Chlorotrimethylsilane as a reagent for gas chromatographic analysis of fats and oils

Chlorotrimethylsilane can be used as a reagent to transform triglycerides into volatile fatty esters. The volatile esters can then be analysed by GC. The results are fully comparable to those obtained by alternative methods used worldwide. The new one-step method can transesterify acylglycerides and esterify free fatty acids at the same time. Chlorotrimethylsilane is cheaper than BF3-MeOH and is likely to permit the use of different alcohols.     

An infrared spectroscopic method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils

A new infrared spectroscopic method suitable for determining total fatty alcohol and fatty acid ester concentrations in industrial oils has been developed. Oil samples were diluted with toluene (1:3 w/w), the toxicity and volatility of which are relatively low compared with more commonly used IR solvents, like carbon tetrachloride or carbon disulfide. Mixture standards were prepared from dodecanol, tetradecanol, octadecanol, methyl stearate and methyl palmitate. Some analytical and statistical tests were performed on the developed method. The recoveries and the repeatability of the method proved to be sufficient for the quantitative determination of fatty alcohol and fatty acid ester additives in industrial oils. Reproducibility testing in another laboratory also produced satisfactory results. The developed method also proved to be relatively quick and simple. This method was developed to satisfy industry’s need to determine the concentrations of these oil additives, and it has already been applied successfully in machinery oil analysis.     

A rapid and reliable direct method for quantifying meat acylglycerides with monomode microwave irradiation

A rapid methodology for direct analysis of meat acylglycerides is proposed. A transesterification is carried out in a microwave reactor consisting of a monomode oven using chlorotrimethylsilane (CTMS) and methanol. High-temperature gas chromatography was used to check the absence of underivatized acylglycerides. Whereas transesterification is complete after 30 s at 90 °C in the microwave method, the reference method needs 2 h to complete this process. Moreover, the CTMS–microwave method shows higher recoveries of individual saturated, monounsaturated and polyunsaturated fatty acids. No influence of microwave irradiation on the composition of the fatty acids was observed.     

Trimethylsulfonium hydroxide as derivatization reagent for the chemical investigation of drying oils in works of art by gas chromatography

A procedure for the determination of fatty acids (FA) and glycerol in oils has been developed. The method includes a derivatization step of the FAs into their methyl esters or a transesterification of the triacylglycerols with trimethylsulfonium hydroxide (TMSH), respectively. The analysis is carried out by gas chromatography with parallel flame ionization and mass spectrometric detection. The parameters involved in the transesterification reaction were optimized. Only the stoichiometric ratio of TMSH:total FA amount showed a significant influence on the reaction yield. Relative standard deviations for 10 replicates were below 3% for all FAs studied and their linearity range was 0.5-50 mmol/L, when using heptadecanoic acid as an internal standard. The final procedure was rapid and required little sample handling. It was then tested on fresh oil samples and presented satisfying results, in agreement with previous works.     

Comprehensive two-dimensional liquid chromatography×gas chromatography: evaluation of the applicability for the analysis of edible oils and fats

Edible fats and oils are complex mixtures containing a wide range of (classes of) compounds. The most important group of compounds are the triglycerides (triacylglycerides, TAGs). Because of the large number of possible fatty acid combinations, an enormous number of TAGs is possible. In the present feasibility study, the applicability of different modes of comprehensive two-dimensional LC×GC for detailed oil and fat analysis is evaluated. Comprehensive LC×GC was found to be an extremely powerful analytical method for the analysis of complex TAG samples. Using the new comprehensive set-ups, TAGs can be separated according to two independent parameters: carbon number vs. number of double bonds, or fatty acid composition vs. number of double bonds. The information content of comprehensive separations by far exceeds that of the current generation of analytical methods. The quantitative results of the separations show a good agreement with data obtained from standard analytical methods. The comprehensive methods studied can also be used for fingerprinting of oil samples, as well as for the analysis of target compounds or compound groups. Highly detailed separations of olive oil samples were obtained. Zooming in on one region of the chromatogram allowed reliable analysis of wax esters without interferences of sterol esters.     

