Chitosan-Ni/Fe Layered Double Hydroxide Composites as an Efficient Sorbent for Gc-Ms Quantitation of Phthalates

Layered double hydroxide (LDH) is considered an efficient sorbent media for the extraction of various chemical pollutants from environmental matrices. In this research, the potential utility of chitosan-nickel/iron LDH (CS-Ni/Fe LDH) composites was examined for the separation and pre-concentration of five phthalates (PAEs: diethylphthalate (DEP), dipropylphthalate (DPP), dibutylphthalate (DBP), benzylbutylphthalate (BBP), and dioctylphthalate (DOP)). The effects of the key parameters controlling their extraction efficiency (e.g., adsorbent amount, flow rate, elution volume, eluent type, solution pH, and ionic strength) were examined. The method detection limit (MDL) for the target PAEs ranged from 0.023-0.033 ng/mL over a 0.1-100 ng/mL range (R2>0.999). The CS-Ni/Fe LDH composite was successfully utilized to extract PAEs in real samples including perfume, cream, bottled water, and bottled milk with recoveries ranging between 97.3-136.8%. The spent CS-Ni/Fe LDH composites could be regenerated up to 30 cycles. The adsorption isotherms were well fitted with the non-linear Langmuir model depicting the formation of monolayered PAE molecules onto CS-Ni/Fe LDH composites. The partition coefficients (mg g-1μM-1) for CS-Ni/Fe LDH were estimated as follows: DOP (802) > DBP (491) > DPP (355) > DEP (248) > BBP (247). Furthermore, the adsorption enthalpy, entropy, and Gibbs free energy values indicate that the adsorption process is spontaneous and exothermic. The CS-Ni/Fe LDH composites were demonstrated to be efficient and fast solid phase extraction (SPE) sorbents for PAEs based on hydrogen bonding and hydrophobic interactions. Accordingly, CS-Ni/Fe LDH composites are expected to lead to new possibilities for capturing PAEs in a highly effective manner.