title: A salting out system for improving the efficiency of the headspace solid-phase microextraction of short and medium chain free fatty acids.
abstract: Given the importance of short and medium chain free fatty acids (FFAs) in several fields, this study sought to improve the extraction efficiency of the solid-phase microextraction (SPME) of FFAs by evaluating salting out agents that appear promising for this application. The salts ammonium sulfate ((NH4)2SO4) and sodium dihydrogen phosphate (NaH2PO4) were tried on their own and in combination (3.7/1), in four different total amounts, as salting out agents in the headspace-SPME-gas chromatographic (HS-SPME-GC) analysis of the FFAs from acetic acid (C2) to decanoic acid (C10). Their performance in a model system of an aqueous standard mixture of FFAs at a pH of 3.5 was compared to that of the more commonly used sodium chloride (NaCl) and sodium sulfate (Na2SO4). All of the salts and salt systems evaluated, in proper amount, gave improved results compared to NaCl (saturated), which instead gave interesting results only for the least volatile FFAs C8 and C10. For C2-C6, the salt system that gave the best results compared to NaCl was (NH4)2SO4/NaH2PO4, in the highest of the four amounts evaluated, with factor increases between 1.2 and 4.1-fold, and NaH2PO4, between 1.0 and 4.3-fold. The SPME extraction efficiency given by the mixture (NH4)2SO4/NaH2PO4 was also assessed on biological and food samples, confirming that overall it performed better than NaCl.
authors.affiliation: Chemistry Division, School of Science and Technology, University of Camerino, V. S. Agostino 1, I-62032 Camerino, MC, Italy. Electronic address: dennis.fiorini@unicam.it.
authors.forename: Dennis
authors.initials: D
authors.lastname: Fiorini
authors.affiliation: Department of Agricultural, Food, and Environmental Sciences, Università Politecnica delle Marche, V. Brecce Bianche, I-60131 Ancona, Italy.
authors.forename: Deborah
authors.initials: D
authors.lastname: Pacetti
authors.affiliation: School of Pharmacy, University of Camerino, V. S. Agostino 1, I-62032 Camerino, MC, Italy.
authors.forename: Rosita
authors.initials: R
authors.lastname: Gabbianelli
authors.affiliation: Chemistry Division, School of Science and Technology, University of Camerino, V. S. Agostino 1, I-62032 Camerino, MC, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Gabrielli
authors.affiliation: Chemistry Division, School of Science and Technology, University of Camerino, V. S. Agostino 1, I-62032 Camerino, MC, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ballini
mesh_terms: D000085:Acetates / Q000032:analysis; D000645:Ammonium Sulfate / Q000737:chemistry*; D000818:Animals; D002611:Cheese / Q000032:analysis; D002849:Chromatography, Gas / Q000379:methods; D003652:Decanoic Acids / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000032:analysis*; D005232:Fatty Acids, Volatile / Q000032:analysis*; D005243:Feces / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D010710:Phosphates / Q000737:chemistry*; D051381:Rats; D012965:Sodium Chloride / Q000737:chemistry*; D052617:Solid Phase Microextraction; D013431:Sulfates / Q000737:chemistry*; D014867:Water; D014920:Wine / Q000032:analysis
chemical_list: D000085:Acetates; D003652:Decanoic Acids; D005230:Fatty Acids, Nonesterified; D005232:Fatty Acids, Volatile; D010710:Phosphates; D013431:Sulfates; D014867:Water; C012036:sodium sulfate; D012965:Sodium Chloride; C031071:decanoic acid; C018279:sodium phosphate; D000645:Ammonium Sulfate
keywords: Ammonium sulfate; Free fatty acids; Salting out; Sodium dihydrogen phosphate; Solid-phase microextraction