HPLC of fatty acid esters of mono- and polyhydric alcohols. Part 1: Analytical separation

This paper shows how simply and yet very rapidly fatty acid esters of monohydric alcohols, but particularly partial and full fatty acid esters of fully hydric alcohols can be separated and determined by means of high-pressure liquid chromatography on LiChrosorb RP-8 with methanol/water. We have separated quantitatively the methylesters of the fatty acids C_8:0 to C_22:0 and C_24:0, the i-propyl-, i-butyl-, n-hexyl- and i-octyl-esters of the even-numbered fatty acids C_8:0 to C_18:0, mono- and difatty acid esters of the 1,3-bis-(2-hydroxyethyl)-5,5-dimethyl-hydantoin, mono-, di- and triesters of the trimethylolpropane as well as the tetraesters of the penta-erythrite.     

Analysis of anthropogenic and biogenic lipids in the aerosol of a coastal area in East Mediterranean Sea

Summary The concentrations of lipids were determined in atmospheric particle samples, collected seasonally, in an urban coastal area of the Island of Crete. Lipid compound classes, such as n-alkanes, hopanes and steranes, PAH, fatty alcohols, fatty acids and fatty acids selts, were determined by GC-FID and GC-MS analysis. The concentrations ranged between 56–215 ng/m³ for n-alkanes, 10–52 ng/m³ for PAH, 2–31 ng/m³ for fatty alcohols, 13–279 ng/m³ for fatty acids and 24–220 ng/m³ for fatty acid salts. -Oxocarboxylic acids were also determined as salts, indicating the atmospheric oxidation of unsaturated fatty acids.     

Metabolites of the marine sponge <Emphasis Type="Italic">Suberites cf. aurantiacus</Emphasis>

Fractions of free sterols and sterol esters were observed in the ethylacetate extract of the marine sponge Suberites cf. aurantiacus and their compositions were determined. It was found that cholesterol was the predominant component in all sterol forms. The esters had a high content of unsaturated long-chain fatty acids (C₂₄–C₂₆). Sterol acetates have not been previously observed in marine invertebrates.     

Capillary GC Determination of Short-Chain Dicarboxylic Acids in Rain,Fog, and Mist

Abstract

A capillary GC and GC-MS method, employing dibutyl esters is described for determining short-chain dicarboxylic acids in rain, fog and mist samples collected in the Los Angeles area. Approximately twenty dicarboxylic acids (C₂-C₁₀) were identified in the water samples, including cis (maleic) and trans (fumaric) unsaturated, saturated, normal, branched and aromatic. Oxalic acid is the dominant acid, followed by succinic and malonic acids. The total concentrations measured are 2.9–51μM, 64–66 μM and 12 μM for rain, fog and mist samples, respectively. These diacids are probably produced by photooxidation of anthropogenic and possibly biogenic organic compounds in the atmosphere.     

Solid-phase microextraction and gas chromatography–mass spectrometry for rapid characterisation of semi-hard cheeses

A headspace solid-phase microextraction (HS-SPME) method in combination with gas chromatography–mass spectrometry (GC–MS) has been used for extraction and identification of components of the volatile fraction of Provola dei Nebrodi, a typical semi-hard Sicilian cheese. Cheese samples from different producers and at different ripening stages have been examined. The effects of various conditions (e.g. sample volume, sample headspace volume, sample heating temperature, extraction time, etc.) on extraction efficiency were studied in order to optimise the technique. The technique used made it possible to identify 61 components: fatty acids from C₂ to C₁₄ and their esters, aldehydes, alcohols, methyl ketones, -lactones, aromatic compounds, hydrocarbons and terpenes. The main components were butanoic, hexanoic and octanoic acids. The linear free fatty acids (FFA) from C₂ to C₁₀ were quantified by using the standard addition method. Calibration curves constructed for the FFA spiked into cheese were highly linear with a correlation coefficient R²>0.998. Significant statistical differences (P0.05) were evident for the even-carbon-number fatty acids during ripening.     

