Dissipation of mecoprop-P, isoproturon, bentazon and S-metolachlor in heavy metal contaminated acidic and calcareous soil before and after EDTA-based remediation

The ability of contaminated farmland soils reclaimed by remediation to dissipate pesticides and thus to mitigate their unwanted environmental effects, i.e., leaching and run-off, was studied. Novel EDTA-based soil washing technology (EDTA and process waters recycling; no toxic emissions) removed 79 and 73% of Pb from acidic and calcareous soil with 740 and 2179 mg kg^-1 Pb, respectively. The dissipation kinetics of four herbicides: mecoprop-P, isoproturon, bentazon and S-metolachlor was investigated under field conditions in beds with maize (Zea mays) and barley (Hordeum vulgare). The biphasic First-Order Multi-Compartment (FOMC) model was used to fit experimental data and calculate the herbicides' half-life (DT₅₀) in soil. Remediation significantly (up to 64%) decreased dehydrogenase activity assessed as a marker of soil microbial activity and prolonged the DT₅₀ of herbicides in acidic soils from 16% (isoproturon) to 111% (S-metachlor). Remediation had a less significant effect on herbicide dissipation in calcareous soils; i.e., mecoprop-P DT₅₀ increased by 3%, while isoproturon and S-metachlor DT₅₀ decreased by 29%. Overall, the dissipation from remediated soils was faster than the average DT₅₀ of tested herbicides published in the Pesticides Properties DataBase. Results demonstrate that EDTA-based remediation of the studied soils does not pose any threat of extended herbicide persistence.

Electrochemical determination of bentazone using simple screen-printed carbon electrodes

Bentazone is one of the most problematic pesticides polluting groundwater resources. It is on the list of pesticides that are mandatory to analyze at water work controls. The current pesticide measuring approach includes manual water sampling and time-consuming chromatographical quantification of the bentazone content at centralized laboratories. Here, we report the use of an electrochemical approach for analytical determination of bentazone that takes 10 s. The electrochemical electrodes were manually screen printed, resulting in the low-cost fabrication of the sensors. The current response was linearly proportional to the bentazone concentration with a R² ~ 0.999. We demonstrated a sensitivity of 0.0987 μA/μM and a limit of detection of 0.034 μM, which is below the U.S. Health Advisory level. Furthermore, the sensors have proved to be reusable and stable with a drop of only 2% after 15 times reuse. The sensors have been applied to successfully quantify bentazone spiked in real groundwater and lake water. The sensing method presented here is a step towards on-site application of electrochemical detection of pesticides in water sources.

Methods comparison, transport and distribution of polar herbicides in the Baltic Sea

Two LC-MS/MS methods including different sample preparation and quantitative processes showed a good agreement for analysis of the herbicides MCPA, mecoprop, isoproturon, bentazon and chloridazon, and the metabolite chloridazon-methyl-desphenyl (CMD) in estuarine waters. Due to different sensitivity of the methods only one could be used to analyze marine samples. The transport of these compounds to the Baltic Sea via ten German estuaries and their distribution between coastal water and sediments was studied. The results showed that all selected compounds can be transported to the Baltic Sea (0.9-747ng/L). Chloridazon, bentazon, isoproturon and CMD were detected (0.9-8.9ng/L) in the coastal waters and chloridazon and isorproturon in the sediments (5-136pg/g d.w.). Levels of contaminants in the sediments could be influenced by the total organic carbon content. Concentrations observed in the Baltic Sea are most likely not high enough to cause acute effects, but long term effect studies are strongly recommended.

Dissipation of bentazone, pyrimethanil and boscalid in biochar and digestate based soil mixtures for biopurification systems

Biopurification systems, such as biofilters, are biotechnological tools to prevent point sources of pesticide pollution stemming from on-farm operations. For the purification processes pesticide sorption and mineralization and/or dissipation are essential and both largely depend on the type of filling materials and the pesticide in use. In this paper the mineralization and dissipation of three contrasting (14)C-labeled pesticides (bentazone, boscalid, and pyrimethanil) were investigated in laboratory incubation experiments using sandy soil, biochar produced from Pine woodchips, and/or digestate obtained from anaerobic digestion process using maize silage, chicken manure, beef and pig urine as feedstock. The results indicate that the addition of digestate increased pesticide mineralization, whereby the mineralization was not proportional to the digestate loads in the mixture, indicating a saturation effect in the turnover rate of pesticides. This effect was in correlation with the amount of water extractable DOC, obtained from the digestate based mixtures. Mixing biochar into the soil generally reduced total mineralization and led to larger sorption/sequestration of the pesticides, resulting in faster decrease of the extractable fraction. Also the addition of biochar to the soil/digestate mixtures reduced mineralization compared to the digestate alone mixture but mineralization rates were still higher as for the biochar/soil alone. In consequence, the addition of biochar to the soil generally decreased pesticide dissipation times and larger amounts of biochar led to high amounts of non-extractable residues of pesticide in the substrates. Among the mixtures tested, a mixture of digestate (5%) and biochar (5%) gave optimal results with respect to mineralization and simultaneous sorption for all three pesticides.

