The analysis of faecal sterols in sediment samples by HPLC-UV using ultrasound-assisted treatment

Abstract

A method was developed for the analysis of faecal sterols in sediment samples by ultrasound-assisted extraction and quantification by HPLC with a UV detector. A reversed-phase C18 column was used to develop the method and optimal conditions were employed for elution under isocratic conditions using a methanol/THF/water (83 : 9 : 8) as the mobile phase. Direct detection of sterols by HPLC is difficult, so a derivatization procedure using benzoyl chloride was performed. A sample treatment using ultrasound-assisted extraction with 40 mL of methylene chloride–methanol (1 : 1) for 30 min without a clean up step was developed. The recoveries obtained ranged from 65 to 89% for the sample spike and from 67 to 101% for the blank spike. The detection limits ranged from 1.90 mg L⁻¹ for β-sitosterol to 4.17 mg L⁻¹ for epicoprostanol. Seven streams of Juiz de Fora city were analysed and the concentrations of coprostanol in the sediment samples varied between 0.01 and 14.48 μg g⁻¹. Except for the farm forest sample stream, all others were considered contaminated by faeces using the parameters and evaluation criteria for this type of contamination.