Quantitative determination of monoglycerides and diglycerides by high-performance liquid chromatography and evaporative light-scattering detection

Neutral lipid classes were separated with normal-phase high-performance liquid chromatography, and mono- and diglycerides were determined with an evaporative light-scattering detector (ELSD). The 1,3-diacylglycerols were resolved from the 1,2-diacylglycerol positional isomers, although some 1,3-diacylglycerols of low molecular weight interfered with the 1,2-diacylglycerols of high molecular weight. For monoglycerides, the separations between 1-(and 3-)acyl and 2-acylglycerols were optimized only between those pairs with identical fatty acyl groups. Samples were dissolved in a solvent mixture and analyzed without derivatization. The results (monoglyceride) obtained from this method agreed well with those derived from gas chromatographic and supercritical fluid chromatographic methods. The universal nature of the ELSD makes this method applicable to oils and emulsifiers containing both saturated and unsaturated fatty acyl moieties.     

Quantitative determination of sodium lauroyl sarcosinate by gas chromatography

A simple and rapid procedure is described for the isolation, silylation and wide-bore capillary gas chromatographic quantitation of sodium lauroyl sarcosinate in personal care products. The sample is dissolved in acidified dimethylformamide to simultaneously acidify/extract the lauroyl sarcosine; an aliquot is then derivatized withbis trimethylsilyltrifluoroacetamide and quantitated by widebore capillary gas chromatography with flame ionization detection.     

Quantitative determination of glycerin in soap by capillary gas chromatography

A simple and rapid procedure is described for the isolation, silylation and capillary gas chromatographic quantitation of the free glycerin content in soap. Free glycerin is determined by mixing the sample with dimethylformamide (DMF), filtering the mixture, silylating an aliquot withbis-trimethylsilyltrifluoroacetamide (BSTFA), and quantitating by capillary GC using flame ionization detection. Silyl derivatization and capillary gas chromatography provide for a quick and easy analysis which allows straightforward automated gas chromatographic analysis instead of the more tedious traditional periodate methods. This procedure also provides reliable quantitation for glycerin levels in soap lower than those measurable with the standard methods.     

The analysis of glycerol by gas chromatography

Commencai glycerol and its organic impurities can be measured accurately by a single gas Chromatographic GC analysis utilizing Tenax-GC® and flame detection.     

Determination of hydroxyls in mono- and diglycerides

A method for the analysis of hydroxyls employing esterification with 3,5-dinitrobenzoyl chloride, followed by titration with tetrabutylammonium hydroxide, has been applied to mono- and diglycerides. Pure mono- and dipalmitins were recovered quantitatively. A commercial glyceryl dioleate was analyzed by this method and the A.O.C.S. pyridine-acetic anhydride procedure with similar results.     

Quantitative determination of BHT in soap products by capillary gas chromatography

A simple and rapid capillary gas chromatography (GC) method is described for the quantitative determination of 2,6-di-tert-butyl-4-methylphenol (BHT) antioxidant in soap bars, fatty acids, and related intermediates. The procedure involves blending the sample with dimethylformamide in the presence of 2,4-di-tert-butylphenol (DTBP) internal standard, filtering the mixture, silylating an aliquot with BSTFA (bis-trimethylsilyltrifluoroacetamide) and quantifying by capillary GC using flame ionization detection. The silyl derivatization and nonpolar capillary column (12 m, methyl silicone, fused silica) provided resolution of BHT from certain fragrance component interferences. The method has a detection limit of approximately 10 ppm. Soaps fortified with BHT showed recoveries of 97.1±3.7% at the 200 ppm level and 92.3 ± 2.2% when spiked at the 75 ppm level. The effect of bar soap storage time on BHT content is also demonstrated.     

Synthesis of mono- and diglycerides in water-in-oil microemulsions

Enzyme-catalyzed esterification was carried out in single-phase, oil-continuous microemulsions. The lipozyme was solubilized, along with glycerol and water, in the aqueous core of water/diethylhexyl sodium sulfosuccinate/hydrocarbon microemulsion system. Upon addition of fatty acid, mono- and diglycerides were formed, due to the esterification reaction taking place at the interface of the droplets in the microemulsion. The initial rate of conversion of oleic acid increases with oil chainlength of the continuous phase whereas final conversion is maximum for hexane. The conversion of stearic acid is 30% whereas conversion of oleic acid is 70%. The percent conversion of various fatty acids in the same continuous medium increases with fatty acid chainlength. The oleic acid/glycerol ratio is an important parameter for optimum conversion of oleic acid into glycerides. The yield can be increased by subsequent addition of glycerol after equilibrium is reached. High-performance liquid chromatography analysis of samples from microemulsions shows the presence of mono- and diglycerides. Possible mechanisms for the abovementioned effects are discussed.     

