,萃取时间为25 min。色谱柱为Hypersil ODS2柱(4.6 mm×250 mm,5μm),流动相为甲醇–0.5%冰乙酸(25∶75),流量为1.0 m L/min,检测波长为265 nm。磺胺嘧啶的质量浓度在0.025~0.500 mg/m L范围内与色谱峰面积呈良好的线性关系,相关系数r=0.999 5,检出限为0.5μg/kg。加标回收率在83.0%~88.2%之间,测定结果的相对标准偏差为2.2%(n=9)。方法的精密度、准确度和基质效应均符合禽蛋样品检测要求,可用于禽蛋中磺胺嘧啶含量的测定。     

毛细管区带电泳法测定甲氧苄胺嘧啶和磺胺甲基异噁唑的离解常数及其在复方新诺明中的含量

报道了利用 ３０ ｍｍｌ／Ｌ ＨＡｃ－ＮａＡｃ为缓冲液测定复方新诺明中甲氧苄胺嘧啶（ＴＭＰ）和磺胺甲基异噁唑（ＳＭＺ）的离解常数及含量的毛细管区带电泳（ＣＺＥ）方法。该方法具有简便、快速、准确等特点。测得ＴＭＰ和ＳＭＺ的ｐＫａ分别为６．６０和５．９０。其平均回收率分别为１０１．５％和９９．６％,最低检出限为０．４８ ｍｇ／Ｌ和０．０２８ ｍｇ／Ｌ,ＲＳＤ为１．２６％和１．１２％。     

磺胺嘧啶的电分析化学特性研究

采用循环伏安，脉冲极谱，计时库仑及计时电位等电化学测试技术研究了磺胺嘧啶的电分析化学特性。在ＰＨ２．０缓冲溶液中，ＳＤ于－０．６６Ｖ处产生一灵敏的示波极谱波，利用此波可测定微量ＳＤ，检测下限为２．４×１０＾－７ｍｏｌ／Ｌ。     

基于长春西汀酸的荧光偏振免疫方法测定磺胺二甲氧基嘧啶

合成了荧光标记物长春西汀酸和示踪物磺胺二甲氧基嘧啶-长春胺酸,并采用薄层色谱法对示踪物进行提纯.以磺胺二甲氧基嘧啶为分析对象,利用示踪物与磺胺二甲氧基嘧啶抗体的特异性反应,采用荧光偏振免疫分析方法(FPIA)研究了荧光标记物的荧光光谱特性.此荧光标记物在357 nm的激发光下,于453 nm处产生一个荧光发射峰;以荧光素为对照,考察了本方法的灵敏性.结果显示,荧光素的检出限仅为2.7 μg/L,而本方法的检测范围为0.5～146 μg/L,检出限达到0.5 μg/L.本方法的RSD为3.0%,重现性好;其它磺胺类药物对磺胺二甲氧基嘧啶的测定不产生明显干扰.运用本方法检测了饲料中磺胺二甲氧基嘧啶,结果与HPLC法相吻合.     

Cutoff radius effect of the isotropic periodic sum and Wolf method in liquid-vapor interfaces of water

As a more economical but similarly accurate computation method than the Ewald sum, the isotropic periodic sum (IPS) method for nonpolar molecules (IPSn) and polar molecules (IPSp), along with the Wolf method are of interest, but the cutoff radius dependence is an important issue. To evaluate the cutoff radius effect of the three methods, a water-vapor interfacial system has been studied by molecular dynamics. The Wolf method can produce adequate results for surface tension compared to that of the Ewald sum (within 2.9%) at a long enough cutoff radius, r(c). However, the estimation of the electrostatic potential profile and dipole orientational function is poor. The Wolf method cannot estimate electrostatic configuration at r(c) ≤ L(z)∕2 (L(z) is the longest lattice of the system). We have found that the convergence of the surface tension and the electrostatic configuration of the IPSn method is faster than that of the IPSp method. Moreover, the IPSn method is most accurate among the three methods for the same cutoff radius. Furthermore, the behavior of the surface tension against the cutoff radius shows a greater difference for the IPSn and IPSp method. The surface tension of the IPSp method fluctuates and presents a similar result to that of the Ewald sum, but the surface tension for the IPSn method greatly deviates near r(c) = L(z)∕3. The cause of this deviation is the difference between the interfacial configuration of the water surface and the cutoff treatment of the IPS method. The deviation becomes insignificant far from r(c) = L(z)∕3. In spite of this shortcoming, the IPSn method gives the most accurate result in estimating the surface tension at r(c) = L(z)∕2. From all the results in this work, the IPSn and IPSp method have been found to be more accurate than the Wolf method. In conclusion, the surface tension and structure of water-vapor interface can be calculated by the IPSn method when r(c) is greater than or equal to the longest lattice of the system. The IPSp method and the Wolf method require a longer cutoff radius than the longest lattice of the system to estimate interfacial properties.     

