苯乙烯/甲基丙烯酸甲酯共聚物组分的测定

用红外光谱和紫外光谱进行共聚物组分定量分析时,如果选择的谱带只与共聚物组分含量有关,而与序列结构无关,即可由均聚物的混合物定量分析得到校正工作曲线。共聚物在这些谱带上的吸光度相当于混合物的吸光度。 Kamiyama等人在用IR研究丙烯酸甲酯/苯乙烯(MA/St)共聚物时,发现羰基吸收峰(1730cm~(-1))的半峰高宽度与MA的含量有关;Gallo用UV研究苯乙烯/甲基丙烯酸甲酯(St/MMA)共聚物时发现263毫微米的吸光度和St.组分含量不是线性关系;     

测定混合物组成及组分含量的热重分析法

采用热重－微商热重法确定混合物的组成及各组分的含量。通过对比混合物和可能组分的热重曲线及其微分曲线，比较它们的最大失重速率温度及在某一特定温度下的失重量可以确定混合物的组成，同时可以确定各组分的含量。该法对各组分含量的测定误差在５％以内，相对标准偏差在６％以内。     

统计模拟分光光度法在增效联磺片分析中应用的研究

本文应用统计模拟分光光度法建立了同时测定增效联磺片三组分含量的分析方法。用全面交叉组合法安排实验，获得有限但足够的实验数据，再用逐步回归法构造在不同波长下吸光度与组分浓度经验关系的“最优”数学模型，用全组合检索法寻优求出未知样品诸组分的含量。为认证此方法用均匀设计安排回收率试验，并对含量测定结果进行了方差分析，结果均令人满意．     

非线性优化迭代-紫外分光光度法同时测定苯甲酸钠和山梨酸钾

提出一种用连续波长的紫外光谱吸光度数据对两组分防腐剂（苯甲酸钠、山梨酸钾）混合物体系的定量分析方法。该方法利用连续波长信息将摩尔吸光系数和待测浓度同时作为自变量,建立非线性优化模型,对于组分浓度差较小的混合物体系经一次优化分析计算可得待测浓度;混合物中浓度差较大的体系经四次左右优化迭代,逐步降低误差得分析结果,相对误差可控制在1．52％之内。分析结果表明该法稳定、准确、简便快速、实用灵活,可对食品防腐剂进行定量测定。     

同时测定三辛妥和三辛胺盐酸盐的双波长分光光度法

提出了利用双波长分光光度法测定三辛胺及三胺盐酸盐的一种新方法,即ＴＯＡ和ＴＯＡ．ＨＣｌ在ＣＣｌ４溶液中与Ｉ２生成电荷转移化合物,其最大吸收波长分别为２９３ｎｍ和２６３ｎｍ,两组分同时存在时可利用吸光度和加和性得联立方程分别求出两组分的含量。     

多波长线性回归—导数吸光光度法同时测定三组分混合物

提出了等吸收点-多波长线性回归-(导数)吸光光度法同时测定三组分混合物的原理,以5-Br-PADAP-溴代十六烷吡啶(CPB)-金属离子显色体系为例,通过测定合成样品及铝合金中的锰、铜、锌.对方法的可行性进行了验证,结果良好.     

正交回归多组分标准加入光度法同时测定污水中的铜、镍、镉和锌

1引言多组分同时测定的光度法都依据比耳定律的线性加和原理，所以对实测样品中存在非线性干扰的多组分体系就很难简单处理。利用正交回归多波长光度法，可以引入反映组分间相互影响的交互作用项，并依据多组分标准加入法的原理，给出各波长处吸光度A（λ）与各待测组分浓度Xi（规范变量）间的关系为：均为回归系数。这里及di分别为组分i的浓度，基准浓度及变化间距。采用标准加入法，就是将含有多个待测组分的待测样中，按正交设计加入一定量的标准溶液，测定各试样溶液在一定显色体系中的吸光度。经回归分析求得回归方程中的回归系数。若…     

用Procrustes旋转-相关光谱数据分解同时光度测定硝酸根和亚硝酸根的探讨

输入具有相同光谱轮廓但不同浓度试样的吸光度数据，通过对相关光谱的分解及Procrustes旋转，可在无需校正试样的情况下获得试样中的组分数、纯组分光谱轮廓和各组分的相对浓度等信息，本文探索将此方法应用于NO-2及NO-3的同时光度测定，获得较好的结果。     

