Analytical methodology for sampling and analysing eight siloxanes and trimethylsilanol in biogas from different wastewater treatment plants in Europe.

Siloxanes and trimethylsilanol belong to a family of organic silicone compounds that are currently used extensively in industry. Those that are prone to volatilisation become minor compounds in biogas adversely affecting energetic applications. However, non-standard analytical methodologies are available to analyse biogas-based gaseous matrixes. To this end, different sampling techniques (adsorbent tubes, impingers and tedlar bags) were compared using two different configurations: sampling directly from the biogas source or from a 200 L tedlar bag filled with biogas and homogenised. No significant differences were apparent between the two sampling configurations. The adsorbent tubes performed better than the tedlar bags and impingers, particularly for quantifying low concentrations. A method for the speciation of silicon compounds in biogas was developed using gas chromatography coupled with mass spectrometry working in dual scan/single ion monitoring mode. The optimised conditions could separate and quantify eight siloxane compounds (L2, L3, L4, L5, D3, D4, D5 and D6) and trimethylsilanol within fourteen minutes. Biogas from five waste water treatment plants located in Spain, France and England was sampled and analysed using the developed methodology. The siloxane concentrations in the biogas samples were influenced by the anaerobic digestion temperature, as well as the nature and composition of the sewage inlet. Siloxanes D4 and D5 were the most abundant, ranging in concentration from 1.5 to 10.1 and 10.8 to 124.0 mg Nm(-3), respectively, and exceeding the tolerance limit of most energy conversion systems.

Extraction and analysis of avermectines in agricultural soils by microwave assisted extraction and ultra high performance liquid chromatography coupled to tandem mass spectrometry.

A method for the analysis of avermectines (abamectine, doramectine and ivermectine) in soils has been developed. The analytes are extracted with acetonitrile/water (90:10) by using microwave assisted extraction. The extract is cleaned-up through solid phase extraction with Oasis HLB cartridges and analyzed by ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Separation is obtained in 3 min. Extraction of analytes from the soil, that is the most critical point, has been studied in detail, and the effect of soil composition and aging time on the analytes recovery has been investigated.

Studies on the extraction of sulfonamides from agricultural soils.

The extraction of six sulfonamides (sulfadiazine, sulfadimidine, sulfathiazole, sulfachloropiridazine, sulfadimethoxine, and sulfaquinoxaline) from soils with different physicochemical characteristics and at several aging times was investigated. Conventional mechanical shaking, microwave-assisted extraction, ultrasound probe-assisted extraction and pressurized liquid extraction techniques were evaluated. The four techniques provided similar results when applied to freshly contaminated soils. However, microwave-assisted extraction was the most suitable to extract sulfonamide aged residues from soils. Microwave-assisted extraction was applied to eight soils aged for 3 months, using acetonitrile:buffer pH 9 (20:80) as the extraction solvent, and recoveries ranged from 15-25% for STZ to 42-64% for SDM.

Determination of ivermectin and transformation products in environmental waters using hollow fibre-supported liquid membrane extraction and liquid chromatography-mass spectrometry/mass spectrometry.

A simple and easy-to-use extraction method for aqueous samples based on hollow fibre-supported liquid membrane (HF-SLM) followed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) was developed to determine ivermectin and transformation products, the monosaccharide (TP1) and the aglycon of ivermectin (TP2). The proposed method attained enrichment factors up to 80, after optimising parameters, such as fibre length, organic solvent, stirring speed, salt level, pH in samples/fibre, extraction time and fibre emptying technique. Method validation with tap and lake water samples provided good linearity and detection limits of 0.2, 1.6 and 0.9 microg/l for ivermectin, TP1 and TP2 in lake water with RSD below 15%.

Analysis of trace levels of sulfonamides in surface water and soil samples by liquid chromatography-fluorescence.

Methods are reported for determining six sulfonamides used as veterinary drugs in water and soil samples. Analytes are isolated from water samples by solid-phase extraction on HBL cartridges and pre-concentration factors of up to 250 were obtained. Soil samples are treated using microwave-assisted extraction of analytes with acetonitrile and further clean up by solid-phase extraction. Determination is carried out by high-performance liquid chromatography using fluorimetric detection with precolumn derivatization with fluorescamine. The separation of the derivatized sulfonamides is performed on an octadecyl column using binary gradient elution with acetate buffer/acetonitrile mixtures. For water analysis, the detection limits of the whole process are in the low nanogram per liter level and recovery rates range from 70 to 104%, with standard deviations 2-11%. For soil analysis, extraction efficiency is evaluated using three soil samples with different physicochemical characteristics. Recovery rates range from 60 to 98% and detection limits are between 1 and 6ngg(-1).