Quantitative determination of triacylglycerol profile of structured lipid by capillary supercritical fluid chromatography and high-temperature gas chromatography

Two analytical methods have been developed for the qualitative and quantitative analyses of triacylglycerol profile of structured lipid (SL)-containing medium-chain and long-chain fatty acids. Supercritical fluid chromatography (SFC) was used in the first method. The SL was dissolved in chloroform/methanol, 95:5 (vol/vol), and analyzed directly using a super-critical fluid chromatograph equipped with temperature and density programming capabilities. No derivatization was required for sample preparation. An SB-methyl-100 capillary column (10 m, 100 μ i.d., 0.25 μ film thickness) was used for the separation of the triacylglycerol species and a flame-ionization detector (FID) was used for the detection. Supercritical fluid carbon dioxide was used as the mobile phase. In the second method, the SL was hydrogenated to complete saturation prior to analysis using gas chromatography at high temperatures of up to 375°C. A DB-5HT capillary column (30 m × 0.32 mm i.d., 0.1 μ film thickness) was used for the separation. FID was used for the detection and helium gas was used as mobile phase. The triacylglycerol species were separated and identified based on their equivalent carbon number (ECN), the total carbon number of the acyl side chains. A calibration curve was constructed using a triacylglycerol mixture containing known amounts of monoacyltriacylglycerol standard materials ranging from ECN 18 (trihexanoin) to ECN 66 (tridocosanoin). The novel triacylglycerol species, ECN 32–43, created by the interesterification of medium-chain triacylglycerol (MCT) and long-chain triacylglycerol (LCT) were separated and identified based on their retention times. These triacylglycerols, ECN 32–43, were absent in the physical mixture of MCT and LCT. The unique triacylglycerol specieis, ECN 32-43, were therefore selected as the fingerprinting region for the qualitative identification of the SL. Quantitation of the novel triacylglycerol species in the SL was achieved by using the integrated peak area of the new species. Both methods were employed successfully to distinguish the physical mixture from the corresponding interesterified SL. Results generated by the two methods were compared and found to be in good agreement.     

Quantitative determination of antioxidants and ultraviolet stabilizers in polymers by high performance liquid chromatography

The quantitative determination of antioxidants and ultraviolet (UV) stabilizers in a polymer matrix has been standardized using HPLC. The additives were extracted out of the matrix using low boiling solvents in order to minimize the degradation of additives at elevated temperatures. Carbon tetrachloride and tetrahydrofuran have been found to be most suitable solvents for low density polyethylene and polypropylene respectively. The method has been found to be highly reproducible and the standard deviation is very low. This method does not suffer from the problems like overlapping frequencies as observed in spectroscopic methods.     

Quantitative determination of polyethylene glycols in nonionic surfactants by high pressure liquid chromatography

A method employing high pressure liquid chromatography has been developed for the quantitative determination of polyethylene glycols in ethoxylated fatty alcohols and alkylphenols. This technique overcomes many of the limitations encountered in previously-reported methods. The polyethylene glycols are separated from the ethoxylated product and other sample components using a 65/35 acetonitrile/water mobile phase and a Bondapak C₁₈/Corasil reversephase column system. The response factor of the differential refractometer detector is determined using Carbowax standards of appropriate molecular weights. The molecular weight of the polyethylene glycols in each sample is approximated using thin layer chromatography prior to the high pressure liquid chromatography calibration and analysis. The precision of this method for the determination of polyethylene glycols is ± 4% relative or better, and the recovery of added polyethylene glycols is quantitative. Application of this method to a wide variety of commercial ethoxylated fatty alcohols and alkylphenols is presented. Presented at the Meeting of the American Oil Chemists’ Society, April 1976, New Orleans.     

Determination of mono- and diglycerides in palm oil,olein and stearin

Partial glycerides are important constituents of palm oil and can have significant effects on the physical properties of products containing palm oil or on the fractionation of palm oil. A method is described for their routine determination in palm oil. By analysis of 28 weekly composite samples of crude palm oil the following results were obtained: free fatty acids, mean=3.76%, range 2.4 to 4.5%; monoglycerides, mean=0.28%, range 0.21 to 0.34%; diglycerides, mean=6.30%, range 5.3 to 7.7%. During detergent fractionation of palm oil, diglycerides concentrate in the palm olein, but monoglycerides concentrate in the palm stearin. Palm fatty acid distillate was found to contain approximately 3% each of mono- and diglycerides. Because the refining and fractionation processes are continuous in the refinery, it is not possible to follow a single identifiable batch of crude palm oil through the refinery. To circumvent this problem, crude palm oil, stearin and olein from the refinery were bleached and steam refined in the laboratory and the partial glyceride contents determined at each stage of processing. Except for fractionation, the content of glycerides did not change during processing. For oil, olein and stearin, monoglycerides were reduced significantly both after bleaching and after steam refining.     