Re-evaluation of groundwater monitoring data for glyphosate and bentazone by taking detection limits into account

Current regulatory assessment of pesticide contamination of Danish groundwater is exclusively based on samples with pesticide concentrations above detection limit. Here we demonstrate that a realistic quantification of pesticide contamination requires the inclusion of "non-detect" samples i.e. samples with concentrations below the detection limit, as left-censored observations. The median calculated pesticide concentrations are shown to be reduced 10(4) to 10(5) fold for two representative herbicides (glyphosate and bentazone) relative to the median concentrations based upon observations above detection limits alone.

Influence of biochar amendments on the sorption-desorption of aminocyclopyrachlor, bentazone and pyraclostrobin pesticides to an agricultural soil

The many advantageous properties of biochar have led to the recent interest in the use of this carbonaceous material as a soil amendment. However, there are limited studies dealing with the effect of biochar on the behavior of pesticides applied to crops. The objective of this work was to determine the effect of various biochars on the sorption-desorption of the herbicides aminocyclopyrachlor (6-amino-5-chloro-2-cyclopropyl-4-pyrimidinacarboxylic acid) and bentazone (3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide) and the fungicide pyraclostrobin (methyl 2-[1-(4-chlorophenyl) pyrazol-3-yloxymethil]-N-methoxycarbanilate) to a silt loam soil. Aminocyclopyrachlor and bentazone were almost completely sorbed by the soils amended with the biochars produced from wood pellets. However, lower sorption of the herbicides was observed in the soils amended with the biochar made from macadamia nut shells as compared to the unamended soil, which was attributed to the competition between dissolved organic carbon (DOC) from the biochar and the herbicides for sorption sites. Our results showed that pyraclostrobin is highly sorbed to soil, and the addition of biochars to soil did not further increase its sorption. Thus, addition of biochars to increase the retention of low mobility pesticides in soil appears to not be necessary. On the other hand, biochars with high surface areas and low DOC contents can increase the sorption of highly mobile pesticides in soil.

Evaluation of the partial renewal of in situ phytoplankton microcosms and application to the impact assessment of bentazon and dimethenamid

Microcosms, each consisting of 2L natural surface seawater maintained in 2.3-L glass bottles, were immersed at a depth of 6m. The renewal of 10% of microcosm volumes was carried out every other day. Phytoplankton-containing seawater was used for renewal (previously filtered through 25-, 50- or 200-μm cut-off). Phytoplankton community pigment analysis (by HPLC) and flow cytometry analysis were performed. After 13 days, data exhibited phytoplankton characteristics in microcosms in the same range as that of the natural surrounding sea water over the same period. Furthermore, in these microcosms, a negative correlation was observed between the filtration cut-off used for renewal water, and the total cell count. Herbicides were tested as commercial mixtures at 1, 10 and 100 μgL(-1) active substance. Both Frontier® (dimethenamid) and Basamais® (bentazon) induced significant modifications of the phytoplankton populations at every concentration tested. Such results suggest a possible disturbance in polluted coastal areas.

Photocatalytic degradation of bentazone in soil washing wastes containing alkylpolyoxyethylene surfactants

Three alkylpolyoxyethylene surfactants bearing the same hydrophobic chain and a different number of oxyethylene groups were investigated as suitable candidates for the soil washing treatment of contaminated soil samples containing bentazone. Comparable good recoveries of the pesticide were obtained working with these surfactants. The photocatalytic treatment of the collected washing wastes, performed in the presence of suspended TiO(2) particles under irradiation with simulated sunlight, leads to the effective degradation of bentazone residues after a time depending on the nature and concentration of the chosen amphiphile. Brij 35 was found to be the best surfactant candidate, giving the faster abatement of the pesticide in the collected wastes. The overall treatment time depends on the bentazone mineralization kinetics, markedly slow in the presence of surfactants. Useful information about the photocatalytic degradation route was obtained from the HPLC-MS analysis of transient intermediates formed in water.

Measurements and modeling of pesticide persistence in soil at the catchment scale

Degradation of pesticides in soils is both spatially variable and also one of the most sensitive factors determining losses to surface water and groundwater. To date, no general guidance is available on suitable approaches for dealing with spatial variation in pesticide degradation in catchment or regional scale modeling applications. The purpose of the study was therefore to study the influence of various soil physical, chemical and microbiological characteristics on pesticide persistence in the contrasting cultivated soils found in a small (13 km(2)) agricultural catchment in Sweden and to develop and test a simple model approach that could support catchment scale modeling. Persistence of bentazone, glyphosate and isoproturon was investigated in laboratory incubation experiments. Degradation rate constants were highly variable with coefficients of variation ranging between 42 and 64% for the three herbicides. Multiple linear regression analysis and Mallows Cp statistic were employed to select the best set of independent parameters accounting for the variation in degradation. Soil pH and the proportion of active microorganisms (r) together explained 69% of the variation in the bentazone degradation rate constant; the Freundlich sorption co-efficient (K(f)) and soil laccase activity together explained 88% of the variation in degradation rate of glyphosate, while soil pH was a significant predictor (p<0.05) for isoproturon persistence. However, correlations between many potential predictor variables made clear interpretations of the statistical analysis difficult. Multiplicative models based on two predictors chosen 'a priori', one accounting for microbial activity (e.g. microbial respiration, laccase activity or the surrogate variable soil organic carbon, SOC) and one accounting for the effects of sorption on bioavailability, showed promise to support predictions of degradation for large-scale modeling applications, explaining up to 50% of the variation in herbicide persistence.

