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     

双波长K系数法同时测定食品中山梨酸和苯甲酸

本文采用双波长K系数法同时测定食品中山梨酸和苯甲酸。山梨酸和苯甲酸的线性范围分别为0～10mg／L、0～40mg／L；样品测定的精密度分别为1．3％～3．7％和1．4％～4．4％；样品加标回收率分别为96．3％～98．7％和96％～102．2％。本法快速、简便、可靠。     

双波长K系数-标准加入-导数分光光度法同时测定钴、镍

1引言双彼长分光光度法通常采用等吸收点法和K系数法，存在灵敏度较低，测量点少而使误差较大的缺点；曾有人提出用双波长标准加入法来提高双波长法的灵敏度，但存在要求具有等吸收点的局限性，操作上也较麻烦．本文将双波长K系数法，标准加入法和导数法三者有机结合，并且独特地同时进行两组分的的标准加入，以一套数据即可完成两组分的同时测定。本方法具有灵敏度高，准确度好，操作简便，适用范围广的优点。2方法原理设样品中有a、b两组分。浓度分别为Ca、Cb，峰值波长对应于λ1、λ2，同时加太浓度为C、C的a、b标准溶液，则波长λ1、…     

双波长吸光度比值K系数法同时测定三组分体系的研究与应用

本文用双波长吸光度比值Ｋ系数法同时测定撒痛风注射液中水杨酸钠，咖啡因和安替比林三组分的含量，其平均回收率及变异系数分别为１０１．５％，０．４０％；９９．９９％，０．３７％；１００．０％，０．３０％。既改善了选择性，又提高了灵敏度，弥补了常规Ｋ系数法的不足。     

测定可见光区分光光度系组成的新方法

本文报道一种测定二元分光光度系组成的新方法,原理新颖,为作者首创,采用双波长分光光度技术消除显色产物的影响,直接测定与显色剂平衡浓度相对应的吸光度,通过简单的计算即可求得产物组成。     

双波长分光光度法同时测定水杨醛和苯酚

利用水杨醛、苯酚的紫外吸收光谱特征及水杨醛在271 nm波长处有一个等吸收点,提出了同时测定水杨醛和苯酚的双波长分光光度法。选择328 nm和271 nm为测定波长,以其回归方程为基础建立了联立方程组,C水杨醛=31.31A328 nm+0.344;C苯酚=44.53A271 nm-1.866A328 nm-0.136,求得组分浓度与吸光度之间的关系,浓度在0.005~0.030 g.L-1范围内符合朗伯-比耳定律。     

双波长K系数-标准加入-导数分光光度法同时测定重油中的钴镍

本文提出了一种同时测定两组分混和物的新方法，即双波长Ｋ系数－标准加入－导数分光光度法，该法同时进行两组分的标准加入，以两个组分的峰值波长为测定波长，又互为参比波长，利用Ｋ系数法以一套吸光度数据同时完成两个组分的测定。本文以ＯＰ－５－Ｂｒ－ＰＡＤＡＰ为显色体系，同时测定了重油中的钴、镍，结果令人满意。本方法简便，灵敏度高。     

双波长K系数－标准加入分光光度法同时测定重油中的钴、

本文提出一种同时测定两组分的新方法，即双波长Ｋ系数－标准加入分光光度法。该法同时进行两组的标准加入，以两个组分的最大吸收波长为测定波长，又互为参比波长，以一套吸光度数据同时完成两个组分的测定。本法已用于重油中钴、镍的同时测定，结果满意     

5-Br-PADAP双波长分光光度法测定酒样中甲醇

用2-(5-溴-2-吡啶偶氮)-5-二乙氨基酚(简写作5-Br-PADAP)作为在乙醇溶液(如酒)中识别甲醇的试剂,在pH 9.0的乙醇溶液中,5-Br-PADAP的吸收峰位于444 nm处,而有甲醇存在时,在552 am处出现新的吸收峰,即吸收峰发生红移,两吸收峰之间相差108 nm,从有甲醇存在的5-Br-PADAP乙醇溶液的吸收光谱上可见到在444nm及552nm两波长处分别有负吸收峰和正吸收峰,在两处的吸光度与甲醇浓度之间呈线性关系,基于以上事实,提出了测定酒中甲醇量的双波长分光光度法,以552nm为测定波长,444am为参比波长,所提出的方法用于测定假冒酒及工业酒精试样中甲醇的含量,测定结果的相对标准偏差(n=8)均小于1%.用标准加入法测得的回收率在98.7%～100.1%之间,对方法所涉及的反应机理也作了简要的讨论.     

