Methyl nonadecanoate

A methodological approach for the simultaneous quantification of glycerol and fatty acids from cork suberin in a single GC run.[Pubmed:31215088]

Phytochem Anal. 2019 Nov;30(6):687-699.

INTRODUCTION: Suberin, as part of plant protective barriers, is one of the most important natural polymers after cellulose and lignin. For a full elucidation of suberin structure the quantification of glycerol, fatty alpha,omega-diacids and omega-hydroxyacids, the major building blocks of suberin, is of primary importance. Glycerol is often lost in the most used analytical procedures or rarely determined by deficient or too laborious techniques. OBJECTIVES: Propose a simple, accessible and reliable methanolysis work-up procedure for an accurate and simultaneous quantification of glycerol and suberin fatty monomers in the same GC run. MATERIAL AND METHODS: Cork from Quercus suber L. was depolymerised by methanolysis. Glycerol was derivatised to an organic soluble form before the suberin monomers recovery in water/organic solvent partition. Gas chromatography flame ionisation detector (GC-FID) response factors were determined for glycerol, ferulic acid and one for each fatty monomer substructure. Additionally, 1,2,4-butanetriol and Methyl nonadecanoate were used as internal standards. RESULTS: The proposed experimental approach allowed the glycerol and all the fatty suberin monomers in the same GC run to be quantified accurately. Glycerol represented 30.6 area%, 14.2 mass% and 38.4 molar% of suberin and the COOH/OH groups ratio was 0.6:1 in the proposed experimental approach in contrast with 0.10 area% and COOH/OH ratio of 3:1 in the most used protocol. Furthermore, omega-hydroxyacids/alpha,omega-diacids mass ratio was 1:1 as opposed to an area ratio of 1.5:1. CONCLUSION: The proposed work-up procedure revealed to be a reliable analytical tool for the complete analysis of suberin allowing the future knowledge to grow towards a better understanding of suberin structure throughout its range and variability.

Development and validation of analytical methodology by GC-FID using hexadecyl propanoate as an internal standard to determine the bovine tallow methyl esters content.[Pubmed:30015311]

J Chromatogr B Analyt Technol Biomed Life Sci. 2018 Sep 1;1093-1094:134-140.

EN 14103:2003 and EN 14103:2011 were developed in order to determine fatty acid methyl ester (FAME) content of biodiesel. The internal standards (IS) of biodiesel include methyl heptadecanoate (MHD) and Methyl nonadecanoate (MND), respectively. However, since these ISs are also present in bovine tallow methyl esters (BTME) or overlapping peaks, they have not been efficient. This work proposes an improved BTME determination method by using hexadecyl propanoate (HDP) as an IS. For this purpose, an analytical methodology by Gas Chromatography-Flame Ionization Detector (GC-FID) was developed and validated, where HDP demonstrated selectivity in retention time between peaks C16:1 and C18:0 for coconut and soybeans methyl esters and BTME, as well as resolution >1.5 for the BTME in split mode 30:1. Trueness in the determination of BTME content using the HDP as an IS was statistically equivalent to confidence interval of 95% for the null hypothesis statistic test, even when only 20% of the HDP was utilized in comparison with the IS concentrations defined by EN 14103:2003 and EN 14103:2011. This allowed the biodiesel analysis to be performed five times more with 1g of HDP. Furthermore, the method developed enabled us to reduce the analysis time by 21.6%, without prejudice to the integration of peaks (C6:0 to C24:1). Regarding the repeatability and intermediate precision tests, results of RSD (%)

A flow-based procedure exploiting the lab-in-syringe approach for the determination of ester content in biodiesel and diesel/biodiesel blends.[Pubmed:28738622]

Talanta. 2017 Nov 1;174:556-561.

