Mass Spectrometric Analysis of Bisphenol A Desorption from Titania Nanoparticles: Ammonium Acetate, Fluoride, Formate, and Hydroxide as Chemical Desorption Agents

Abstract

Bisphenol A (BPA) is a widely used chemical in several consumer products and a well-studied environmental toxicant, and therefore, its accurate measurement is highly demanded. However, the co-presence of nanoparticles as an emerging class of contaminants could result in inaccurate determination of BPA due to binding of BPA onto nanoparticle surface. In this study, mass spectrometry (MS) was used to investigate desorption of BPA bound on the surface of titania (TiO2) nanoparticles in water. Ammonium acetate, fluoride, formate, and hydroxide were evaluated as chemical agents for their desorption capabilities. The percentages of recovery, adsorption, and desorption were determined by this new method without requiring any prior separation of nanoparticles from BPA. MS analysis demonstrated the desorption of BPA by 10–20 mM of ammonium hydroxide for a mixture of 5 µg/mL BPA and 10 µg/mL TiO2 nanoparticles, with a desorption efficiency of 72 ± 1%. Due to adsorption of BPA onto the nanoparticle surface that was inefficient for electrospray ionization, the resulting abundance of target ions could be reduced in the detection of BPA by mass spectrometry. As such, these findings collectively promise an accurate determination of the total BPA concentration in water whether it exists in the free or bound form. Efficient desorption of contaminants from the surface of nanoparticles would improve the accuracy of the contaminant analysis by mass spectrometry.

Polyaniline-Coated TiO2Nanorods for Photocatalytic Degradation of Bisphenol A in Water

“…A peak observed at m / z 93.1 was attributed to the cleavage of two base phenolic molecules of BPA producing a fragment with the formula C 6 H 5 O. These degradation products were consistent with those reported in the literature. − …”

“…This fragment resulted from a loss of a methyl group, producing a carbocation, [C 14 H 13 O 2 + ]. Another peak with m / z 135.1 was produced and this was attributed to [C 9 H 11 O + ] which was produced as a result of the cleavage of the alkyl-phenyl bond and possible degradation of BPA . A peak observed at m / z 93.1 was attributed to the cleavage of two base phenolic molecules of BPA producing a fragment with the formula C 6 H 5 O.…”

Ion-Trap Mass Spectrometric Analysis of Bisphenol A Interactions With Titanium Dioxide Nanoparticles and Milk Proteins

“…By comparing the rate of peak intensity decrease, it was obvious that BPA did not bind efficiently with TiO 2 nanoparticles in the presence of sodium formate, because the peak intensities of m/z 251.0 (corresponding to free BPA) in Figure 3a were significantly higher than those in Figure 3b. A previous work had determined a 40% efficiency for ammonium formate (2 mM) to desorb BPA from TiO 2 nanoparticles [20]. Early aggregation of the nanoparticles (at concentrations below 175 µg/mL) was likely happening in the absence of formate, as evidenced by the straight decrease of peak intensity sum with increasing TiO 2 concentrations (rather than following a curve in the shape of Langmuir isotherm).…”

“…Numerous low-intensity peaks appearing along the baseline from m/z 100 to m/z 1200 could be ascribed to a distribution of TiO 2 nanoparticles with different sizes carrying various positive charges originating from TiO + [75]. It should be noted that BPA contains a hydrogen atom at the tertiary carbon atom in the α-position of each benzene ring and a hydroxyl group [20], enabling mass spectrometric detection of the deprotonated molecular and product ions using negative polarity as well. Interestingly, the negative-polarity ESI-ITMS spectrum showed reproducible peaks at m/z 455.95-457.69 for [2BPA − H] − (spectrum not shown), albeit at a lesser intensity (and hence, lower sensitivity for quantitative analysis) than those peaks observed above using positive polarity.…”

“…There is mounting evidence that adsorption of BPA onto various solid particles can jeopardize the accuracy of quantitative water analysis [19]. More importantly, engineered nanomaterials such as titanium dioxide (TiO 2 ) and mixed metal oxides may possess binding properties towards BPA [20][21][22]. On the other hand, trace BPA in wastewater samples could be preconcentrated with magnetic iron oxide (Fe 3 O 4 )-graphene oxide nanocomposite or magnetite nanoparticles as the adsorbent [23,24].…”