Haptens and monoclonal antibodies for immunoassay of imidazolinone herbicides

A set of haptens structurally resembling the herbicide imazethapyr (PURSUIT) was synthesized and used to derive monoclonal antibodies (MAbs) and direct and indirect competition enzyme immunoassays (EIAs) which could detect imazethapyr, imazaquin (SCEPTER), imazapic (CADRE), and imazamox (RAPTOR) in the 3-30 ng/mL (parts per billion) range, and imazapyr (ARSENAL) and imazamethabenz-methyl (ASSERT) in the 300-500 ppb range. Two MAbs, 3A2 and 3A5, had affinities of 10-75 nM for imazethapyr. MAbs 1A5, 1D2, and 3A5 were specific for the S isomers of the herbicides. Some MAbs were stable in solutions containing up to 15% methanol and 5% acetonitrile in indirect EIAs. Plates coated with hapten conjugates for indirect EIA could be stored frozen. Selectivity for the imidazolinones by some MAbs varied with different coating conjugates. These MAbs and haptens should prove useful in immunochemical analysis and residue recovery methods for imazethapyr and other imidazolinone herbicides.     

Adsorption of imidazolinone herbicides on smectite-humic acid and smectite-ferrihydrite associations.

Adsorption of imazapyr (IMZ), imazethapyr (IMZT), and imazaquin (IMZQ) was studied on two smectite-humic acid and two smectite-ferrihydrite binary systems prepared by treating a Wyoming smectite with a humic acid extracted from soil (4 and 8% w/w of the smectite) and with just-precipitated synthetic ferrihydrite (8 and 16% w/w of the smectite). Adsorption of the three herbicides on the smectite was not measurable at pH >4.5, presumably because of negative charges on the surface of the smectite. Adsorption on the smectite-humic acid systems was also not measurable, presumably because of negative charges on the surface, despite the high affinity of the three herbicides for humic acid, the adsorption order of which was IMZ < IMZT < IMZQ. Adsorption decreased in the order IMZ < IMZT < IMZQ on the smectite-ferrihydrite systems and IMZQ < IMZT < IMZ on ferrihydrite, although here the differences were small. These results show that even though pure smectite cannot adsorb herbicides, it modifies the adsorption capacity of ferrihydrite. The mutual interaction of active phases such as humic acid, ferrihydrite, and smectite alters the characteristics of the resulting surface and hence the adsorption process. Investigations of herbicide adsorption have been seen to produce more reliable results if conducted on polyphasic systems rather than on single soil components.     

Synthesis of dimethyl derivatives of imidazolinone herbicides: their use in efficient gas chromatographic methods for the determination of these herbicides

The dimethyl derivatives of imazaquin, imazapyr, imazmethapyr, imazethapyr, 2-[4,5 dihydro-1, 4-dimethyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methoxymethyl- 3-pyridine carboxylic acid, 2-[4,5-dihydro-1,4 -dimethyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4-methyl benzoic acid, and 2-[4,5-dihydro-1,4-dimethyl-4-(1-methyl ethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl benzoic acid were prepared and fully characterized. The availability of these derivatives has led to the development of efficient and multiresidue gas chromatographic methods for trace level analysis of imidazolinone herbicides in matrixes such as water, soybean, and soil.     

