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. The proposed method was successfully applied for the determination of cadmium in rice samples.