Selectivity and efficiency enhancement of supercritical fluid extraction by application of reactive additives. I. The analysis of calcium montanate using citric acid as a complexing agent

It has been demonstrated that calcium montanate (a mixture of aliphatic hydrocarbons, fatty acid esters of C₂₈–C₃₂ acids, the calcium salts of these fatty acids, and the acids themselves) can be selectively extracted with supercritical fluids. By use of carbon dioxide, carbon dioxide containing 10% methanol, and carbon dioxide containing 10% methanol and citric acid (as a further additive), the various compound classes could be isolated with high selectivity. The addition of citric acid results in the complexation of Ca²⁺ and the simultaneous formation of the free fatty acids, which are soluble in the extractant.     

Nonglyceride complex of the seed oil ofOnopordum acanthium

Extraction of the comminuted seeds has yielded an oil from which have been isolated: C₃₃-C₂₅, C₁₈ and C₁₇ paraffinic hydrocarbons, C_18:1, C_18:2, C_18:3, C_17:1, C_17:2 and C_17:3 olefinic hydrocarbons, ethyl esters of C_32:0, C_31:0, C_30:0, C_29:0, and C_28:0 fatty acids, sterols with molecular weights of 414, 412, and 400, and the alcohols α-amyrin and lupeol with their natural acetates. Extraction of the uncomminuted seeds has shown that the paraffinic hydrocarbons, ethyl esters, and alcohol acetates pass into the oil from the husks of the seeds. This is the first time that the C_31:0 and C_29:0 fatty acids have been detected as natural compounds, and it is the first time that the ethyl esters of C₃₄, C₃₃, C₃₂, C₃₁, and C₃₀ fatty acids have been isolated from seed oils of higher plants.     

Recycling HPLC of p-Bromophenacyl Esters of Saturated C35–56 Fatty Acids from Mycobacterium Tuberculosis H37Ra on a Silica Column

Abstract

The p-bromophenacyl esters of saturated C_35–56 fatty acids from Mycobacterium tuberculosis H37Ra were separated according to structural classes on a silica column by high performance liquid chromatography (HPLC). The sample was cycled five times during HPLC. Highly purified C_35–38 esters were obtained by this method. Further HPLC fractionation on a reverse-phase column (C₁₈-bonded silica) gave complete separation of most of the remaining fractions. By combining mass spectrometry with HPLC separations, many of the fatty acid esters were tentatively identified.     

Determination of fatty acids in atmospheric samples via GC/MS

Summary Atmospheric precipitation and aerosol samples are characterized by a complex mixture of several organic compounds. A simple method for the simultaneous determination of the main compound classes by GC/MS is presented. In detail, seasonal variations of C₈–C₃₂ fatty acids in precipitation in a semirural area have been studied. Total fatty acids concentrations of 7–53 g/l were detected. Summer rain is characterized by high amounts of fatty acids >C₂₀ and lower amounts of C₁₁–C₂₀ species. Two effects may be responsible: larger emission rates of fatty acids during vegetation periods and an increased influence of vapour phase due to higher temperatures during summer. CPI values showed no general trend; lower CPI values for winter rain could not be observed. This would be expected if anthropogenic sources play an important role. Monounsaturated fatty acids (C_16:1, C_18:1) were more abundant during winter than in summer. High concentrations of polyunsaturated fatty acids (C_18:x) could be detected during summer. High relative concentrations of the potential oxidation products of the unsaturated species, nonanedioic acid and w-oxononanoic acid, are associated with relatively low concentrations of their precursors.     

