Preparation of fecal samples for assay of volatile fatty acids by gas-liquid chromatography and high-performance liquid chromatography.
We describe a procedure for preparing fecal samples for determination of volatile fatty acids (VFAs) by gas-liquid chromatography (GLC) and "high-performance" liquid chromatography (HPLC). The simple, one-step procedure involves only ultrafiltration through a membrane with a molecular-mass cutoff of 3000 Da. As revealed by the GLC chromatograms, ultrafiltration appears to be as effective as steam distillation in sample clean-up. It also enables higher, more reproducible analytical recoveries of long-chain VFAs. The VFA content of the filtrate can also be measured by HPLC. Use of the ion-exclusion mechanism completely resolves isobutyric acid and butyric acid on a cation-exchange column. The mean (+/- SD) percentage distribution values of VFAs (measured by GLC) from five healthy subjects were 56.0 +/- 3.5 (acetic acid), 17.0 +/- 5.3 (propionic acid), 2.9 +/- 1.5 (isobutyric acid), 18.8 +/- 5.8 (butyric acid), 2.3 +/- 1.2 (isovaleric acid), and 2.9 +/- 0.8 (valeric acid).
Chen
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HM
USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030.
Lifschitz
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CH
D000085:Acetates / Q000032:analysis; D019342:Acetic Acid; D000328:Adult; D002087:Butyrates / Q000032:analysis; D020148:Butyric Acid; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D005232:Fatty Acids, Volatile / Q000032:analysis*; D005243:Feces / Q000032:analysis*; D045782:Hemiterpenes; D006801:Humans; D007223:Infant; D058610:Isobutyrates; D010421:Pentanoic Acids / Q000032:analysis; D011422:Propionates / Q000032:analysis; D012016:Reference Values; D014462:Ultrafiltration
D000085:Acetates; D002087:Butyrates; D005232:Fatty Acids, Volatile; D045782:Hemiterpenes; D058610:Isobutyrates; D010421:Pentanoic Acids; D011422:Propionates; D020148:Butyric Acid; C008216:isovaleric acid; C020380:isobutyric acid; C038780:n-pentanoic acid; C029658:propionic acid; D019342:Acetic Acid