The interaction of triazine herbicides with humic acids

Summary Although the binding of pesticides to organic carbon in soil, especially to humic acid (HA), is well recognized, the mechanisms have not been completely explained. This publication deals with adsorption of atrazine and terbuthylazine by humic acid under different experimental conditions, including adsorption times longer than those used hitherto. Direct HPLC analysis of HA suspensions is assessed as an alternative to more complicated techniques for estimation of free triazines, and compared with combined solid-phase extraction and HPLC. Experimental conditions such as time of exposure, addition of neutral salt, pH of the suspension, and HA concentration have a significant impact on the extent of triazine adsorption. At alkaline pH, triazines become partitioned in the HA fraction because of its hydrophobicity, whereas at acidic pH hydrogen-bonding probably occurs between triazine molecules and humic acid polymers. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

高效液相色谱/大气压化学电离质谱快速分析水中痕量有机磷农药

用反相液谱短柱实现了６种有机磷农药（乙酰甲胺磷、甲基对硫磷、杀螟硫磷、喹硫磷、二嗪农、辛硫磷）的高效液相色谱／大气压化学电离质谱（ＨＰＬＣ／ＡＰＣＩＭＳ）快速分析。此技术可以很好地实现水中痕量有机磷农药的测定,一次联机分析仅需１０ｍｉｎ。文中还讨论了二嗪农的碰撞诱导解离（ＣＩＤ）碎片谱。二嗪农和喹硫磷的检出限可低达０．０９ｎｇ和０．１ｎｇ。     

Adsorption of Pesticides onto Granular Activated Carbon: Determination of Surface Diffusivities Using Simple Batch Experiments

The Homogeneous Surface Diffusion Model (HSDM) has been successfully used to predict the adsorption kinetics for several chemicals inside batch adsorber vessels. In addition to the adsorption equilibrium, this model is based on external mass transfer and surface diffusion. This paper presents the determination of the surface diffusion coefficient (D _s) using a differential column batch reactor (DCBR). The adsorption kinetics for three pesticides onto granular activated carbon have been established experimentally. Their corresponding three diffusion coefficients were determined by fitting the computer simulations to the experimental concentration-time data. The results show that this original apparatus increases by an order of magnitude the range of reachable diffusion coefficient compared to perfectly mixed contactors. Moreover the computed D _s values are more accurate because of the better assessment of the external mass transfer coefficient (k _f) for fixed beds.     

固相萃取法与基质固相分散法在橙子中有机磷农药残留分析中的应用

建立了固相萃取(SPE)-反相高效液相色谱(RP-HPLC)同时测定橙子中痕量辛硫磷、二嗪农有机磷农药残留量的方法。样品经甲醇超声提取、C18固相萃取柱净化后,采用液相色谱柱分离,以乙腈-水(体积比为85∶15)为流动相等度洗脱,于254 nm下紫外检测。结果表明:在0.1～10.0 mg/L和0.4～10.0 mg/L范围内,辛硫磷、二嗪农的质量浓度与峰面积呈良好的线性关系;样品的加标平均回收率为87.3%～102.7%,相对标准偏差(RSD)为0.9%～4.9%。将该分析结果与用基质固相分散法(MSPD)处理样品所得的结果相比较,发现SPE对二嗪农的提取效果较好,而MSPD对辛硫磷的提取效果较好,但两种方法都能较好地净化样品,均能满足残留量的分析要求。     

气相色谱-串联质谱法测定土壤中的有机氯农药

建立了气相色谱-串联质谱测定土壤中有机氯农药的方法,同时测定了上海郊区的20个农业土壤。样品前处理包括加速溶剂萃取(弗罗里硅土池内净化)和凝胶渗透色谱净化在线浓缩。采用多反应监测模式的气相色谱-串联质谱分析有机氯农药,降低了背景干扰,提高了分析的灵敏度。在0.001～2 mg/L的质量浓度范围内,各种农药标准溶液的线性相关系数均大于0.995。分别向3种实际土壤样品中添加农药的混合标准溶液,所测定的有机氯农药的平均回收率为65.9%～140.0%,相对标准偏差为1.5%～20.3%(n=5)。有机氯农药的检出限（S/N=3）为0.1～3.0 μg/kg,定量限（S/N=10）为0.3～8.0 μg/kg。实际土壤样品的测定结果表明：六六六(1.82～3.70 μg/kg)和六氯苯(0.94～9.8 μg/kg)有少量检出,滴滴涕的检出率高达100%,其含量范围较宽(1.08～308.76 μg/kg),平均值为53.28 μg/kg,其中85%的样品中滴滴涕含量/(滴滴伊+滴滴滴)含量的比值小于1,表明滴滴涕主要来自于早期的使用     

Headspace liquid-phase microextraction using ionic liquid as extractant for the preconcentration of dichlorodiphenyltrichloroethane and its metabolites at trace levels in water samples

A novel technique, high temperature headspace liquid-phase microextraction (HS-LPME) with room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]) as extractant, was developed for the analysis of dichlorodiphenyltrichloroethane (p,p′-DDT and o,p′-DDT) and its metabolites including 4,4′-dichlorodiphenyldichloroethylene (p,p′-DDE) and 4,4′-dichlorodiphenyldichloroethane (p,p′-DDD) in water samples by high performance liquid chromatography with ultraviolet detection. The parameters such as salt content, sample pH and temperature, stirring rate, extraction time, microdrop volume, and sample volume, were found to have significant influence on the HS-LPME. The conditions optimized for extraction of target compounds were as follows: 35% NaCl (w/v), neutral pH condition, 70 °C, 800 rpm, 30 min, 10 μL [C₄MIM][PF₆], and 25 mL sample solutions. Under the optimized conditions, the linear range, detection limit (S/N = 3), and precision (R.S.D., n = 6) were 0.3-30 μg L⁻¹, 0.07 μg L⁻¹, and 8.0% for p,p′-DDD, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.1% for p,p′-DDT, 0.3-30 μg L⁻¹, 0.08 μg L⁻¹, and 7.2% for o,p′-DDT, and 0.2-30 μg L⁻¹, 0.05 μg L⁻¹, and 6.8% for p,p′-DDE, respectively. Water samples including tap water, well water, snow water, reservoir water, and wastewater were analyzed by the proposed procedure and the recoveries at 5 μg L⁻¹ spiked level were in the range of 86.8-102.6%.     

