Analyse par spectrométrie de masse d’hormones stéroïdiennes dans les eaux usées et abattement par oxydation chimique

The effect of steroid hormones on the aquatic and terrestrial environment is well documented and can occur at very low concentrations. The primary sources responsible for their introduction in the environment are numerous, but they originate mainly from human and animal releases. Several human health issues are thought to be the result of exposure to steroid hormones as well as other endocrine disruptive compounds. The risks associated with years of exposure, in conjunction with the cumulative or synergic effect of these substances, must not be ignored. Therefore, a pro-active, rather than reactive, approach should be considered.   With this in mind, new analytical methods were developed for the detection and quantification of steroid hormones in surface and waste waters. The first was based on a novel sample introduction method, the laser diode thermal desorption with an atmospheric chemical ionization source, the LDTD-APCI, coupled with tandem mass spectrometry (MS/MS). The main advantages of the LDTD-APCI is the short analysis time, i.e. 15 seconds per sample, because no chromatographic separation is used prior to ionization. The optimization of several parameters (laser power, laser pattern, transfer gas flow rate as well as deposition volume and solvent) involved in the LDTD-APCI source are discussed in order to better understand their impact on the efficiency of ionization and method development. The sample pre-concentration of analytes in surface water was performed by manual solid phase extraction (SPE) to demonstrate method applicability to real environmental samples. The LDTD-APCI-MS/MS method detection limits range from 13 to 43 ng L-1 for the selected steroid hormones. The second approach consisted of an on-line SPE method followed by liquid chromatography coupled tandem mass spectrometry LC-MS/MS with injection volumes ranging from 1 to 10 mL, depending upon the expected steroid hormone concentrations and matrix type. The method was applied to wastewater samples from two treatment plants with different processes. The role of sample pre-treatment, i.e. the filtration step and conservation conditions, on the analyses was evaluated. The on-line SPE-LC-MS/MS gave reproducible values while reducing sample preparation time (15 min per sample), compared to manual SPE followed by an LC-MS/MS analysis. The limits of detection of the method for the selected steroid hormones ranged from 8 to 60 ng L-1.   In order to better eliminate the selected steroid hormones in drinking water treatment plants, their oxidation by chlorine and potassium permanganate was determined. The effect of pH, temperature and type of water matrix (ultrapure versus wastewater) on the second order rate constants was assessed and discussed. The oxidation yields by chlorine for estrogens were between 53 and 97% with half-lives from 0.6 min to 53 min, whereas for progestogens with potassium permanganate the corresponding yields ranged from 78 to 94% with half-lives ranging from 10 min and 60 min.

Keyphrases: permanganate, steroid hormones, laser diode thermal desorption, liquid chromatography, mass spectrometry, oxidation, chlorine, permanganate