水铁矿对磷的吸附及胶体态磷迁移能力预测

土壤中流失的磷进入水体容易引起富营养化污染。目前对于铁矿物胶体结合态磷在土壤孔隙介质中的稳定性和迁移能力的认识还存在不足。本研究采用吸附试验,考察水铁矿对磷的吸附特征以及pH、离子强度和胡敏酸对磷在液相、水铁矿胶体和水铁矿固体上分布的影响;通过DLVO理论,预测水铁矿胶体结合态磷的稳定性和迁移能力。结果表明,假二级动力学模型(R~2=0.964)更适合用于描述磷在水铁矿上的吸附过程,磷在水铁矿上的吸附受液膜扩散、内部扩散和化学吸附等过程控制。Freundlich模型(R2=0.970)对等温吸附的拟合效果好,说明水铁矿对磷的吸附为多层吸附过程。从Langmuir模型参数可知,水铁矿对磷的最大理论吸附量为22.55mg·g~(-1)。水铁矿对磷的吸附能力随pH的升高而降低,随离子强度的升高而升高。然而,低离子强度和高pH有利于反应体系中水铁矿胶体的释放。无论胡敏酸是否存在,在碱性且离子强度不高(1～10mmol·L~(-1))的条件下,有约5%～20%的磷会与水铁矿胶体结合,且这些磷-水铁矿胶体之间的静电斥力较大。根据DLVO理论计算可知,这些带负电荷的胶体之间稳定性较好,在土壤中有一定迁移能力。在实际农业活动中,磷肥的过量施用可能会使大量的磷酸根离子吸附在铁矿物上,促进土壤孔隙水中形成稳定的、带负电的铁矿物胶体,这种磷-铁矿物复合胶体的迁移很可能成为磷迁移的另一种形式。本研究结果可为胶体促进下磷淋失风险评估提供理论和数据支撑。     

Role of root exudates on the sorption of arsenate by ferrihydrite

Iron oxy‐hydroxides in soil are known to have a large affinity for arsenate (As(V)) inorganic species. At the soil–root interface such mineral components are embedded by mucilaginous material that is secreted from continuously growing root cap cells. In order to determine the role of plant mucilages in As(V) sorption by iron oxy‐hydroxides, we layered a calcium (Ca)‐polygalacturonate network (CaPGA) on to amorphous iron (Fe) (III) hydroxide (ferrihydrite, Fh) particles. The scanning electron micrographs of the CaPGA network coating the ferrihydrite (Fh–CaPGA) show a regular structure with a honeycomb‐like pattern where interlacing fibrils form a porous system. The FT‐IR spectra of Fh–CaPGA suggest that CaPGA fibrils are retained by the surface Fe(III) nuclei of Fh through electrostatic interactions. The sorption experiments carried out at pH 4.3 and 5.8 indicated a smaller amount of As(V) sorbed by Fh–CaPGA than by Fh alone, being less after 3 and 24 hours of reaction by about 70 and 30%, respectively. The sorption of As(V) by Fh was also studied in the presence of caffeic acid (CAF), an important root exudate. Simultaneous sorption kinetics show that As(V) sorption by Fh is almost independent of CAF concentration, indicating a greater affinity of arsenate ions towards the Fh surfaces. However, the amount of As(V) sorbed by the Fh coated by CaPGA, in the presence of 0.25, 0.5 and 1.0 mm CAF, is markedly smaller by about 20, 27 and 40%, respectively, than that found in the As(V)–CAF‐Fh ternary systems. This is caused mainly by redox reactions involving CAF and the surface Fe(III) nuclei of Fh leading to the formation of CAF oxidation products which prevent As(V) sorption.     

Effect of maize root mucilage on phosphate adsorption and exchangeability on a synthetic ferrihydrite

 This study was conducted to determine the influence of root mucilage (RM) from Zea mays, polygalacturonic acid (PGA), and galacturonic acid (GA), on the adsorption, desorption, and exchangeability of orthophosphate (P) on a synthetic ferrihydrite in deionized water. The adsorption rate and affinity on the oxide decreased in the order P>GA>PGA≥RM. The results suggest that P and GA were adsorbed by ligand exchange on Fe-OH surface sites, while RM and PGA might in addition also be adsorbed by hydrogen and van der Waals bonds to the oxide surface. Whereas P and GA could be adsorbed at sites located inside the micropores of ferrihydrite aggregates, PGA and RM probably remained on the external surfaces because of their large molecular weight. The preliminary adsorption of organic compounds decreased the subsequent P adsorption. The larger decrease of P adsorption occurred when dry ferrihydrite powder was directly added to the RM/water suspension. This effect was due to the flocculation of ferrihydrite aggregates, which limited the transport of P to the adsorption sites. Preliminary adsorption of GA also decreased P adsorption, because both compounds competed for the same Fe-OH sites. The ability of the organic compounds to desorb P from the ferrihydrite was not very pronounced and decreased in the order GA>PGA≥RM. The preliminary adsorption of organic compounds on the oxide resulted in an increase in isotopically exchangeable P in 300 min compared to the treatment without organic compounds. However, because of its higher affinity for the oxide surface, P exchangeability was not modified when P was added before the organic compounds. Received: 23 July 1999     