Elucidation of fatty acid profiles in vegetable oils exploiting group-type patterning and enhanced sensitivity of comprehensive two-dimensional gas chromatography

The present research is focused on the use of comprehensive 2-D GC (GCxGC) for the thorough elucidation of fatty acid (FA) profiles contained in vegetable oils; the samples analysed consisted of extra-virgin olive oil and refined hazelnut oil. The enhanced sensitivity and the formation of group-type patterns provided by GCxGC enabled the identification and quantification of both well-known and rather unexpected FAs contained in the lipid matrices. Peak assignment was, in most cases, supported by using pure standard compounds. Of particular interest was the identification of a series of odd-numbered FAs in both samples. The results attained to demonstrate the usefulness of GCxGC also for the analysis of supposedly low-complex samples.     

Development and application of an analytical method for the determination of storage lipids, fatty acids and fatty alcohols in Calanus finmarchicus

A method was developed for the determination of the major storage lipids, wax ester and triglycerides, in the copepod Calanus finmarchicus. A variation of the Folch method was used to extract the lipid. The method was scaled down to enable the extraction of either pooled (-1 mg) or individual (approximately 200 microg) copepods. The major lipid classes were identified using TLC and quantified using HPLC coupled with evaporative light scattering detection. Analysis of laboratory reference materials indicated that this method underestimated the minor triglyceride component, but gave a good estimate of the major wax ester component. The fatty acid and fatty alcohol composition of the C. finmarchicus were determined following trans-esterification of the lipid extract in methanol. Fatty acids and fatty alcohols were initially identified by comparison with authentic standard and by mass spectroscopy. Using GC with flame ionisation detection the normalised area percentage of the fatty alcohols and fatty acid methyl esters was determined simultaneously in one run for either pooled or individual copepod samples. These methods were applied to C. finmarchicus collected from the Irminger Sea, North Atlantic in 2001 and 2002.     

The use of high performance liquid chromatography for the quality survey of frying fats and oils

Summary During the process of deep fat frying the frying fat or oil undergoes complex chemical reactions which lead to its deterioration. For the quality survey of frying fats or oils the time-consuming determination of total polar components by column chromatography is an approved standard method. High performance liquid chromatography (HPLC) can be used to substitute this technique. Moreover, HPLC proved to be a useful tool for the determination of the qualitative and quantitative composition of fatty acid and polar substances which change during the frying process. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Rapid procedure for the isolation and analysis of fatty acid and fatty alcohol fractions from wax esters of marine zooplankton

A rapid and simple method for the isolation of fatty acid methyl esters and fatty alcohols from the lipid fraction of marine zooplankton is described. Wax esters are the dominant lipid class in most calanoid copepods and trans-esterification results in a high fatty alcohol content in the analytical extract. Current procedures for the separation and purification of lipid classes by preparative thin-layer chromatography are time-consuming and are subject to low recovery of the analytes. In this method, fatty acid methyl esters and fatty alcohols were separated by liquid chromatography using silica or honded amino-silica as the stationary phase. The procedure is equally applicable to the analysis of zooplankton with low wax ester (and hence fatty alcohol) content, for example, a number of species of euphausiid and, generally, for samples of low mass.     

Fast GC for the analysis of fats and oils

Fast and conventional GC techniques were both applied to ten different lipidic matrices and the results then compared. The fats and oils were of fish, animal, and vegetable origin and were all simultaneously transesterified with acidic methanol before performing batch analysis of the fatty acid methyl esters (FAMEs) obtained. All FAMEs samples were consecutively analyzed three times by each method. The fast method significantly reduced the time required for analysis by a factor of 5 while maintaining a similar resolution. Furthermore, the reproducibility of relative quantitative data was measured on going from one method to the other. Peak identification was achieved through conventional GC‐MS in combination with linear retention index values contained in a home library and information derived from comprehensive 2D GC group patterns.     

A novel infrared spectrophotometric method for the rapid determination of petroleum hydrocarbons, and animal and vegetable oils in water

To determine the concentrations of total oils,petroleum hydrocarbons,and animal and vegetable oils in water,the conventional analytical methods involve two scans as well as a step of magnesium silicate adsorption to remove the animal and vegetable oils in water samples.In this study,a novel analytical method was developed to determine the above oils in wastewater samples through just one scan—the concentration of animal and vegetable oils,and that of total oils were determined by measuring the absorbance of the >C=O bond in the peak area between 1750 cm and 1735 cm^-1,and of the C-H bond at 2930 cm^-1,2960 cm,and 3030 cm^-1,respectively.The concentration of petroleum hydrocarbons was then calculated by subtracting the concentration of animal and vegetable oils from that of total oils.Compared with the well-known analytical method GB/T 16488-1996,the novel approach displayed similar accuracy in the quantitative determination of oils in wastewater samples,but significantly reduced material cost and operation time.     

