Determination of peroxide value by fourier transform near-infrared spectroscopy

A Fourier transform-near infrared (FT-NIR) method originally designed to determine the peroxide value (PV) of triacylglycerols at levels of 10–100 PV was improved upon to allow for the analysis of PV between 0 and 10 PV, a range of interest to the edible oil industry. The FT-NIR method uses convenient disposable glass vials for sample handling, and PV is determined by spectroscopically measuring the conversion of triphenylphosphine (TPP) to triphenylphosphine oxide (TPPO) when reacted with hydroperoxides. A partial-leastsquares calibration was developed for 8 mm o.d. vials by preparing randomized mixtures of TPP and TPPO in a zero-PV oil. The method was validated with samples prepared by gravimetric dilution of oxidized oil with a zero-PV oil. It was shown that the American Oil Chemists’ Society primary reference method was quite reproducible (±0.5 PV), but relatively insensitive to PV differences at lower (0–2) PV. The FT-NIR method on the other hand was shown to be more accurate overall in tracking PV, but slightly less reproducible (0.9 PV) due to working close to the limit of detection. The sensitivity and reproducibility of the FT-NIR method could be improved upon through the use of larger-diameter vials combined with a detector having a wider dynamic range. The proposed FT-NIR PV method is simple to calibrate and implement and can be automated to allow for routine quality control analysis of edible fats and oils.     

离心光度法测定铜的研究

研究了铜（Ⅱ）－硫氰酸铜－结晶紫灵敏显色反应和离心光度法测定微量铜的分析条件。在λｍａｘ＝５９８ｎｍ处的表观摩尔吸光系数ε＝２．２４×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，铜（Ⅱ）量在１．００～１４．０μｇ／１０ｍＬ范围内呈线性关系。方法简便，选择性好，用于化学试剂中微量铜的测定，结果满意。     

分光光度法测定甘氨酸钠的含量

本文采用分光光度法对甘氨酸钠的含量进行测定.考察了波长、pH值、显色剂用量、缓冲溶液用量、水浴温度以及水浴时间对测量的影响.在优化的条件下,线性范围为2.0～12.0μg·mL-1(r=0.99962),样品平均回收率为98.4%,相对标准偏差0.41%.     

Determination of peroxide value in thermally oxidized crude palm oil by near infrared spectroscopy

A near infrared (NIR) spectroscopic method was developed to measure peroxide value (PV) in crude palm oil (CPO). Calibration standards were prepared by oxidizing CPO in a fermentor at 90°C. A partial least squares (PLS) calibration model for predicting PV was developed based on the NIR spectral region from 1350 to 1480 nm with reference to single-point baseline at 1514 nm. The optimization of calibration factors was guided by the predicted residual error sum of squares test. The standard error of calibration obtained was 0.156 over the analytical range of 2.17–10.28 PV and the correlation coefficient (R ²) was 0.994. The method was validated with an independent set of samples which was prepared in the same manner on a different day. A linear relationship between the American Oil Chemists’ Society and the NIR methods was obtained with R ² of 0.996 and standard error of performance of 0.17. This study has demonstrated that the prediction of PV in the NIR region is possible. The method developed is rapid, with total analysis time less than 2 min, is environmentally friendly, and its accuracy is generally good for quality control of CPO.     

催化光度法测定超痕量铅

本文在碱性介质plumbum(Ⅱ)中对H2O2氧化还原型酚酞显色反应的催化作用,建立了一个测定超痕量铅的高灵敏催化光度法。反应产物的最大吸收波长位于556nm。大多数常见离子不干扰,该法可用于测定水等试样中的超痕量铅。     