Factors responsible for rapid dissipation of acidic herbicides in the coastal lagoons of the Camargue (Rhône River Delta, France)

This study was aimed at investigating which processes cause acidic herbicides (e.g., bentazone, MCPA and dichlorprop) to rapidly disappear in the lagoons of the Rhône delta, which are peculiar brackish and shallow aquatic environments. The use of the model MASAS (Modeling of Anthropogenic Substances in Aquatic Systems) revealed that sorption, sedimentation, volatilization, flushing and abiotic hydrolysis had a minor role in the attenuation of the investigated herbicides. Laboratory scale biodegradation and photodegradation studies were conducted to better assess the significance of these two processes in the natural attenuation of herbicides in brackish (lagoons) waters with respect to fresh waters (canals draining paddy fields). Herbicide biodegradation rates were significantly lower in lagoon water than in canal water. Consequently, photodegradation was the main dissipation route of all investigated herbicides. The contribution of indirect photolysis was relevant for MCPA and dichlorprop while direct photolysis dominated for bentazone removal. There is a need to further investigate the identity of phototransformation products of herbicides in lagoons.

Transport and degradation of pesticides in a biopurification system under variable flux, Part I: a microcosm study

The efficiency of a biopurification system, developed to treat pesticide contaminated water, is to a large extent determined by the chemical and hydraulic load. Insight into the behaviour of pesticides under different fluxes is necessary. The behaviour of metalaxyl, bentazone, linuron, isoproturon and metamitron was studied under three different fluxes with or without the presence of pesticide-primed soil in column experiments. Due to the time-dependent sorption process, retention of the pesticides with intermediate mobility was significantly influenced by the flux. The higher the flux, the slower pesticides will be sorbed, which resulted in a lower retention. Degradation of the intermediate mobile pesticides was also submissive to variations in flux. An increase in flux, led to a decrease in retention, which in turn decreased the opportunity time for biodegradation. Finally, the presence of pesticide-primed soil was only beneficial for the degradation of metalaxyl.

Transport and degradation of pesticides in a biopurification system under variable flux Part II: A macrocosm study

Transport of bentazone, isoproturon, linuron, metamitron and metalaxyl were studied under three different flows in macrocosms. The aim was to verify the observations from Part I of the accompanying paper, with an increase in column volume and decrease in chemical and hydraulic load. Very limited breakthrough occurred in the macrocosms for all pesticides, except bentazone, at all flows. From batch degradation experiments, it was observed that the lag time of metamitron and linuron decreased drastically in time for all flows, indicating a growth in the pesticide degrading population. This in contrast to isoproturon and metalaxyl, where an increase in lag time could be observed in time for all flows. From the batch degradation experiments, it could be concluded that the influence of flow on the lag time was minimal and that the inoculation of the pesticide-primed soil had a little surplus value on degradation.

[Determination of biphenyl ether herbicides in water using HPLC with cloud-point extraction]

OBJECTIVE

To determine residues of multiple biphenyl ether herbicides simultaneously in water using high performance liquid chromatography (HPLC) with cloud-point extraction.

METHODS

The residues of eight biphenyl ether herbicides (including bentazone, fomesafen, acifluorfen, aclonifen, bifenox, fluoroglycofenethy, nitrofen, oxyfluorfen) in water samples were extracted with cloud-point extraction of Triton X-114. The analytes were separated and determined using reverse phase HPLC with ultraviolet detector at 300 nm. Optimized conditions for the pretreatment of water samples and the parameters of chromatographic separation applied.

RESULTS

There was a good linear correlation between the concentration and the peak area of the analytes in the range of 0.05-2.00 mg/L (r = 0.9991-0.9998). Except bentazone, the spiked recoveries of the biphenyl ether herbicides in the water samples ranged from 80.1% to 100.9%, with relative standard deviations ranging from 2.70% to 6.40%. The detection limit of the method ranged from 0.10 microg/L to 0.50 microg/L.

CONCLUSION

The proposed method is simple, rapid and sensitive, and can meet the requirements of determination of multiple biphenyl ether herbicides simultaneously in natural waters.

GIS based ArcPRZM-3 model for bentazon leaching towards groundwater

Groundwater contamination due to pesticide applications on agricultural lands is of great environmental concern. The mathematical models help to understand the mechanism of pesticide leaching in soils towards groundwater. We developed a user-friendly model called ArcPRZM-3 by integrating widely used Pesticide Root Zone Model version 3 (PRZM-3) using Visual Basic and Geographic Information System (GIS) based Avenue programming. ArcPRZM-3 could be used to simulate pesticide leaching towards groundwater with user-friendly input interfaces coupled with databases of crops, soils and pesticides. The outputs from ArcPRZM-3 could be visualized in user-friendly formats of tables, charts and maps. In this study we evaluated ArcPRZM-3 model by simulating bentazon leaching in soil towards groundwater. ArcPRZM-3 was applied to 37 sites in Woodruff County, Arkansas, USA to observe the daily average dissolved bentazon concentration for soybean, sorghum and rice at a depth of 1.8 m for a period of two years. Nineteen ranks of bentazon leaching potential were obtained using ArcPRZM-3 for all sites having different soil and crop combinations. ArcPRZM-3 simulation results for bentazon were compatible with the field monitored data in term of relative ranking and trend, although some uncertainties exist. This study indicated that macropore flow mechanism would be important in analyzing the effect of irrigation on groundwater contamination due to pesticides. Overall, ArcPRZM-3 could be used to simulate pesticide leaching towards groundwater more efficiently and effectively as compared to PRZM-3.