A capillary electrophoresis-tandem mass spectrometry methodology for the determination of non-protein amino acids in vegetable oils as novel markers for the detection of adulterations in olive oils

A new analytical methodology based on capillary electrophoresis-mass spectrometry (CE-MS(2)) is presented in this work, enabling the identification and determination of six non-protein amino acids (ornithine, β-alanine, GABA, alloisoleucine, citrulline and pyroglutamic acid) in vegetable oils. This methodology is based on a previous derivatization with butanol and subsequent separation using acidic conditions followed by on-line coupling to an ion trap analyzer for MS(2) detection established through an electrospray-coaxial sheath flow interface. The electrophoretic and interface parameters were optimized obtaining the separation of all compounds in less than 15 min and with resolutions higher than 5. The proposed method was validated by assessing its accuracy, precision (RSD<7% for corrected peak areas), LODs and LOQs (between 0.04-0.19 ng/g and 0.06-0.31 ng/g, respectively) and linearity range (R(2)>0.99), and it was used in order to identify the selected non-protein amino acids in soybean oils, sunflower oils, corn oils and extra virgin olive oils. MS(2) experiments performed the fingerprint fragmentation of these compounds allowing to corroborate ornithine and alloisoleucine in seed oils but not in olive oils. The method was applied to identify and quantify olive oil adulterations with soybean oil detecting in a single run the amino acids in mixtures up to 2% (w/w). The results showed a high potential in using these compounds as novel markers for the detection of adulterations of extra virgin olive oils with seed oils. Thus, the developed method could be considered a simple, rapid and reliable method for the quality evaluation of extra virgin olive oil permitting its authentication.     

Ozonolysis of olefins,V: Emulsion ozonization of methyl linoleate and methyl linolenate in aqueous alkaline hydrogen peroxide

Summary The ozonolysis of methyl linoleate and methyl linolenate in neutral and alkaline aqueous emulsions of hydrogen peroxide was investigated. Besides the expected products such as dimethyl malonate (3b), dimethyl azelate (3h) and methyl hexanoate (2a) further homologous methyl esters of dicarboxylic acids (3a–g), oxo carboxylic acids (4a, b, e–h) and hydroxy carboxylic acids (4c, d) could be detected by GC/MS analysis. Furthermore a method for separation of 8-hydroxyoctanoic acid (4d) by methylation and extraction of the reaction mixture containing the ozonolysis products is described.

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Ozonolyse von Olefinen, V: Ozonolyse von Linol-und Linolensäuremethylester in wäßriger alkalischer Emulsion von Wasserstoffperoxid

Zusammenfassung Die Ozonolyse von Linol- und Linolensäuremethylester wurde in neutraler bzw. alkalischer wäßriger Emulsion von Wasserstoffperoxid untersucht. Dabei wurden im Reaktionsgemisch mittels GC/MS neben Malonsäuredimethylester (3b), Azelainsäuredimethylester (3h) und Hexansäuremethylester (2a) weitere homologe Dicarbonsäuren (3a–g), Oxocarbonsäuren (4a, b, e–h) und Hydroxycarbonsäuren (4c, d) nachgewiesen. Weiters wurde eine Methode ausgearbeitet, mit der es gelang, 8-Hydroxyoctansäure (4d) — eine hinsichtlich ihrer biologischen Aktivität bedeutende Verbindung — durch Methylierung und Extraktion aus dem Reaktionsgemisch abzutrennen.

     

Quantification of fatty acids as methyl esters and phospholipids in cheese samples after separation of triacylglycerides and phospholipids

