Determining leaching of bisphenol A from plastic containers by solid-phase microextraction and gas chromatography–mass spectrometry

Enzymatic determination of BPA by means of tyrosinase immobilized on different carbon carriers

Different tyrosinase carbon paste modified electrodes to determine bisphenol A (BPA) concentration in aqueous solutions have been constructed. Variables examined were in the carbon paste composition and in particular: (i) the immobilized enzyme amount; (ii) the carbon type (powder, single or multi-walled nanotubes); (iii) the nature of the pasting oil (mineral oil, hexadecane and dodecane). For each biosensor type the amperometric response was evaluated with reference to the linear range and sensitivity. Constant reference has been made to the amperometric signals obtained, under the same experimental conditions, towards the catechol, a specific phenolic substrate for tyrosinase. The most efficient biosensors were those constructed by using the following composition for the carbon paste: 10% of tyrosinase, 45% of single wall carbon nanotubes (SWCN) and 45% of mineral oil. This biosensor formulation displayed the following electrochemical characteristics: a sensitivity equal to 138 microA/mM, LOD of 0.02 microM (based on three times the S/N ratio), linear range of 0.1-12 microM and response time of 6 min. This experimental work represents a first attempt at construction of a new carbon nanotube-tyrosinase based biosensor able to determine the concentration of BPA, one of the most ubiquitous and hazardous endocrine disruptors which can pollute the drinking and surface water, as well as many products of the food chain.

Evaluating the impacts of some environmentally relevant factors on the availability of bisphenol A with negligible-depletion SPME

The effect of some environmentally relevant factors including salinity, pH, and humic acids on the availability of bisphenol A (BPA) was evaluated by using the negligible-depletion solid-phase microextraction (nd-SPME) biomimetic method. With the variation of salinity (0-500 mM NaCl) and pH (5.0-8.5) of aqueous solutions, the partition coefficients of BPA between the nd-SPME fiber and the aqueous solution varied in the range of logD=3.55-3.86, which indicates that the salinity and pH can influence the availability of BPA. By using Acros humic acid as model dissolved organic matter (DOM), it was also demonstrated that the environmental factors such as salinity and pH could affect the partitioning of BPA between DOM and aqueous solutions. The determined partition coefficients of BPA between dissolved organic carbon (DOC) and aqueous solutions were in the range of logD(DOC)=4.03-5.60 for Acros humic acid solutions with 1-50 mg l(-1) DOC. The influence of salinity and pH on logD(DOC) was more significant at low concentration (0-5 mg l(-1)) of DOC.

Optimisation of a solid-phase microextraction method for the determination of parabens in water samples at the low ng per litre level

A procedure for the determination of five esters of p-hydroxybenzoic acid (parabens) in water samples is presented. Analytes (methyl, ethyl, propyl, butyl and benzyl paraben) are concentrated on a solid-phase microextraction (SPME) fibre, converted on their tert-butyldimethylsilyl derivatives and selectively determined using gas chromatography in combination with tandem mass spectrometry (GC-MS/MS). Influence of different factors on the efficiency of extraction and on-fibre derivatization steps is described in detail. For all species, the highest enrichment factors were achieved using a polyacrylate (PA) fibre exposed directly to stirred water samples, containing 150 mg/ml of sodium chloride, at room temperature. Performance of the further on-fibre derivatization reaction was also maximum at room temperature, considering a short exposition period of the SPME fibre to vapours of the silylation reagent. Under optimised conditions, the proposed method achieved quantification limits from 0.001 to 0.025 ng/ml and it was free of matrix effects; therefore, external calibration can be used as the quantification technique. From our knowledge, this work describes the first application of SPME and gas chromatography to the determination of parabens in water. The analysis of a limited number of real samples revealed the presence of parabens in raw sewage water at concentrations up to 3 ng/ml.