分光光度法测定化妆品中的甲醇

建立了一种1,2-萘醌-4-磺酸钠（NQS）分光光度法直接测定化妆品中甲醇的新方法。研究表明,在pH为13.00的KCl-NaOH缓冲溶液中,甲醇电离生成的甲氧离子（CH₃O^-）能够催化氢氧根离子（OH^-）与1,2-萘醌-4-磺酸钠反应形成橙红色的2-羟基-1,4-萘醌,其最大吸收波长为450nm。甲醇浓度在0.010mg/mL～4.000mg/mL范围内与吸光度呈现良好的线性关系。线性回归方程为A=0.0018+0.1714c（mg/mL）,相关系数为0.9998,检测限为0.005mg/mL。平均回收率在98.5%～105%。依本法取3份样品分别测7次,变异系数为2.5%～4.8%。该方法具有检出限低、快速、准确、灵敏度高以及经济实用等优点。     

可见光分光光度法测定头孢曲松钠

基于头孢曲松钠能被Fe3+氧化,Fe3+被还原为Fe2+,Fe2+与铁氰化钾生成可溶性普鲁士蓝,通过测定生成的普鲁士蓝在733nm处的吸光度,建立了测定头孢曲松钠的新方法。头孢曲松钠含量在0.11~7.20μg·m L-1范围内与吸光度呈良好线性关系,线性回归方程A=0.2717ρ(μg·m L-1)+0.0325,相关系数R=0.9992,表观摩尔系数ε=1.8×105L·(mol·cm)-1。测定了市售头孢曲松钠粉针剂的含量,平均回收率为100.5%,结果令人满意。     

Determination of individual tocopherols by derivative spectrophotometry

The second order derivative UV spectra of α-, β-, γ- and σ-tocopherols showed small differences that allowed development of a derivative spectrophotometric method for determining individual tocopherols in a mixture. The procedure consists of measuring the second derivative spectrum of the sample at four specified wavelengths and calculating each concentration by means of a method for multicomponent analysis that uses mixtures as standards. Vegetable oils and other fatty products usually require a previous clean-up process (under study) in order to remove interfering substances.     

直接分光光度法测定高铁酸盐的含量

采用直接分光光度法对高铁酸盐含量进行了研究,改进了高铁酸盐溶液的预处理方法,考察了影响高铁酸盐溶液稳定性和测定结果的主要因素,如高铁酸盐溶液的pH、溶剂和溶液温度等。结果表明,采用G4型玻璃砂芯漏斗过滤法对高铁酸盐溶液预处理后,用质量分数为2%的次氯酸钾溶液为稀释溶剂,当温度低于20 ℃时,在其最大吸收波长505 nm处测定,可以获得准确的测定结果。     

5-Br-PADAP分光光度法测定微量铁

研究了 Fe( ) - 5- Br- PADAP体系的反应条件 ,在 p H=5.5时 ,Fe( ) -5- Br- PADAP能形成稳定的紫红色配合物 ,可用于试样中微量铁的快速测定 ,方法选择性好 ,灵敏度高 ,在波长 555nm处测量 ,表观摩尔吸光系数为 7.9× 1 0 P4。     

分光光度法测定苯中的微量氯

用分光光度法测定苯中微量Cl-含量;用亚沸水萃取苯,待水静置分层后用硫氰酸盐分光光度法对其中的微量氯进行测定。方法的回归方程为Y=0.0013C,相关系数为0.9962,回收率为93.3%~97.6%,相对标准偏差为4.1%。     

动力学光度法测定糖中的痕量钴

在NH3-NH4Cl缓冲液中,柠檬酸存在下,痕量钴能灵敏地催化H2O2氧化荧光桃红的反应,建立了一种测定痕量钴的新方法。考察了反应的影响因素,研究了该催化反应的最佳条件及动力学参数,探讨了反应机理。该法线性范围为0~0.6μg/10mL,检测限为5.97×10-10g.mL-1。可用于糖中痕量钴的测定。     

阻抑退色光度法测定维生素C含量

基于痕量维生素C能灵敏地阻抑KBrO3与5-溴-(2-吡啶偶氮)-二乙氨基酚(5-Br-PADAP)间的氧化还原反应,建立了分光光度法测定痕量维生素C的新方法.在H2SO4介质和30 ℃条件下,于波长463 nm处,维生素C含量在0.02～0.15 g/L范围内符合比尔定律,检出限为2.62×10-4 g/L.方法用于银翘片和猕猴桃样品中维生素C含量的测定,相对标准偏差分别为2.20%和2.53%,测定结果与碘量法测定结果基本一致,加标回收实验显示回收率在98.1%～100.7%之间.     

