气相色谱法测定饮用水及其源水中灭草松和2,4-滴

采用气相色谱ECD检测器同时分离检测水中灭草松和2,4-滴两种农药.水样中灭草松和2,4-滴在酸性条件下经乙酸乙酯萃取,然后用碘甲烷溶液酯化,生成较易挥发的甲基酯类衍生物,用毛细管气相色谱-电子捕获检测器分离测定.对衍生方式、温度和时间进行了优化,分别使用ECD和FPD检测器测定灭草松,而ECD检测灵敏度高.本法的最低检测质量浓度为灭草松0.15 μg/L,2,4-滴0.050 μg/L.方法灵敏度和精密度均满足分析要求.     

固相萃取-气相色谱法测定水体中2,4-滴和灭草松的残留量

提出了固相萃取-气相色谱法测定水体中2,4-滴和灭草松残留量的方法。用硝酸将1.0 L水样酸度调至pH小于2,然后以6.0 mL·min^-1流量过活化好的HLB pro固相萃取柱，用10.0 mL水淋洗，再用10.0 mL乙酸乙酯洗脱。收集洗脱液，氮吹至近干，加入500μL N,N-二甲基甲酰胺二甲缩醛和1.0 mL正己烷，于160℃衍生50 min。衍生结束后，取出，冷却至室温，加入2.0 mL饱和氯化钠溶液，待分层后，取0.8 mL上层有机相过0.22μm有机相滤膜，滤液按照仪器工作条件进行测定。结果表明：2,4-滴和灭草松的衍生产物分别为2,4-滴甲酯和灭草松甲酯；2,4-滴和灭草松的质量浓度在0.01～0.50 mg·L^-1内与对应的衍生产物峰面积呈线性关系，检出限(3.143s)为0.003～0.010μg·L^-1;对实际加标样品进行精密度试验，测定值的相对标准偏差(n=6)均小于7.0%;生活饮用水、地表水、城镇污水和海水加标样品中，目标物回收率为81.3%～95.4%。     

高效液相色谱法测定水中酸性除草剂灭草松和2,4-滴

使用高效液相色谱法对地表水与饮用水中的灭草松与2,4-滴同时进行测定。采用固相萃取法预处理样品,富集浓缩后用高效液相色谱法测定。方法检出限均为3μg/L,回收率分别在88%~110%与86%~118%间,精密度RSD均在2%~4%之间。比国家新的饮用水卫生标准参考方法(GB/T 5750-2006)提供的样品衍生化后用气相色谱法测定的方法操作较为简便,结果也能满足分析要求,可应用于实际工作。     

离子交换固相萃取-气相色谱-质谱联用法测定方便面皮复合包装袋中2,4-二氨基甲苯的迁移量

建立了方便面皮复合包装袋中2,4-二氨基甲苯迁移量的离子交换固相萃取-气相色谱-质谱联用检测方法。样品用4%（v/v）乙酸溶液浸泡,然后采用MCX混合型阳离子交换柱富集净化,以5.0 mL水淋洗小柱,用3.0 mL 5%（v/v）氨化甲醇洗脱样品,洗脱液经过溶剂交换,七氟丁酸酐衍生后,用气相色谱-质谱联用仪对目标物进行检测,外标法定量。2,4-二氨基甲苯在1~50 μg/L范围内,线性相关系数（r）为0.9991,检出限（S/N=3）为0.2 μg/L,定量限（S/N=10）为0.6 μg/L,回收率在89.0%~94.2%之间,相对标准偏差为1.9%~3.6%。该方法的前处理过程无需调节提取液的pH值,也不需要液液萃取,大幅简化了前处理过程,降低了有机溶剂的消耗,具有操作便捷、结果准确的优点,适用于方便面皮复合包装袋中2,4-二氨基甲苯迁移量的检测。     

薄层色谱法分离测定1，5-苯并硫氮杂(艹+卓)-α-氯代-β-内酰胺

摘要：用薄层色谱法分离测定了反应混合物中的1,5-苯并硫氮杂（艹+卓）-α-氯代-β-内酰胺。采用透射法锯齿扫描,定量分析的变异系数小于5％,最低检测限为0.114μg,定量校正线性相关系数0.9952,方法的平均回收率为96.75％,方法简便、快速。     

