Simultaneous determination of fenpropimorph and the corresponding metabolite fenpropimorphic acid in soil

Summary An analytical procedure for the simultaneous determination of fenpropimorph and its main metabolite fenpropimorphic acid in soil is reported. Extraction with acetone/water (2:1), liquid/liquid partition with dichloromethane and clean-up using gel permeation chromatography is employed to concentrate the analytes. Methylation of the polar metabolite is absolutely required for GC/MS and GC/NPD. The parent compound fenpropimorph is not influenced by this derivatization step. The detection limits are 0.005 mg/kg for fenpropimorph and 0.010 mg/kg for fenpropimorphic acid.     

Volatilization of 14C-Labelled Fenpropimorph after Application to Plants and Soil under Simulated Outdoor Conditions

Abstract

The volatility of fenpropimorph was investigated in a laboratory chamber constructed for studying the volatilization of “4C-labelled pesticides from plant and soil surfaces. Summer barley was cultivated on experimental platforms (0.5 m²) filled with soil and treated in an application chamber with ¹⁴C-labelled fenpropimorph formulation (Corbel^R) at the beginning of ear emergence. After application, the platform was transferred into the volatilization chamber where a 96 h outdoor weather scenario was simulated. The results of three experiments demonstrated that up to 60% of the initial total radioactivity could be released from the plant-soil system within 96 h, most of it being the unchanged ¹⁴C-fenpropimorph which undergoes a fast oxidative (degradation by solar irridation in the atmoshpere. Furthermore, ¹⁴CO, was detected in quantities of 1.1 to 1.8%. After plant extraction, however, mainly polar metabolites, such as fenpropimorh acid, were found four days alter application by Radio-HPLC-analysis. In order to evaluate the volatilization behaviour of fenpropimorph sprayed to bare soils, three additional experiments were carried out showing a volatilization rate of 11.4% at most, much lower than those of plant surfaces.     

Degradation of Isoproturon in Soil in Relation to Changes of Microbial Biomass and Activity in Small-Scale Laboratory and Outdoor Studies

Abstract

The soil degradation of isoproturon under standardized laboratory conditions was compared to that carried out in an outdoor experiment using lysimeters. After application of ¹⁴C-labelled formulated isoproturon (1.5 kg A.I./ha), radiochemical analysis, as well as microbial investigations, were performed to relate changes in soil microbial biomass to its capability of degrading isoproturon. The results showed that the microbial biomass, as well as its dehydrogenase activity, varied under field conditions due to fluctuations of temperature and soil moisture. In the laboratory experiment the microbial biomass decreased during the 100 day experimental period, this reduction being the result of the experimental conditions. Consequently, the herbicide was degraded more quickly in the outdoor experiment where leaching, formation of ¹⁴CO₂ uptake by plants, and photolysis also took place, than in the laboratory experiment. Further microbiological investigation in the laboratory experiment showed that specific populations known to be responsible for the metabolic degradation of the compound were enhanced in the isoproturon-treated soil.     

Movement of Phosphamidon in Soil Columns

Abstract

Adsorption and movement of phosphamidon, a systemic non-ionic insecticide, was studied using two different types of Indian soil, clay loam and silt loam, of alluvial origin. Equilibrium adsorption coefficient, K, values determined by batch slurry technique were in the order: clay loam>silt loam. The distribution coefficient, K_d , for both soils in batch adsorption as well as in columns was also calculated. The phosphamidon movement measured in soil columns during water infiltration was in the order: silt loam > clay loam. This order was anticipated from the K and K_d values. A larger amount of water was needed for leaching the phosphamidon to 60 inches in clay loam than in silt loam soil.     

Estimation of distribution coefficient of polonium in geological matrices around uranium mining site

In case of ground (groundwater) contamination or contaminants release from the disposal modules (facilities) to the geo-environment, the fate of contaminant transport is mainly governed by the parameter called distribution (partition) coefficient, K _d. It is a measure of sorption of contaminants to soils. For that the sorption of polonium in soil were carried out using laboratory batch method in different soil samples collected from different places around Turamdih uranium mining site. The kinetics of polonium sorption were also carried out at different time intervals which clearly indicates that sorption equilibrium for polonium achieved at around 72 h. The K _d for polonium varies from 1,443 to 7,501.3 L/kg in soil samples. Chemical characterization of soil and ground water samples were carried out to know the effect of various chemical parameters with distribution coefficient of polonium.     