分光光度法测定茶叶中微量铅（Ⅱ）

用三氯甲烷作萃取剂,通过Pb2＋和双硫腙的配位显色反应,研究了茶叶中微量铅含量的测定方法。实验结果表明,在pH=10.5的三酸缓冲溶液中,有色溶液的最大吸收波长为510 nm,Pb2＋质量浓度在0 mg/L～2.0 mg/L符合朗伯-比尔定律,加标回收率为98.9%～102.2%,重现性较好。本法用于测定茶叶中的Pb（Ⅱ）,简单易行、结果可靠。     

分光光度法测定油田水样中的硫酸根离子

建立了油田水中SO42-的分光光度测定法。在稀盐酸介质中BaCrO4与SO42-反应生成BaSO4沉淀,并定量置换出CrO42-。溶液经煮沸,并调节至碱性,以沉淀过量的BaCrO4,离心分离后,于420 nm处以试剂空白作参比,测定上清液中CrO42-的吸光度。硫酸根浓度在8.0~120μg/mL范围内符合比耳定律,检出限为4.0μg/mL,相对标准偏差为2.84%(n=8),回收率在97.0%~103%。     

邻菲罗啉分光光度法测氯乙烯单体中含铁

介绍了用邻菲罗啉分光光度法对氯乙烯单体中铁含量的测定方法,并就吸收曲线、邻菲罗啉铁络合物的稳定性、显色剂浓度对照试验、邻菲罗啉与铁的摩尔比、溶液酸度对络合物的影响以及共存离子消除等条件进行了探讨,以更好地满足实际检测工作的需要。     

分光光度法测定湿法磷酸中二氧化硅

以草酸为掩蔽剂,消除PO_4~(3-)及Fe~(3+)对分光光度法测定SiO_2的干扰,通过实验得出分光光度法测定湿法磷酸中SiO_2含量的方法。结果表明,显色剂钼酸铵10 mL,掩蔽剂草酸10 mL,显色时间30 min,加标回收率在95%~105%;结果较重量法、容量法更加准确。该法快速、便捷,有一定的应用价值。     

分光光度法测定纺织品中可萃取重金属铜

采用超声萃取-分光光度法测定了模拟人工汗液条件下纺织品中可萃取重金属铜的含量。研究了模拟汗液条件下显色反应及测定的最佳条件(λmax=435 nm,V NaOH=0.54 mL,V显色剂=1.0 mL),并进行了加标回收实验。结果表明,该法测定结果准确、操作简便、快速,可用于纺织品中重金属铜的测定。     

分光光度法测定L-天冬氨酸锰中锰的含量

本文介绍了分光光度法测定L-天冬氨酸锰中锰含量的方法,L-天冬氨酸锰首先在浓H2SO4-H2O2体系中消化,然后在H3PO4-KIO4的氧化体系中,于526nm处测定吸光度。在2.0~20μg.mL-1线性范围内与吸光度呈良好的线性关系,线性方程为:A=39.77162C-0.00475,相关系数r=0.99999,样品平均回收率为99.7%,标准偏差0.14%。     

催化光度法测定水中痕量银

建立了催化光度法测定水中痕量银的方法,讨论了影响指示反应的最佳条件。结果表明,Ag浓度在0～40μg·L-1范围内符合比尔定律,用于水中的痕量银的测定,回收率均在97%以上,样品的相对标准偏差RSD4%。