Mass spectrometric analysis of bisphenol A desorption from ceria nanoparticles: l-histidine versus l-lysine as biochemical desorption co-agents

Mass spectrometry (MS) was used to investigate desorption of bisphenol A (BPA) bound on the surface of ceria (CeO2) nanoparticles in water. Two amino acids, l-lysine and l-histidine were evaluated as biochemical agents for their desorption capability as a result of their competitive adsorption on CeO2 nanoparticle surface through their α-carboxyl, α-amino and side chain amine groups, either on their own or in synergy with formic acid or ammonium acetate (NH4Ac). The recovery, adsorption, and desorption percentages were calculated from the abundances of target adduct ions determined by direct-infusion MS without requiring any prior separation of nanoparticles from the BPA sample solution. MS analysis demonstrated the efficient desorption of BPA by L-histidine and NH4Ac at neutral pH. Various influential factors on desorption efficiency were investigated. A desorption efficiency of (78 ± 3)% was achieved for a 10 μg/mL BPA pre-mixed with 20 μg/mL CeO2 nanoparticles for 3 h in the dark under the following experimental conditions: 1 mM l-histidine, 5 mM NH4Ac, pH = 7.2, and desorption time of 1 h at room temperature. Further evaluation of various CeO2 nanoparticle concentrations up to 100 μg/mL (10-fold higher than BPA concentration) confirmed no significant decrease in the desorption efficiency. The desorption method is efficient, simple, robust, fast, environmentally friendly, and MS compatible. It would lead to more accurate determination of both the free and bound forms of BPA with co-existing nanoparticles in water.