Influence of surfactants on the leaching of bentazone in a sandy loam soil

BACKGROUND

Surfactants are very often used for more efficient pesticide spraying, but knowledge about their influence on the leaching potential for pesticides is very limited. In the present study, the leaching of the herbicide bentazone [3-isopropyl-1H-2, 1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] was measured in columns with sandy loam soil with or without the addition of a non-ionic surfactant, octylphenol ethylene oxide condensate (Triton X-100, Triton), and an anionic surfactant, sodium dodecylbenzenesulfonate (SDBS), and in the presence of both surfactants (SDBS + Triton).

RESULTS

The mobility of bentazone (B) increased in the following order: B + Triton (slowest) < B + SDBS + Triton < B < B + SDBS (fastest). When Triton X-100 was applied to the soil together with bentazone, the leaching of bentazone in the soil decreased significantly compared with leaching of bentazone without the addition of surfactant. SDBS and Triton X-100 neutralised their influence on the leaching speed of bentazone in the soil columns when both surfactants were applied with bentazone.

CONCLUSION

From the study it can be concluded that, depending on their properties, surfactants can enhance or reduce the mobility of bentazone. By choosing a non-ionic surfactant, bentazone mobility can be reduced, giving time for degradation and thereby reducing the risk of groundwater pollution.

Testing MACRO (version 5.1) for pesticide leaching in a Dutch clay soil

Testing of pesticide leaching models against comprehensive field-scale measurements is necessary to increase confidence in their predictive ability when used as regulatory tools. Version 5.1 of the MACRO model was tested against measurements of water flow and the behaviour of bromide, bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide] and imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] in a cracked clay soil. In keeping with EU (FOCUS) procedures, the model was first calibrated against the measured moisture profiles and bromide concentrations in soil and in drain water. Uncalibrated pesticide simulations based on laboratory measurements of sorption and degradation were then compared with field data on the leaching of bentazone and imidacloprid. Calibrated parameter values indicated that a high degree of physical non-equilibrium (i.e. strong macropore flow) was necessary to describe solute transport in this soil. Comparison of measured and simulated bentazone concentration profiles revealed that the bulk of the bentazone movement in this soil was underestimated by MACRO. Nevertheless, the model simulated the dynamics of the bentazone breakthrough in drain water rather well and, in particular, accurately simulated the timing and the concentration level of the early bentazone breakthrough in drain water. The imidacloprid concentration profiles and its persistence in soil were simulated well. Moreover, the timing of the early imidacloprid breakthrough in the drain water was simulated well, although the simulated concentrations were about 2-3 times larger than measured. Deep groundwater concentrations for all substances were underestimated by MACRO, although it simulated concentrations in the shallow groundwater reasonably well. It is concluded that, in the context of ecotoxicological risk assessments for surface water, MACRO can give reasonably good simulations of pesticide concentrations in water draining from cracking clay soils, but that prior calibration against hydrologic and tracer data is desirable to reduce uncertainty and improve accuracy.

Spectrophotometric determination of pipazethate HCl, dextromethorphan HBr and drotaverine HCl in their pharmaceutical preparations

A simple, accurate and highly sensitive spectrophotometric method is proposed for the rapid determination of pipazethate hydrochloride, dextromethorphan hydrobromide and drotaverine hydrochloride using chromotrope 2B (C2B) and chromotrope 2R (C2R). The method consists of extracting the formed ion-associates into chloroform in the case of pipazethate HCl and dextromethorphan HBr or into methylene chloride in the case of drotaverine HCl. The ion-associates exhibit absorption maxima at 528, 540 and 532 nm with C2B and at 526, 517 and 522 nm with C2R for pipazethate HCl, dextromethorphan HBr and drotaverine HCl, respectively. The calibration curves resulting from the measurements of absorbance-concentration relations (at the optimum reaction conditions) of the extracted ion-pairs are linear over the concentration range 4.36-52.32 microg mL(-1) for pipazethate, 3.7-48.15 microg mL(-1) for dextromethorphan and 4.34-60.76 microg mL(-1) for drotaverine, respectively. The effect of acidity, reagent concentration, time, solvent and stoichiometric ratio of the ion-associates were estimated. The molar absorptivity and Sandell sensitivity of the reaction products were calculated. Statistical treatment of the results reflects that the procedure is precise, accurate and easily applied for the determination of the drugs under investigation in pure form and in their pharmaceutical preparations.

