Layer Chromatography-flame Ionization Detection Research Articles

Thin-Layer Chromatography–Flame Ionization Detection

Thin layer chromatography–flame ionization detection (TLC–FID) is a versatile analytical technique that can be used for fast analysis of organic compounds. It has been implemented in past decades for the analysis of lipids and petrochemical products, but rarely in other fields. Despite the improvement in the latest Iatroscan model and the introduction of an automatic programmable sample spotter, this system is still struggling to gain acceptance in universities and major research laboratories. The reason behind this might be a lack of awareness on the potential application of this system to other fields of analytical chemistry. This review presents TLC–FID as a mature and reliable, state of the art technique that combines the separation power of TLC with FID as a universal detector, which can be applied to the analysis of a wide variety of organic compounds. Basic operational procedures and previous literature, including its potential for ultrafast analysis of commercial samples, are discussed in order to create awareness on the potentials of this piece of equipment to other fields.

Production of monoolein from oleic acid and glycerol in supercritical carbon dioxide media: A kinetic approach

Esterification of free fatty acids (FFA) with glycerol in supercritical carbon dioxide (SC-CO 2) media to produce designer monoacylglycerols (MAG) for food, cosmetic, and pharmaceutical industries, was conducted to elucidate the reaction kinetics and provide the reaction mechanism. Reactions were conducted in SC-CO 2 at 10–30 MPa, 170–250 °C in a batch stirred reactor using an anhydrous glycerol to oleic acid initial molar ratio (gly/oleic) of 10:1, 1:1 and 1:2 and in supercritical nitrogen at 10 MPa and 250 °C using 10:1 gly/oleic. Samples were collected as a function of time and MAG, diacylglycerol, triacylglycerol and FFA concentrations were determined using thin layer chromatography–flame ionization detection. The rate of MAG formation at 50% of equilibrium concentrations (Rate-50%) increased significantly ( p ≤ 0.05) with temperature but was not affected by pressure or supercritical media ( p > 0.05). Rate-50% values for 10:1 and 1:1 gly/oleic were similar ( p > 0.05) but higher ( p ≤ 0.05) than that for 1:2 gly/oleic. Equilibrium concentration of MAG significantly ( p ≤ 0.05) decreased with decreased initial glycerol concentration. The calculated rate constants provided a better understanding of the mechanism and are essential for optimal process design.

Kinetic modeling of glycerolysis–hydrolysis of canola oil in supercritical carbon dioxide media using equilibrium data

Glycerolysis–hydrolysis reactions to produce monoacylglycerol (MAG) and diacylglycerol (DAG) used in the production of functional foods and nutraceuticals were conducted in supercritical carbon dioxide (SC-CO 2) media to elucidate the reaction kinetics, provide the reaction mechanism and assess the potential catalytic agent involved. Reactions were conducted in an electrically heated, magnetically stirred autoclave at 250 °C, 10–30 MPa, anhydrous glycerol/canola oil molar ratio of 34:1 and initial water content of 0 to 8% (w/w). Reactions were also conducted in supercritical nitrogen at 250 °C, 10 MPa, and 8% (w/w) initial water. Samples were collected as a function of time and the concentrations of MAG, DAG, free fatty acids (FFA) and triacylglycerol (TAG) were obtained using thin layer chromatography–flame ionization detection. The maximum rate of MAG formation at 20 MPa was significantly higher ( p ≤ 0.05) than that at 30 MPa, but similar ( p > 0.05) to that at 10 MPa; a finding that has economical impact because a pressure of 10 MPa can be reached without the use of a high-pressure pump. Rates of MAG formation in SC-CO 2 and -N 2 media were similar ( p > 0.05) thereby demonstrating that SC-CO 2 does not contribute to catalysis. The maximum rate of MAG production at 10 MPa was significantly higher ( p ≤ 0.001) for reaction with 4% (w/w) initial water compared with anhydrous reactions and was significantly lower ( p ≤ 0.05) compared to that of reaction with 8% (w/w) initial water. Although this study was unable to identify the catalytic reagent, it did show that water played an important role. Reactions were carried out up to 14 h and equilibrium was reached at 9 h. The average equilibrium composition (mol%) obtained at 9–10 h for the reactions conducted at 10–30 MPa with 4–8% (w/w) water was 66–71% MAG, 13–15% DAG, 13–17% FFA and 0–1% TAG. A MAG concentration of >65% is higher than that obtained in conventional glycerolysis where the concentration of MAG generally does not exceed 58%. Such findings not only demonstrate improved yields but also lead to a better understanding of the complex mechanisms of simultaneous glycerolysis–hydrolysis reactions and are critical for optimal process design targeting the MAG and DAG products.

Lipid content and composition of dominant copepods in the Oyashio waters analyzed by the thin layer chromatography flame ionization detection method

Lipid content and composition of some dominant copepods inhabiting the Oyashio waters were analyzed by the thin layer chromatography flame ionization detection (TLC/FID) method. Copepod samples were collected dur- ing the RV Shoyo-maru cruise from September 18 to October 15 in 1988. A new three-step development: the first in hexane and diethyl ether (66 : 4, v/v), the second in hexane, diethyl ether and formic-acid (55 : 15 : 0.5) and the last in hexane and benzene (1 : 1), single scan method by TLC/FID was found to be useful for separation and analysis of lipids in boreal copepods. As a result, the eight species of calanoid copepods analyzed in this study could be divided into two groups according to their lipid class proportions. One group consisted of copepods containing many wax esters and in- cludes Neocalanus flemingeri, N. cristatus, Pseudocalanus minutus, Metridia pacifica and M. okhotensis. The other group containing many triglycerides includes Eucalanus bungii, Pleuromamma abdominalis and Acartia omorii. I have deduced that copepods storing wax esters could have long periods of dormancy in winter and consume lipids mainly for reproduction, while copepods storing triglycerides could overwinter without a period of dormancy and be opportunistic

Ultrasound extraction and thin layer chromatography–flame ionization detection analysis of the lipid fraction in marine mucilage samples

This paper reports an analytical procedure based on ultrasound to extract lipids in marine mucilage samples. The experimental conditions of the ultrasound procedure (solvent and time) were identified by a FT-IR study performed on different standard samples of lipids and of a standard humic sample, before and after the sonication treatment. This study showed that diethyl ether was a more suitable solvent than methanol for the ultrasonic extraction of lipids from environmental samples because it allowed to minimize the possible oxidative modifications of lipids due to the acoustic cavitation phenomena. The optimized conditions were applied to the extraction of total lipid amount in marine mucilage samples and TLC–flame ionization detection analysis was used to identify the relevant lipid sub-fractions present in samples.