A rapid method for determining the oxidation of n-3 fatty acids

The stability of unsaturated fatty acids to oxidation was monitored by following gas chromatographic (GC) analyses of headspace volatiles in comparison to changes in polyunsaturated fatty acids (PUFA) and increases in malonaldehydevia the 2-thiobarbituric (TBA) assay. Pure standards of linoleic acid (Lo) and n-3 fatty acids [eicosapentaenoic (EPA) and docosahexaenoic acid (DHA)] were added to headspace vials, equilibrated in air for 10 min, followed by heating at 80°C in teflon-capped vials for different time intervals. Headspace analysis showed increases in acetaldehyde, propenal, and propanal, corresponding to the oxidation of n-3 fatty acids, whereas hexanal production corresponded to losses of linoleic acid. The analysis of propanal by GC-headspace after only five minutes of heating appeared to be the most effective method of monitoring the oxidation of n-3 fatty acids, as indicated by correlations between TBA values and loss of PUFA. The oxidation of Lo, EPA and DHA appeared to be a function of the number of double bonds. Correlations between PUFA depletion, TBA values and volatile formation indicate that under the prescribed conditions of this experiment, GC-headspace analysis of propanal and pentane/hexanal is an excellent method for following the oxidation of selected n-3 fatty acids and linoleic acid.     

An automatized method for determination of free fatty acids

An automated colorimetric method is described for determining free fatty acids (FFA) in vegetable oils using the flow injection analysis (FIA) technique. In this procedure, an almost linear relationship exists between the peak height and the FFA concentration. Liquid samples can be poured directly into the sample cups on the sampler for an automatic analysis of the FFA content. The dynamic range of this method is from 0.01 to almost 5%. Samples with higher FFA content must be diluted before analysis. The sample capacity is 12–20 injections/hr. No evidence of the existence of the earlier proposed cage-like complex (Cu(II)(FFA)₂)₂ in the organic phase was observed in this study.     

A rapid low temperature method for preparation of methyl esters of fatty acids

A rapid method for preparation of methyl esters of fatty acids in lipids has been accomplished by forming the sulfuric acid complex of the lipid in ethyl ether at the temp of a dry ice-acetone bath. Decomposition of the complex with methanol results in direct formation of methyl esters of the fatty acids. A comparison was made of gas liquid chromatography (GLC) analysis of fatty acid composition of several fats using methyl esters prepared by this and by two other methods. Results of this comparison reveal that the method is not only rapid but provides complete reaction with no apparent changes in the fatty acids. Mich. Agr. Exp. Sta. Pub. No. 3503. Presented at the AOCS meeting in Chicago, 1964.     

An improved method for the analysis of ruminant fats

A method is described for the separation of saturated methyl esters from mercuric acetate adducts of unsaturated esters using an ion exchange resin. The esters thus separated were analyzed by gas chromatography on a short wide-bore capillary column containing a bonded polyethyleneglycol liquid phase. Detailed analyses of sheep and beef depot fats can be produced more rapidly and with greater accuracy using this methodology than with that currently available.     

An improved micro-extraction cell for supercritical fluid extraction and chromatography of fatty acids

An improved supercritical fluid micro-extraction cell of increased reliability was designed for on-line supercritical fluid extraction and chromatography (SFE/SFC) of food and other lipid-related samples. The key components in the modified cell include a Swagelok stainless steel reducing union with a dual ferrule as the cell, with polyetherether-ketone (PEEK) ferrules and nuts to connect the cell to the control valve. The new cell did not leak under all conditions examined (100–500 atmospheres, 40–80°C), even after numerous extractions (>250). The quantitative performance of the cell was evaluated with fatty acid standard solutions, technical grade fatty acid sources and wheat flour. The percent relative error (%RE) for the fatty acid standards and technical-grade fatty acid samples was ≤6.0% for oleic, linoleic and linolenic acid. The %RE for oleic and linoleic acid in the whole-wheat samples was ≤10%. The results demonstrate that the new extraction cell can be used for quantitative extractions and that the sensitivity of the SFE/SFC technique is excellent. Similar SFE/SFC methods could prove useful in studying the interaction of free fatty acids with various food components such as enzymes, amylose and proteins.     

