Accurate determination oftrans isomers in shortenings and edible oils by infrared spectrophotometry

A procedure is described for the accurate analysis of thetrans content of fats and oils in the range of 0.5–36%trans. This procedure is shown to be more accurate than other current infrared spectrophotomeny methods. This increased accuracy is obtained by using a 2-component calibration standard mixture and measuring the samples as methyl esters. Good agreement between this method and the measurement oftrans content by a gas chromatography procedure is demonstrated.     

A rapid method for the determination oftrans unsaturation in fats and derivatives

Thetrans unsaturation present in samples of unsaturated fats and derivatives may be determined from measurement of the infrared absorbance at two wavelengths, one due totrans configuration of a double bond and the other due to the ester or acid group. The ratio of the two absorbance values has a linear relationship with thetrans unsaturation content. Thus, a drop of sample is diluted with CS₂ and the infrared absorbance measured at 10.36 μ and at 8.5–8.6 μ if esters and 10.7 μ if acids. To calculate the per cent isolatedtrans double bonds in the sample, the ratio of the two absorbance values is substituted into the linear equation which was developed from known samples. The method is rapid since the sample need not be weighed nor made up to a known volume and thus may be applied to samples such as those collected from a gas chromatograph or after thin layer chromatography. Presented at the AOCS Meeting, New York, October 1968.     

The application of packed column gas chromatographic analysis to the determination oftrans unsaturation

A study of the separation of synthetic mixtures ofcis andtrans methyl octadecenoate with packed column gas chromatography indicated its usefulness for such analyses. Several margarines were analyzed by this method and the results compared with those obtained by the infrared spectroscopic method. Reasonable agreement between both methods was obtained, but the gas chromatographic determination yielded lower values (average 3.8%). The presence oftrans unsaturation was also shown in selected samples of human milk and blood lipids.     

红外分光光度法测定水中石油类的不确定度评定

介绍了红外分光光度法测定水中石油类的方法原理,分析过程中不确定度的来源,介绍了不确定度分量的评定,合成标准不确定度的计算,扩展不确定度测评以提高测试结果的准确度。     

A rapid method for the estimation oftrans unsaturation in hydrogenated oils and fats

Glycerides and methyl esters of fatty acids containingtrans unsaturation both show peaks at 10,38 μ. The absorptivities of the glycerides (a_10.38 μ) have a straight line relationship with the concentration of thetrans unsaturation, calculated as methyl elaidate. This relationship has been utilized as a quick method for estimating thetrans unsaturation in hydrogenated fats such as Vanaspati. The infrared spectrum of a given hydrogenated fat is taken in the region of 9–11 μ, the absorptivity at thetrans-peak is calculated, and the corresponding methyl elaidate content is read from a graph.     

Determination ofcis unsaturation in oils by near infrared spectroscopy

An analytical method has been developed capable of giving reproducible and accurate determinations of thecis unsaturation present in refined oils, hydrogenated oils, and finished shortenings. Molar absorptivity measurements indicate that similar methods are applicable to the analyses of mixed esters or fatty acids. The method depends upon the measurement of a band in the near infrared at 2.143 μ that is caused bycis unsaturation. The following pertinent conclusions are drawn from data obtained in this investigation.

1. The areas under the absorption bands forcis polyenes are integral multiples of the areas under the bands ofcis monoenes.
2. Thecis content of oils containing less than 10%trans triglycerides can be determined accurately by measuring the area under the absorption band.
3. Accurate results can be obtained for samples containing quantities oftrans fatty acids in excess of 10% if a point baseline is used and the peak absorbance measured.

     

油标对红外光度法测定水中油的影响

油标准物质的选择是红外分光光度法测定水中油的重要环节,选择了两种不同的油标,采用红外分光光度法对水中油进行了分析,结果表明,油标不同,测量结果不同。理想的油标是从待测水样中提取,这样的油标的组成才能与被测水样中油的组分相同,红外光谱图基本相同,测定结果才准确可靠。     

Simplified method for the determination oftrans monoenes in edible fats by TLC-GLC

Several modifications of an established thin-layer chromatography-gas-liquid chromatography (TLC-GLC) procedure for quantitatingtrans unsaturated fatty acids in edible fats are presented. These refinements considerably simplify the procedure without affecting accuracy. The modifications include: i) the use of pre-coated silica sheets, dynamically impregnated with Ag⁺, which allow separated bands to be cut off with a pair of scissors; and ii) the use of stearic acid in the deliberately combined saturated andtrans monounsaturated fatty acid methyl ester bands as an (endogenous) internal standard.Trans values thereby obtained agree favorably with the results from the conventional technique.     

微乳液增溶导数分光光度法直接测定水中可溶性磷酸盐

研究了在OP微乳液的作用下，用一阶导数磷钼蓝分光光度法直接测定水中可溶性磷酸盐的最佳条件。OP微乳液大大改变了磷钼蓝的最大吸收波长，并提高了测定的稳定性和灵敏度。本法可有效地消除硅、砷和悬浮物等的干扰，其服从比耳定律的线性范围为0-1.92mg/L，检出限为0.007mg/L，加标回收率在98％－101％之间，测定准确、快速。     

Comparison of FTIR and capillary gas chromatographic methods for quantitation oftrans unsaturation in fatty acid methyl esters

A computer-assisted method has been developed for estimation of isolatedtrans unsaturation using the peak area of thetrans absorbance band at 966 cm-1from FTIR spectra of fatty acid methyl esters. Peak areas were used to determine thetrans content of weighed standards containing from 0 to 100% methyl elaidate and of hydrogenated soybean oil samples containing up to 36%trans unsaturation. These data for percenttrans by FTIR were compared to corresponding data obtained by capillary gas chromatography and the AOCS Official Method 14-61. Determination of isolatedtrans composition in oils using peak areas gave values with the smallest standard deviation for weighed standards and values within 4% of those obtained by capillary gas chromatography and the AOCS Official Method for hydrogenated samples. Presented at the AOCS meeting in Phoenix, AZ in May 1988. To whom correspondence should be addressed.     