Estimation of distribution coefficient of uranium around a uranium mining site

Distribution coefficient (K _d) of uranium and its daughter products are very important for migration study around uranium mining sites. Since the distribution coefficient depends very much on the soil and groundwater chemistry, generation of site specific K _d is very important. In the literature there is a large variation of K _d values of uranium. For realistic prediction of contaminant migration, literature K _d value is not very effective. So site specific experimental K _d values are required. The present study emphasizes on the estimation of site specific distribution coefficient for uranium around a uranium mining site. The soil and groundwater parameters which affect the K _d value of uranium have also been estimated. Soil and groundwater samples from nine locations around Turamdih uranium mining site were collected and chemically characterized for various parameters. The distribution coefficient of uranium in top and one meter depth soil samples from above locations were estimated using laboratory batch method. The distribution coefficient of uranium varies from 69 ± 4 to 5524 ± 285 l/kg. No significant difference in uranium K _d values was observed for top and one meter depth soil samples. In the top and one meter depth soil samples uranium K _d values vary from 129 ± 8 to 5524 ± 285 and 69 ± 4 to 3862 ± 195 l/kg respectively. For the estimation of distribution coefficient of uranium different parameters like equilibration time, solid to solution ratio, method of tracer addition to solution, solid-solution separation method etc. have been optimized. The distribution coefficient of uranium determined in the present study will be used for the migration study of uranium around uranium mining sites.     

Plutonium-239 sorption and transport on/in unsaturated sediments: comparison of batch and column experiments for determining sorption coefficients

Sorption (distribution) coefficients of plutonium were most often derived by static batch experiments. However, it is not clear how unsaturated flow conditions including moisture content and pore water velocity change the sorption coefficients. Transport experiments of plutonium through the unsaturated sediments packed into the columns were then performed in order to determine the sorption coefficients (column-K _ds). Static batch experiments were also conducted to obtain batch-K _ds and then compare the differences between batch-K _ds and column-K _ds. The results show that unsaturated flow conditions had no significant effect on column-K _ds, and the average column-K _d value was 1.74 ± 0.02 m³/kg. By comparison, batch-K _d values spanned several orders of magnitude, regardless of the specified liquid–solid conditions. Moreover, the batch-K _d (22.7 m³/kg) at the standard L/S (4 mL/g) recommended by ASTM D 4319 was over an order of magnitude larger than the average column-K _d.     

High-Performance Gel Permeation Chromatography of Pectins

Abstract

A high-performance gel permeation chromatographic (GPC) method was developed to determine the molecular weight distribution of pectins. The chromatographic system consisted of a hydrophilic coated silica (SynChropak) as the packing and a pH 3.7 acetate buffer as the mobile phase. By use of this system, high-methoxy, low-methoxy, and amidated pectins could be analyzed within fifteen minutes. By determining partition coefficients (K_d) of pectins as a function of mobile phase composition, K_d values were found to be independent of ionic strength from 0.055 to 0.7 M using pH 3.7 acetate buffers, which was in agreement, with intrinsic viscosity data.     

分子印迹固相萃取-高效液相色谱法测定猪肉中红霉素残留

采用沉淀聚合法,以红霉素（erythromycin,ERY）为模板,甲基丙烯酸（methacrylic acid,MAA）为功能单体,乙二醇二甲基丙烯酸酯（ethyleneglycoldimethacrylate,EGDMA）为交联剂,甲醇/乙腈（1:4,v/v）为致孔剂制备了ERY分子印迹聚合物（molecularly imprinted polymers,MIPs）。通过扫描电镜、平衡吸附实验等对制备的印迹和非印迹聚合物进行表征和测定,结果表明所制备的MIPs对ERY具有特异性吸附作用。Scatchard分析证明MIPs对ERY的吸附存在两类不同结合位点,最大表观结合量（Q_max）和平衡解离常数（K_d）分别为Q_max1=45.24 mg/g,K_d1=0.028 g/L; Q_max2=87.53 mg/g,K_d2=0.20 g/L。以制备的MIPs为吸附剂的分子印迹固相萃取柱,结合高效液相色谱法能够快速检测猪肉样品中的ERY残留,线性范围为0.5~50 mg/L（r²=0.9994）,检出限（S/N=3）为0.2 mg/kg。猪肉样品中不同添加水平下ERY的加标回收率为95.2%~104.2%,相对标准偏差（RSD）小于5%。该方法选择性好,灵敏、可靠,可用于猪肉等复杂食品样本中ERY残留的检测。     

