Determination of fat in leather by the use of supercritical fluid extraction combined with on-line piezoelectric detection

Leather samples were prepared and characterized as 'in house' matrix standa rds for the determination of fat. The Soxhlet standard method was used to e stablish the reference fat content in every standard sample. Sample homogen eity and stability were examined under specific storing conditions. The mat erials were subsequently used as matrix standards for the determination of fat in leather samples, using supercritical fluid extraction (SFE) with on- line piezoelectric detection. Real samples were weighed in the extraction S FE thimble, previously loaded with 1 g of diatomaceous earth. A temperature of 45 degreesC and a CO2 fluid density of 0.85 g ml(-1) were used for extr action. The linear calibration range thus achieved was 0.001-0.040% m/m tot al fat (related to the weight of the leather) and the relative standard dev iation +/-3% (n = 11; P = 0.05). The results were compared with (t)hose obt ained with the Soxhlet method and no significant differences were found.