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Abstract
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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 nanosorbent,
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 ìg L.1 with a correlation coefficient of 0.9975. The
limit of detection and relative standard deviation for l-tryptophan
were 0.01 ìg 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.
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