Selective modification of clay minerals for the adsorption of herbicides widely used in olive groves

Ground and surface water contamination by herbicides applied to olive groves in Spain and other Mediterranean countries is demanding strategies to prevent and remediate the environmental problems repeatedly caused by such herbicides. In this study, six different organic cations (L-carnitine, spermine, hexadimethrine, tyramine, phenyltrimethylammonium, and hexadecyltrimethylammonium) were incorporated into Na-rich Wyoming montmorillonite (SWy-2) and Ca-rich Arizona montmorillonite (SAz-1) at two different loadings (50% and 100% of the cation exchange capacity of the clays) as a strategy to enhance the affinity of the clay minerals for three herbicides widely used in olive groves: terbuthylazine, diuron, and MCPA. The modified montmorillonites were characterized and tested as adsorbents of the herbicides through batch adsorption tests. At the experimental conditions used, some of the modified montmorillonites removed more than 95% of the herbicide initially present in aqueous solution, whereas the unmodified clays removed less than 15%. All three herbicides displayed very strong affinities for SAz-1 exchanged with hexadecyltrimethylammonium cations, particularly when these were incorporated at 100% of the cation exchange capacity of the clay mineral. Terbuthylazine and diuron also displayed very strong affinities for SWy-2 exchanged with L-carnitine and spermine, respectively. The chemical characteristics of the organic cation greatly influenced the adsorptive properties of the resultant organoclay. The herbicides were in general reversibly adsorbed by the modified clays. The results indicate that some of the tested modified clays could be suitable for the removal of the assayed herbicides from contaminated water and also as possible supports for the design of slow release formulations of such herbicides to attenuate their environmental impact when used in high-risk scenarios such as olive groves.     

Transformations induced in ferrihydrite by oven-drying

Synthetic ferrihydrite preparations are metastable and on oven-drying are shown to undergo significant transformation to more stable crystalline products the composition of which depends on the properties of the initial ferrihydrite. For a poorly ordered sample produced by rapid neutralization of a ferric nitrate solution, the dominant product was well-crystalline hematite (α-Fe₂O₃), the amount depending on the temperature at which drying was accomplished. Freeze-drying prevented alteration of the ferrihydrite to more crystalline forms and, compared with any of the oven dried samples, minimized the change in rate of dissolution in acid ammonium oxalate solution. For a more ordered ferrihydrite produced by slow neutralization, oven-drying caused the formation of some goethite (α-FeOOH) with little or no hematite. The different transformation pathway for the more ordered ferrihydrite is attributed to 1) formation of larger polymers by slow growth during neutralization, resulting in a limited supply of the very small polymers which transform readily to hematite on heating, and 2) the probability of concomitant growth of goethite nuclei within the ferrihydrite allowing preferred transformation to goethite during oven-drying.     

Soil organic matter and the adsorption and decomposition of the herbicides atrazine and linuron

Soil was subjected to a variety of treatments so as to provide a series of materials with different organic residues. These preparations were inoculated with an aqueous extract of untreated soil, then incubated at 20°C with atrazine or linuron and rates of herbicide degradation were followed. The rates were lowest when virtually all the organic matter had been removed by peroxidation. The most rapid break-down occurred in samples which had been successively extracted with ethanol + toluene, hot water, dilute acid and dilute alkali. It is suggested that the organic residue left after this sequence contained hydrolysed materials that were easily metabolized and hence could support the most active microbial population. There was no relationship between extent of adsorption and decomposition rate.     