The ester content is an important parameter to be monitored in biodiesel for evaluation of the transesterification reaction yield and for assessing the purity of the final product. This is also a relevant quality parameter in diesel/biodiesel blends to avoid frauds, because legislation establishes a minimum amount of biodiesel to be added to diesel. The official method EN14103 requires the addition of an alternative internal standard (Methyl nonadecanoate) for analysis of biodiesel from bovine tallow because the methyl heptadecanoate is found in high amounts in this product. In this work, it is proposed a fast, simple, practical, and environmental friendly flow-based spectrophotometric procedure, which exploits the formation of the violet complex between Fe(III) and the hydroxamate generated by the reactions of the alkyl esters with hydroxylamine. All involved steps are carried out inside the syringe pump of a sequential injection analyzer (lab-in-syringe approach). A single phase is attained by using ethanol as mediator solvent between the organic sample and aqueous soluble reagents. Linear responses for biodiesel samples and diesel/biodiesel blends were obtained from 4-99%(v/v) to 2.0-40%(v/v) methyl esters, described by the equations: A = 0.342 + 0.00305C (r = 0.997) and A = 0.174 + 0.00503C (r = 0.999), respectively. The analytical curve can be obtained by in-line dilution of a methyl linoleate stock solution. For biodiesel samples, the coefficient of variation (n = 10), limit of detection (99.7% confidence level), and sampling rate were estimated at 0.8%, 0.36%(v/v), and 15h(-1), respectively, whereas the corresponding values for the blend samples were 0.20%, 0.03%(v/v), and 12h(-1), respectively. The procedure consumes only 860mug of hydroxylamine, 366mug of Fe2(SO4)3.H2O, and 2.0mL ethanol and generates ca. 3.0mL of residue per determination. The results agreed with those obtained by official methods EN14103/2011 e EN14078, at the 95% confidence level.

Improved gas chromatography-flame ionization detector analytical method for the analysis of epoxy fatty acids.[Pubmed:24161147]

J Chromatogr A. 2013 Nov 29;1318:217-25.

In this study an improved method for analysis of epoxy fatty acids is reported. Data obtained from analysis of polar fatty acids has previously been presented, but due to the high number of compounds that co-elute in the polar fraction, the resultant chromatograms are complex which may lead to compromising the accuracy of the data. A three steps separation of fatty acid methyl esters (FAMEs) by solid-phase extraction (SPE) on a silica gel column to remove hydroxy fatty acid interferences was proposed. This approach is opposed to a two step separation procedure that has been often used to prevent analytical interferences caused by non-altered fatty acids. A gas chromatograph with a flame ionization detector (GC-FID) equipped with a polar CP-Sil 88 column was used. Quantification was based on the use of Methyl nonadecanoate (C19:0), as an internal standard. Individual mono epoxy fatty acids were well separated without co-eluting compounds. The optimized method was finally applied to screen epoxy fatty acids in 37 fresh oil samples. Results obtained for the total epoxy fatty acids were in the range 0.03-2mgg(-1) of oil with repeatability coefficient of variation (CV) ranging from 2.8 to 9.9% for duplicate analysis showing that the results obtained are repeatable.

Synthesis and surface properties of new ureas and amides at different interfaces.[Pubmed:16460082]

Langmuir. 2006 Feb 14;22(4):1619-25.

The influence of the urea and amide group in the alkyl chain of Methyl nonadecanoate on the surface properties is investigated and compared. For that purpose, the ureas CH3O2C-(CH2)m-NHCONH-(CH2)n-CH3 (n + m = 14) [1 (m = 2), 3 (m = 3), and 5 (m = 4)] and the amides CH3O2C-(CH2)m-NHCO-(CH2)n-CH3 (n + m = 15) [2(m = 2), 4 (m = 3), and 6 (m = 4)] were synthesized. The pi/A isotherms of the ureas show up to the attainable temperature of 313 K no LE phase, which indicates a very stable LC phase. The amides exhibit a two phase plateau region, with the exception of 2. The different behavior is connected with the hydrogen bond energies, which are stronger with the ureas in the LC than in the LE phase, whereas those of the amides have a similar strength in both phases. The effect of hydrogen bonds in self-assembled molecules of N,N'-dialkylurea CH3-(CH2)m-NHCONH-(CH2)n-CH3 (m + n = 14) [7 (n = 2)] was visualized by STM at the octylbenzene/graphite interface. Compound 7 forms a lamella structure with a periodicity of one molecule length. The tilt angle of 86 degrees +/- 2 degrees to the edge of the lamella points to a nearly orthogonal arrangement of the molecules. It indicates two equivalent bonds between the aza-hydrogens and the carbonyl oxygen. A similar arrangement is proposed for the LC phase of the ureas at the air/water interface.