Determination of the individual fatty acid composition of neutral- and phospholipids as well as the phospholipid content of dairy food and other foodstuffs are important tasks in life sciences. For these purposes, a method was developed for the separation of lipids (standards of triolein and diacylphosphatidylcholines as well as three cheese samples) by solid-phase extraction using a self-packed column filled with partly deactivated silica. Non-halogenated solvents were used for the elution of the lipid classes. Cyclohexane/ethyl acetate (1:1, v/v) served for the elution of neutral lipids, while polar lipids were eluted with three solvents (ethyl acetate/methanol, methanol, and methanol/water) into one fraction. The separated lipid fractions were transesterified and the individual fatty acids were quantified by using gas chromatography coupled to electron ionization mass spectrometry (GC/EI-MS) in the selected ion monitoring (SIM) mode. The recovery rate for standard phosphatidylcholines was ∼90% and cross-contamination from neutral lipids was negligible. The method was applied to cheese samples. Quantitative amounts of individual fatty acids in the phospholipid fraction were <0.002-0.29% of total lipids from camembert, <0.002-0.12% of total lipids from mozzarella, and <0.002-0.18% of total lipids in a goat cream cheese. Differences in the fatty acid pattern of neutral and polar lipids were detected. The quantity of the fatty acids determined in the phospholipid fraction was divided by the factor 0.7 in order to convert the fatty acid content into the phospholipid content of the cheese samples. This factor is based on the contribution of 16:0 to dipalmitoylphosphatidylcholine (DPPC). The resulting DPPC equivalents (DPPC_eq) were found to be representative for the average contribution of fatty acids to all classes of phospholipids in dairy products. Using this approach, the phospholipid content of lipids from mozzarella, camembert, and goat cream cheese was 0.60%, 1.42% and 0.79%, respectively.     

Gas chromatography-mass spectrometry coupled with pseudo-Sadtler retention indices, for the identification of components in the essential oil of Curcuma longa L.

Gas chromatography-mass spectrometry was applied to the cyclohexane extract of Curcuma longa L. The chromatographic conditions generated retention indices very close i.e., greater than 99.9%, to those reported for structures in the Sadtler Standard Gas Chromatography Retention Index Library. In addition to the extensively reported sesquiterpene ketones, this essential oil extract contained a series of saturated and unsaturated fatty acids. Wiley mass spectra library matching for the free fatty acids, their trimethylsilyl esters and methyl esters narrowed their identity down to a few candidates. Combining this information with the retention indices of the fatty acid methyl esters in the Sadtler library allowed the identification of some of the double bond positions.     

(Vapor + liquid) equilibrium for the binary systems {water + glycerol} and {ethanol + glycerol, ethyl stearate, and ethyl palmitate} at low pressures

This work reports the experimental measurements {(vapor + liquid) equilibrium} for the systems {water(1) + glycerol(2)}, {ethanol(1) + glycerol(2)}, {ethanol(1) + ethyl stearate(2)}, and {ethanol(1) + ethyl palmitate(2)}. Boiling temperatures were measured using an Othmer-type ebulliometer over a pressure range of 14 kPa to 96 kPa. The experimental data were well correlated using the NRTL and UNIQUAC models. The performance of the UNIFAC-Dortmund model in relation to predicting the phase equilibrium of the systems was also studied.     

酸性酯交换-气相色谱-质谱法同时测定植物油中氯丙二醇酯和缩水甘油酯

建立了一种气相色谱-质谱同时测定植物油中3-氯丙二醇酯、2-氯丙二醇酯和缩水甘油酯的方法.称取0.25 g样品,依次加入内标工作液、四氢呋喃和酸性溴化钠溶液,50℃水浴反应15 min,加入6 g/L碳酸氢钠溶液终止反应,使用正己烷提取,上层液经氮气吹干后用四氢呋喃溶解.随后加入1.8％(v/v)硫酸-甲醇溶液于40℃...     

GC-MS法鉴别食用油和餐饮业中废弃油脂的研究

用气相色谱 质谱联用(GC MS)方法对7种餐饮业中废弃油脂(简称废油脂)和5种合格成品食用油(简称食用油)中所有脂肪酸进行分析。研究发现,废油脂中部分不饱和脂肪酸受到氧化,使脂肪酸相对不饱和度(U R)值明显小于同种类食用油中的脂肪酸相对不饱和度(U R)值,其脂肪酸的质量分数分布与同种类的食用油中脂肪酸的质量分数分布有很大的区别,以及绝大部分废油脂中存在较大量矿物油。研究表明,脂肪酸相对不饱和度(U R)值和脂肪酸的质量分数分布可以鉴别废油脂。     

GC-FTIR and GC-MS in odour analysis of essential oils

The analysis of odour components in East Indian Sandalwood Oil (Santalum album L.) and in Patchouli Oil (Pogostemon cablin Benth.) based on GC-, GC-FTIR- and GC-MS-data resulted in the identification of-santalene,-santalal,-santalal, epi--santalal,-santalol,-santalol, (E)--santalol,-bergamotol and spirosantalol in Sandalwood Oil and of (–)-patchoulol,-guaiene,-patchoulene, seychellene,-bulnesene, norpatchoulenol and pogostol in Patchouli Oil as the most intense aroma compounds of these oils.