Copper adsorption behavior of three Malaysian rice soils

Abstract

Copper (Cu) deficiency exists in different rice growing areas of Malaysia. A study on Cu adsorption was carried out in three Malaysian rice soils (Idris, Tebengau, and Kangar series) using six levels of Cu (0, 100, 200, 300, 400, and 500 ug g^‐1). The data on Cu adsorption were fitted into Langmuir, Freundlich, and Temkin equations. Adsorption data were also correlated with pH, cation exchange capacity, and organic matter content of the soils. The effect of Cu addition on redox potential (Eh) of the soils was also measured. The Eh values were correlated with equilibrium solution Cu concentrations. Copper adsorption increased gradually with increasing level of added Cu in all the soils. The rate of increase was the highest in Kangar series followed by Tebengau and Idris, respectively. Correlation between Cu adsorption and pH was significant (r=0.772) whereas correlation of adsorption with either organic matter content or cation exchange capacity was nonsignificant. Copper adsorption in two soils (Idris and Tebengau) fitted Langmuir, Freundlich, and Temkin equations whereas Cu adsorption in the Kangar soil fitted Freundlich and Temkin equations. Redox potential (Eh) of the soils increased gradually with increasing level of added Cu. The rate of increase was the highest in Idris followed by Kangar and Tebengau soils, respectively. The relationship between equilibrium solution Cu concentration and redox potential was significant. The results of this study indicated that copper adsorption is mainly dependent on soil pH. In soils with higher adsorption capacity, more Cu fertilizer may be needed to get immediate crop response.     

胶体存在时不同质地土壤对锌镉的吸附试验研究

以重金属离子Zn和Cd及胶体为对象,通过等温静态批量平衡吸附试验,分析了3种不同质地土壤对Zn、Cd单一吸附和等量竞争吸附特征,胶体对土壤吸附Zn、Cd的影响,并用Langmuir和Freundlich方程对试验结果进行了拟合。结果表明,随着平衡液中Zn2+、Cd2+浓度的增加,土壤对Zn、Cd的吸附量逐渐增大;3种质地土壤对Zn、Cd吸附量顺序为砂壤>粉壤>壤砂土;Zn2+、Cd2+共存时,土壤对这两种离子的吸附量比单一离子存在的情况下明显下降;胶体存在时抑制了土壤对Zn的吸附,促进了土壤对Cd的吸附;就本试验来说,Freundlich方程拟合效果优于Langmuir方程。     

Migration of phosphate into aggregated particles of ferrihydrite

The slow reaction of phosphate with aggregated particles of ferrihydrite, after initial rapid phosphate sorption, was investigated by measuring the changes, with time and temperature, in the amount of phosphate sorbed, and the extractability of the sorbed phosphate. The ferrihydrite was, subsequently, recovered and examined by infra–red spectrometry (IR) and electron probe micro–analysis.
Phosphate continued to react with ferrihydrite for at least 90 d at 25°C, but was completely recovered by extraction with 0.1 m NaOH. The IR spectra of sorbed phosphate was insensitive to the temperature and duration of the reaction. Electron probe micro–analysis of the aggregates showed that phosphate migrated to surface sorption sites within the aggregated particles of ferrihydrite.
There was no evidence for the formation of surface coatings of ferric phosphate, for changes in the type of bonding, or for penetration of phosphate into the crystal lattice. The slow reaction was attributed to the migration of phosphate to surface sorption sites of decreasing accessibility within aggregates.     

三种铁氧化物的磷吸附解吸特性以及与磷吸附饱和度的关系

采用三种人工合成铁氧化物(针铁矿、赤铁矿和水铁矿)比较了结晶态和无定形铁氧化物对磷的吸附—解吸特性以及与磷吸附饱和度的关系。结果表明,三种铁氧化物的磷吸附特性均可用Langumir方程来描述,相关系数均大于0.9,达到极显著水平。从磷最大吸附量(Qm)、吸附反应常数(K)和最大缓冲容量(MBC)三项吸附参数综合考虑,水铁矿(无定形)对磷的吸附无论在容量还是强度方面均比结晶态铁氧化物针铁矿和赤铁矿大得多。水铁矿吸附的磷比针铁矿和赤铁矿所吸附的磷更难解吸;水铁矿的大量活性表面并没有表现出增加磷释放的作用。磷吸附饱和度有望作为评价土壤或铁氧化物磷吸附—解吸的强度和容量因子的一个综合指标。     

Effects of herbicides on three vesicular-arbuscular fungi associated with winter wheat (Riticum aestivum L.)

