RESUMEN
Fifteen phenolic compounds were determined in rice grains by ultrasound assisted extraction and ultra-performance liquid chromatography with photodiode array detection. Primarily, an UAE method has been developed and validated for the extraction of phenolics from rice grains. For the optimization, a Box-Behnken Design based on six factors including extraction temperature (10-70⯰C), solvent composition (0-50% methanol in water), cycle (0.2-0.7â¯s-1), ultrasound amplitude (30-70%), and solvent to sample ratio (2.5:1 to 5:1) was employed. Multi-response optimization (MRO) was performed to develop a simultaneous extraction method of 15 phenolics. The optimal UAE conditions were: extraction temperature 45⯰C, time 25â¯min, cycle 0.4â¯s-1, ultrasound amplitude 47%, solvent composition 80% methanol in water at pH 4.25, and sample to solvent ratio 1:5. Linearity, LODs, LOQs, precision and recovery were determined. In addition, the method was successfully applied to analyse a number of rice samples with different varieties.
Asunto(s)
Oryza/química , Fenoles/análisis , Sonicación/métodos , Cromatografía Líquida de Alta Presión , Límite de Detección , Fenoles/aislamiento & purificación , Estándares de Referencia , Solventes/químicaRESUMEN
A Box-Behnken design was used in conjunction with multiresponse optimization based on the desirability function to carry out the simultaneous separation of tryptophan and 15 derivatives by Ultra Performance Liquid Chromatography. The gradient composition of the mobile phase and the flow rate were optimized with respect to the resolution of severely overlapping chromatographic peaks and the total run time. Two different stationary phases were evaluated (hybrid silica and a solid-core-based C18 column). The methods were validated and a suitable sensitivity was found for all compounds in the concentration range 1-100µgL-1 (R2>0.999). High levels of repeatability and intermediate precision (CV less than 0.25% and 1.7% on average for the retention time and the signal area, respectively) were obtained. The new method was applied to the determination tryptophan and its derivatives in black pigmented glutinous and non-glutinous rice grain samples.