Nickel-aluminum layered double hydroxide as a nanosorbent for selective solid-phase extraction and spectrofluorometric determination of salicylic acid in pharmaceutical and biological samples

The nickel-aluminum layered double hydroxide (Ni-Al LDH) was synthesized by a simple co-precipitation method and used as a solid-phase extraction (SPE) sorbent for separation and pre-concentration of trace levels of salicylic acid (SA) from aqueous solutions. Extraction of analyte is based on the adsorption of salicylate ions on the Ni-Al (NO3-) LDH and/or their exchanging with LDH interlayer NO3- ions. The retained analyte on the LDH was stripped by 3 mol L-1 NaOH solution and its concentration was subsequently determined spectrofluorometrically at lambda(em) = 400 nm with excitation at lambda(ex) = 270 nm. Various parameters affecting the extraction efficiency of SA on the Ni-Al (NO3-) LDH, such as pH, amount of nano-sorbent, sample loading flow rate, elution conditions, sample volume and matrix effects were investigated. In the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.12 mu g L-I and 40. respectively. The relative standard deviation (RSD) for six replicate determinations of 10 mu g L-1 SA was 2.3%. The calibration graph using the pre-concentration system was linear in the range of 0.3-45 mu g L-1 with a correlation coefficient of 0.9985. The optimized method was successfully applied to the determination of SA in blood serum, willow leaf and aspirin tablet. (C) 2011 Elsevier B.V. All rights reserved.