Summary We studied the effects of field application rates of four herbicides (Avenge, Ceridor, Dicurane, and Harrier) on spore germination and infection of wheat roots by three species of Glomus grown under conditions of low P availability. Low concentrations of Ceridor (bifenox, mecoprop) and Harrier (mecoprop, ioxynil, clopyralid) inhibited spore germination while higher concentrations were stimulatory. Avenge (difenzoquat methyl sulphate) prevented spore germination completely, while Dicurane (chlortoluron) had no effect. The herbicide applications had no significant effect on the infection rates of any of the three fungi except Harrier on G. geosporum. The herbicide treatments did, however, affect plant growth and ear yields. Ceridor and Harrier increased ear yields, while Dicurane showed marked phytotoxic effects.     

基质固相分散萃取-高效液相色谱串联质谱法测定土壤中残留的磺酰脲类除草剂

建立了基质固相分散萃取-高效液相色谱串联质谱法(MSPD-HPLC-MS/MS)测定土壤中3种磺酰脲类除草剂(氯磺隆、甲磺隆、苯磺隆)残留的分析方法。对基于球磨的基质固相分散萃取条件进行了详细优化,最终确定最佳条件为:0.2 g土壤样品、0.8 g HC-C18粉末状分散剂与直径为8 mm的小钢珠一起球磨10 min后,转移至空的玻璃萃取小柱,用10 m L乙腈洗脱,氮气吹干后用甲醇定容至0.6 m L,再经0.22μm的滤膜抽滤后装入自动进样瓶中。用Syncronis C18反相色谱柱分离,以甲醇(A)~1‰甲酸溶液(B)为流动相进行梯度洗脱,选择反应监测(SRM)模式下进行检测。氯磺隆在20~200μg·kg~(-1),甲磺隆和苯磺隆在10~200μg·kg~(-1)范围内线性良好,相关系数r在0.997 9~0.999 5。土壤样品的平均加标回收率在84.7%~104.6%,相对标准偏差在4.5%~7.9%(n=5)。方法的检出限(S/N=3)0.32~0.68μg·kg~(-1)。该方法简单、效率高、干扰少、回收率高,满足土壤中除草剂的残留分析要求。     

磷酸盐在水铁矿及水铁矿-胡敏酸复合体表面的吸附

The adsorption of phosphate onto ferrihydrite (FH) and two FH-humic acid (HA) complexes, obtained by co-precipitating FH with low (FH-HA1) and relatively high amounts of humic acid (FH-HA2), was studied through kinetics and isotherm experiments to determine the differences in phosphate adsorption between FH-HA complexes and FH and to reveal the mechanism of phosphate adsorption onto two soil compositions. The isoelectric point (IEP) and the specific surface area (SSA) of the mineral decreased as the particle porosity of the mineral increased, which corresponded to an increase in the amount of organic carbon. The adsorption capacity of phosphate was higher on FH than on FH-HA1 and FH-HA2 at the scale of micromoles per kilogram. The initial adsorption rate and adsorption affinity of phosphate decreased with an increase in the amount of HA in the mineral. The sensitivity of phosphate adsorption to the change in the pH was greater for FH than for FH-HA complexes. Ionic strength did not affect the adsorption of phosphate onto FH and FH-HA1 at a lower pH, and the increase in the ionic strength promoted phosphate adsorption at a higher pH. However, for the FH-HA2 complex, the increase in the ionic strength inhibited the adsorption of phosphate onto FH-HA2 at a lower pH and increased the adsorption at a higher pH.     

