Determination of cadmium in rice samples using amino-functionalized metal-organic framework by a pipette tip solid phase extraction

In this study, the amino-functionalized metal-organic framework (NH2-MOFs) was used as an adsorbent for the extraction of cadmium in rice samples based on the pipette tip solid phase extraction (PT-SPE) before determined by the flame absorption spectrometry (F-AAS). The pH of the sample solution, initial concentration of the cadmium, the volume of the sample, elution ‎conditions, and the amount of adsorbent on the recovery of the cadmium were investigated and ‎optimized. The results showed that the best extraction efficiency of cadmium was obtained at pH 5.0, 2500.0 µL of cadmium solution, and 20.0 ‎µL of HCl (10% V/V) ‎ as eluent solvent. First, the cooking rice was transferred to a beaker and hydrochloric acid/nitric acid was added to it as a digestion process before analysis by the PT-SPE procedure. The limit of detection of this method was found to be 0.03 µg L-1 with a relative standard deviation of ≤ 2.5 % (for seven replicate analyses of 50 µg L-1 of cadmium). The linear and dynamic ranges were achieved at 0.3 -14.5 µg L-1 and 0.3 -150 µg L-1, respectively.  The adsorption capacity of sorbent and enrichment factor was 175 mg g-1 and 125 folds, respectively.