稀土(镧、铈)-茜素配位剂双核配合物组成和稳定常数的测定

研究了茜素配位剂与稀土的二元反应,从La(Ce)-茜素的吸收光谱着手,分析讨论了它们的反应机理,并拟定了一个既可区分单核与多核,又可测定稳定常数的方法.     

Geometry optimization of bimetallic clusters using an efficient heuristic method

In this paper, an efficient heuristic algorithm for geometry optimization of bimetallic clusters is proposed. The algorithm is mainly composed of three ingredients: the monotonic basin-hopping method with guided perturbation (MBH-GP), surface optimization method, and iterated local search (ILS) method, where MBH-GP and surface optimization method are used to optimize the geometric structure of a cluster, and the ILS method is used to search the optimal homotop for a fixed geometric structure. The proposed method is applied to Cu(38-n)Au(n) (0 ≤ n ≤ 38), Ag(55-n)Au(n) (0 ≤ n ≤ 55), and Cu(55-n)Au(n) (0 ≤ n ≤ 55) clusters modeled by the many-body Gupta potential. Comparison with the results reported in the literature indicates that the present method is highly efficient and a number of new putative global minima missed in the previous papers are found. The present method should be a promising tool for the theoretical determination of ground-state structure of bimetallic clusters. Additionally, some key elements and properties of the present method are also analyzed.     

A new cation-exchange method for accurate field speciation of hexavalent chromium

A new method for field speciation of Cr(VI) has been developed to meet present stringent regulatory standards and to overcome the limitations of existing methods. The method consists of passing a water sample through strong acid cation-exchange resin at the field site, where Cr(III) is retained while Cr(VI) passes into the effluent and is preserved for later determination. The method is simple, rapid, portable, and accurate, and makes use of readily available, inexpensive materials. Cr(VI) concentrations are determined later in the laboratory using any elemental analysis instrument sufficiently sensitive to measure the Cr(VI) concentrations of interest. The new method allows measurement of Cr(VI) concentrations as low as 0.05 μg l⁻¹, storage of samples for at least several weeks prior to analysis, and use of readily available analytical instrumentation. Cr(VI) can be separated from Cr(III) between pH 2 and 11 at Cr(III)/Cr(VI) concentration ratios as high as 1000. The new method has demonstrated excellent comparability with two commonly used methods, the Hach Company direct colorimetric method and USEPA method 218.6. The new method is superior to the Hach direct colorimetric method owing to its relative sensitivity and simplicity. The new method is superior to USEPA method 218.6 in the presence of Fe(II) concentrations up to 1 mg l⁻¹ and Fe(III) concentrations up to 10 mg l⁻¹. Time stability of preserved samples is a significant advantage over the 24-h time constraint specified for USEPA method 218.6.     

Development and validation of a sequential-injection method with chemiluminescence detection for the high throughput assay of the total antioxidant capacity of wines

This work reports a sequential-injection analysis (SIA) method with chemiluminescence (CL) detection for the rapid assay of the total antioxidant capacity (TAC) in wines. The method exploited the Co(II)-catalysed CL reaction of luminol with hydrogen peroxide in alkaline medium. Zones of sample, hydrogen peroxide, catalyst (Co(II) solution) and alkaline luminol were sequentially aspirated into the holding coil of the SIA manifold. Then, the flow was reversed and the stacked zones were directed to the CL detector. As the zones overlapped, antioxidants in the samples scavenged a portion of hydrogen peroxide and the decrease in the CL intensity was monitored and related to the TAC. The chemical and geometric conditions were studied and the method was validated in terms of linearity, accuracy (trueness and precision), matrix effects, signal additivity and robustness. The reproducibility of the method (expressed as the between-days % relative standard deviation) was between 2.5 and 3.4% and the trueness (expressed as the % recovery in wines spiked with gallic acid) was in the range 96.7-97.3%. The sampling frequency was 60 samples h⁻¹. The proposed SIA-CL method was compared with the DPPH method and the Folin-Ciocalteau (FC) method for the analysis of 25 wine samples.     

