Determination of chlorinated acid herbicides in vegetation and soil by liquid chromatography/electrospray-tandem mass spectrometry

The method presented uses reversed-phase liquid chromatography with negative electrospray ionization and tandem mass spectrometry to analyze 9 chlorinated acid herbicides in soil and vegetation matrixes: clopyralid, dicamba, MCPP, MCPA, 2,4-DP, 2,4-D, triclopyr, 2,4-DB, and picloram. A 20 g portion is extracted with a basic solution and an aliquot acidified and micropartitioned with 3 mL chloroform. Vegetation samples are subjected to an additional cleanup with a mixed-mode anion exchange solid-phase extraction cartridge. Two precursor product ion transitions per analyte are measured and evaluated to provide the maximum degree of confidence in results. Average recoveries for 3 different soil types tested ranged from 72 to 107% for all compounds with the exception of 2,4-DB at 56-99%. Average recoveries for the 3 different vegetation types studied were lower and ranged from 53 to 80% for all compounds.     

特丁二甲硅烷基衍生化气相色谱-质谱法检测尿中4种苯氧羧酸类除草剂

建立了尿中2,4-滴(2,4-D)、2,4-滴丙酸(2,4-DP)2、甲4氯(MCPA)和2甲4氯丙酸(MCPP)4种苯氧羧酸类除草剂的气相色谱-质谱(GC-MS)分析方法。尿样加氯化钠饱和,酸化后用乙醚萃取,萃取物进行特丁二甲硅烷基(TBDMS)衍生化后分析。尿中4种除草剂的浓度在3~3 000 ng/mL范围内工作曲线的线性关系良好,检出限在1 ng/mL以下,3、100和1 000 ng/mL水平加标回收率在97.0%~102.2%之间,精密度在6.2%~14.2%之间。该法灵敏,可用于中毒者和职业接触者尿中苯氧羧酸类除草剂的分析。     

Acidic herbicides in surface waters of Lower Fraser Valley, British Columbia, Canada

In the period 2003-2005 a study was conducted to determine the occurrence, spatial and temporal distribution of five acidic herbicides in the Lower Fraser Valley (LFV) region of British Columbia, Canada. A high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) method capable of detecting analytes at the sub ng/L level was developed for this study. Samples were collected and analyzed from two references, five agricultural, two urban and five agricultural and urban mixed sites. Only (4-chloro-2-methylphenoxy)acetic acid and triclopyr were detected at the reference sites. The highest concentration of herbicide detected at the reference sites was 0.109ng/L for (4-chloro-2-methylphenoxy)acetic acid. Varying levels of all of the herbicides monitored were detected at the urban, agricultural and the mixed sites. For the urban sites the highest concentration of herbicide detected was 66.6ng/L for 2-(4-chloro-2-methylphenoxy)propanoic acid. For the agricultural sites the highest concentration of herbicide detected was 345ng/L for (2,4-dichlorophenoxy)acetic acid (2,4-D). For the mixed sites the highest concentration of herbicide detected was 1230ng/L for 2,4-D. Overall the mixed sites showed highest concentrations and detection frequencies followed by the agricultural and urban sites. With few exceptions higher concentrations of herbicides were observed for samples collected during spring than for samples collected during fall. The detected concentrations of herbicides were evaluated against established water quality criteria. Herbicide data presented in this study provide reference levels for future pesticide monitoring programs in the region.     

Optimisation of the separation of herbicides by linear gradient high performance liquid chromatography utilising artificial neural networks

An artificial neural network (ANN) was employed to model the chromatographic response surface for the linear gradient separation of 10 herbicides that are commonly detected in storm run-off water in agricultural catchments. The herbicides (dicamba, simazine, 2,4-D, MCPA, triclopyr, atrazine, diuron, clomazone, bensulfuron-methyl and metolachlor) were separated using reverse phase high performance liquid chromatography and detected with a photodiode array detector. The ANN was trained using the pH of the mobile phase and the slope of the acetonitrile/water gradient as input variables. A total of nine experiments were required to generate sufficient data to train the ANN to accurately describe the retention times of each of the herbicides within a defined experimental space of mobile phase pH range 3.0-4.8 and linear gradient slope 1-4% acetonitrile/min. The modelled chromatographic response surface was then used to determine the optimum separation within the experimental space. This approach allowed the rapid determination of experimental conditions for baseline resolution of all 10 herbicides. Illustrative examples of determination of these components in Milli-Q water, Sydney mains water and natural water samples spiked at 0.5-1 μg/L are shown. Recoveries were over 70% for solid-phase extraction using Waters Oasis^® HLB 6 cm³ cartridges.     

