用于透射比标定的高精度分光光度测量装置

本文主要介绍了所研制的高精度分光光度测量装置的结构、原理,讨论了非线性校正的方法,并对测量装置的误差进行了分析,最后与国内外同类装置进行了比较。     

PLS–分光光度法同时测定三组分阳离子染料

将偏最小二乘法用于可见分光光度分析,建立一种同时测定阳离子黄X–8GL、阳离子红X–FG、阳离子艳蓝RL三组分混合染料含量的新方法。在380～780 nm范围内,将测定的26组混合溶液的吸光度值作为校正集,另8组混合溶液的吸光度值作为预测集,结合二阶差分法确定最佳主成分数。测得三组分混合体系中校正集的相关系数分别为0.9988,0.9994,0.9964;交互验证均方根误差(RMSECV)分别为0.0754,0.1852,0.2168;预测集的相关系数分别为0.9984,0.9996,0.9981;预测均方根误差(RMSEP)分别为0.1086,0.1877,0.2515。该方法无需样品分离,可为染色过程中多组分染料浓度的在线监测提供技术支撑。     

一种提高化妆品中甲醛含量检测的稳定性和灵敏度的双波长光谱方法

提出了一种基于双波长光谱法(以500 nm吸光度为基准并结合414 nm处的吸光度)快速测定化妆品中甲醛含量的方法。结果表明:采用单波长的计算方法(不考虑基线漂移)产生的误差时,平行试验结果之间的相对标准偏差(RSD)可达11.5%,而该方法的RSD最大仅为0.46%。同时该方法能够有效地校正扣除萃取液颜色和基线漂移的影响,且定量下限为7.4 mg/kg。该方法具有分析时间短、操作便捷、灵敏度高、结果准确的优点,适用于化妆品中甲醛的检测。     

使用"空白对比法"测量吸光度原理的一种简单解释

在分析化学、仪器分析及吸收光谱法专著中,关于吸光度测量都讲到,为了校正测量中溶剂的吸收、容器的吸收、光的散射和界面反射等因素的影响,必须采用“空白对比法”.但为什么采用“空白对比法”就能校正上述因素的影响,却未讲清楚,故有作探讨的必要. 按吸光度定义的要求,通过试液光强的减弱应该只与被测物(吸光物)有关,即     

铕锌二甲酚橙配合物吸光度的加和性及其应用于铕,锌的光度测定

实验证实:铕-二甲酚橙(XO)和锌-XO的混合物吸光度(A)等于Eu-XO和Zn-XO吸光度之和.偏差小于±2%.如改用稀土-XO代替Eu-XO,偏差小于±3%.利用这加和性,已设计铕,锌的分光光度法.     

在单波长分光光度计上进行双波长分光光度法的光度误差讨论

讨论了在单波长分光光度计上进行普通、双波长光度法测量的光度误差 ,给出了相对误差的表达式 ,并绘制出dc/c对透光度 (或吸光度 )图 ,为紫外 可见分光光度测量时选择合适的吸光度 (或透光度 )范围提供了理论基础     

人工神经网络用于化学数据解析的研究(Ⅰ)──逼近规律与过拟合

对多层前传网络的过拟合问题进行了探讨。定义了逼近误差和逼近度作为人工神经网络(ANN)的建模评价指标。通过应用于多元非线性校正的数值模拟和实际药物光度分析数据解析,表明该指标意义明确,便于掌握,且能较好地定量表述ANN逼近规律的程度。     