Determination of two phototransformation products of bentazone using quadrupole time-of-flight mass spectrometry

The transformation products 2-(isopropylcarbamoyl)phenylsulfamic acid and 2-(1-hydroxypropane-2-yl)-1,2-dihydroindazol-3-one could be determined during the photolysis of the herbicide bentazone. Degradation experiments were carried out with different types of water in a natural sunlight simulating system. Besides the anticipated hydroxylated bentazone, the second transformation product was identified by means of exact mass measurement using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC/QqToF MS). Both phototransformation products occurred in all water types tested. The required irradiation time was matrix dependent. 2-(Isopropylcarbamoyl)phenylsulfamic acid was detected in a drainage channel in the Ebro river delta (Catalonia, Spain).

Spectrophotometric determination of pipazethate hydrochloride in pure form and in pharmaceutical formulations

Three simple, sensitive, and reproducible spectrophotometric methods (A-C) for the determination of pipazethate hydrochloride (PiCl) in pure form and in pharmaceutical formulations are described. The first and second methods, A and B, are based on the oxidation of the drug by Fe3+ in the presence of o-phenanthroline (o-phen) or bipyridyl (bipy). The formation of tris-complex upon reactions with Fe3+-o-phen and/or Fe3+-bipy mixture in an acetate buffer solution of the optimum pH values was demonstrated at 510 and 522 nm, respectively, with o-phen and bipy. The third method, C, is based on the reduction of Fe(III) by PiCl in acid medium and subsequent interaction of Fe(II) with ferricyanide to form Prussian blue, which exhibits an absorption maximum at 750 nm. The concentration ranges are from 0.5 to 8, 2 to 16, and 3 to 15 microg/mL for Methods A-C, respectively. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The molar absorptivity, Sandell sensitivity, and detection and quantitation limits were calculated. The developed methods were successfully applied to the determination of PiCl in bulk and pharmaceutical formulations without any interference from common excipients. The relative standard deviations were < or =0.83% with recoveries of 98.9-101.15%.

Simulating solute transport in a structured field soil: uncertainty in parameter identification and predictions

Dual-permeability models have been developed to account for the significant effects of macropore flow on contaminant transport, but their use is hampered by difficulties in estimating the additional parameters required. Therefore, our objective was to evaluate data requirements for parameter identification for predictive modeling with the dual-permeability model MACRO. Two different approaches were compared: sequential uncertainty fitting (SUFI) and generalized likelihood uncertainty estimation (GLUE). We investigated six parameters controlling macropore flow and pesticide sorption and degradation, applying MACRO to a comprehensive field data set of bromide andbentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2dioxide] transport in a structured soil. The GLUE analyses of parameter conditioning for different combinations of observations showed that both resident and flux concentrations were needed to obtain highly conditioned and unbiased parameters and that observations of tracer transport generally improved the conditioning of macropore flow parameters. The GLUE "behavioral" parameter sets covered wider parameter ranges than the SUFI posterior uncertainty domains. Nevertheless, estimation uncertainty ranges defined by the 5th and 95th percentiles were similar and many simulations randomly sampled from the SUFI posterior uncertainty domains had negative model efficiencies (minimum of -3.2). This is because parameter correlations are neglected in SUFI and the posterior uncertainty domains were not always determined correctly. For the same reasons, uncertainty ranges for predictions of bentazone losses through drainflow for good agricultural practice in southern Sweden were 27% larger for SUFI compared with GLUE. Although SUFI proved to be an efficient parameter estimation tool, GLUE seems better suited as a method of uncertainty estimation for predictions.

Time effect on bentazone sorption and degradation in soil

Previous sorption/desorption batch experiments have indicated that bentazone is weakly sorbed by soils. In addition, field experiments have shown that 4% of the bentazone sprayed can be leached to drainage water. In order to complete bentazone characterisation, we have assessed the effect of time on its behaviour in contrasting soils. In laboratory studies, bentazone was added to three topsoils (sandy, loamy and clay soils). Bentazone degradation, sorption/desorption kinetics and isotherm measurements were carried out at different times. At 160 days after treatment, bentazone mineralisation amounts varied from 2.1% (sandy soil) to 14% (clay soil). The extractable amounts became lower (from 97% after treatment to 12% after 160 days for the clay soil) and a greater number of desorption series was needed to obtain these products. Nevertheless, at the end of the experiments, a small amount of bentazone was still extracted by water. At the same time, bound residues of bentazone reached 65% in clay soil. Statistical analysis indicated effects of both residence time and soil type on bentazone behaviour.

Preferential flow of bromide, bentazon, and imidacloprid in a Dutch clay soil

Leaching to ground water and tile drains are important parts of the environmental assessment of pesticides. The aims of the present study were to (i) assess the significance of preferential flow for pesticide leaching under realistic worst-case conditions for Dutch agriculture (soil profile with thick clay layer and high rainfall) and (ii) collect a high-quality data set that is suitable for testing pesticide leaching models. The movement of water, bromide, and the pesticides bentazon [3-isopropyl-1H-2, 1,3-benzothiadiazine-4(3H)-one-2,2-dioxide] and imidacloprid [1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine] was monitored in a clay soil for about 1 yr. The 1.2-ha field was located in the central part of the Netherlands (51 degrees 53' N, 5 degrees 43' E). The soil was a Eutric Fluvisol cropped with winter wheat (Triticum aestivum L.). Tile drains were present at a 0.8- to 0.9-m depth and the ground water level fluctuated between a 0.5- and 2-m depth. All chemicals were applied in spring. None of the soil concentration profiles showed bimodal concentration distributions. However, for each substance the highest concentration in drain water was found in the first drainage event after its application, which indicates preferential flow. This preferential flow is probably caused by permanent macropores that were present in the 0.3- to 1.0-m layer. At the time of the first drainage event, the drain water concentration of each substance was about an order of magnitude higher than its ground water concentration. Thus, the flux concentrations in drain water proved to be a more sensitive detector of preferential flow than the resident concentrations in the soil profile and the ground water.