SPE-LC-MS-MS Determination of Phenoxy Acid Herbicides in Surface and Ground Water

A novel method has been developed and validated for the analysis of six phenoxy acid herbicides (dicamba, 2,4-D, MCPA, dichlorprop, mecoprop and MCPB) in surface and ground waters. After solid-phase extraction on Isolute ENV+, analysis was by LC-MS-MS without using derivatization. The limits of quantitation are from 0.01 to 0.05 μg L⁻¹. Average recoveries in method validation (spiking levels: limit of quantitation and 10 times limit of quantitation) ranged from 76.5 to 108.3%, with relative standard deviations of < 13.6%. The method was applied to real surface and ground water samples which gave average recoveries (spiking level: 0.1 μg L⁻¹) ranging from 82.7 to 94.8%, with relative standard deviations of < 19.3%.

     

基于分子络合的分散液液微萃取与高效液相色谱联用检测环境水样中2种苯氧羧酸类除草剂

建立了基于分子络合的分散液液微萃取（DLLME）方法,以磷酸三丁酯为萃取剂,以甲醇为分散剂,与高效液相色谱联用检测了环境水样中麦草畏和2,4-二氯苯氧乙酸（2,4-D酸）2种苯氧羧酸类除草剂,对影响前处理效果的因素（包括水样的pH值、萃取剂的种类和体积、分散剂的种类和体积、反萃液的pH值、反萃液的体积和盐浓度等）进行了详细考察,在最佳萃取条件下（水样体积10 mL,水样的pH值为0~1.0、100 μL磷酸三丁酯萃取剂、1000 μL甲醇分散剂、0.01 mol/L的氢氧化钾反萃液的体积为80 μL）,2种苯氧羧酸类除草剂在0.50~1000 μg/L范围内具有良好的线性,相关系数不小于0.9985,麦草畏和2,4-D酸的检出限分别为0.44 μg/L和0.49 μg/L,富集倍数分别为85和90,在实际样品中的加标回收率为75.7%~104.0%。该方法基于分子络合反应机理,将新型萃取剂磷酸三丁酯应用于分散液液微萃取,与HPLC联用实现了麦草畏和2,4-D酸的富集与检测,为环境水样中苯氧羧酸类除草剂的检测提供了新的前处理方法。     

Formation of derivatives of chlorophenoxy acids and some other herbicides

Summary A fuming sulphuric acid-ethanol esterification method has been applied to chlorophenoxy acids and some other herbicides. This method is compared with esterification by iodoethane and diazomethane. The chlorophenoxy acids studied were: 2,4-D, dichlorprop, MCPA, MCPB, mecoprop and 2,4,5-T. Other herbicides studied were: benazolin, bentazone, bromophenoxime, bromoxynil, chlorthal, dicamba, 3,6-dichloropicolinic acid, dinoseb, ethephon, fluroxypyr, glyphosate, haloxyfop, ioxynil, picloram, 2,3,6-TBA and triclopyr. Fuming sulphuric acid-ethanol esterification can be successfully applied to chlorophenoxy acids, benazolin, 3,6-dichloropicolinic acid, dinoseb, fluroxypyr, haloxyfop, picloram and triclopyr. The reproductibility of the method is ±5%.     

固相萃取-衍生化-气相色谱法测定血液中的3种苯氧羧酸类除草剂

建立了一种血液中2,4-二氯苯氧乙酸(2,4-D)、2-(2,4-二氯苯氧)-丙酸(2,4-DP)和4-氯-2-甲基-苯氧乙酸(MCPA)3种苯氧羧酸类除草剂的分析方法.血样用0.1 mol/L盐酸稀释后用GDX401大孔树脂吸附、用乙醚洗脱,萃取物用二氯丙醇在硫酸催化下进行酯化衍生,衍生物经气相色谱-电子捕获检测.2,4-D、2,4-DP和MCPA的检测限分别为20,8和40 ng/mL.定量分析用2,4-二氯苯乙酸作内标,线性关系和回收率结果均令人满意.     

