Filter paper modified with polyaniline as a sorbent for solid-phase microextraction of cadmium ions

Trace levels of heavy metals are widely spread out in the environment due toindustrial and agricultural processes. The monitoring of these elements in a great variety ofenvironmental and biological samples is required because of their toxicity. Cadmium is one ofthe most known hazardous elements to human health which accumulates in the body mainly inthe Kidneys and Liver. Direct determination of a low level of cadmium with the well-available۲technique of flame atomic absorption spectroscopy is not possible due to the complexity of theenvironmental sample as well as the limitation of the instrument detection limit. Thus, aseparation and preconcentration step before its determination is required. Among variousmicroextraction methods reported for the separation and preconcentration of cadmium ions,solid-phase microextraction (SPME) has the advantages of reduction of analyzing time, use ofless amount of solvent, high preconcentration factor, ease of manipulation, and simplicity ofautomation [۱-۲]. In this study, a new, environmentally friendly sorbent based on biopolymerwas fabricated and applied for thin-film microextraction (TFME) of cadmium ions from variousmatrices. Filter paper which is mostly composed of cellulose, a biodegradable polymer, wasmodified by polyaniline [۳]. The resulting positively charged modified filter paper was used asthe sorbent in TFME of cadmium ions as its anionic complex of CdI۴-۲. The sorbed analyte waseluted from the sorbent by ۰.۵ mL of sodium hydroxide (۰.۵ mol L-۱) and quantified by flameatomic absorption spectrometry. Factors influencing the sorption and desorption of the anioniccomplex of cadmium were investigated and optimized. Under the optimized conditions, themethod exhibited a linear dynamic range of ۰.۲۵-۲۵ μg L−۱, a detection limit of ۰.۰۶ μg L-۱, andan enrichment factor of ۲۰۰. The relative standard deviation for the determination of cadmiumions (n = ۶) at ۳ μg L-۱ was ۳.۴%. The proposed method was successfully applied to thedetermination of cadmium ions in various environmental water samples.