Development of polyacrylamide chromium oxide as a new sorbent for solid phase extraction of As(III) from food and environmental water samples

A new hybrid polyacrylamide chromium oxide (PACO) was synthesized and characterized by elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDX, transmission electron microscopy (TEM), thermal and infrared spectral studies. The application of PACO as a solid phase extraction sorbent in environmental analysis is reported for the first time using arsenic as a model target. The sorption of As(III) onto PACO has been studied through batch and column techniques. The adsorption equilibrium data were analyzed by Langmuir and Freundlich isotherm models. The experimental data obeyed the pseudo second order kinetic model. The effects of adsorption and desorption conditions for arsenic(III) including initial pH of the sample, solution volume and flow rate of the sample solution, eluent and its flow rate were investigated and optimized prior to its determination by spectrophotometry and inductively coupled plasma-atomic emission spectrometry (ICP-AES). As(III) can be quantitatively retained on PACO over the pH range 6.5-7.5 from sample volume up to 500 mL and then eluted completely with 5 mL of 0.5 M HNO3 + NaNO3. Under the optimal conditions, the enrichment factor was 100. The RSD values for day to day and column to column precision were found to be 3.91% and 4.55% respectively, at a 6 mu g L-1 As(III) level. The recoveries of arsenic in the environmental water samples were above 95% with 500 mL water samples. The proposed method has been applied successfully to the analysis of total inorganic arsenic in water samples, basmati rice and tobacco cigarettes.