高效液相色谱法测定精对苯二甲酸中微量杂质

建立了高效液相色谱法（HPLC）同时测定精对-苯二甲酸（PTA）中微量杂质4-羧基苯甲醛（4-CBA）、对-甲基苯甲酸（P-TOL）和苯甲酸（C7H6O2）含量的方法。采用的色谱柱为Shim-PackWAX-1柱，流动相为0.1mol/L NH3H2PO4 6%CH3OH，(pH4.5)，检测波长为254nm。PTA中微量杂质4-CBA、P-TOL和C7H6O2的含量分别为0.59-235.20mg/kg、4.52-392.00mg/kg和0.28-24.55mg/kg时线性关系良好，其线性相关系数分别为0.9998、0.9997和0.9999。苯甲酸加样平均回收率99.03％，RSD0.37％。     

衍生化-手性毛细管色谱分离和测定水中的2,4-滴丙酸

建立了一种采用手性气相色谱分离、测定水中2,4-滴丙酸(DCPP)的分析方法。通过对样品的酯化处理降低了被测物的沸点,提高了其挥发性;利用手性气相色谱-ECD检测灵敏度高、量程宽的优点,实现了水中DCPP的手性分离、定量分析,平均回收率达90％。该方法安全、快速、准确,可用于水中2,4-滴丙酸和2,4-滴丙酸甲酯对映体定量分析。     

气相色谱法同时测定西草净、丁草胺和噁草灵

采用气相色谱法,以癸二酸二正丁酯为内标物,对新研制的复合型稻田除草剂26％丁··西乳油进行了一次性定量分析。色谱条件为5％SE-302m×3mm的玻璃柱,柱温为210℃,检测温度为230℃。方法的回收率为98．62％～100．77％,线性相关系数大于0．999。方法准确、简便、快速。     

不经分离,高敏,连续光度滴定混合物中钕和铁

提出以Ｆｅ（３＋）（Ｎｄ（３＋）－ＣＡＳ－ＣＰＢ－Ｃ２Ｈ５ＯＨ作为不经分离、高敏、连续光度配合滴定混合物中Ｆｅ（３＋）和Ｎｄ（３＋）的多元胶束配合指示体系。滴定Ｆｅ（３＋）和Ｎｄ（３＋）的适宜ｐＨ分别为２．３～３．２和６．０～８．６。用ＥＤＴＡ目视滴定Ｆｅ（３＋）时，终点处由蓝紫变粉红色，对比度大（Δλ＝１３０ｎｍ）、灵敏度高（配合物摩尔吸光系数ε（６３０）＝１．１４×１０５Ｌ·ｃｍ（－１）·ｍｏｌ（－１），至少可检测０．４μｇ／ｍＬ，滴定线性范围为０～２．８μｇ／ｍＬ。线性相关系数为０．９９９４；目视滴定Ｎｄ（３＋）时，终点处由绿色变橙黄，Δλ＞１８０ｎｍ，ε（６３０）＝７．６×１０４，至少可检测１μｇ／ｍＬ，滴定线性范围０～３．７μｇ／ｍＬ，线性相关系数０．９９９４。对于铁钕硼混合物样品则不经分离在６３０ｎｍ处连续光度滴定，可更精密、高敏、准确地确定终点，变异系数１．７６％～２．８６％，标准加入回收率９６％～１０４％，且简便、快速。     

气相色谱法同时测定西草净、丁草胺和噁草灵

 采用气相色谱法,以癸二酸二正丁酯为内标物,对新研制的复合型稻田除草剂26％丁··西乳油进行了一次性定量分析。色谱条件为5％SE-302m×3mm的玻璃柱,柱温为210℃,检测温度为230℃。方法的回收率为98．62％～100．77％,线性相关系数大于0．999。方法准确、简便、快速。     

Synthesis,characterization and application of dummy-template molecularly imprinted microspheres for 2,4-d butyl ester