A simple and rapid colorimetric method for determination of free fatty acids for lipase assay

A simple and rapid colorimetric method was developed to determine the lipase activity for fat splitting. Free fatty acids produced by lipase from triacylglycerols were determined by observing the color developed using cupric acetate-pyridine as a color developing reagent. This modified method requires only a few minutes to determine the free fatty acids, whereas it takes over 20 min by the conventional methods which require solvent evaporation and centrifugation steps. The sensitivity and reproducibility of the method were good for caproic, caprylic, capric, lauric, myristic, palmitic, stearic and oleic acids.     

An improved reversed-phase thin-layer chromatography method for separation of fatty acid methyl esters

Resolution of fatty acid methyl esters (FAME) by thin-layer chromatography often is complicated by co-migration of certain acyl-isomers in heterogeneous mixtures. However, a novel reversed-phase thin-layer chromatography method which employs 10% (wt/vol) silver nitrate in a mobile phase containing acetonitrile/1,4-dioxane/acetic acid (80:20:1, vol/vol/vol) allows one-dimensional resolution of a wide range of acyl-methyl esters. This innovation enables improved separation of saturated FAME ranging from C₁₂ to C₂₂, and geometric isomers of C₁₄ to C₂₂ unsaturated FAME by thin-layer chromatography.     

An improved rapid physicochemical assay method for aflatoxin in peanuts and peanut products

A practical, short cut, sensitive method for more rapidly determining aflatoxin in peanuts and peanut products has been developed. This was in response to the need to reduce the time required for analyses of peanut products in process. Through reductions in solvent volumes, utilization of pressure filtration for clarification, and substitution of liquid:liquid extraction for a lengthy column clean up, equivalent results are possible in less than one half the time required for the current official procedures. Sensitivity, precision and accuracy are comparable to the current methods for raw nuts and peanut butter. It is now possible to analyze a given ground sample of peanuts within a period of less than 90 min and one analyst can assay more than 16 samples within an 8 hr working day. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

The control of fatty acid composition in glycerolipids

The continued suggestion that the ratio of saturated to unsaturated acids in the diet can influence the general health of a mammal is still not easily explained at a biochemical level. Studies on the metabolism of glycerophosphatides show that the enzymes involved appear to differ in the degree of selectivity toward substrates with different amounts of unsaturation. In general, each individual acid will have its own characteristic metabolic fate. The acyl-CoA:acyl-GPC acyltransferases have a marked specificity for both the position to be acylated and the particular acyl-CoA involved. In some cases, the observed distributions of fatty acids in naturally occurring lecithins and triglycerides are similar to the distributions predicted from in vitro studies of the acyltransferase enzymes. Other enzymatic steps, such as acid activation and N-methylation, can also be shown to influence the fatty acid composition of the glycerolipids. The relative importance of these metabolic processes must now be determined.     

异氰酸酯的简单合成法

异氰酸酯是合成磺酰脲类降血糖药物的重要中间体 ,在有机合成中也有着广泛的应用。异氰酸酯有多种制备方法 :( 1 )胺与光气反应 ;( 2 )酰基叠氮物经 Cirtius重排反应制备 ;( 3 )以 CO2 为甲酰化试剂与胺作用 ,经 POCl3 或 P2 O5脱水制备 ;( 4)以 COS为酰化试剂在三乙胺存在下与胺作用 ,再与 Cl COSC2 H5反应制备 ,其中方法 ( 1 )应用较为广泛。我们改变反应溶剂 ,并采用价格相对较低的三光气 (固体光气 )代替常温下为气态的剧毒光气与胺反应。由于三光气为白色或淡黄色固体 ,易于运输、称量 ,因此简化了反应操作条件 ,而且产率较高。…     

Fatty acids: XXIII. A rapid method for the preparation of C18 furanoid fatty ester involving dry-column chromatography

A rapid method for the synthesis of methyl 9,12-epoxyoctadeca-9,11-dienoate from methyl ricinoleate was developed. Methyl ricinoleate was oxidized to the corresponding keto ester, which was treated with mercury (II) acetate to give the required furanoid ester. Dry column silica gel chromatography was used for the purification process and was found to be reliable and efficient.     

