Fabrication of polyethyleneimine-based monolithic adsorbent for onsite enrichment of heavy metal ions in aqueous samples prior to quantification with atomic absorption spectroscopy

Efficient separation and enrichment plays a vital role in the accurate monitoring of trace heavy metal ions (HMs). However, most of the existing sample pretreatment processes are carried out in the lab. It not only encounters the many disadvantages existing in the lab-based sample preparation methods, but also influences the true concentrations of studied metal ions in actual water samples. To circumvent the dilemmas, a new polyethyleneimine-based monolithic adsorbent (PBMA) was in-situ fabricated and used as the extraction medium of lab-developed in-tip microextraction device (IMD) for onsite extraction of HMs in water samples. The PBMA fabricated in the beneficial conditions contained plentiful amino groups and presented superior enrichment performance towards studied ions (Cu 2+ , Pb 2+ and Cd 2+ ). The preconcentration factors and adsorption capacities were 141–192 and 13.8–17.1 mg/g, respectively. In addition, the PBMA exhibited good fabrication repeatability (RSDs<7 %) and regeneration (could be reused more than 50 times). Moreover, the adsorption behaviors and extraction mechanism was studied in detail. Under the optimal extraction parameters, the introduced PBMA/IMD technique was used to onsite isolate and enrich Cu 2+ , Pb 2+ and Cd 2+ in real water samples and then using atomic absorption spectrometry to quantify the concentrations. The established approach exhibited wide linear ranges (0.10–1000 ng/L) and high sensitivity (limits of detection ranged from 0.00071 ng/L to 0.0026 ng/L). The current study supplied a new strategy for onsite separation and enrichment of HMs in various waters, and the developed method may become an alternative technique for the reliable monitoring of HMs at ultra-trace levels.