title: Simultaneous determination of free and total glycerol in biodiesel by capillary electrophoresis using multiple short-end injection.
abstract: A rapid method for the simultaneous determination of free glycerol (FG) and total glycerol (TG) in biodiesel by CE using a short-end multiple injection (SE/MI) configuration system is described. The sample preparation for FG involves the extraction of glycerol with water and for TG a saponification reaction is carried out followed by extraction as in the case of FG. The glycerol extracted in both cases is submitted to periodate oxidation and the iodate ions formed are measured on a CE-SE/MI system. The relevance of this study lies in the fact that no analytical procedure has been previously reported for the determination of TG (or of FG and TG simultaneously) by CE. The optimum conditions for the saponification/extraction process were 1.25% KOH and 25°C, with a time of only 5 min, and biodiesel mass in the range of 50.0-200.0 mg can be used. Multiple injections were performed hydrodynamically with negative pressure as follows: 50 mbar/3s (FG sample); 50 mbar/6s (electrolyte spacer); 50 mbar/3s (TG sample). The linear range obtained was 1.55-46.5 mg/L with R(2) > 0.99. The LOD and LOQ were 0.16 mg/L and 0.47 mg/L, respectively for TG. The method provides acceptable throughput for application in quality control and monitoring biodiesel synthesis process. In addition, it offers simple sample preparation (saponification process), it can be applied to a variety biodiesel samples (soybean, castor, and waste cooking oils) and it can be used for the determination of two key parameters related to the biodiesel quality with a fast separation (less than 30 s) using an optimized CE-SE/MI system.
authors: Department of Chemistry, Federal University of Santa Catarina, Florianopolis, SC, Brazil.
authors: Daniel Alfonso
authors: DA
authors: Spudeit
authors: Marcel
authors: M
authors: Piovezan
authors: Maressa D
authors: MD
authors: Dolzan
authors: Jacqueline Pereira
authors: JP
authors: Vistuba
authors: Mônia Stremel
authors: MS
authors: Azevedo
authors: Luciano
authors: L
authors: Vitali
authors: Marcone Augusto
authors: MA
authors: Leal Oliveira
authors: Ana Carolina
authors: AC
authors: Oliveira Costa
authors: Gustavo Amadeu
authors: GA
authors: Micke
mesh_terms: D056804:Biofuels / Q000032:analysis*; D019075:Electrophoresis, Capillary / Q000379:methods*; D005990:Glycerol / Q000032:analysis*; D007700:Kinetics; D057230:Limit of Detection; D010938:Plant Oils; D015203:Reproducibility of Results; D013696:Temperature
chemical_list: D056804:Biofuels; D010938:Plant Oils; D005990:Glycerol
keywords: Biodiesel; CE; Free glycerol; Short-end multiple injections; Total glycerol