The evaluation of different sorbents for the preconcentration of phenoxyacetic acid herbicides and their metabolites from soils

A procedure using alkaline extraction, solid-phase extraction (SPE) and HPLC is developed to analyze the polar herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) together with their main metabolites in soils. An ion-pairing HPLC method is used for the determination as it permits the baseline separation of these highly polar herbicides and their main metabolites. The use of a highly cross-linked polystyrene-divinylbenzene sorbent (PS-DVB) gives the best results for the analysis of these compounds. This sorbent allows the direct preconcentration of the analytes at the high pH values obtained after quantitative alkaline extraction of the herbicides from soil samples. Different parameters are evaluated for the SPE preconcentration step. The high polarity of the main analytes of interest (2,4-D and MCPA) makes it necessary to work at low flow rates (< or =0.5 mL min(-1)) in order for these compounds to be retained by the PS-DVB sorbent. A two stage desorption from the SPE sorbent is required to obtain the analytes in solvents that are appropriate for HPLC determination. A first desorption with a 50:50 methanol:water mixture elutes the most polar analytes (2,4-D, MCPA and 2CP). The second elution step with methanol permits the analysis of the other phenol derivatives. The humic and fulvic substances present in the soil are not efficiently retained by PS-DVB sorbents at alkaline pH's and so do not interfere in the analysis. This method has been successfully applied in the analysis of soil samples from a golf course treated with a commercial product containing esters of 2,4-D and MCPA as the active components.     

苯氧羧酸类农药在高岭石表面吸附的理论研究

构建了高岭石铝氧八面体层表面模型Al₁₃O₄₈H₅₇和硅氧四面体层表面模型Si₁₃O₃₇H₂₂,采用B3LYP/6-31G(d,p)方法, 对其与2,4-二氯苯氧乙酸(2,4-D)、 2,4-二氯苯氧丙酸(2,4-DP)、 2,4-二氯苯氧丁酸(2,4-DB)、 2-甲基-4-氯苯氧乙酸(MCPA)、 2-甲基-4-氯苯氧丙酸(MCPP)和2-甲基-4-氯苯氧丁酸(MCPB)等苯氧羧酸类农药分子间的相互作用及吸附性质进行了研究, 包括优化的几何构型、 结构参数、 吸附能及自然键轨道(NBO)电荷. 八面体层表面的中心原子(OH2, OH3及OH11)与四面体层表面的中心原子(O2, O3及O11)并未表现出明显的吸附活性. 相较于侧链为乙酸基的分子, 含有丙酸基或丁酸基的分子因带有更多的吸附位点而具有较强的吸附性. 研究发现MCPP的吸附性高于MCPA. 结合2,4-D的吸附性高于MCPA的结论, 可以推断2,4-D与MCPA更倾向于吸附在高岭石的硅氧层表面. 因此在农药施用的过程中, 应充分考虑各分子的活性及其与高岭石表面的作用强弱, 确保淋洗对去除农药在土壤中残留的可行性.     

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).     

Separation and determination of 2,4-D, dicamba and 2,4,5-T in tobacco by nonaqueous capillary electrophoresis

A practical method for residue analysis of 2,4-D, dicamba and 2,4,5-T in baked tobacco leaves has been developed using nonaqueous CE (NACE). The herbicide residues of 2,4-D, dicamba and 2,4,5-T in tobaccos were extracted by ultrasonication with ethyl acetate, followed by a cleanup procedure with gel permeation chromatography. The separation of 2,4-D, dicamba and 2,4,5-T by NACE was optimized based on orthogonal experiment design with four factors at three levels. The optimal NACE condition was established with the running buffer of 40.0 mmol/L ammonium acetate in 90% CH3CN (apparent pH 10.2), and the applied voltage of -25 kV over a capillary of 50 microm id x 46 cm (37.5 cm to the detector window), which gave a baseline separation of 2,4-D, dicamba and 2,4,5-T within 15 min. The LOD were ca. 0.4-0.6 microg/mL for the three herbicides, whereas the overall recovery ranged from 80.8 to 84.1%. The proposed method has been successfully applied to measure 300 real tobacco samples, and the residue profiles of the three herbicides in tobacco samples were obtained and evaluated.     

尿中3种苯氧羧酸类除草剂的气相色谱分析法

本文研究了2,4-滴、2,4-滴丙酸和2甲4氯3种苯氧羧酸类除草剂用硫酸、三氯化硼、氯化氢和三氟乙酸等4种催化剂的甲醇、乙醇、丙醇、丁醇、戊醇、苯甲醇、三氟乙醇、五氟丙醇、二氯丙醇和五氟苯甲醇等10种醇的酯化衍生反应条件,在此基础上建立了尿中3种苯氧羧酸类除草剂的各种衍生化气相色谱电子俘获检测方法,其中较灵敏的方法2,4-滴和2,4-滴丙酸的检出限低于10 ng/mL,2甲4氯的检出限低于20ng/mL,适于职业接触者和中毒者的尿分析。     