Simultaneous HPLC Determination of Five Flavonoids in Flos Inulae

A simple and accurate reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed for simultaneous determination of five flavonoids, spinacetin, quercetin, luteolin, 6-methoxyluteolin, and isorhamnetin, in an extract of the flowers of Inula britannica L., an important Traditional Chinese Medicine (TCM). Samples were extracted with 80% ethanol. Optimum separation and detection were achieved on an ODS-3 column with a methanol–acetonitrile gradient containing 0.49% (v/v) citric acid as mobile phase. The flow rate was 1.0 mL min⁻¹ and detection was at 360 nm. All calibration plots revealed linearity was good (r ² = 0.999) within the concentration ranges tested. Repeatability was evaluated by performing intra-day and inter-day assays; relative standards deviations (RSD) were less than 2.8%. Recovery of the five flavonoids was between 91.5 and 103.6%, with RSD less than 6.5%. The method was successfully used for analysis of seven samples of Flos Inulae from different parts of China and was found to be simple and efficient.     

Simultaneous LC-DAD and LC-MS Determination of Ellagitannins, Flavonoid Glycosides, and Acyl-Glycosyl Flavonoids in Cistus salvifolius L. Leaves

A rapid and inexpensive HPLC method has been developed for simultaneous separation of the three main classes of polyphenol in the leaves of Cistus salvifolius L. Time devoted to extraction of polyphenols, which was performed using small volume of solvent, did not exceed 120 min. We identified three ellagitannins (punicalagin and related compounds), a total of ten glycosyl derivatives of quercetin and myricetin, and two coumaroyl glucosyl kaempferols by use of both diode-array detection (DAD) and mass spectrometry. The polyphenol composition of C. salvifolius leaves, which may contribute to the metabolic plasticity of the species, may explain its distribution in infertile soils of the Mediterranean area, and may also indicate this shrub is an important source of metabolites of potential use in human health care.     

Simultaneous Determination of Nine Flavonoids in Dalbergia odorifera by LC

A rapid and accurate HPLC method has been developed for the simultaneous determination of nine major flavonoids, namely 3-hydroxymelanettin, melanettin, stevenin, butein, isoliquiritigenin, dalbergin, 2,4-dihydroxy-5-methoxybenzophenone, pinocembrin, 4-methoxydalbergione in Dalbergia odorifera. The samples were separated on an Aglient Zorbax SB-C₁₈ column (250 × 4.6 mm, 5 m) with a gradient of acetonitrile and 1% aqueous acetic acid (/) at a flow rate of 1.0 mL min^–1 and detected at 350 nm. The complete separation was obtained within 30 min for the nine target flavonoids. All calibration curves showed good linearity (r² > 0.999) within test ranges. The repeatability was evaluated by intra- and inter-day assays and RSD values were less than 4.0%. The recoveries were between 92.0% and 104.5%. The developed method was successfully applied to the analysis of 32 commercial samples of D. odorifera.     

Determination of Bioactive Flavonoids in Rhododendron Dauricum L. by Capillary Electrophoresis with Electrochemical Detection

A method based on capillary electrophoresis with electrochemical detection (CE-ED) has been developed for the determination of bioactive flavonoids in the traditional Chinese herbal medicine, Rhododendron dauricum L. The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 70 mmol L^?1 borate buffer (pH=9.2) within 20 min. A 300 μm diameter carbon disk electrode has a good response at + 0.90 V (vs. SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N = 3) ranging from 2 × 10^?8 g mL^?1 to 2 × 10^?7 g m^?1 for the analytes. The method has been successfully applied for the analysis of real sample, with satisfactory results.     

Simultaneous Determination of Nine Major Flavonoids in Sophora flavescens by RP-LC

A liquid chromatographic method was applied to determine trifolirhizin, kushenol K, kushenol L, kushenol N, kushenol X, kurarinone, norkurarinone, isokurarinone and kushenol A in the roots of Sophora flavescens, namely Kushen in China. The samples were separated on a YMC-C₁₈ column (250 × 4.6 mm, 5 μm) with a gradient of methanol and 0.3% aqueous acetic acid (v/v) at a flow rate of 0.8 mL min^?1 and detected at 295 nm. The complete separation was achieved within 45 min for the nine major flavonoids. All calibration curves expressed good linearity (r ² > 0.999) within the test range. The recovery of this method was 92.3–106.9%. The assay was successfully applied to the quantification of nine flavonoids in 26 samples of Kushen. The results indicated that this developed LC assay could be readily utilized as a quality control method for the Chinese herb medicine Kushen.     

Simultaneous Determination of Four Flavonoids in Pigeonpea [Cajanus cajan (L.) Millsp.] Leaves Using RP-LC-DAD

A simple and accurate RP-HPLC method using photodiode array detection (PAD) was developed for the simultaneous determination of four flavonoids, namely quercetin (QU),luteolin(LU),apigenin(AP) and isorhamnetin (IS) in pigeonpea leaves.Extract samples were separated on HIQ SIL C₁₈V column using methanol-acetonitrile-water(31:10:59, v/v/v) as mobile phase.The flavonoids were detected at 254.5 nm for QU and IS, and at 345 nm for LU and AP.Contents were determined with satisfactory repeatability (R. S. D. < 2.2%) and recovery (97.27 – 99.98%). The developed method was found to be simple and efficient.