比值光谱一阶导数法同时测定苯酚和间苯二酚

以二元混合物的光谱除以其中某一组分的标准光谱而得到的比值光谱，对波长求导，可将重叠光谱分开而消除干扰，从而可方便的完成二组分混合体系中各组分的测定，     

比值导数波谱法分析食品中抗氧化剂

利用混合物的波谱除以干扰组分的波谱得比值波谱，对波长求导得比值导数波谱，由此可消除干扰组分的吸光度叠加效应。该法能有效地对三组分混合物体系进行分析。利用此法对没食子酸丙酯(PG)、2，4，5-三羟基丁酰苯(THBP)和叔丁基对苯二酚(TBHQ)所组成的三组分混合体系进行分析，结果满意。     

A new heating strategy in electrothermal atomic absorption spectrosmetry for better absorbance–time curves at high atomization rate

The results previously obtained by using fast heating in electrothermal atomic absorption spectrometry are considerably improved by using a new heating sequence which can be summarized as transverse–longitudinal heating mode. The absorbance vs. time curves, obtained with the new heating mode, follow almost perfectly a simple model in which only diffusion is considered as the force acting on the atomic vapor. From the fitting of the experimental absorbance vs. time data points with theoretical values, it is possible to calculate both the absorbance, when all atoms injected are assumed to be present, and their diffusion coefficient. Both values can be calculated by a simple software approach without the operator intervention. The asymptotic absorbance calculated in this way is the maximum absorbance physically obtainable and is the basis for standardless analysis.     

Spectrophotometric analysis of simultaneous protolysis equilibria

Simultaneous protolysis equilibria can be spectrophotometrically analysed easily by means of absorbance diagrams. The dissociation constants K(1) and K(2) can be determined directly from distinct points on the absorbance diagram by correlation with a photometric titration plot of absorbance vs. pH. Furthermore, from the absorbance diagram the ratio K (2)K (1) can be evaluated from the ratio of corresponding sides, and pH-measurement is not necessary. The titration systems of a mixture of 2-nitroso-l-naphthol-4-sulphonic acid with P-nitrophenol, and a mixture of P-nitrophenol with o-nitrophenol have been analysed by these methods, and are described as examples.     

Guidance for selecting the measurement conditions in the dye-binding method for determining serum protein: theoretical analysis based on the chemical equilibrium of protein error.

A methodology for selecting the measurement conditions in the dye-binding method for determining serum protein has been studied by a theoretical calculation. This calculation was based on the fact that a protein error occurs because of a reaction between the side chains of a positively charged amino acid residue in a protein molecule and a dissociated dye anion. The calculated characteristics of this method are summarized as follows: (1) Although the reaction between the dye and the protein occurs up to about pH 12, a change in the color shade, called protein error, is observed only in a pH region restricted within narrow limits. (2) Although the apparent absorbance (the absorbance of the test solution measured against a reagent blank) is lower than the true absorbance indicated by the formed dye-protein complex, the apparent absorbance correlates with the true absorbance with a correlation coefficient of 1.0. (3) At a higher dye concentration, the calibration curve is more linear at a higher pH than at a lower pH. Most of these characteristics were similarly observed experimentally in the reactions of BPB, BCG and BCP with human and bovine albumins. It is concluded that in order to ensure the linearity of the calibration curve, the measurement should be performed at a higher dye concentration and sufficiently high pH where the detection sensitivity is satisfied.     

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。     

Experimental evidence of the reversibility of the first stage of protein adsorption at a hydrophobic quartz surface near the isoelectric point

The reversibility of the first stage of adsorption of zwitterionic cytochrome c on a hydrophobic quartz surface was investigated using time‐resolved slab optical waveguide (SOWG) absorption spectroscopy. Using a novel prism‐free broadband coupling approach, absorbance data were collected successfully at a 50 ms time interval during the first few seconds after solution–surface contact. Near the isoelectric point where the cytochrome c molecules possess a net charge of zero and hence cannot be influenced by an electric field, the speed at which adsorption proceeded was found to be dependent on cytochrome c concentration as well as on surface hydrophobicity. It was also observed that the degree of protein adsorption increased as the surface hydrophobicity was increased. Within 6 s the adsorption process appeared to be reversible, as revealed by extremely low chi‐squared values when the absorbance data were fitted into the reversible Langmuir‐type kinetic model. The standard Gibbs free energy of adsorption was also calculated from the absorbance data. Copyright © 2003 John Wiley & Sons, Ltd.     