不同环境条件杂环农药三维荧光光谱发射特性研究

掌握不同环境因素下的光谱发射特性是农药准确测量的前提。以多菌灵、西维因、麦穗宁三种杂环农药为研究对象,研究了农药在不同pH值和常见阴、阳离子条件下的三维荧光光谱发射特性,并初步分析了Fe3+和Cu2+对三种农药的荧光猝灭机制。结果表明,多菌灵和麦穗宁均具有两个荧光峰,西维因仅有一个荧光区域,三种农药的主要荧光峰分别位于λ_ex/λ_em=280/300,310/340和280/335 nm,多菌灵和麦穗宁的次荧光峰Peak B分别位于λ_ex/λ_em=245/305 nm,λ_ex/λ_em=250/340 nm;多菌灵与麦穗宁随pH值变化表现为相似的荧光发射特征,在酸性/碱性降低时,荧光强度增大;酸性条件下西维因的荧光发射强度无明显变化,但在碱性条件下,随pH值的减小荧光强度不断增强;三种农药在pH值6.16～7.4范围内均可获得较好的荧光发射特征。水中CO2-₃,SO2-₄,NO-₃,Cl-,HPO2-₄,HCO-₃,Mg2+,Zn2+,NH+₄,Na+,Ca2+和K+等12种常见离子对多菌灵,西维因和麦穗宁的荧光发射特性无明显影响。Fe3+与Cu2+离子通过静态荧光猝灭反应, 影响三种农药的荧光发射强度。随着离子浓度的增加荧光强度不断降低,在实际测量中,需重点考虑Fe3+和Cu2+对测量结果的影响。该研究结果为水体杂环农药的准确测量提供了基础数据。     

液相色谱-四极杆/ 飞行时间质谱快速筛查与确证苹果、番茄和甘蓝中的281种农药残留

建立了苹果、番茄和甘蓝中281种农药残留的QuEChERS结合液相色谱-四极杆/飞行时间质谱(LC-Q-TOF/MS)快速筛查方法。方法采用1%醋酸乙腈提取样品,经丙基乙二胺(PSA)净化,LC-Q-TOF/MS测定。281种农药在苹果、番茄和甘蓝中3个添加水平下的回收率在70%～120%范围的比例分别为98.6%、99.3%和98.2%;回收率的相对标准偏差(RSD)均≤20%(n=5);在0.25～10倍最大残留限量(MRL)的含量范围内,线性相关系数r²≥0.99的农药比例分别为95.7%、96.1%和98.2%;检出限分别为0.03～4.47、0.01～4.49和0.02～3.61 μg/kg。本方法采用精确质量数据库和谱图库检索的方式,实现了不用农药标准品对照而完成对果蔬中农药残留的快速筛查,提高了定性鉴别的准确性。应用所建立的方法对30个市售果蔬样品进行筛查,共检出13种农药残留。其中,甘蓝中甲胺磷的含量超过了GB 2763-2012《食品安全国家标准\5食品中农药最大残留限量》和欧盟的MRL;番茄中鱼藤酮的含量超出欧盟的MRL。     

气相色谱-质谱法同时测定番茄制品中拟除虫菊酯类农药残留

番茄制品经乙腈提取,盐析,氟罗里硅土固相萃取小柱净化,微池电子捕获检测器(μECD)负化学源质谱(NCI—MS)并联对净化液进行检测,一次进样可对番茄制品中的9种拟除虫菊酯类农药残留准确定量和确证。μECD回收率为87．6％～107．0％;相对标准偏差为5．5％～11．3％;检出限为0．0005～0．005mg／kg;负化学源选择离子(NCI-SIM)模式回收率为91．9％～109．7％;相对标准偏差为5．2％～12．7％;检出限为0．0005～0．005mg／kg(氯菊酯除外),两者之问没有显著的差别。该法快速、灵敏、准确,各项技术指标均满足农药残留检测的要求。     

超高效液相色谱-四极杆-飞行时间质谱法快速筛查茶叶中的204种农药残留

利用超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF/MS)技术建立了茶叶中204种农药残留的快速筛查和确证检测方法。样品采用乙腈提取,经Carb-PSA固相萃取小柱净化,用乙腈-甲苯(3:1, v/v)洗脱,采用UPLC-Q-TOF/MS检测,外标法定量。建立了204种农药的一级精确质量数据库和二级谱图库,通过化合物的精确质量数、保留时间、同位素比值等信息对检测结果进行自动检索,从而在无对照标准品的情况下完成了204种农药的定性鉴定。结果表明,该方法可以同时对茶叶中204种农药残留进行快速筛查,在10、20、50 μg/kg 3个添加水平下的平均回收率为68.1%~117.2%,相对标准偏差为3.1%~18.9%。定量限均小于10 μg/kg。采用本方法对4份阳性样品进行检测,所得结果与GB/T 23205-2008的检测结果基本一致。该方法快速、灵敏、准确,可用于茶叶中204种农药残留的快速筛查。