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The headspace solid-phase microextraction (HS-SPME) of some odorous organic compounds [volatile fatty acids (VFAs), phenols and indoles] from animal wastes was optimised using an experimental design approach. The variables affecting the HS-SPME process studied were as follows: type of fibre, pH of the slurry (3-7), addition of sodium chloride (0-1 mol L(-1)), sample volume (10-30 mL), exposure time (10-30 min), exposure temperature (25-50 degrees C), desorption time (3-10 min) and desorption temperature (230-310 degrees C). As for the sorbent, three different types of fibres were studied: 50/30 microm divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS), 100 microm PDMS and 85 microm CAR/PDMS. Methylation VFAs was observed when fibres containing PDMS were used. The analytes studied in the optimisation procedure were acetic acid, propanoic acid, butanoic acid, 3-methylbutanoic acid, pentanoic acid, phenol, 4-methylphenol, 4-ethylphenol, indole and skatole (3-methylindole). In order to study the influence of the variables on the responses of the compounds, a Plackett-Burman design was built using the Unscrambler program. The optimisation was carried out using real samples. In order to take into account the matrix effect on the calibration curves, standard solutions were prepared using a purged cow slurry free from the analytes of interest. Repeatability within and among days, accuracy and detection limits were calculated from these calibration curves.
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PMID:Experimental design to optimise the analysis of organic volatile compounds in cow slurry by headspace solid-phase microextraction-gas chromatography-mass spectrometry. 1704 41

In biosecure composting, animal mortalities are so completely isolated during the degradation process that visual inspection cannot be used to monitor progress or the process status. One novel approach is to monitor the volatile organic compounds (VOCs) released by decaying mortalities and to use them as biomarkers of the process status. A new method was developed to quantitatively analyze potential biomarkers--dimethyl disulfide, dimethyl trisulfide, pyrimidine, acetic acid, propanoic acid, 3-methylbutanoic acid, pentanoic acid, and hexanoic acid--from field-scale biosecure mortality composting units. This method was based on collection of air samples from the inside of biosecure composting units using portable pumps and solid phase microextraction (SPME). Among four SPME fiber coatings, 85 microm CAR/PDMS was shown to extract the greatest amount of target analytes during a 1 h sampling time. The calibration curves had high correlation coefficients, ranging from 96 to 99%. Differences between the theoretical concentrations and those estimated from the calibration curves ranged from 1.47 to 20.96%. Method detection limits of the biomarkers were between 11 pptv and 572 ppbv. The applicability of the prepared calibration curves was tested for air samples drawn from field-scale swine mortality composting test units. Results show that the prepared calibration curves were applicable to the concentration ranges of potential biomaker compounds in a biosecure animal mortality composting unit.
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PMID:Air sampling and analysis method for volatile organic compounds (VOCs) related to field-scale mortality composting operations. 1951 32