偏最小二乘紫外分光光度法同时测定甲基苯甲醛三种同分异构体

将偏最小二乘法(PLS)用于紫外分光光度数据的解析,建立了同时测定甲基苯甲醛3种同分异构体的模型。在230～304 nm范围内,将测得的48个样品的吸光度值作为校正集,另18个样品的吸光度值作为预测集用于建模。所建立的邻、间、对甲基苯甲醛模型的平均回收率分别为101.2%、100.2%和98.9%;均方根误差(RMSE)分别为0.2667、0.3853和0.2118;预测浓度范围分别为4.6～16.2μg/mL、5.8～17.4μg/mL和6.5～20.6μg/mL。讨论了混合物中3种同分异构体浓度比例对测定结果的影响,并确定了最佳的浓度比例范围。对模拟样品进行加标回收率试验。并通过与顺、反丁烯二酸两种同分异构体测定结果的比较,得出了有意义的结论。     

人工神经网络用于化学数据解析的研究（I）：逼近规律与过拟合

对多层前传网络的过拟合问题进行了探讨，定义了逼近误差和逼近度作为人工神经网络（ＡＮＮ）的建模评价指标，通过应用于多元非线性校正的数值模拟和实际药物光度分析数据解析，表明该指示明确，便于掌握，且能较好的地定量表述ＡＮＮ逼近规律的程度。     

三波长校正光度法测定水果蔬菜中多菌灵残留量

研究了三波长光度法测定水果蔬菜中多菌灵残留量的最佳测定条件,在pH8．3的条件下,测定278,281和290nm波长处的吸光度,计算出校正吸光度,校正吸光度与多茵灵含量在0～50μg范围内呈线性关系,相关系数为0．9991,方法检出量为0．773μg;样品的加标回收率在93．5％～101．0％范围内,测定结果满意。     

抗生素效价测定仪校准用光谱中性滤光片的研制

根据浊度法抗生素效价测定仪吸光度的有效测量范围和液体培养基培养过程中吸光度逐渐降低的特点,选用中性灰色玻璃研制了吸光度标称值分别为0.3,0.5,0.7,1.0的光谱中性滤光片组标准物质。用紫外可见近红外分光光度计对研制的标准物质的均匀性、正反面和稳定性进行测试,吸光度均匀性最大值为0.002 0,吸光度正反面最大差值为0.000 4,吸光度稳定性最大值为0.002 5,符合二级标准物质要求,经评定标准物质吸光度的相对扩展不确定度为1%(k=2)。将该标准物质的定值结果与上一级计量标准中国计量科学研究院的校准结果进行比对验证,结果表明研制的标准物质定值准确,可用于抗生素效价测定仪吸光度准确性和溯源性校准。     

New Baseline Correction Method Using Near-Infrared Absorption of Water in Water/Acetonitrile Gradient High-Performance Liquid Chromatography with Far-Ultraviolet Absorbance Detection

We have previously reported the development of a far-ultraviolet (FUV) absorbance detector capable of detecting wavelengths down to 175 nm in high-performance liquid chromatography (HPLC). Although the FUV detector can detect substances with weak to non-existent ultraviolet (UV) absorption (e.g., sugars at 185 nm and peptides at 190 nm), a large baseline drift occurs in the gradient elution due to differences in the FUV absorbance properties of water and acetonitrile. To overcome the problem of baseline drift, we have proposed a new baseline correction method using the absorption of water at 1450 nm. It is well known that water has a relatively large absorption peak at 1450 nm in the near-infrared (NIR) region. By contrast, acetonitrile used in reversed-phase HPLC shows negligible absorbance compared to water at 1450 nm. Sugars and peptides also show negligible absorbance at 1450 nm. Thus, it is expected that changes in absorbance at 1450 nm only reflect the volume fraction of water in the gradient elution. The baseline correction method by a linear combination of FUV and NIR chromatograms was applied to the HPLC separation of sugars and peptides in water/acetonitrile-gradient HPLC coupled with FUV detection. The results showed that flat baselines were successfully obtained in the gradient HPLC coupled with FUV detection.     

