Effective methods for the determination of triphenyltin residues in surface water and soil samples by high-performance liquid chromatography with tandem mass spectrometry.

Monitoring of triphenyltin (TPhT) in the environment, particularly to control its misuse in agriculture, is of great importance because of its high toxicity. In this work, methods for determination of TPhT residues in surface water and soil samples by liquid chromatography with tandem mass spectrometry (LC-MS/MS) were developed and validated. Different sample volumes and pH and elution solvent types and volumes were evaluated for solid phase extraction (SPE) of TPhT in surface water samples. The optimized conditions were 500 mg sorbent Strata C18-E, 100 mL of the sample, pH adjusted to 9.0 and 1 mL of methanol containing acetic acid as the eluent. For a 10 g soil sample, the extraction was established using a modified QuEChERS method with 10 mL of acidified acetonitrile followed by a clean-up step by dispersive solid phase extraction (dSPE) with C18. A full factorial 23 design of experiments was applied to optimize the sample preparation method for soil samples. Practical method limits of quantification were 0.1 µg L-1 and 10 µg kg-1 for surface water and soil samples, respectively. Satisfactory accuracy, with recoveries from 86 to 107% for surface water and 72 to 87% for soil samples, as well as good precision, with an overall relative standard deviation (RSD) from 3 to 8% was observed. The validated methods were applied to real samples and some residues of TPhT were found, especially in soil samples (30 to 190 mg kg-1), indicating the suitability for routine analysis.

Evaluation of the rotating disk sorptive extraction technique with polymeric sorbent for multiresidue determination of pesticides in water by ultra-high-performance liquid chromatography-tandem mass spectrometry.

The use of pesticides has been associated with the increase of productivity of crops and control of vectors that cause diseases. However, excessive use of these compounds can cause human health and environmental problems, especially regarding to water resources. In this work, a method for multiresidue determination of 62 pesticides in surface water using the rotating disk sorptive extraction (RDSE) technique for sample preparation and ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) for analysis was optimized and validated. The parameters time and rotational disk velocity for the extraction step, types and amounts of sorbents, sample pH, ionic strength, time and velocity of the rotating disk in the desorption step, as well different desorption solvents were evaluated. The best results were obtained using 50mL of sample, acidified at pH 2.0, and 2.5g of sodium chloride. The selected velocity of rotation in the extraction step was 1600rpm for 80min. Inside the disk cavity, a small amount (20mg) of the polymeric sorbent Oasis® HLB was used. The desorption step was performed immerging the disk in 3mL of methanol and rotating the disk at 1600rpm for 60min. Procedural calibration curves showed linearity between 0.05 or 0.1-2µgL-1, with r2>0.99 for all compounds. The method presented practical limit of quantification of 0.05 or 0.1µgL-1 and suitable accuracy and precision, with recoveries from 70.1 to 119.9% and RSD≤20% for the levels 0.05, 0.1, 0.5 and 2µgL-1. The validated method was applied to surface water samples from different river and residues of atrazine, azoxystrobin, clomazone, difenoconazole, epoxiconazole, propoxur, simazine and tebuconazole were found in the range of 0.06-0.35µgL-1. The results indicate that the proposed method is suitable for the determination of pesticide residues in surface water, allowing an easy and simultaneously preparation of several samples with low material consumption.

Imazethapyr and imazapic, bispyribac-sodium and penoxsulam: zooplankton and dissipation in subtropical rice paddy water.

Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is necessary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zooplankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD5, boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experiment (88 days after herbicide treatment).

Determination of pesticide residues and related compounds in water and industrial effluent by solid-phase extraction and gas chromatography coupled to triple quadrupole mass spectrometry.

Pollution of drinking water supplies from industrial waste is a result of several industrial processes and disposal practices, and the establishment of analytical methods for monitoring organic compounds related to environmental and health problems is very important. In this work, a method using solid-phase extraction (SPE) and gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) was developed and validated for the simultaneous determination of pesticide residues and related compounds in drinking and surface water as well as in industrial effluent. Optimization of the method was achieved by using a central composite design approach on parameters such as the sample pH and SPE eluent composition. A single SPE consisting of the loading on a polymeric sorbent of 100 mL of sample adjusted to pH 3 and elution with methanol/methylene chloride (10:90, v/v) permitted the obtaining of acceptable recoveries in most cases. The concentration factor associated with sensitivity of the chromatographic analysis permitted the achievement of the method limit of detection values between 0.01 and 0.25 µg L(-1). Recovery assays presented mean recoveries between 70 and 120% for most of the compounds with very good precision, despite the different chemical nature of the compounds analyzed. The selectivity of the method, evaluated through the relative intensity of quantification and qualification ions obtained by GC-QqQ-MS/MS, was considered adequate. The developed method was finally applied to the determination of target analytes in real samples. River water and treated industrial effluent samples presented residues of some compounds, but no detectable residues were found in the drinking water samples evaluated.