An automated gas-liquid chromatographic method of measuring free fatty acids in canola

An automated method for measuring free fatty acids (FFA) in canola seed was developed by using gas-liquid chromatography (GLC). The results from the GLC method were linearly related (r²=+0.98) to those obtained with the traditional method involving Soxhlet extraction followed by a titration. In a nested experiment of over 11 different seedlots, the extraction and injection errors were 0.11 and 0.018%, respectively, of the total variation. The variation attributed to sampling within a seedlot was twice the variation attributed to extraction and injection errors combined. A seed sample size of at least 10 mL was needed to prevent the standard deviation from increasing as the FFA mean increased. The GLC method was precise and rapid, and also identified which fatty acids were being cleaved from the oil, but a linear adjustment improved accuracy.     

An improved mixed anhydride technique for fatty amide synthesis

Amides of fatty acids normally prepared in fair-to-good yield and purity by conventional mixed carboxylic-carbonic anhydride techniques can be prepared in higher yield and improved purity by use of a modified method called “inverse addition.” By reversal of the classical order of mixing of the reactants and, with the use of excess alkyl chlorocarbonate, side reactions are suppressed and yields are improved. ARS, USDA.     

An improved laboratory reattachment method for the rapid assessment of adult barnacle adhesion strength to fouling-release marine coatings

Modifications have been made to the previously described adult barnacle laboratory reattachment method to enhance and improve the overall utility of this technique for rapidly assessing the efficacy of novel fouling-release marine coating technologies. These modifications include the use of an immobilization template to secure barnacles onto the coating surfaces during the underwater reattachment process, the development of a semi-automated push-off device to enable consistent and reproducible force gauge measurements and the implementation of a software tool to measure the diameter of barnacle base plates for adhesion strength calculations. A series of experimental siloxane?Cpolyurethane and control coatings were evaluated with both the original and improved laboratory reattachment methodologies. Significantly higher adhesion strengths were obtained on these coatings using the improved reattachment method. Furthermore, only the improved reattachment method was able to discern significant differences in the performance of the siloxane?Cpolyurethane coatings based on differences in compositional components. In this regard, the siloxane?Cpolyurethane coatings containing the poly-caprolactone end groups attached to the poly(dimethylsiloxane) (PDMS) backbone exhibited significantly higher reattached barnacle adhesion strengths than the aminopropyl-terminated PDMS containing coatings. It was also shown that the utilization of barnacles with 5?C6?mm base plate diameters, rather than 7?C8?mm diameters, significantly enhanced the strength or tenacity of adhesion to the surface of the control coatings. The results of the improved laboratory reattachment evaluation of experimental siloxane?Cpolyurethane and control coatings were in good agreement with barnacle adhesion measurements obtained for the same coatings with static ocean immersion testing in the field.     

单硬脂酸甘油酯合成方法的改进

用丙酮保护的一锅合成法,即通过甘油与丙酮在对甲苯磺酸催化下反应制得异亚丙基甘油,在催化剂如吡啶、乙酸钠、乙醇钠等的催化下与相对便宜的原料三硬脂酸甘油酯反应,无机酸水解后制得单硬脂酸甘油酯。研究了酯化反应过程中物料配比、催化剂类型及用量对反应的影响,结果表明:碱性催化剂中又以吡啶的催化效果最好,n(甘油)∶n(三硬脂酸甘油酯)=1.00∶0.35,吡啶用量为甘油质量的4.0%时,可以得到质量分数为93.86%,收率为86.92%的单硬脂酸甘油酯。     

诺氟沙星合成方法的改进

1-乙基-6-氟-7-氯-1,4-二氢-4-氧代喹啉-3-羧酸与哌嗪在聚乙二醇催化下反应,以高收率得到诺氟沙星。     

An improved instrument for the rapid determination of capacitance in electrochemical systems

The design and operation of an instrument for the direct, continuous monitoring of electrode capacitance under potentiostatic conditions is described. Accurate values of the capacitance can be obtained over two orders of magnitude of capacitance, even in the presence of low parallel resistances.