Dummy-template molecularly imprinted microspheres were synthesized via precipitation polymerization employing 2,4-D isooctyl ester as the template molecule instead of 2,4-D butyl ester, while methacrylic acid and divinylbenzene were used as functional monomer and cross-linker in acetonitrile or a mixture of acetonitrile and toluene. The microspheres were characterized by scanning electron microscopy, laser particle size analyzer and fourier transform infrared spectrometry. Binding capacity experiment showed that the molecularly imprinted polymers prepared in a mixture of acetonitrile and toluene had a high binding capacity. The performance of microspheres was further assessed by equilibrium binding and kinetic adsorption experiments. The results showed that the apparent maximum adsorption reached up to 1.35 mg·g^?1 within 10 min. Based on the dummy-template microspheres, a molecularly imprinted solid phase extraction-gas chromatography method was developed for the selective analysis of 2,4-D butyl ester in soil samples. The mean recoveries of 2,4-D butyl ester from blank soil samples ranged from 85.9 to 99.3% with relative standard deviations of 4.5–14.3% (n = 5). The limit of detection and the limit of quantification of 2,4-D butyl ester were 0.8 μg·kg^?1 and 2.3 μg·kg^?1, respectively.     

Optimization of preparation conditions for activated carbon from palm oil fronds using response surface methodology on removal of pesticides from aqueous solution

Palm oil fronds were used to prepare activated carbon using the physiochemical activation method, which consisted of potassium hydroxide (KOH) treatment and carbon dioxide (CO₂) gasification. The effects of variable parameters activation temperature, activation time and chemical impregnation ratios (KOH: char by weight) on the preparation of the activated carbon and for the removal of pesticides: bentazon, carbofuran and 2,4-Dichlorophenoxyacetic acid (2,4-D) were investigated. Based on the central composite design (CCD), two factor interaction (2FI) and quadratic models were respectively employed to correlate the effect of variable parameters on the preparation of activated carbon used for the removal of pesticides with carbon yield. From the analysis of variance (ANOVA), the most influential factor on each experimental design response was identified. The optimum conditions for preparing the activated carbon from oil palm fronds were found as follows: activation temperature of 750 °C, activation time of 2 h and chemical impregnation ratio of 2.38. The percentage error between predicted and experimental results for the removal of bentazon, carbofuran and 2,4-D were 8.2, 1.3 and 9.2%, respectively and for the yield of the palm oil frond activated carbon was 5.6.     

Application of NaClO-treated multiwalled carbon nanotubes as solid phase extraction sorbents for preconcentration of trace 2,4-dichlorophenoxyacetic acid in aqueous samples

Multiwalled carbon nanotubes functionalized by oxidation of original multiwalled carbon nanotubes with NaClO were prepared and their application as solid phase extraction sorbent for 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated systemically, and a new method was developed for the determination of trace 2,4-D in water samples based on extraction and preconcentration of 2,4-D with solid phase extraction columns packed with NaClO-treated multiwalled carbon nanotubes prior to its determination by HPLC. The optimum experimental parameters for preconcentration of 2,4-D, including the column activating conditions, the amount of the sorbent, pH of the sample, elution composition, and elution volume, were investigated. The results indicated 2,4-D could be quantitatively retained by 100 mg NaClO-treated multiwalled carbon nanotubes at pH 5, and then eluted completely with 10 mL 3:1 (v/v) methanol-ammonium acetate solution (0.3 mol/L). The detection limit of this method for 2,4-D was 0.15 μg/L, and the relative standard deviation was 2.3% for fortified tap water samples and 2.5% for fortified riverine water sample at the 10 μg/L level. The method was validated using fortified tap water and riverine water samples with known amount of 2,4-D at the 0.4, 10, and 30 μg/L levels, respectively.     

Solid-phase extraction of acidic herbicides

A discussion of solid-phase extraction method development for acidic herbicides is presented that reviews sample matrix modification, extraction sorbent selection, derivatization procedures for gas chromatographic analysis, and clean-up procedures for high-performance liquid chromatographic analysis. Acidic herbicides are families of compounds that include derivatives of phenol (dinoseb, dinoterb and pentachlorophenol), benzoic acid (acifluorfen, chloramben, dicamba, 3,5-dichlorobenzoic acid and dacthal--a dibenzoic acid derivative), acetic acid [2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)], propanoic acid [dichlorprop, fluazifop, haloxyfop, 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) and silvex], butanoic acid [4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB)], and other miscellaneous acids such as pyridinecarboxylic acid (picloram) and thiadiazine dioxide (bentazon).     

