Solid-phase extraction of ltryptophan from food samples utilizing a layered double hydroxide nano-sorbent prior to its determination by spectrofluorometry

In this research, a simple method was developed for the separation and determination of l-tryptophan in aqueous solutions. The method consists of a solid-phase extraction (SPE) cleanup system utilizing a column packed with nickel-aluminum layered double hydroxide as a nano-sorbent, followed by a spectrofluorometric detection step. Some factors influencing the SPE efficiency, including pH, the sample flow rate, the elution conditions and the amount of nano-sorbent were evaluated and optimized. The selectivity of the presented SPE method with regard to l-tryptophan was studied in the presence of other amino acids and potentially interfering ions. Under optimum conditions, the calibration graph was linear in the range of 0.1-120.0 A mu g L-1 with a correlation coefficient of 0.9975. The limit of detection and relative standard deviation for l-tryptophan were 0.01 A mu g L-1 and 0.62 %, respectively. The maximum sorption capacity of the sorbent for l-tryptophan was 37.6 mg g(-1). The method was successfully applied to determine l-tryptophan in several food samples with recoveries in the range of 96.2-104.2 % for the spiked samples.