A New Organophosphorus Insecticides Removal Process Using Fly ASH

Abstract

Fly ash and soil mixtures with a range of fly ash content from 1 to 100% were used to study adsorption and desorption of four organophosphorus insecticides, ethyl parathion, methyl parathion, fenitrothion and fenthion, in batch experiments. The object of the study was to develop a treatment process using fly ash as sorbent material to isolate/immobilize organic contaminants from aqueous solutions. The adsorption isotherms fit the Freundlich equation x/m=K_dC^1/n. The K_d values increase with the increase of the fly ash content. The isotherms seem to fit the S type, in mixtures of soil with a fly ash content from 0 to 10%, which implies that adsorption becomes easier as the concentration in the liquid phase increases. In mixtures of soil with a fly ash content from 25 to 50% the isotherms become L type and correspond to a decrease of site availability as the solution concentration increases. Finally in mixtures of soil with a fly ash content over 50%, C type adsorption was observed which correspond to a constant partition of the insecticides between the bulk solution and the adsorbent. Mass balance estimations show that the mean percent amounts of insecticides for a range of concentration 0.5–15 mg/l, removed by adsorption in the soil sample are 81.56 % for ethyl parathion, 48.97 % for methyl parathion, 67.06 % for fenitrothion and 86.65 % for fenthion. The adsorption increases as the fly ash content increased and reach the 100% in the “pure” fly ash. The adsorbed amounts of insecticides in mixtures of soils with >50% fly ash content, are up to 99%. In contrast, the amounts of desorption in water decrease as the fly ash content increase.

The results of this research demonstrate that the fly ash shows a significant capacity for adsorption of organophosphorus compounds from aqueous solution and can be used for pesticide removal process.     

POLAROGRAPHIC REDUCTION OF TRIPHENYLTIN FLUORIDE

Abstract

Polarographic reduction of triphenyltin fluoride in aqueous ethanol yields a one electron, irreversible wave. The product is hexaphenylditin. Formation of hexaphenylditin on the electrode surface causes non-linearity of the i_d versus concentration curve at high concentrations.     

Extrapolation studies on adsorption of thorium and uranium at different solution compositions on soil sediments

Study on adsorption of thorium and uranium radionuclides by a soil sediment as a function of ionic composition of Ca, Mg and Na has been carried out. Experimentally determined slopes represents an average of adsorption on soil sediments having different relative affinities for thorium, uranium, calcium and magnesium. Both thorium and uranium were found to be adsorbed to ion-exchange sites together with calcium and magnesium cations as effective competitors An extrapolated equation for the distribution coefficientK _d was formed for both radionuclides thorium and uranium at the specified site where the soil sediments were sampled. The combined cation concentration of both calcium and magnesium in solution correlates linearly with the measuredK _d ^Th,U values.     

A review on distribution coefficient (Kd) of some selected radionuclides in soil/sediment over the last three decades

This review paper presents the different methods to estimate K_d and subsequent compiles of the K_d data on U, Ra, Th, ¹³⁷Cs and ⁶⁰Co in soil/sediment under various aquatic medium based on the extensive literature survey over the last 3-decades (1990–2019). The estimated K_d values show a very wide range and make more difficult to derive generic value. The finding suggests that K_d values are to be estimated for site-specific conditions while assessing the radionuclide transport modeling and risk analysis around the nuclear facilities. Review includes research papers, reports, reviewed papers, dissertations, published compilations and other technical documents.

     

Anodic Polarographic Behaviour of Hydrolyzed Penicillin V

Abstract

The electroactivity of a degradation product from penicillin V is described. This electroactive product is formed by acidic hydrolysis at pH 4.0 and heating at 90°C for 60 minutes.

This derivative has not been identified, but would seem to contain a thiol group. It gives a diffusion controlled anodic polarographic wave with a peak potential of -0.204 V versus SCE at pH 4.0.

The developed method has been applied to the analysis of penicillin V dosage forms and a recovery of 100.8 has been obtained.     

HPLC-Methods for Separation and Quantitation of Reserpin and its Main Degradation Products

Abstract

An analytical method suitable for the stability control of dosage forms containing reserpine by HPLC is described. Besides reserpine the method quantitatively determines isoreserpine, 3,4-didehydroreserpine, trimethoxybenzoic acid, and renoxidine. The additional degradation products reserpic acid, and the secondary oxidation product 3,4,5,6-tetradehydroreserpine are qualitatively recorded.     

Molecular Imprinting of Small Molecules with Organic Silanes: Fluorescence Detection

Abstract

Small molecules, peptides, and proteins can be imprinted using mixtures of organic silanes. Molecular imprints may serve as artificial receptors, i.e., biosensor sensing elements for detection of chemical and biological toxins, drugs, and environmental hazards. One method for detection of imprint-bound molecules is fluorescence. Molecular imprints to N-acetyltryptophanamide (NATA) and fluorescein were prepared, and their respective binding constants determined using steady-state fluorescence spectroscopy. Stern-Volmer fluorescence quenching plots of imprint-bound molecules using potassium iodide (KI) and acrylamide indicate bound molecules are shielded from the solvent environment. Scatchard plot analysis revealed two binding affinities, i.e., aK_d = 0.13 and 2.5 μM for NATA binding to NATA imprints. Interestingly, NATA exhibited higher affinity, i.e., K_d = 1.3 and 35 nM, for the fluorescein imprint. These data support the usefulness of fluorescence techniques in molecular imprint-based detection technology.     