Determination of metal complexes of ethylenediaminetetraacetate in the presence of organic matter by high-performance liquid chromatography

A high-performance liquid chromatography method is described here for the determination of the Cd(II), Co(II), Cu(II), Pb(II), and Zn(II) complexes of ethylenediaminetetraacetate (EDTA) in municipal wastewaters and surface waters. The method involves separation by ion-exchange chromatography on a reversed-phase C18 column coated with ion-pair reagent, followed by post-column conversion to FeEDTA and subsequent detection by UV absorbance. Although Co(II) and Cu(II) coelute, they can be quantified by analyzing absorbance by CuEDTA2- prior to post-column conversion. The method detection limit of 6-8 x 10(-8) M (5-7 ng) is an order of magnitude improvement over previous UV absorbance post-column reaction methods. The technique can be used in the presence of organic matter encountered in matrices such as untreated wastewater without pre-concentration or sample cleanup.     

Employing Theories Far beyond Their Limits—The Case of the (Boguer‐) Beer–Lambert Law

For spectroscopists, the (Bouguer‐)Beer–Lambert law is unquestionably an essential principle, since it is inseparably linked with one of the most important quantities in spectroscopy, the absorbance. In spite of its importance, a quantitative discussion of the legitimacy of relating the transmittance, the quantity that is usually measured, to the absorbance by assuming a logarithmic relation between both quantities cannot be found in literature. In this contribution, we quantitatively discuss, based on examples, the errors that can be introduced by disregarding the exact solution based on Maxwell's equations and show that these errors can easily exceed one order of magnitude. We also re‐derive the Beer–Lambert law, thereby providing guidance as how to convert transmittance into absorbance properly.     

The effect of the exchangeable metallic cation on the colloid properties of laponite treated with acridine orangea spectrophotometric study

The adsorption of the cationic dye acridine orange (AO) by different monoionic laponites leads to changes in the colloid properties of this synthetic mineral in aqueous solutions. The organic cation is adsorbed by the mechanism of cation exchange. Small amounts of adsorbed dye keep the clay in a peptized state with all metallic cations. Greater amounts of AO result in the neutralization of the electric charge of the clay, and its flocculation. In excess AO the charge of the clay platelets becomes positive and the clay is peptized. The colloid properties are studied by absorbance curves in which the absorbance is described as a function of the degree of saturation with constant clay concentrations or with constant dye concentrations. In the absorbance curves three regions can be identified. The transition between the first and second or the second and third regions depend on the exchangeable metallic cation initially present in the clay. The spectrophotometric method is useful in identifying the presence of tactoids and flocculation mechanism, whether it results in card-house or in book-house flocs.     

Peak profile characteristics and atomization mechanisms for selenium in the presence of mercury for graphite furnace atomic absorption spectrometry

Summary Time resolved absorbance profiles, as well as the effects of inorganic acids and mercury salts, have been studied for selenium graphite furnace atomic absorbance signals. Conventional furnace operating procedures and wall atomization were used. Absorbance profiles were found to be sensitive to the mass of the counter ion and mercury present. Negative shifts in the appearance temperature were noted for low levels of mercury salts, whilst the higher levels of mercury caused only slight increasing shifts in the appearance temperature. Peak-area absorbance increases with mercury mass, but a steady-state absorbance was reached above a certain mercury chloride concentration. If mercury is present, a thermal dissociation of a mercury selenium compound is the suggested Se atomization mechanism.     

A useful UV spectroscopic method for the determination of the concentration of diethylenetriamine (DETA) in aqueous mineral flotation solutions

An alternative method for the determination of the concentration of diethylenetriamine (DETA) in aqueous mineral flotation solutions is described. This method is based on the formation of a DETA-Ni(II)-sulphite complex, which shows a UV absorption maximum at 285 nm that varies linearly with the concentration of DETA throughout the 0-50 mg l(-1) DETA range. A high concentration of Ni(II) is used to offset the effect of any Cu(II) or Ni(II) ions that may already be present in the industrial plant solutions under analysis. The intensity of the absorbance maximum is dependent on the sulphite ion concentration, but this problem is overcome by measuring the absorbances when the test solutions are spiked with different concentrations of DETA and then extrapolating the absorbance versus DETA concentration plot to zero absorbance to obtain the original concentration of DETA in the test solutions.