Solid-phase microextraction of N-nitrosamines

A method was developed for the extraction of seven N-nitrosamine compounds from water by solid-phase microextraction (SPME). The method developed requires a total analysis time of only 1.25 h for both extraction and detection (versus 3-20 h for other isolation techniques). Three gas chromatography (GC) detection systems were tested with the SPME method, nitrogen chemiluminesence detection (NCD), nitrogen-phosphorus detection (NPD) and chemical ionization mass spectrometry (CI-MS), with method detection limits (MDLs) found in the ng/L range. This method was used to analyze wastewater samples and showed excellent selectivity of extraction. The detection limits of this method for N-nitrosodimethylamine (NDMA) range from 30 to 890 ng/L as a function of detector type. The excellent selectivity of SPME in addition to the fast analysis time would make this method ideal for general surveys, wastewater analysis and laboratory studies (e.g. degradation kinetics or formation potential).     

蔬菜和食用菌中氨基甲酸酯类农药残留检测技术

建立了丙酮和乙腈(体积比85:15)提取,凝胶渗透色谱(GPC)法和PSA(N-丙基乙二胺)固相萃取柱2种方法净化,超高效液相色谱-串联质谱（UPLC-MS/MS）同时检测菠菜、黄瓜、大葱、蘑菇、香菇、木耳、牛肝菌和胡萝卜中19种氨基甲酸酯类农药,同位素稀释法定量。实验结果表明,GPC法净化,回收率为70.1%～95.7%;PSA固相萃取柱净化,回收率为70.2%～94.9%。方法的检出限均为1×10-5 g/kg。各种NMCs在确定的添加范围内线性关系良好,线性相关系数r均＞0.99,所建立的检测方法实用、准确、灵敏度高。     

铬铁矿中铁的快速测定方法研究

研究了铬铁矿中铁的测定方法问题。基于测定铬铁矿中铬的溶样方法原理和对传统无汞测铁程序的改进研究,推荐了一个测定铬铁矿中铁的快速方法模式:试样经沸腾硫酸湿烧(～330℃)、磷-硫混合酸溶解、直接用三氯化钛溶液还原铁(Ⅲ→Ⅱ)、过量钛(Ⅲ)自然被氧化后,用常规法滴定之。所提供的快速方法测得之结果准确可靠(RSD=0.55%～0.80%,n=8),适于普遍推广应用。     

Grafting of vanadyl acetylacetonate onto organo-hexagonal mesoporous silica and catalytic activity in the allylic epoxidation of geraniol

Vanadyl(IV) acetylacetonate ([VO(acac)₂]) was grafted onto a hexagonal mesoporous silica (HMS) using three different methodologies: method A – direct complex immobilisation; method B – functionalisation of the HMS with 3-aminopropyltriethoxysilane (APTES) followed by the complex immobilisation; and method C – treatment of the APTES functionalised support prepared by method B with trimethylethoxysilane (TMS) to deactivate eventually unreacted surface silanol groups, followed by complex grafting.     

气相色谱测定牦牛骨中脂肪酸的甲酯化方法比较

利用气相色谱（GC）技术,采用酸水解提取脂质,比较了6种甲酯化法（乙酰氯-甲醇法、H₂SO₄-甲醇法、HCl-甲醇法、KOH-甲醇法、KOH-甲醇+H₂SO₄-甲醇法和KOH-甲醇+HCl-甲醇法）对脂肪酸测定的影响,优选牦牛骨中脂肪酸测定的最佳方法。37种脂肪酸标准样品在0.28~250.00 mg/L范围内线性关系良好,相关系数均大于0.99（除C4：0外）。碱酯化法和酸碱结合法几乎无法测出牦牛骨中的脂肪酸,其测得的总脂肪酸含量小于0.20 g/100 g。乙酰氯-甲醇法测得的总脂肪酸含量（13.61 g/100 g）显著高于H₂SO₄-甲醇法（总脂肪酸含量为11.68 g/100 g）和HCl-甲醇法（总脂肪酸含量为3.18 g/100 g）测得的结果。乙酰氯-甲醇法和H₂SO₄-甲醇法的日内和日间精密度分别为0.27%~8.60%和0.34%~2.64%,两种方法中脂肪酸的回收率为83.06%~105.54%。结果表明,酸水解-乙酰氯-甲醇法是牦牛骨中脂肪酸测定的最佳方法。C18：1n9c、C16：0、C18：0和共轭亚油酸（CLA）是牦牛骨的主要脂肪酸,其总和达脂肪酸总量的85%以上,饱和脂肪酸与不饱和脂肪酸含量比值约为1：2。牦牛骨中脂肪酸的研究为骨资源脂质的有效利用提供了重要依据。