Chromatographic analyses of fatty acid methyl esters by HPLC-UV and GC-FID

Abstract

Um método analítico por cromatografia líquida de alto rendimento com detecção ultravioleta (HPLC-UV) (método A) foi utilizado na determinação simultânea dos valores totais de triacilglicerídeos, diacilglicerídeos, monoacilglicerídeos e ésteres metílicos de ácidos graxos na alcólise de diferentes óleos (algodão, canola, girassol, milho e soja). As análises foram realizadas a 40 °C por 20 min usando gradiente de metanol (MeOH) e 2-propanol-hexano 5:4 (v/v) (PrHex): 100% de MeOH em 0 min, 50% de MeOH e 50% de PrHex em 10 min mantido com eluição isocrática por 10 min. Outro método por HPLC-UV (método B) com eluição isocrática de acetonitrila por 34 min foi utilizado na determinação da composição de ácidos graxos de óleos analisando seus derivados de éster metílico. Os conteúdos foram analisados com satisfatória repetibilidade (desvio padrão relativo, RSD < 3%), linearidade (r 2 > 0,99) e sensibilidade (limite de quantificação). O método B foi comparado com o método oficial cromatográfico gasoso com detecção através de ionização por chama (GC-FID) da American Oil Chemists' Society (AOCS) na determinação de ésteres metílicos de ácidos graxos (FAME) em amostras reais de biodiesel.An analytical method using high performance liquid chromatography with UV detection (HPLC-UV) (method A) was used for simultaneous determination of total amounts of triacylglycerides, diacylglycerides, monoacylglycerides and fatty acid methyl esters in alcoholysis of different oil (cotton, canola, sunflower, corn and soybean) samples. Analyses were carried out at 40 °C for 20 min using a gradient of methanol (MeOH) and 2-propanol-hexane 5:4 (v/v) (PrHex): 100% of MeOH in 0 min, 50% of MeOH and 50% of PrHex in 10 min maintained with isocratic elution for 10 min. Another HPLC-UV method (method B) with acetonitrile isocratic elution for 34 min was used to determine the fatty acid composition of oils analyzing their methyl ester derivatives. Contents were determined with satisfactory repeatability (relative standard deviation, RSD < 3%), linearity (r 2 > 0.99) and sensitivity (limit of quantification). Method B was compared with an official gas chromatographic method with flame ionization detection (GC-FID) from American Oil Chemists' Society (AOCS) in the determination of fatty acid methyl esters (FAME) in biodiesel real samples.Keywords: biodiesel, triacylglycerides, gas chromatography, liquid chromatography, methyl ester IntroductionThe direct use of fats and oils (mainly composed by triacylglycerides) in diesel engines is problematic and can lead to many problems, such as carbon deposit due to its poor atomization, high viscosity and thickening of lubricating oil as a consequence of its low volatility. 1,2 There are many possible solutions to address the viscosity problem, which are dilution with diesel fuel, microemulsions with short chain alcohols and pyrolysis or transesterification of triacylglycerides. Transesterification is a widespread process used for obtaining biodiesel and involves the catalyzed reaction of triacylglycerides (TAGs) a...

Application of HPLC (High Pressure Liquid Chromatography) for Analysis of Lard in the Meatball Product Combined with PCA (Principal Component Analysis)

“…Many product hydrolyses will detect in analysis TGA using HPLC-UV. This result was reported by Carvalho et al [20] that the HPLC-UV can analyze the methyl ester, free fatty acid, monoglycerides, diglycerides, and TGA with different retention times. Hence, this is evidence to controlling the process of making the meatball.…”

Evaluating the Potential of Biodiesel Production through Microalgae Farming in Photobioreactor and High Rate Ponds from Wastewater Treatment

“…oil, it was analyzed the final composition of the sample by high performance liquid chromatography (HPLC) using a method published elsewhere. 13 The reaction was followed up by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance ( 1 H NMR). FTIR was obtained using a Shimadzu Prestige-21 equipment, with an attenuated total reflectance (ATR) cell, 7 mm optical path and 10 reflections, using a nominal spectral resolution of 4 cm -1 and 32 scans.…”

“…The analysis was conducted following a method described in the literature. 13 The solvent gradient consists of 100% methanol and 0% isopropanol/hexane (5:4, v:v) in 0 min. The concentration of the isopropanol/hexane mixture (5:4 v:v) gradually increases until 10 min of analysis when it reaches 50:50 v:v with methanol, maintaining the mixture up to 17 min, when methanol is raised again to 100% up to 23 min, finishing the analysis.…”

Nuclear Magnetic Resonance (1.40 T) and Mid Infrared (FTIR-ATR) Associated with Chemometrics as Analytical Methods for the Analysis of Methyl Ester Yield Obtained by Esterification Reaction

“…The FAME content in the final product was measured by high-performance liquid chromatography (HPLC), resulting in a conversion of 98.5%. 30 Standard and real samples preparation 21 standard samples were prepared with known amounts of fatty acids and FAME (binary mixture, m/m) with concentrations in the range of 0-100% in 5% steps, at room temperature, using a semi-analytical scale (Mettler, ± 0.001 g). The acid indexes for all samples were first determined by titration (method AOCS Cd 3a-63): 0.3 g of the sample was dissolved in a mixture of toluene and isopropylic alcohol (1:1, v:v) and then titrated with an alcoholic solution of KOH (0.1 M) using phenolphthalein as indicator.…”