Forensic differentiation of biogenic organic compounds from petroleum hydrocarbons in biogenic and petrogenic compounds cross-contaminated soils and sediments

“Total petroleum hydrocarbons” (TPHs) or “petroleum hydrocarbons” (PHCs) are one of the most widespread soil pollutants in Canada, North America, and worldwide. Clean-up of PHC-contaminated soils and sediments costs the Canadian economy hundreds of million of dollars annually. Much of this activity is driven by the need to meet regulated levels of PHC in soil. These PHC values are legally required to be assessed using standard methods. The method most commonly used in Canada, specified by the Canadian Council of Ministers of the Environment (CCME), measures the total hydrocarbon concentrations in a soil by carbon range (Fraction 1: C₆–C₁₀; Fraction 2: C₁₀–C₁₆, Fraction 3: C₁₆–C₃₄: and Fraction 4: C₃₄+). Using the CCME method, all of the materials extractible by a mixture of 1:1 hexane:acetone are considered to be petroleum hydrocarbon contaminants. Many hydrocarbon compounds and other extractible materials in soil, however, may originate from non-petroleum sources. Biogenic organic compounds (BOCs) is a general term used to describe a mixture of organic compounds, including alkanes, sterols and sterones, fatty acids and fatty alcohols, and waxes and wax esters, biosynthesized by living organisms. BOCs are also produced during the early stages of diagenesis in recent aquatic sediments. BOC sources could include vascular plants, algae, bacteria and animals. Plants and algae produce BOCs as protective wax coating that are released back into the sediment at the end of their life cycle. BOCs are natural components of thriving plant communities. Many solvent-extraction methods for assessing soil hydrocarbons, however, such as the CCME method, do not differentiate PHCs from BOCs. The naturally occurring organics present in soils and wet sediments can be easily misidentified and quantified as regulated PHCs during analysis using such methods. In some cases, biogenic interferences can exceed regulatory levels, resulting in remediation of petroleum impacts that are not actually present. Consequently, reliance on these methods can trigger unnecessary and costly remediation, while also wasting valuable landfill space. Therefore, it is critically important to develop new protocols to characterize and differentiate PHCs and BOCs in contaminated sediments. In this study, a new reliable gas chromatography–mass spectrometry (GC–MS) method, in combination with a derivatization technique, for characterization of various biogenic compounds (including biogenic alkanes, sterols, fatty acids and fatty alcohols) and PHCs in the same sample has been developed. A multi-criteria approach has been developed to positively identify the presence of biogenic compounds in soil and sediment samples. More than thirty sediment samples were collected from city stormwater management (SWM) ponds and wetlands across Canada. In these wet sediment samples, abundant biogenic n-alkanes, thirteen biogenic sterols, nineteen fatty carboxylic acids, and fourteen fatty alcohols in a wide carbon range have been positively identified. Both PHCs and BOCs in these samples were quantitatively determined. The quantitation data will be used for assessment of the contamination sites and toxicity risks associated with the CCME Fraction 3 hydrocarbons.     

Lipids of the petals ofCarthamus tinctorius

The following compounds have been identified in the lipids of the petals ofCarthamus tinctorius: C₃₂ and C₂₉ isoparaffins; free fatty acids, the main component of which is palmitic acid; 33 esters of phytol, esterified with three groups of fatty acids — paraffinic, isoparaffinic, and monoenoic of the C₉–C₂₆ series; and β-sitosterol and its β-D-glucopyranoside.     

Catalytic Ethanolysis of Kraft Lignin into High‐Value Small‐Molecular Chemicals over a Nanostructured α‐Molybdenum Carbide Catalyst

We report the complete ethanolysis of Kraft lignin over an α‐MoC_1?x/AC catalyst in pure ethanol at 280 °C to give high‐value chemicals of low molecular weight with a maximum overall yield of the 25 most abundant liquid products (LP25) of 1.64 g per gram of lignin. The LP25 products consisted of C₆–C₁₀ esters, alcohols, arenes, phenols, and benzyl alcohols with an overall heating value of 36.5 MJ kg^?1. C₆ alcohols and C₈ esters predominated and accounted for 82 wt % of the LP25 products. No oligomers or char were formed in the process. With our catalyst, ethanol is the only effective solvent for the reaction. Supercritical ethanol on its own degrades Kraft lignin into a mixture of small molecules and molecular fragments of intermediate size with molecular weights in the range 700–1400, differing in steps of 58 units, which is the weight of the branched‐chain linkage C₃H₆O in lignin. Hydrogen was found to have a negative effect on the formation of the low‐molecular‐weight products.     