Molar absorptivities of 2,4-D, cymoxanil, fenpropidin, isoproturon and pyrimethanil in aqueous solution in the near-UV

The absorption spectra of five pesticides, namely 2,4-dichloro-phenoxy acetic acid (2,4-D), cymoxanil, fenpropidin, isoproturon and pyrimethanil, have been measured in aqueous solution using a set-up consisting of two parallel absorption cells coupled to a CCD detector. The absolute values of their molar absorptivity coefficients epsilon were determined in the wavelength-range 240-344 nm with a deuterium-lamp at room temperature (298+/-2 K). Using the Beer-Lambert law, values of epsilon were also determined at 253.7 nm with a Hg-Lamp: epsilon = 145+/-14 for 2,4-D, epsilon = 7940+/-920 for cymoxanil, epsilon = 196+/-14 for fenpropidin, epsilon = 7330+/-880 for isoproturon, epsilon = 13200+/-1400 for pyrimethanil (in units of M(-1) cm(-1)). The quoted errors correspond to 2 sigma obtained from the least square fit analysis and the estimated systematic error of 5% due to the uncertainties in aqueous concentrations. For all the studied compounds, the absorbances measured were lower than 2.3 and did not exhibit any deviation from the Beer-Lambert's law. Our experimental data are discussed and compared to UV spectra of similar molecules when such data were available in the literature. Based on their UV spectra and the calculated fractions of these pesticides in the aqueous phase, their direct photolysis under sunlight environment could occur, except may be for fenpropidin, either in water surfaces or in aqueous droplets contained in the atmospheric clouds.     

气相色谱–质谱法测定棉花中苯氧羧酸类除草剂

采用气相色谱–质谱联用法检测棉花中3种苯氧羧酸类除草剂[2,4-D,2,4,5-T,2-甲-4-氯丁酸(MCPB)]的残留量。样品用甲酸酸化的丙酮提取,硫酸催化甲酯化反应,用气相色谱–质谱联用仪测定。采用HPLC法与GC–MS法对提取与衍生化步骤进行优化。2,4-D,2,4,5-T,MCPB 3种化合物在0.075~7.5 mg/kg范围内线性均良好,检出限分别为0.5,0.5,0.8μg/kg,测定结果的相对标准偏差分别为4.1%,4.3%,4.0%(n=5),方法回收率分别为93.6%,95.5%,93.9%。该方法各项指标均可满足检测要求。     

Determination of 2,4-dichlorophenoxyacetic acid and silvex in water with high-performance liquid chromatography

The determination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4,5-trichlorophenoxy) propionic acid (Silvex) in water at the μg l^-1 level is based on liquid/ liquid extraction and high-performance liquid chromatography. Sample preparation for water samples is simplified. The ranges of linear response are 50 ng to 60 μg for 2,4-D and 30 ng to 60 μg for Silvex. The average recoveries of 2,4-D at the 10 μg l^-1 and 1 μg l^-1 levels are 91% and 120%, respectively, while the average recoveries of Silvex at the 10 μg l^-1 and 1 μg l^-1 levels are 85% and 110%, respectively.     

Dechlorination of 2,4-dichlorophenoxyacetic acid using biochar-supported nano-palladium/iron: Preparation,characterization, and influencing factors

