title: Detailed faecal fat analysis using Fourier transform infrared spectroscopy: Exploring the possibilities.
abstract: OBJECTIVE
  Fourier transform infrared (FTIR) spectroscopic determination of faecal fat is a simple and elegant alternative for the classical Van De Kamer approach. Besides quantification of the total amount of fat, analysis of the lipase hydrolysis efficiency (fatty acid/triglyceride ratio), fatty acid chain length and trans-unsaturated fatty acids could provide a better monitoring of dietary treatment.
  
  
  METHODS
  Stool samples (26 routine samples and 36 cystic fibrosis patients) were analysed with the Perkin Elmer Spectrum Two® spectrometer (3500-450cm-1). Fatty acid/triglyceride ratio was calculated using the absorbance ratio at 2855:1746cm-1. To estimate lipase hydrolysis efficiency, sample ratios were compared with the ratio of butter and pure free fatty acids. Mean fatty acid chain length was calculated using the absorbance ratio at 2855:1709cm-1. The absorbance at 966cm-1was used to trace the presence of trans-type unsaturated fatty acids.
  
  
  RESULTS
  Butter showed a low fatty acid/triglyceride ratio (1.21) and pure free fatty acids a high fatty acid/triglyceride ratio (6.76). Mean fatty acid/triglyceride ratio of routine stool samples was 4.16±1.01. The applicability of fatty acid/triglyceride ratios was also tested in cystic fibrosis patients under treatment with a mean of 4.92±0.98. Relative absorbance contribution per carbon atom was 0.06 (ratio 1.06 for C18 standard, 0.91 for C16 standard). The mean ratio of the stool samples was 1.12 (mean acyl chain length of C19), with values ranging from 0.73 (C12) to 1.68 (C28). The presence of traceable amounts of trans-unsaturated fatty acids was also demonstrated.
  
  
  CONCLUSIONS
  For the analysis of faecal material, FTIR provides unique information, difficult to obtain using other techniques. These findings offer perspectives for diet monitoring in patients with (non-)pancreatic malabsorption.
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: De Koninck
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Nys
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium.
authors.forename: Brent
authors.initials: B
authors.lastname: Vandenheede
authors.affiliation: Department of Paediatrics, Ghent University Hospital, Gent, Belgium.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Van Biervliet
authors.affiliation: Department of Nephrology, Ghent University Hospital, Gent, Belgium.
authors.forename: Marijn M
authors.initials: MM
authors.lastname: Speeckaert
authors.affiliation: Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium. Electronic address: joris.delanghe@ugent.be.
authors.forename: Joris R
authors.initials: JR
authors.lastname: Delanghe
mesh_terms: D005223:Fats / Q000032:analysis* / Q000145:classification; D005243:Feces / Q000737:chemistry*; D006801:Humans; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D005223:Fats
keywords: Faecal fat; Fatty acid chain length; Fourier transform infrared spectroscopy; Lipase hydrolysis efficiency; Trans-unsaturated fatty acids