Nonglyceride complex of the seed oil ofOnopordum acanthium

Extraction of the comminuted seeds has yielded an oil from which have been isolated: C₃₃-C₂₅, C₁₈ and C₁₇ paraffinic hydrocarbons, C_18:1, C_18:2, C_18:3, C_17:1, C_17:2 and C_17:3 olefinic hydrocarbons, ethyl esters of C_32:0, C_31:0, C_30:0, C_29:0, and C_28:0 fatty acids, sterols with molecular weights of 414, 412, and 400, and the alcohols -amyrin and lupeol with their natural acetates. Extraction of the uncomminuted seeds has shown that the paraffinic hydrocarbons, ethyl esters, and alcohol acetates pass into the oil from the husks of the seeds. This is the first time that the C_31:0 and C_29:0 fatty acids have been detected as natural compounds, and it is the first time that the ethyl esters of C₃₄, C₃₃, C₃₂, C₃₁, and C₃₀ fatty acids have been isolated from seed oils of higher plants.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 612–615, September–October, 1979.     

Lipids of the fruit of Feijoa sellowiana

The composition and amounts of liposoluble substances in the flesh and peel of feijoa fruit has been investigated. About 30 groups of lipid substances have been identified. The main groups of lipids in the flesh were triacylglycerols, sterols, cerebrosides, ceramide phosphate inositol oligosides, sulfoquinovosyldiacylglycerols, phosphatidic acids, phosphotidylglycerols and phosphatidylcholines. In the peel, hydrocarbons, sterols, esters of fatty acids and lower alcohols, cerebrosides, digalactosyldiacylglycerols, ceramide oligosides, phosphatidylglycerols, and include predominated. The fatty acids of the flesh were found to include 15 representatives (C_12:0–C_28:0), and those of the flesh 11 representatives tives (C_12:0–C_18:3).M. V. Lomonosov Technological Institute of the Food Industry, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 464–467, July–August, 1991.     

Lipids of the fruit of Feijoa sellowiana

The composition and amounts of liposoluble substances in the flesh and peel of feijoa fruit has been investigated. About 30 groups of lipid substances have been identified. The main groups of lipids in the flesh were triacylglycerols, sterols, cerebrosides, ceramide phosphate inositol oligosides, sulfoquinovosyldiacylglycerols, phosphatidic acids, phosphotidylglycerols and phosphatidylcholines. In the peel, hydrocarbons, sterols, esters of fatty acids and lower alcohols, cerebrosides, digalactosyldiacylglycerols, ceramide oligosides, phosphatidylglycerols, and include predominated. The fatty acids of the flesh were found to include 15 representatives (C_12:0–C_28:0), and those of the flesh 11 representatives tives (C_12:0–C_18:3). M. V. Lomonosov Technological Institute of the Food Industry, Odessa. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 464–467, July–August, 1991.     

An improved derivatization method for sensitive determination of fatty acids by high-performance liquid chromatography using 9-(2-hydroxylethyl)-carbazole as derivatization reagent with fluorescence detection

Summary Tagging techniques with reagents used for fluorescent detection for short and long-chain fatty acids using high-performance liquid chromatography are evaluated in terms of the tagging reactions, handing, flexibility, stability of the reagents. Emphasis is given to the applications of the tagging techniques to relatively high molecular mass fatty acids. The fatty acids or carboxylic compounds were derivatized to their corresponding esters with 9-(2-hydroxy ethyl)-carbazole (HEC) in acetonitrile at 60°C with N, N′-carbonyldiimidazole (CDI) as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters of C₁−C₂₀ fatty acids was completely separated with 45 min using gradient elution on a reversed-phase C₁₈ column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (λ_ex 293 nm). Studies on derivatization conditions indicated that fatty acids react rapidly and smoothly with HEC in the presence of CDI and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility for fatty acids derivatives. The relative standard deviations (n=6) for each fatty acid derivative are <5.0%. The detection limits are at 38–57 fmol levels for C₁₄−C₂₀ fatty acids and lower levels for <C₁₄ fatty acids.     