Organoselenium/Tellurium-Bearing Macroacyclic and Cyclic Ligand Systems and Their Complexation Reactions

Abstract

A series of phenol-substituted acyclic Schiff bases, 2,6-{RE(CH₂) _n N═C(CH₃)}₂-C₆H₂(4-CH₃)(OH), (E = Te: R = C₆H₅, n = 2(L _a), 3(L _b); R = C₆H₄-4-OCH₃, n = 2(L _c), 3(L _d); E = Se: R = C₆H₅, n = 2(L _e), 3(L _f)), of the type E₂N₂O have been synthesized by condensation of 2,6-diacetyl-4-methylphenol with arylchalcogenoalkylamines. This ligand framework is useful for designing molecular complexes with a variety of coordination modes depending upon the nature of the central metal atom. The reactivity of the tellurium-bearing macroacyclics ligands towards Zn(II), Cd(II), and Hg(II) has been examined. The ligands L _a?L _d with Zn(II) and Cd(II), and only L _a and L _b with Hg(II) form complexes of composition M₂X₄L, (X = Cl or Br), whereas L _c and L _d with Hg(II) give products of composition HgBr₂L. The modes of ligand interaction with Zn(II) and Cd(II) are different than that with Hg(II).

Following a multistep reaction involving abstraction of bridged Br atoms and subsequent addition of more ligand, the mercury complex, Hg₂Br₄L has been used for developing metallocyclic system of the type [Hg₂Br₂L₂]²⁺. The latter has been found to encapsulate Zn(II) and Cd(II) to give multimetallic systems.     

Efficient Synthesis and Fungicidal Activities of 2-Alkylthiobenzofuro[3,2-d]Pyrimidinones

2-Alkylthiobenzofuro[3,2-d]pyrimidinones 5 and 6 were synthesized by S-alkylation of 2,3-dihydro-2-thioxobenzofuro[3,2-d]pyrimidin-4(1H)-ones 4, which were obtained via aza-Wittig reaction of iminophosphorane 2 with CS₂ and further reaction of the product with various amines. Compounds 5 and 6 exhibited fungicidal activity. For example, compound 6a, which has a small N-substituted methyl group, showed the best inhibitive activity (91%) against Dothiorella gregaria at 50 mg/L.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Determination of Triazines and N-Methylcarbamate Pesticides in Water by High-Performance Liquid Chromatography-Diode Array Detection

A rapid and selective method for the simultaneous determination of triazine herbicides (atrazine, its degradation product desethylatrazine, simazine, prometryn, terbutryn) and N-methylcarbamate insecticides (propoxur, carbaryl and methiocarb) in surface water has been developed. A 0.5 L of the water sample was preconcentrated by passage through a 1 g C₁₈ solid-phase extraction cartridge. The retained compounds were eluted with 5 mL of methanol from the cartridge. The pesticides were separated and quantified by reversed-phase high-performance liquid chromatography with UV diode-array detection. Analytical separation was performed using a concave gradient elution with acetonitrile and water on a C₁₈ column. Prometryn and terbutryn were determined at 240 nm; propoxur, methiocarb at 204 nm and the others at 220 nm. Recoveries varied from 85 to 102% over concentrations at 0.025 and 0.2 µg L^?1. The limits of detection for the compounds investigated are in the range of 0.005-0.012 µg L^?1.     

Quantification of thorium and uranium sorption to contaminated sediments

Desorption tests, using a sequential extraction method, were used to characterize and quantify thorium and uranium sorption to contaminated wetland sediments collected from the Department of Energy's Savannah River Site located in South Carolina. In situ distribution coefficients, or K _d values (K _d = C _solid/C _liquid), were determined. Sequential extraction data were used to assign solid-phase radionuclide concentrations (C _solid) that, by definition, should represent only the reversibly sorbed fraction. A series of selective and sequential extractions was used to determine desorption K _d values. Thorium K _d values ranged from 115 to 2255 ml/g. Uranium K _d values ranged from 170 to 6493 ml/g. Compared to sorption K _d values, these desorption K _d values were appreciably greater because they captured the aging process of the radionuclides with the sediment, making the radionuclide more refractory. Compared to nonsite-specific data, these in situ K _d values improved accuracy, were more defensible, and removed unnecessary conservatism for subsequent transport and risk calculations. Additional tests were conducted to provide geochemical information relevant for selecting appropriate remediation technologies for the contaminated site. Thorium and uranium were associated with labile fractions and were not concentrated with the smaller sediment particles. These findings suggest that phytoremediation or heap leaching, and not soil washing, are viable remediation approaches for this site.