In the present study, peanut shell, a green waste raw material, was used to prepare biochar (BC) and to obtain BC-supported nano-palladium/iron (BC-nPd/Fe) composites for removing 2,4-dichlorophenoxyacetic acid (2,4-D) from water. Characterization analysis demonstrated that nPd/Fe particles were well dispersed on the BC surface with weakened magnetic properties. The average particle diameter and specific surface area of nPd/Fe were 101.3 nm and 6.7 m² g⁻¹, whereas the corresponding values of the BC-nPd/Fe materials were 88.8 nm and 14.8 m² g⁻¹, respectively. Several factors were found to influence the dechlorination of 2,4-D, including the weight ratio of BC to Fe, Pd loading ratio, initial solution pH, 2,4-D concentration, and reaction temperature. Dechlorination results indicated that the 2,4-D removal and phenoxyacetic acid (PA) generation rates were 44.1% and 20.1%, respectively, in the nPd/Fe system, and 100.0% and 92.1%, respectively, in the BC-nPd/Fe system. The dechlorination of 2,4-D was well described by the pseudo-first-order kinetic model (R² > 0.97), and the observed rate constants k_obs were 0.0042 min (nPd/Fe) and 0.0578 min (BC-nPd/Fe), respectively. The reaction mechanism indicated that the dechlorination hydrogenation was the main process to remove 2,4-D from water in the BC-nPd/Fe system. In addition, BC inhibited the formation of a passivation layer on the particle surface during the reaction, thus maintaining the high reactivity of BC-nPd/Fe. The easy preparation technique, high 2,4-D dechlorination capacity, and mild reaction conditions suggest that BC-nPd/Fe may be a promising alternative composite to remove 2,4-D from water.     

Rapid analysis of 2,4-D in soil samples by modified Soxhlet apparatus using HPLC with UV detection

The 2,4-dichlorophenoxy acetic acid (2,4-D) is used as a systemic herbicide to control broadleaf weeds in wheat, corn, range land/pasture land, sorghum, and barley. In this study, a fast and efficient method is developed by selection of modified extraction apparatus and high-performance liquid chromatography (HPLC)-UV conditions for the determination of 2,4-D in soil samples. The method is applied to the study of soil samples collected from the agricultural field. The herbicide is extracted from soil samples by acetonitrile in a modified Soxhlet apparatus. The advantages of the apparatus are that it uses small volume of organic solvent, reduced time of extraction, and better recovery of the analyte. The extract is filtered using a very fine microfiber paper. The total extract is concentrated in a rotatory evaporator, dried under ultrahigh pure N2, and finally reconstituted in 1 mL of acetonitrile. HPLC-UV at 228 nm is used for analysis. The herbicide is identified and quantitated using the HPLC system. The method is validated by the analysis of spiked soil samples. Recoveries obtained varied from 85% to 100% for spiked soil samples. The limit of quantitation (LOQ) and the limit of detection (LOD) are 0.010 and 0.005 parts per million (ppm), respectively, for spiked soil samples. The LOQ and LOD are 0.006 and 0.003 ppm for unspiked soil samples. The measured concentrations of 2,4-D in spiked soil samples are between 0.010 and 0.020 ppm with an average of 0.016 +/- 0.003 ppm. For unspiked soil samples it is between 0.006 ppm and 0.012 ppm with an average of 0.009 +/- 0.002 ppm. The measured concentrations of 2,4-D in soil samples are generally low and do not exceed the regulatory agencies guidelines.     

A Method for Determination of Low Levels of Exposure to 2,4-D and 2,4,5-T

A method has been developed for the determination of trace quantities of 2,4-dichloro-phenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2,4-dichlorophenol (2,4-DCP), and 2,4,5-trichlorophenol (2,4,5-TCP) in human and rat urine. The method involves acid hydrolysis of the phenolic conjugates, extraction of the free phenols and acids, ethylation with diazoethane, silica-gel column chromatography clean-up of the derivatized urine extract, and gas chromatographic determination using the electron-capture detector. The average recoveries of 2,4-D, 2,4,5-T, 2,4-DCP, and 2,4,5-TCP from rat urine spiked with known amounts of the herbicides and their phenols were 94%, 98%, 92%, and 90%, respectively. The limits of detection for 2,4-D, 2,4,5-T, DCP, and TCP in rat urine were: 0.05, 0.01, 0.10, and 0.01 ppm, respectively. The method was used to analyze urine of rats given various levels of 2,4-D and 2,4,5-T by gavage. Results showed that levels of exposure of 3.75 mcg/kg for 2,4-D and 5.0 mcg/kg for 2,4,5-T in rats can be detected in urine within 24 hr from exposure. Urine samples from occupationally exposed people were analyzed and found to contain 0.2 to 1.0 ppm 2,4-D and 0.05 to 3.6 ppm 2,4,5-T.