Mesoporous silica based MCM-41 as solid-phase extraction sorbent combined with micro-liquid chromatography-quadrupole-mass spectrometry for the analysis of pharmaceuticals in waters.

This paper reports the first application of the silica based mesoporous material MCM-41 as a sorbent in solid phase extraction, to pre-concentrate pharmaceuticals of very different polarity (atenolol, nadolol, pindolol, timolol, bisoprolol, metoprolol, betaxolol, ketoprofen, naproxen, ibuprofen, diclofenac, tolfenamic acid, flufenamic acid and meclofenamic acid) in surface waters. The analytes were extracted from 100mL water samples at pH 2.0 (containing 10(-3) mol/L of sodium chloride) by passing the solution through a cartridge filled with 100 mg of MCM-41. Following elution, the pharmaceuticals were determined by micro-liquid chromatography and triple quadrupole-mass spectrometry. Two selected reaction monitoring transitions were monitored per compound, the most intense one being used for quantification and the second one for confirmation. Matrix effect was found in real waters for most analytes and was overcome using the standard addition method, which compared favorably with the matrix matched calibration method. The detection limits in solvent (acetonitrile:water 10:90, v/v) ranged from 0.01 to 1.48 µg/L and in real water extracts from 0.10 to 3.85 µg/L (0.001-0.0385 µg/L in the water samples). The quantitation limits in solvent were in the range 0.02-4.93 µg/L, whereas in real water extracts were between 0.45 and 10.00 µg/L (0.0045 and 0.1000 µg/L in the water samples). When ultrapure water samples were spiked at two concentration levels of each pharmaceutical (0.1 and 0.2 µg/L) and quantified using solvent based calibration graphs, recoveries were near 100%. However, recoveries for most pharmaceuticals were comparable or better than de described above, when river water samples (spiked at the same concentration levels) were quantified by the standard addition method and slightly worse using the matrix matched calibration method. Five real samples (two rivers, one dam and two fountain water samples) were analyzed by the developed method, atenolol, timolol, betaxolol, nadolol and diclofenac being found in some of them, at levels higher than their quantitation limits.

Sorption and leaching of atrazine and MCPA in natural and peat-amended calcareous soils from Spain.

The sorption and leaching of atrazine and MCPA (0.02 M CaCl(2) aqueous solution at 25 degrees C) by a calcareous soil from Southeastern Spain, after organic carbon (OC) amendment with a commercial peat (from 0.18% to 4.61% OC), were studied in batch and soil column experiments. Adsorption capacity (K(f)) values, obtained by fitting the experimental data to the Freundlich equation, ranged from 0.24 mg kg(-)(1) for MCPA sorption on the original soil to 5.47 mg kg(-)(1) for atrazine sorption on the peat-amended soil containing 4.61% OC. The breakthrough curves obtained from the step-function soil column experiments indicated that the amount of herbicide adsorbed ranged from 17.5 mg kg(-)(1) for MCPA in the original soil to 331 mg kg(-)(1) for atrazine in the peat-amended soil containing 1.67% OC. The results obtained from the pulse experiments indicate that the mobility of MCPA is much greater than that corresponding to atrazine.