一种新型在线近红外光谱分析仪的研制

研制了一种新型的电荷耦合器件(CCD)在线近红外光谱分析仪，它由光谱仪系统、电源电路与控制系统、光纤及其附件与流通池系统、防爆系统、样品前处理系统、模型界外样品抓样系统、实时光谱测量和化学计量学软件等部分组成。在兰州炼油厂联合重整装置上连续5个月的工业实验表明，该仪表测定汽油辛烷值的准确性为0．3个辛烷值单位，重复性为0．2个辛烷值单位，具有准确性高、稳定性好、测量速度快、安全性强、自动化程度高和分析测试项目扩展性宽等特点。该仪表可与APC技术或其它自动化系统联用，对石化等大型生产装置的技术进步将产生积极的推动作用。     

Oil-in-water analysis using supercritical fluid extraction interfaced with fixed wavelength infrared detection

The combination of a direct aqueous supercritical fluid extraction system interfaced to a fixed wavelength infrared detector; measuring CH₂ (ν_asymmetric) absorbance at 2930 cm^?1, has been successfully developed for the analysis of oil-in-water. Using an optional, in-line silica gel treatment procedure, method accuracy for determining Brent Delta crude oil in spiked 500 mL water samples was 92.0% to 94.5% with RSD 4.7% to 6.5%. The supercritical fluid extraction-infrared method enables a second analysis of the same water sample without silica gel treatment. For second sets of analyses without silica gel treatment, method accuracy for determining Brent Delta crude oil in spiked 500 mL water samples was 87% to 96.0% with RSD 7.5% to 9.5%. Results of this study indicate that the silica gel treatment procedure reduces the calculated level of Brent Delta crude oil-in-water by 6.6–12.4% relative to samples analysed without silica gel treatment. The results of a study involving Fourier transform infrared spectroscopy indicate a limit of detection for n-decane of approximately 0.5 mg L^?1 by measuring CH₂ (ν_asymmetric) absorbance using the supercritical fluid extraction-infrared method. Sample preparation using direct aqueous supercritical fluid carbon dioxide extraction provides an indefinite means for the use of infrared techniques to measure oil-in-water.     

一种消除在线多通道近红外分析仪各通道光谱差异的方法

针对在线多通道近红外分析仪因光纤耦合器件加工精度和装配过程存在细微差异而引起通道间光谱不一致的问题,在对光谱差异进行解析的基础上,提出了一种运算简捷、且在实际应用中易于实现的平均光谱差值校正(MSSC)方法,并与常用的模型传递算法如斜率／偏差(S／B)算法、分段直接校正(PDS)算法,以及通过偏最小二乘-人工神经网络(PLS-ANN)建立多通道混合校正模型进行了对比。结果表明,该方法可有效消除各通道所测光谱之间存在的差异,实现了多通道分析模型的通用性。     

Experimental comparison of multi-channel analyzer. Dead-time corrections for short-lived radionuclides

The accuracy of the live-time circuit of a 400-channel analyzer was studied in detail, and was found to be unsatisfactory even for long-lived radionuclides. It was found that automatic live-time correction with the multi-channel analyzer gave rise to increasing positive errors with increasing count rate; this overall positive error was composed of a positive error due to the slowness of the electronic circuitry, and a smaller negative error due to the finite pulse-width. Adequate correction could be performed by feeding the information from the dead-time output of the multi-channel analyzer to an external live-time circuit with variable oscillator frequency and pulse-width. Four methods for dead-time correction were compared experimentally in the case of short-lived radionuclides (T as low as 7 sec): the method of Bartošek et al., the method of Schonfeld, the use of a sufficiently short counting time as compared to the half-life, and the live-time mode of counting without additional correction. These four methods were applied to the determination of oxygen and silicon in rocks by 14 MeV neutron activation analysis. Results are given for USGS standard rock G-2. Research associate of the I. I. K. W.     

