title: A microfluidic device for the automated derivatization of free fatty acids to fatty acid methyl esters.
abstract: Free fatty acid (FFA) compositions are examined in feedstock for biodiesel production, as source-specific markers in soil, and because of their role in cellular signaling. However, sample preparation of FFAs for gas chromatography-mass spectrometry (GC-MS) analysis can be time and labor intensive. Therefore, to increase sample preparation throughput, a glass microfluidic device was developed to automate derivatization of FFAs to fatty acid methyl esters (FAMEs). FFAs were delivered to one input of the device and methanolic-HCl was delivered to a second input. FAME products were produced as the reagents traversed a 29 μL reaction channel held at 55 °C. A Design of Experiment protocol was used to determine the combination of derivatization time (T(der)) and ratio of methanolic-HCl:FFA (R(der)) that maximized the derivatization efficiencies of tridecanoic acid and stearic acid to their methyl ester forms. The combination of T(der) = 0.8 min and R(der) = 4.9 that produced optimal derivatization conditions for both FFAs within a 5 min total sample preparation time was determined. This combination of T(der) and R(der) was used to derivatize 12 FFAs with a range of derivatization efficiencies from 18% to 93% with efficiencies of 61% for tridecanoic acid and 84% for stearic acid. As compared to a conventional macroscale derivatization of FFA to FAME, the microfluidic device decreased the volume of methanolic-HCl and FFA by 20- and 1300-fold, respectively. The developed microfluidic device can be used for automated preparation of FAMEs to analyze the FFA compositions of volume-limited samples.
authors.affiliation: Department of Chemistry and Biochemistry, Florida State University, 95 Chieftain Way, Tallahassee, FL 32306, USA.
authors.forename: Cindy T
authors.initials: CT
authors.lastname: Duong
authors.forename: Michael G
authors.initials: MG
authors.lastname: Roper
mesh_terms: D056804:Biofuels; D004952:Esters / Q000032:analysis / Q000138:chemical synthesis*; D005230:Fatty Acids, Nonesterified / Q000032:analysis / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008745:Methylation; D046210:Microfluidic Analytical Techniques; D013229:Stearic Acids / Q000138:chemical synthesis
chemical_list: D056804:Biofuels; D004952:Esters; D005230:Fatty Acids, Nonesterified; D013229:Stearic Acids; C031183:stearic acid