Development of an FIA system with amperometric detection for determination of bentazone in estuarine waters

On the basis of its electrochemical behaviour a new flow-injection analysis (FIA) method with amperometric detection has been developed for quantification of the herbicide bentazone (BTZ) in estuarine waters. Standard solutions and samples (200 microL) were injected into a water carrier stream and both pH and ionic strength were automatically adjusted inside the manifold. Optimization of critical FIA conditions indicated that the best analytical results were obtained at an oxidation potential of 1.10 V, pH 4.5, and an overall flow-rate of 2.4 mL min(-1). Analysis of real samples was performed by means of calibration curves over the concentration range 2.5x10(-6) to 5.0x10(-5) mol L(-1), and results were compared with those obtained by use of an independent method (HPLC). The accuracy of the amperometric determinations was ascertained; errors relative to the comparison method were below 4% and sampling rates were approximately 100 samples h(-1). The repeatability of the proposed method was calculated by assessing the relative standard deviation (%) of ten consecutive determinations of one sample; the value obtained was 2.1%.

Formation of bound residues of 8-hydroxybentazon by oxidoreductive catalysts in soil

This study was performed to determine which oxidoreductive catalysts were most efficient in catalyzing the binding of 8-hydroxybentazon to soil humic substances. 8-Hydroxybentazon was completely transformed by an oxidoreductive enzyme, laccase of Myceliophthora thermophila, at pH 3.0-7.0 within 30 min. When abiotic catalysts, manganese(IV), iron(III), and aluminum oxides were used in the same pH range, 8-hydroxybentazon was completely transformed only by manganese(IV) oxide (delta-MnO2), but a relatively small amount of 8-hydroxybentazon was transformed by iron(III) oxide and aluminum oxide. The adsorption of 8-hydroxybentazon in the soil showed an H-type and coincided well with the Langmuir isotherm. To better understand the factors involved in the rapid and strong binding of 8-hydroxybentazon with soil humic substances, 8-hydroxybentazon transformation by oxidoreductive catalysts was studied in various soil conditions: air-dried, preincubated, sterilized, and iron(III) oxide and manganese(IV) oxide free. 8-Hydroxybentazon was completely transformed within 24 h in the decreasing order of preincubated, air-dried, and sterilized soils. However, little transformation was observed in the iron(III) oxide and manganese(IV) oxide free soils. These results suggest that the major catalyst responsible for the rapid and strong binding of 8-hydroxybentazon to soil humic substances is a metal oxide, manganese(IV) oxide, not a soil oxidoreductive enzyme.

Rate of bentazone transformation in four layers of a humic sandy soil profile with fluctuating water table

The rate of transformation of a pesticide as a function of the depth in the soil is needed as an input into computations on the risk of residues leaching to groundwater. The herbicide bentazone was incubated at 15 degrees C in soil materials derived from four layers at depths of up to 2.5 m in a humic sandy soil profile with a fluctuating water table (0.8 to 1.4 m), while simulating the redox conditions existing in the field. Gamma-irradiation experiments indicated that bentazone is mainly transformed by microbial activity in the soil. The rate constant for transformation was highest in the humic sandy top layer; it decreased with depth in the sandy vadose subsoil. However, material from the top of the phreatic aquifer had a higher rate constant than that from the layers just above. The presence of fossil organic material in the fluviatile water-saturated sediment probably stimulated microbial activity and bentazone transformation. The changes in the transformation rate constant with depth showed the same trend as those in some soil factors, viz organic carbon content, water-extractable phosphorus and microbial density as measured by fluorescence counts. However, the (low) concentration of dissolved organic carbon (DOC) in the top of the aquifer did not fit the trend. The rate constant for bentazone transformation in the layers was higher at lower initial contents of the herbicide.

Conductimetric determination of reproterol HCl and pipazethate HCl and salbutamol sulphate in their pharmaceutical formulations

A simple and sensitive conductimetric method for the determination of salbutamol sulphate and reproterol and pipazethate hydrochlorides is presented based on their ion associates with phosphotungstic and phosphomolybdic acids. The effect of solvent, molar ratio, reagent concentration and temperature were studied, and the solubility products of the formed ion associates were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.82-100.54, 99.75-100.12 and 99.95-100.40%, and coefficient of variation 0.28-0.52, 0.16-0.36 and 0.19-0.33 for salbutamol sulphate, reproterol HCl and pipazathate HCl, respectively.

