In this study, a method for the determination of 3-(4-methylbenzylidene)camphor (4-MBC) and 2-ethylhexyl 4-(dimethylamino)benzoate (OD-PABA) in river water samples employing cork as the SPME (solid-phase microextraction) fiber was developed. The extraction parameters optimized were pH, ionic strength and extraction time and temperature. For the extraction step, the sample pH was studied in univariate experiments while the extraction time, temperature and ionic strength were evaluated using a central composite design. The optimal extraction conditions were sample pH 4.0, extraction time 70 min, sample temperature 80 °C and sodium chloride concentration 6% (m v-1). The limits of quantification for 4-MBC and OD-PABA were 0.1 and 0.01 µg L-1, respectively. The linear correlation coefficients were greater than 0.97 for both analytes and the developed method showed recovery values between 67 and 107%. In an evaluation of the fiber-to-fiber reproducibility (fibers produced by different analysts), the relative standard deviation (RSD) was lower than 11% (n = 6).

Microbial volatile organic compounds (MVOCs) are present in several production processes in biotechnology. In this study it is evaluated the viability of use of a method involving solid-phase microextraction (SPME), in vivo SPME, in the extraction of MVOCs, associated with the pigment production process by the Monascus fungus. PDMS/Car/DVB (50/30 µm) fiber in the headspace mode (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used to fermentation broth study. Seventeen compounds were found associated with the presence of the fungus, being the main ones ethanol, 2-methyl-propanol, 3-methyl-butanol, 2-methyl-butanol and 2-phenyl-ethanol. These compounds have maximum concentration of 313.87, 5.51, 2.37, 0.95 and 0.70 mg L-1. The values of biomass and red pigment found for fermentation for ten days were 4.03 ± 0.21 g L-1 and 3.96 ± 0.17 (UA480). Regular MVOC productions were observed in this study, which were useful in the prediction and control of fermentation by Monascus fungus.

<p>A new single-drop microextraction approach is proposed for the extraction of compounds with a wide range of volatilities from tap water samples with separation/detection by gas chromatographymass spectrometry. This new microextraction mode is called direct immersion-headspace-single drop microextraction (DI-HS-SDME). Trihalomethanes (THMs), hydrocarbons with low molecular weight (benzene, ethyl benzene and xylenes) and polycyclic aromatic hydrocarbons (PAHs) were the model compounds. Ten milliliters of tap water samples and drop volume of 1.5 µL of 1-octanol were used. The optimal condition for DI-HS-SDME mode was 80 min of total extraction time (48 min at 40 °C in DI-SDME mode and 32 min at 12 °C in HS-SDME mode) and the addition of 1.2 g of NaCl. The analytical figures of merit were evaluated, the limits of detection ranged from 0.03 µg L^-1 for o-xylene and ethyl benzene to 6 µg L^-1 for THMs. The proposed method represents a promising alternative for the analysis of aqueous matrices which contain compounds with very different ranges of volatility.</p>