Role of exogenously supplied ferulic and p-coumaric acids in mimicking the mode of action of acetolactate synthase inhibiting herbicides

Chlorsulfuron and imazethapyr (herbicides that inhibit acetolactate synthase; ALS, EC 4.1.3.18) produced a strong accumulation of hydroxycinnamic acids that was related to the induction of the first enzyme of the shikimate pathway, 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (EC 2.5.2.54). The exogenous application of two hydroxycinnamic acids, ferulic and p-coumaric acids, to pea plants resulted in their internal accumulation, arrested growth, carbohydrate and quinate accumulation in the leaves, and the induction of ethanolic fermentation. These effects resemble some of the physiological effects detected after acetolactate synthase inhibition and suggest important roles for ferulic and p-coumaric acids in the mode of action of herbicides inhibiting the biosynthesis of branched chain amino acids.     

The H+/M2+ exchange stoichiometry of calcium and zinc adsorption by ferrihydrite

The specific adsorption of Ca²⁺ and Zn²⁺ by ferrihydrite results in the net release of H⁺. The rate and H⁺/M²⁺ exchange stoichiometry of this reaction were monitored with a pH-stat. A rapid reaction of less than 6 min was followed by a slower reaction which continued at a diminishing rate for at least 2 days. Adsorption of Ca²⁺ at pH 7.8 and Zn²⁺ at pH 5.4 resulted in the net release of 0.92 and 1.70 mol H⁺/mol M²⁺ adsorbed, respectively. For Zn²⁺ adsorption, this stoichiometry was shown to be independent of pH. These estimates agree well with independent estimates based on the pH dependence of adsorption. The difference between the Ca²⁺ and Zn²⁺ stoichiometries was related to the differing acidity of the –OH₂ ligands attached to the adsorbed ions.     

Denitrification in soil: Effects of herbicides

The effects of 20 herbicides on denitrification of nitrate in three soils were studied by determining the effects of 10 and 50μgg^?1 soil of each herbicide on the amounts of nitrate lost and the amounts of nitrite, N₂O and N₂ produced when soil samples were incubated anaerobically after treatment with nitrate. The herbicides used were butylate, EPTC, chlorpropham, propham, diuron, linuron, monuron, siduron, alachlor, trifluralin, 2,4-D amine, 2,4-D ester, atrazine, cyanazine, metribuzin, simazine, dalapon, chloramben, dicamba and dinoseb.None of the herbicides studied significantly affected denitrification of nitrate when applied at the rate of 10 μg g^?1 soil, but dinoseb increased the ratio of N₂ to N₂O in the gaseous products of denitrification when applied at this rate. Butylate, EPTC, diuron, simazine and dalapon had no significant effect on denitrification when applied at the rate of 50μgg^?1 soil, whereas metribuzin and dinoseb enhanced denitrification when applied at this rate. The influence of the other herbicides on denitrification when applied at the rate of 50μgg^?1soil depended on the soil, but all enhanced or inhibited denitrification in at least one soil.     

Degradation of diphenyl ether herbicides in soils

The gas chromatographic determination of CNP (2,4,6-trichlorophenyl 4-nitrophenyl ether), nitrofen (2,4-dichlorophenyl 4′-nitrophenyI ether), chlomethoxynil (2,4-dieblorophenyl 3′-methoxy-4′-nitrophenyl ether), CFNP (2,4-dichloro-6-fluorophenyl 4-nitrophenyl ether) and their amino derivatives in soils were carried out. Good recoveries from soils were obtained for the diphenyl ethers. On the other hand, satisfactory recoveries from soils were also obtained for the amino derivatives at high concentrations, but the recoveries at lower concentrations averaged about 66% for the least recovered compound.

The degradation of several diphenyl ether herbicides in two paddy soils were compared under flooded and upland conditions. The degradation was much slower under upland than under flooded conditions. Considerable amounts of their amino derivatives were produced in soils under flooded conditions, but not under upland conditions. It was suggested that the diphenyl ethers to the amino derivatives involved both chemical and microbial processes. CNP and chlomethoxynil degraded faster at lower concentrations than at higher ones.