中空纤维三相液相微萃取-高效液相色谱法测定环境水样中7种苯氧羧酸类除草剂

建立了利用中空纤维三相液相微萃取-高效液相色谱联用技术(HF-LPME-HPLC)同时测定环境水中痕量麦草畏(dicamba)、氟草烟(fluroxypyr)、4-氯苯氧乙酸(4-CPA)、2甲4氯(MCPA)、2,4-滴(2,4-D)、2,4-滴苯氧丁酸(2,4-DB)和2甲4氯苯氧丁酸(MCPB)等7种苯氧羧酸类除草剂的分析方法。考察了萃取剂﹑接受相和给出相pH值、萃取时间﹑搅拌速度和盐效应等对检测的影响,通过正交试验优化萃取条件,得到的最佳萃取条件为正辛醇作萃取剂,给出相pH为3,接受相pH为12,萃取30 min,搅拌速度400 r/min。结果表明7种除草剂在较宽的线性范围内线性良好,相关系数为0.9953～0.9988,检出限(信噪比为3)为0.2～1.0 μg/L,富集倍数为76.7～121,加标回收率为68%～104%,相对标准偏差为3.2%～8.1%。该法灵敏度高、操作简单、检测快速、有机溶剂消耗少,为环境水样中痕量苯氧羧酸类除草剂残留的分析提供了有益的参考。     

Differential pulse polarography of some herbicides derived from 2,4-dichlorophenoxyacetic acid

Summary A method has been developed for the differential pulse polarographic determination of 2,4-D, 2,4-DP, MCPA and MCPP residues in irrigation waters. The method involves a chloroform extraction of acidified water samples, back extraction into alkali solution and a further extraction of the acidified residue into chloroform. Subsequently, the residues are nitrated and the herbicide concentration is determined by differential pulse polarography. The determination limits of the method were found to be 30 g/l for 2,4-D and MCPA and 40 g/l for 2,4-DP and MCPP.

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Differential-Puls-Polarographie einiger von 2,4-Dichlorphenoxyessigsäure abgeleiteter HerbicideII. Bestimmung von Herbicidrückständen in Berieselungswasser

Zusammenfassung Ein Verfahren wurde ausgearbeitet zur Bestimmung von 2,4-D, 2,4-DP, MCPA und MCPP in Berieselungswasser. Die Methode umfaßt eine Chloroformextraktion der angesäuerten Probe, Rückextraktion in alkalische Lösung, erneute Chloroformextraktion der wieder angesäuerten Lösung, Nitrierung und anschließende puls-polarographische Bestimmung. Noch 30 g/l 2,4-D und MCPA sowie 40 g/l 2,4-DP und MCPP können erfaßt werden.

Dedicated to Prof. Dr. E. Blasius on his 60th birthday     

整体柱在线固相微萃取-高效液相色谱同步富集检测水中的苯氧羧酸类除草剂

采用C18毛细管整体柱作为固相微萃取整体柱,构建在线固相微萃取-高效液相色谱联用系统,同步富集检测环境水样中的5种苯氧羧酸类除草剂。详细考察了联用系统运行条件对富集检测的影响。联用系统运行最佳参数为:固相微萃取整体柱长度20 cm,进样流速0.04 mL/min,进样13 min,洗脱流速0.02 mL/min,洗脱5 min。在最佳条件下,5种苯氧羧酸类除草剂的检出限为:9 μg/L (苯氧丙酸)、4 μg/L (2-(2-氯)-苯氧丙酸)、4 μg/L (2-(3-氯)-苯氧丙酸)、5 μg/L (2,4-二氯苯氧乙酸)、5 μg/L (2-(2,4-二氯苯氧基)丙酸)。与HPLC系统直接进样对比,联用系统对5种检测对象表现出优良的富集能力。5种苯氧羧酸类除草剂的回收率在79.0%~98.0%之间(RSD≤3.9%)。该方法成功应用于水样中5种苯氧羧酸类除草剂的检测,结果令人满意。     

Microwave assisted solvent extraction and coupled-column reversed-phase liquid chromatography with UV detection use of an analytical restricted-access-medium column for the efficient multi-residue analysis of acidic pesticides in soils.