Correction of inner-filter effect in fluorescence excitation-emission matrix spectrometry using Raman scatter

Fluorescence excitation-emission matrix (EEM) spectroscopy is a useful tool for interpretation of fluorescence information from natural water samples. One of the major problems with this technique is the inner-filter effect (IFE), i.e. absorption of light at both the excitation and emission wavelengths. The common solutions are to either dilute the sample or apply some form of mathematical correction, most often based on the measured absorbance of the sample. Since dilution is not always possible, e.g. in on-line or in situ EEM recordings, and corrections based on absorbance are hampered primarily by the use of a separate absorbance instrument, neither of these solutions is optimal. In this work, we propose a mathematical correction procedure based on the intensity of Raman scatter from water. This procedure was found to reduce the error after correction by up to 50% in comparison with two absorbance correction procedures. Furthermore, it does not require the use of a separate absorbance measurement, and it is applicable to on-line and in situ EEM recordings, where the IFE would otherwise cause problems.     

磁场作用下葡萄糖近红外光谱检测技术研究

采用傅立叶变换红外光谱仪(FTIR)研究了磁场强度对葡萄糖溶液近红外光谱的影响,发现磁场作用下葡萄糖的近红外光谱吸收强度和部分峰位发生显著变化。分析了磁场对葡萄糖溶液近红外光谱吸收的影响机理。采用偏最小二乘回归法(PLS)建立了磁场作用下葡萄糖溶液的定量分析模型,使用验证集进行验证。研究结果表明,磁场对葡萄糖分子基团偶极矩产生诱导作用,使偶极矩增大,吸收增强;同时磁场作用下,葡萄糖分子趋于沿平行于磁场的方向排列,其基团振动频率(特征吸收峰)吸光度与浓度变化的线性关系得到极大的改善。该研究有助于提高葡萄糖分子吸收强度及其测量精度,为进一步提高血糖检测精度提供技术支持。     

鱼粉近红外光谱模型传递应用研究

为探讨光栅型与傅里叶变换型近红外分析仪之间模型传递的应用效果,选取国产鱼粉为近红外光谱样本,DS2500F型近红外分析仪为源仪器,MPA型近红外分析仪为目标仪器,采用分段直接校正(PDS)方法实现近红外光谱传递。分别建立水分、粗蛋白质、粗脂肪、蛋氨酸和赖氨酸等组分的预测模型,通过交互验证决定系数(R2cv)、交互验证标准误差(RMSECV)、马氏距离(MD)、系统偏差(Bias)、预测均方根误差(RMSEP)和相对分析误差(RPD)等参数,多维度评估光谱传递后所建预测模型的效果。结果表明,DS2500F仪器的近红外光谱传递到MPA型仪器时,所建国产鱼粉的水分、粗蛋白质、粗脂肪、蛋氨酸、赖氨酸的预测模型与MPA型仪器原始预测模型各参数对比无显著差异,预测效果基本一致,说明国产鱼粉在DS2500F仪器上的近红外光谱通过传递可以替代MPA型仪器的原始光谱,间接实现了模型传递,且具有良好的适用性和共享性,可提高近红外预测模型的应用效率。     

Supported capillary membrane sampling-gas chromatography on a valve with a pulsed discharge photoionization detector

The objective of this study was to develop and evaluate a simple miniaturized approach to gas chromatography termed supported capillary membrane sampling-gas chromatography on a valve (SCMS-GCOV). The prototype instrument uses a pulsed discharge photoionization detector (PDPID) as the GC detector. Two different analyzers were constructed. The first used a bench scale SCMS-GC. The second was a miniaturized SCMS-GCOV analyzer. The SCMS-GCOV analyzer was used to monitor the concentrations of trihalomethanes (THM4) in drinking water. Details are given for the construction of the SCMS-GC-PDPID and the SCMS-GCOV-PDPID analyzers. The results of method detection limit, accuracy and precision studies are reported for analysis of THM4 and are compared to other methods of THM4 analysis. Side-by-side comparison studies are conducted between the SCMS-GCOV and USEPA 502.2 with promising results.