Flow injection potentiometric determination of pipazethate hydrochloride

New plastic membrane electrodes for pipazethate hydrochloride based on pipazethatium phosphotungstate, pipazethatium phosphomolybdate and a mixture of the two were prepared. The electrodes were fully characterized in terms of composition, life span, pH and temperature and were then applied to the potentiometric determination of the pipazethate ion in its pure state and pharmaceutical preparations under batch and flow injection conditions. The selectivity of the electrodes towards many inorganic cations, sugars and amino acids was also tested.

Development of a solid-phase extraction method for phenoxy acids and bentazone in water and comparison to a liquid-liquid extraction method

A rapid solid-phase extraction (SPE) method was developed for the determination of bentazone and the phenoxy acids 2,4-D, dichlorprop, MCPA, and mecoprop in Norwegian environmental water samples. Cartridges with a high-capacity cross-linked polystyrene-based polymer were used for off-line preconcentration. The effects of elution solvent, elution volume, sample volume, sorbent mass, pH, and flow rate on the recoveries of the pesticides were investigated using HPLC. Average recovery of >90% was achieved with 500 mg sorbents using 2 mL of methanol with 5% NH3 as elution solvent. The recoveries were independent of sample pH in the tested range of pH 1-7. Using a sample volume of 200 mL, the limits of determination for the phenoxy acids and bentazone are 0.02 microg/L. Sample volumes up to 2000 mL at a flow rate of 60 mL/min could be handled without any loss of analytes, which makes it possible to lower the limits of determination. The SPE method was compared to a routinely used liquid-liquid extraction method. Three different water matrices spiked at 1.0 and 0.05 microg/L were extracted, and the quantification was performed by GC-MS. Both methods permitted the determination of phenoxy acids and bentazone in distilled water, creek water, and well water down to a level of 0.05 microg/L with recoveries >80% for 200 mL samples. Important advantages of the SPE method compared to the liquid-liquid extraction method were the short extraction times, lack of emulsions, use of disposable equipment, and reduced consumption of organic solvents.

Chiral resolution of the enantiomers of 7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide using high-performance liquid chromatography on cellulose-based chiral stationary phases

Analytical high-performance liquid chromatography (HPLC) methods using derivatized cellulose chiral stationary phases (CSPs) were developed for the separation of the enantiomers of 7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide ((+/-) IDRA21). In previous studies, (+/-) IDRA21 has been found to have an interesting inhibitory effect on the desensitization of alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid (AMPA) receptor and improve cognition in animals. This compound possess one chiral carbon atom, but very little information has been reported on the stereoselectivity of his activity. Therefore resolution of the enantiomers of this compound and subsequent identification of stereospecificity in his pharmacological actions are clearly matters of interest. The resolution were made under normal- and reversed-phase conditions using a mobile phase consisting of n-hexane:2-propanol (70/30, v/v) and water:acetonitrile (60/40, v/v) respectively, and a CSP of silica-based cellulose tris-3,5-dimethyl-phenylcarbamate (Chiralcel OD and Chiracel OD-R). The enantiomeric nature of eluates was confirmed by circular dichroism (CD) spectra. A baseline separation (R(S) > 1.5) was obtained in both cases. Furthermore the isolation of optical isomers of (+/-) IDRA21 was performed using a semipreparative column packed with the same cellulose OD CSP.

[Determination of bentazon and 2,4-D butyl in mixture formulation by HPLC]

Bentazon and 2,4-D butyl(the active ingredients of Cao Di) were determined by reversed phase HPLC aimultancously using methanol/acetonitrile/citrate buffer(pH 3.1) as a mobile phase on Shim-pack clc-CN column. Results showed that the linear correlation and recovery of 2,4-D butyl were 1.000 and (100.2 +/- 0.8)% respectively, and those of bentazon were 1.000 and (98.6 +/- 0.9)% respectively. The coefficients of variation for bentazon and 2,4-D butyl were all was 0.37%.

Semi-permeable surface analytical reversed-phase column for the improved trace analysis of acidic pesticides in water with coupled-column reversed-phase liquid chromatography with UV detection. Determination of bromoxynil and bentazone in surface water

The coupled-column (LC-LC) configuration consisting of a 3 microm C18 column (50 x 4.6 mm I.D.) as the first column and a 5 microm C18 semi-permeable-surface (SPS) column (150 x 4.6 mm I.D.) as the second column appeared to be successful for the screening of acidic pesticides in surface water samples. In comparison to LC-LC employing two C18 columns, the combination of C18/SPS-C18 significantly decreased the baseline deviation caused by the hump of the co-extracted humic substances when using UV detection (217 nm). The developed LC-LC procedure allowed the simultaneous determination of the target analytes bentazone and bromoxynil in uncleaned extracts of surface water samples to a level of 0.05 microg/l in less than 15 min. In combination with a simple solid-phase extraction step (200 ml of water on a 500 mg C18-bonded silica) the analytical procedure provides a high sample throughput. During a period of about five months more than 200 ditch-water samples originating from agricultural locations were analyzed with the developed procedure. Validation of the method was performed by randomly analyzing recoveries of water samples spiked at levels of 0.1 microg/l (n=10), 0.5 microg/l (n=7) and 2.5 microg/l (n=4). Weighted regression of the recovery data showed that the method provides overall recoveries of 95 and 100% for bentazone and bromoxynil, respectively, with corresponding intra-laboratory reproducibilities of 10 and 11%, respectively. Confirmation of the analytes in part of the samples extracts was carried out with GC-negative ion chemical ionization MS involving a derivatization step with bis(trifluoromethyl)benzyl bromide. No false negatives or positives were observed.