红外分光法测定水中石油类

用多波长红外分光测油仪测定水中石油类，灵敏度高，所以测定结果准确，操作简单，方法线性好。文中测定了该方法的准确度及精密度。     

Separation of triglycerides by chain length and degree of unsaturation on silica HPLC columns

Triacylglycerols can be separated by both chain length and number of double bonds using micro particulate silica high pressure liquid chromatography columns with isooctane, diethyl ether, and acetic acid solvent mixtures. The separations obtained are the reverse of those observed with μ-Bondapak C₁₈ columns (Waters Associates); i.e., longer chain length triglycerides elute from the column earlier than their shorter chain homologs, and saturated triglycerides elute before the more unsaturated ones. Base line separation was obtained between tristearin, triolein, trilinolein, and trilinolenin. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Quantitative determination of unsaturation in oils by using an automatic-titrating hydrogenator

A procedure was developed to adapt an automatic-titrating hydrogenator to the rapid determination of unsaturated carbon-carbon bonds in seed oils. Its utility as a research tool for detecting unusual types of unsaturation was demonstrated by analysis of 35 oils. When the hydrogen-iodine value of an oil determined by the hydrogenator differed significantly from the iodine value by the Wijs method, the presence of unsaturation such as acetylenic or conjugated double bonds was indicated. For repetitive analysis of samples of the same oil, or of oils having nearly the same extent of unsaturation, the hydrogenator can successfully accomodate injection of a new sample every 2 to 5 min. Possible utility of the method for monitoring samples from a processing plant is apparent. Biometrical Services, ARS, USDA. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Gas chromatographic separation of triglycerides based on their degree of unsaturation

Gas liquid chromatographic separation of long chain triglycerides based on their degree of unsaturation has been carried out on a polar siloxane, SILAR 10C. The equivalent chain lengths of triglycerides with 36–54 acyl carbons and 0–9 double bonds are presented. The resolution of triglycerides of coconut oil by combining argentation thin layer chromatography and gas chromatography on SILAR 10C is described.     

Detection and measurement of hydroperoxides by near infrared spectrophotometry

Summary Near-infrared spectra have been measured on a group of hydroperoxides of fatty acid esters and related substances. Only those substances having an −OOH group were found to absorb at 1.46 and 2.07 μ. Dialkyl peroxides and ozonized unsaturated substances had no such maxima in their near infrared spectra although they had high iodometric peroxide values. In a study of the thermal decomposition of methyl oleate hydroperoxide and a study of the autoxidation of methyl linoleate, the intensity of absorption at 1.46 and 2.07 μ paralleled the iodometric peroxide value. This work was aided by grants-in-aid from the Hormel Foundation, the Atomic Energy Commission (Contract AT-11-1-108), the Office of Naval Research (Contract N8 onr66218), the National Live Stock and Meat Board, and the National Diary Council. Hormel Institute Publication No. 170.     

紫外分光光度法快速测定伊马替尼含量

建立一种快速检测和定量测定伊马替尼含量的方法。以含1‰三氟乙酸的乙腈溶液溶解伊马替尼碱后,采用紫外分光光度法,在272 nm处对溶液中伊马替尼含量进行测定。结果表明,伊马替尼浓度在1.5~15.0μg/m L范围内,与吸收值的线性关系良好(R~2=0.999 73),平均加标回收率为100.20%(RSD=0.11%,n=9)。该方法快速、简便、准确、重现性好,可用于伊马替尼产品的质量控制。     

紫外分光光度法快速测定伊马替尼含量

建立一种快速检测和定量测定伊马替尼含量的方法。以含1‰三氟乙酸的乙腈溶液溶解伊马替尼碱后,采用紫外分光光度法,在272 nm处对溶液中伊马替尼含量进行测定。结果表明,伊马替尼浓度在1.5¹5.0μg/m L范围内,与吸收值的线性关系良好(R15.0μg/m L范围内,与吸收值的线性关系良好(R²=0.999 73),平均加标回收率为100.20%(RSD=0.11%,n=9)。该方法快速、简便、准确、重现性好,可用于伊马替尼产品的质量控制。     

橡胶不饱和度的化学法测定

介绍了橡胶不饱和度的测定方法,卤化法测定具有简便、快速和实用的特点。     

Semiautomatic analysis of serum triglycerides and cholesteryl esters by infrared absorption

An instrument has been developed for the semiautomatic analysis of mixtures of triglycerides and cholesteryl esters. The method is based on high-resolution infrared spectrophotometry, and has previously been shown to be applicable to the determination of these components in the nonionic fraction of human serum lipids. A simple nonrecording grating spectrophotometer has been suitably modified to carry out this analysis; and appropriate computing circuitry has been coupled with it for performing the two-component calculation. The supplementary electronics consist of operational amplifiers, a logarithmic conversion circuit, a digital voltmeter, and a printer. Automatic operation is accomplished by a control mechanism, which programs the measurements, the steps in the calculations, and print-out of the results. Sample preparation consists of an extraction of lipids from serum in such a way as to exelude phospholipids. This may be done in a single step, although a two-step procedure—total lipid extraction followed by adsorption separation of the phospholipids—appears to be more reliable. Measurements are made on a solution of the neutral lipid fraction in carbon tetrachloride.