Determination of urinary bisphenol A by coacervative microextraction and liquid chromatography-fluorescence detection.

Total (free plus conjugated) urinary BPA is currently being used to assess human exposure to this contaminant. This work proposes the use of coacervates made up of reverse micelles of decanoic acid for the microextraction of BPA, prior to its determination by liquid chromatography and fluorescence detection (lambda(ex)=276 nm and lambda(em)=306 nm), with the aim of simplifying sample treatment and reducing analysis time and costs in epidemiologic studies. The procedure involves the enzymatic hydrolysis of 7 mL of urine and then the addition of decanoic acid (100mg) and tetrahydrofurane (1 mL), conditions under which the coacervate (extractant phase, approximately 167 microL) forms in situ and instantaneously. The overall procedure takes about 20 min and several samples can be simultaneously treated using conventional lab equipment (i.e. stirrers and centrifuges). Extractions were independent of the pH and temperature in the ranges studied (1-4 and 25-50 degrees C) rendering the method robust. Recoveries in samples ranged between 88 and 95% and the practical detection limit was 0.197 microgL(-1), which is below the usual concentrations of BPA in urine (ranges reported 0.4-149 microgL(-1)). The actual concentration factor provided by the method was 38. The precision of the method, expressed as relative standard deviation, was 4.5%. The method was successfully applied to the determination of total BPA in urine from eight healthy volunteers. BPA was detected in all the samples at concentrations ranging between 4.03 and 49 microgL(-1).

Decanoic acid reverse micelle-based coacervates for the microextraction of bisphenol A from canned vegetables and fruits.

Decanoic acid reverse micelle-based coacervates were proposed for the extraction of bisphenol A (BPA) from canned vegetables and fruits prior to its determination by liquid chromatography and fluorescence detection at lambda(exc) = 276 nm and lambda(em) = 306 nm. The procedure involved the extraction of minute quantities (300-700 mg) of homogenized food sample with an aqueous solution containing 10% of THF and 0.5% of decanoic acid, conditions under which the coacervate (around 340 microL) formed in situ and instantaneously. The overall sample treatment, which included extraction and centrifugation, took about 25-30 min, and several samples could be simultaneously treated using conventional lab equipment. No clean-up or solvent evaporation were required. Extraction efficiencies mainly depended on the decanoic acid and THF concentration in the aqueous solution and were not affected by the pH or the temperature in the ranges studied (1-4 and 20-60 degrees C, respectively). Recoveries in samples ranged between about 81 and 96%. The precision of the method, expressed as relative standard deviation, was about 3% and the quantitation limit was around 9 ng g(-1), which was far below the current specific migration limit (SML) set for BPA by the EU Commission (600 ng g(-1)). The method was successfully applied to the determination of BPA in the solid content of canned fruit salad, peaches in syrup, mango slices, red peppers, sweetcorn, green beans and peas. BPA was present at concentrations in the range from 7.8 to 24.4 ng g(-1) in canned fruits and from 55 to 103 ng g(-1) in canned vegetables.

Study of the influence of water matrix components on admicellar sorbents.

Hemimicelle-based and/or admicelle-based solid-phase extraction (SPE) has recently been proved to be a fruitful strategy for the extraction and concentration of a wide variety of organic pollutants. This research focus on the effect of river and wastewater matrix components on the adsorption of sodium dodecyl sulfate (SDS) onto alumina, which is the most-used sorbent in hemimicelle-based and/or admicelle-based SPE, and we discuss the analytical consequences of the modifications observed. The effect of electrolytes (0.1 M NaCl), precipitating agents (127 and 333 mg L(-1) CaCl2) and major organic components in wastewater (19.8 mg L(-1) carbohydrates, proteins and fats and 10 mg L(-1) linear alkylbenzene sulfonates (LAS) and rivers (8 mg L(-1) humic acid) on the SDS adsorption isotherm was investigated. Also, the global effect of matrix components was assessed using a river sample. Three types of sorbents were considered (hemimicelles, mixed hemimicelles/admicelles and admicelles). Electrolytes were found to compete with surfactant molecules for charge surface sites in the early part of the hemimicellar region; precipitating agents yield insoluble salts with the aqueous surfactant in equilibrium with admicelle-based sorbents; and organic matter did not have any influence at all. The matrix component concentrations investigated were above the usual range present in rivers and wastewater, which makes this study applicable to a wide number of environmental water samples. From the results obtained, simple rules were established to prevent and detect matrix-induced surfactant adsorption modifications, which permits us to know, a priori, the suitability of these sorbents for a specific application and allows the development of more straightforward and robust methods.

Hemimicelle-based solid-phase extraction of estrogens from environmental water samples.

Hemimicelles and admicelles of sodium dodecyl sulfate (SDS) on alumina and cetyltrimethyl ammonium bromide (CTAB) on silica were evaluated for the concentration and purification of the priority estrogens estrone (E(1)), 17beta-estradiol (E(2)) and ethynylestradiol (EE(2)) from sewage and river samples. Retention was based on analyte-sorbent hydrophobic and cation-pi interactions. Parameters affecting the SPE of estrogens on both types of sorbents were comparatively investigated. Adsolubilization was quantitative for SDS hemimicelles/admicelles and CTAB admicelles. SDS hemimicelle-coated alumina was the sorbent selected on the basis of the lower elution volume required and the higher sample flow rate allowed. Combination of estrogen adsolubilization-based SPE with liquid chromatography-diode array/fluorescence detection permitted the quantification of the target compounds with detection limits ranging from 20 to 100 ng l(-1). The relative standard deviation ranged from 3 to 8%. The approach developed was applied to the determination of estrogens in raw and treated sewage and river samples. The recovery found for estrogens in these environmental matrices was between 85 and 105%.