New modified carbon based solid phase extraction sorbent prepared from wild cherry stone as natural raw material for the pre-concentration and determination of trace amounts of copper in food samples

Abstract

A new activated carbon (AC) adsorbent was prepared from cherry stone of native wild cherry shrub of Kurdistan as raw material. The AC was modified by acidic and microwave modification methods and applied as dispersive solid phase extraction (dSPE) sorbent. Hydrochloric (15% w/w) and nitric (32.5% w/w) acids were used to oxidize the porous surface of AC and to change its surface chemistry. Acidic functional groups on acidic modified AC (AM-AC) sample were seen in related FT-IR spectrum. Also, microwave radiation led to significant changes in porous structure of modified sample especially increasing its surface area from 120.07 m2 g−1 to 160.2 m2 g−1, based on results of BET experiments. SEM images showed porous structure in prepared sorbent. In the next step, the acidic and microwave modified AC (AMM-AC) was used in dSPE process at ng mL−1 concentration levels for extraction and pre-concentration of Cu (II) prior to flame atomic absorption spectrometric determination. Various parameters affecting the process were evaluated. The optimum sorbent amount, extraction time, pH and extraction temperature were found to be 15 mg, 15 min, 7 and 30 °C, respectively. In the concentration range from 0.8 to180 ng mL−1, the calibration curve was linear with correlation coefficient (r) of 0.9983. The enrichment factor 100 was obtained. The relative standard deviation was 3.87% (for n = 7), the limit of detection was 0.31 ng mL−1, and relative recoveries in food samples were in the range of 95.7–103.6%.