Determination of bentazon residues in water by high-performance liquid chromatography. Validation of the method

A method for determination of bentazon residues in water has been developed. The method involves solid-phase extraction with C18 extraction tubes and high-performance liquid chromatographic analysis. A C18 column and guard column were used with UV detection at 230 nm, a mobile phase of methanol-water (60:40, v/v) at pH 4.6 (phosphoric acid) and a flow-rate of 0.8 ml/min. After optimization of the extraction and separation conditions, the method was validated. The method developed can be used for determination of bentazon in water, within the international limits of 0.1 microgram/l, with a 500-fold pre-concentration.

Evaluation of herbicide migration from water to gorgonzola and mozzarella cheeses in industrial processing

The possibility of migration of atrazine, simazine, terbuthylazine, molinate and bentazon herbicides from contaminated water used in the manufacture of gorgonzola and mozzarella cheeses was verified in an industrial plant in an agricultural area in northern Italy. In a milk-processing plant, water samples were drawn from five wells; samples of milk, curd and finished products were collected from the respective production lines. In all samples, the herbicide residues were detected by gas chromatographic analysis. The results show that herbicide residues detected in water were not found in the finished products even if residues were found in the intermediate products (curd).

Determination of phenoxyacid herbicides in water

Novel clean-up techniques for a polymeric precolumn (PLRP-S) for the subsequent determination of bentazone and eight phenoxy acid herbicides in surface water samples are described. After preconcentration of the components at pH 3 on a 10 x 2 mm I.D. precolumn, the technique consists of a clean-up with 1000 microliters of 0.1 mol/l sodium hydroxide solution (pH 12.5) and of a heartcut consisting of four precolumn bed volumes of eluent directed to waste followed by ten precolumn bed volumes of eluent directed to the analytical column. Analytical separation is performed with acetonitrile-water (30:70) containing 0.005 mol/l of tetrabutylammonium hydrogensulphate (pH 8.3) (which is also the desorption eluent during heartcutting) on a polymeric analytical column (PLRP-S). With 25 ml of surface water, spiked at 0.25 and 1 microgram/l, applied to the precolumn, recoveries for all components were over 85% with a relative standard deviation (n = 5) of ca. 9% at 0.25 microgram/l and ca. 2% at 1 microgram/l. Detection limits in surface water samples are 0.05-0.1 microgram/l. Owing to automation, the total analysis time is ca. 30 min.

Enantiomers of benzothiadiazine diuretics by direct chromatographic resolution of the racemic drugs

A number of racemic benzothiadiazine diuretics and two carbonyl analogue drugs were resolved into their optical isomers by liquid chromatography on chiral polyacrylamides 1. Enantiomeric resolution, which was, in some cases, almost complete, depended considerably on the substitution of the heterocyclic moiety of the drug molecules. Synthesis of the new adsorbent lb is described. The enantiomers of the benzothiadiazines penflutizide (2a) and bendroflumethiazide (2b) in high optical purity, as well as enriched (+)-buthiazide (2j) were obtained by repeated chromatography on a semipreparative scale. Chiroptical data, optical purity employing the chromatographic method, and first-order racemization kinetics as a function of pH in aqueous solutions were determined.

Ion-pair extraction cleanup for liquid chromatographic determination of bentazon in crops and soil

Bentazon was selectively extracted as an ion pair with tetrabutylammonium ion into dichloromethane. This technique was used to clean up crop and soil samples before determination of bentazon by reverse phase liquid chromatography and UV detection. Recoveries from potatoes, cucumbers, wheat grain, and clay soil were 77-103%, with a detection limit of 0.02 mg/kg.

Application of conventional (DC) and differential pulse polarography (DPP) to the quality control of benzothiadiazines in tablets. Simultaneous determination of hydrochlorothiazide and dihydralazine sulphate in mixtures with minimization of interaction by the use of a zero covariance in the calibration

A previous study of the polarographic behaviour of 14 benzothiadiazines having diuretic properties enabled possible reaction mechanisms to be proposed and gave the opportunity to determine the best conditions for analytical application. The results obtained with benzthiazide as an example of the unsaturated compounds, bendrofluazide as the dihydro compound, and hydrochlorothiazide determined together with dihydralazine are reported. The electroactivity of these last two substances was made the object of a mathematical study for the correction of reciprocal interference.

HPLC determination of benzthiazide in biologic material

An assay was developed for benzthiazide in plasma, urine and feces, using high performance liquid chromatography (HPLC). A reverse-phase column was employed, with quantitation af 280 nm, using polythiazide as an internal standard. In three of four human subjects who received a 50 mg benzthiazide tablet the plasma concentrations were below the 10 ng ml-1 sensitivity limit of the assay, and the urinary recovery averaged less than one per cent of the dose. One subject received a 50 mg dose as both a tablet and a solution; the urinary recoveries for these two doses were 1.7 and 10.4 per cent, respectively. Fecal samples, obtained from two subjects who received 50 mg tablets, were estimated to contain approximately 80 per cent of the administered dose.