Separation of a Homologous Series of Long-Chain Fatty Alcohols (C49-C58) From Mycobacterium Tuberculosis H37Ra by High Performance Liquid Chromatography

Abstract

Fatty alcohols were obtained from the saponified chloro-form-methanol extract of Mycobacterium tuberculosis H37Ra by extraction with diethyl ether and partially purified by silicic acid column chromatography. The long-chain fatty alcohols (C₄₉-C₅₈) were separated from the shorter-chain alcohols by Sephadex LH-20 column chromatography and further fractionated into saturated and unsaturated alcohols by argentation thin-layer chromatography. These two fractions were analyzed by proton nuclear magnetic resonance spectro-scopy, derivatized to the 3,5-dinitrobenzoyl esters, and fractionated on a C₁₈-bonded silica column by high performance liquid chromatography (HPLC). Complete separation of esters differing by two carbon units and partial separation     

Identification,quantification and Chrastil modelling of wheat straw wax extraction using supercritical carbon dioxide

Supercritical carbon dioxide (scCO₂) can be used as a “green” selective solvent for extractions of wheat straw waxes. For the first time, the crude extraction yields of wheat straw waxes and the yields of a single high value group of components (wax esters) using various scCO₂ conditions (305.15 to 373.15 K and 7.5 to 40 MPa) have been modelled using the Chrastil equation (Chrastil, 1982). The model accurately predicts both the crude yield and percentage of valuable wax esters within the extracts enabling maximum extraction efficiency. The key compounds within the waxes (fatty acids, sterols, fatty alcohols, wax esters, β-diketones and alkanes) have been identified and quantified. This study highlighted that, 14,16 hentriacontanedione was extracted at critical temperature and pressure in concentrations of 1000 μg.g⁻¹ straw. This molecule could demonstrate significant potential as a natural chelate for metal recovery and also in the formation of super-hydrophobic coatings.     

Instrumental HPTLC of Aflatoxins: Fluorescence Enhancement by Corn Free Fatty Acids

Abstract

Greater than 100% recoveries using instrumental HPTLC were observed for aflatoxin (AFT) analysis in spiked corn samples. I₂ detection of spots over-laying AFT B₁ and B₂ were identified by GLC as C₁₆ ^?c18 free fatty acids (FFA). These FFA were found to enchance the fluorescence of AFT B₁ from 13.7% to 35.7% greater than controls resulting in >100% recoveries. The inclusion of glacial acetic acid in the TLC mobile phase resulted in an increased mobility of the FFA which eliminated the positive interference on AFT fluorescence. Recoveries using the modified developing solvent then gave values in acceptable ranges.     

Carbon-13 spin–lattice relaxation in strongly associated molecules: Carboxylic acids

¹³C spin–lattice relaxation times determined for the protonated carbons of carboxylic acids and methyl esters give indications of solution dimerization with the free acids. Since isopthalic and fumaric acids have two carboxyl functions they are able to polymerize in solution. Unlike the case for molecular aggregation due to weak hydrogen bonding in solution (e.g. alcohols, phenols), the ¹³C T₁ values of mono carboxylic acids are not significantly affected by dilution to c. 10^?2 M. Variable temperature T₁ measurements of both the mono and dibasic acids gave activation energies for molecular reorientation of the order of 2 kcal mol^?1, considerably lower than E_a for hydrogen bonded alcohols and comparable with E_a for the unassociated methyl esters of propionic and benzoic acids.