Rapid determination of free fatty acids in vegetable oils by gas liquid chromatography

Determination of the free fatty acids in small quantities of vegetable oil is accomplished by gas liquid chromatography. The free fatty acids are isolated from a hexane solution of the vegetable oil into an aqueous solution of trimethylphenylammonium hydroxide (TMPH). Due to the alkalinity of TMPH, the free fatty acids readily partition into this aqueous phase. Injection of the free fatty acid-TMPH salts into a gas chromatograph results in pyrolytic methylation of the free fatty acid salts—yielding the methyl esters. Excellent results were obtained when this new procedure was used on neutral lipid oils containing known amounts of free fatty acids and compared with the results obtained by a modified BF₃/MeOH esterification procedure. When compared to the AOCS titration procedure, this new procedure gave comparable results. This new procedure has advantages over the AOCS procedure: it is more sensitive and gives quantitative results for individual free fatty acids. This new procedure also has several advantages over the modified BF₃/MeOH esterification procedure: it is easily and more rapidly performed, there is no deposition of glyceride on the column when the sample is injected, and because there is quantitative recovery, the new procedure is more sensitive and can be used on oils with a low weight percentage of free fatty acids.     

Quantitative analysis of short chain fatty acids using gas liquid chromatography

The short-chain fatty acids, propionic to pelargonic, have been analyzed by gas liquid chromatography, as their butyl, phenacyl, and decyl esters to overcome losses due to their volatility. The three methods are compared and the decyl ester procedure offers the most advantages. Presented in part at the AOCS meeting in Los Angeles, Calif., 1959. Issued as N.R.C. No. 7261. National Research Council of Canada Postdoctorate Fellow 1957–1959.     

Interfacial tension of oil-water systems containing technical mono- and diglycerides

1. Technical mono- and diglyceride products have been prepared from cottonseed oil stearine, and the effectiveness of these products in lowering the interfacial tension at vegetable oil-water interfaces has been investigated.
2. When both monoglycerides and diglycerides are present in the oil phase, the surface activity of the is less than 1/100th that of the monoglycerides on a weight for weight basis; hence the interfacial tension is substantially a function of the monoglyceride content.
3. The interfacial tensions against water of such oils as peanut, cottonseed, and soybean are practically the same, and their interfacial tensions are lowered by practically equal amounts for equal additions of a given monoglyceride preparation.
4. A concentration of 1% of monoglycerides in the oil phase will lower the interfacial tension at the oil-water interface to approximately one-half that which is observed when no monoglycerides are present. A concentration of 6% of monoglycerides in the oil phase will lower the interfacial tension approximately to zero.

     

Ethanolysis of rapeseed oil: Quantitation of ethyl esters,mono-, di-, and triglycerides and glycerol by high-performance size-exclusion chromatography

High-performance size-exclusion chromatography (HPSEC) was used to evaluate the influence of different variables affecting the transesterification of rapeseed oil (RSO) with anhydrous ethanol and sodium ethoxide as catalyst. The effect of temperature, ethanol/RSO molar ratio, catalyst concentration, and time can be interpreted by observing the variations of the reaction medium composition. HPSEC has made the quantitation of ethyl esters, mono-, di-, and triglycerides and glycerol possible. The best results for laboratory-scale reactions were obtained at 80°C with a 6:1 molar ratio of EtOH/RSO and 1% of NaOEt by weight of RSO.     

气相色谱法同时测定敌百虫和毒死蜱的含量

使用1m×3mm(id)的玻璃柱,内填3%OV 17/ChromosorbWAW DMCS,以4,4'二异丙基联苯为内标物,采用FID检测器和柱程序升温,对试样中的敌百虫和毒死蜱进行分离和定量测定。方法的线性相关系数为0.9997,敌百虫的相对标准偏差为0.45%,毒死蜱为0.69%,敌百虫的回收率为99.5～100.1%,毒死蜱为99.6～100.2%。本法适用于4.5%混配剂中敌百虫和毒死蜱含量的测定。     

Quantitative gas chromatography,using retention times

Diffusion of an injected sample within a gas chromatographic column does not begin from a point source but from a band. Therefore the method of calculating relative areas by using retention time × peak height may require a correction factor to give a more accurate estimate of peak areas. When this correction was applied, the analysis was comparable with that obtained by the more time-consuming triangulation method.     

Quantitative analysis of copolyamides and copolyesters by gas chromatography

Procedures were developed for the analysis of copolyesters and copolyamides by saponification or hydrolysis of the copolymers to their component dicarboxylic acids, glycols, amino acids, or diamines and quantitatively identifying these by gas chromatography. The alcohols, amines and acids were converted to volatile trimethylsilyl derivatives for the analysis, and linear correlations were observed between carbon atom contents of these derivatives and retention times in the chromatograph.     

Analysis of whole beeswax by gas liquid chromatography

Gas liquid chromatographic analysis of unfractionated beeswax (treated with diazomethane) using Dexsil 300 as liquid phase gives a good separation of hydrocarbons, free fatty acids as methyl esters, and long chain monoesters. These components can be estimated using internal standards and together account for ca. 65% of the wax. Petroleum hydrocarbon or fatty acid adulterants can be detected. Unsaturated hydrocarbons are partially resolved from the corresponding saturated compounds. Issued as NRCC No. 12775.