A screening method has been developed for the determination of acidic pesticides in various types of soils. Methodology is based on the use of microwave assisted solvent extraction (MASE) for fast and efficient extraction of the analytes from the soils and coupled-column reversed-phase liquid chromatography (LC-LC) with UV detection at 228 nm for the instrumental analysis of uncleaned extracts. Four types of soils, including sand, clay and peat, with a range in organic matter content of 0.3-13% and ten acidic pesticides of different chemical families (bentazone, bromoxynil, metsulfuron-methyl, 2,4-D, MCPA, MCPP, 2,4-DP, 2,4,5-T, 2,4-DB and MCPB) were selected as matrices and analytes, respectively. The method developed included the selection of suitable MASE and LC-LC conditions. The latter consisted of the selection of a 5-microm GFF-II internal surface reversed-phase (ISRP, Pinkerton) analytical column (50 x 4.6 mm, I.D.) as the first column in the RAM-C18 configuration in combination with an optimised linear gradient elution including on-line cleanup of sample extracts and reconditioning of the columns. The method was validated with the analysis of freshly spiked samples and samples with aged residues (120 days). The four types of soils were spiked with the ten acidic pesticides at levels between 20 and 200 microg/kg. Weighted regression of the recovery data showed for most analyte-matrix combinations, including freshly spiked samples and aged residues, that the method provides overall recoveries between 60 and 90% with relative standard deviations of the intra-laboratory reproducibility's between 5 and 25%; LODs were obtained between 5 and 50 microg/kg. Evaluation of the data set with principal component analysis revealed that the parameters (i) increase of organic matter content of the soil samples and (ii) aged residues negatively effect the recovery of the analytes.     

Highly efficient microextraction of chlorophenoxy acid herbicides in natural waters using a decanoic acid-based nanostructured solvent prior to their quantitation by liquid chromatography–mass spectrometry

Solvents used in microextraction require high solubilising capability to efficiently extract the target compounds. In this article, nanostructured solvents made up of alkyl carboxylic acids (ACAs) aggregate are proposed for the efficient microextraction of acidic pesticides from natural waters. The target compounds were chlorophenoxy acid herbicides (CPAHs) widely used in agriculture, forestry and gardening (viz. 2,4-D, MCPA, MCPP, 2,4,5-T and MCPB). The supramolecular solvents (SUPRASs) tested were generated from solutions of reverse micelles of octanoic (OcA), decanoic (DeA) and dodecanoic (DoA) acid in THF by the addition of water, which acted as the coacervating agent. The DeA-based SUPRAS was the most efficient extractant for CPAHs; actual concentration factors (ACFs) of 260 for 2,4-D, 290 for MCPA, and 400 for MCPP, 2,4,5-T and MCPB were obtained. The explanation for so high ACFs can be found in the extremely efficient retention mechanisms that the DeA-based SUPRAS provides for CPAHs (i.e. formation of hydrogen bonds and hydrophobic interactions), and the high number of binding sites that it contains (i.e. the concentration of biosurfactant in the SUPRAS was 0.56 mg μL⁻¹). Both characteristics permitted to effectively extract the target analytes in a low volume of solvent (about 2 μL of solvent per mL of sample). Others assets of the proposed supramolecular solvent-based microextraction (SUSME) approach included recoveries no dependent on matrix composition, rapidity (sample treatment spent about 15 min), use of low volume of sample (63 mL per analysis) and simplicity (no special lab equipments was needed). Combination with liquid chromatography/ion–trap mass spectrometry [LC–(IT)MS] afforded method quantitation limits for CPAHs within the interval 22–30 ng L⁻¹. The precision of the method, expressed as relative standard deviation (n = 11, [CPAH] = 200 ng L⁻¹), was in the range 2.9–5.8%. The applicability of the method to the analysis of natural waters was assessed by determining the target analytes in fortified river and underground water samples.     

Analysis of phenoxyacetic acid herbicides as biomarkers in human urine using liquid chromatography/triple quadrupole mass spectrometry

Phenoxyacetic acids are widely used herbicides. The toxicity of phenoxyacetic acids is debated, but high-level exposure has been shown to be hepatotoxic as well as nephrotoxic in animal studies. An inter-species difference in toxic effects has been found, with dogs particularly susceptible. In this study a method using liquid chromatography/triple quadrupole mass spectrometry (LC/MS/MS) is described for the analysis of 4-chloro-2-methylphenoxyacetic acid (MCPA), and its metabolite 4-chloro-2-hydroxymethylphenoxyacetic acid (HMCPA), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in human urine. The urine samples were treated by acid hydrolysis to degrade possible conjugations. The sample preparation was performed using solid-phase extraction. Analysis was carried out using selected reaction monitoring (SRM) in the negative ion mode. Quantification of the phenoxyacetic acids was performed using [(2)H(3)]-labeled MCPA and 2,4-D as internal standards. The method was linear in the range 0.05-310 ng/mL urine and has a within-run precision of 2-5%. The between-run precision in lower concentration ranges was between 6-15% and between 2-8% in higher concentration ranges. The limit of detection was determined to 0.05 ng/mL. The metabolites in urine were found to be stable during storage at -20 degrees C. To validate the phenoxyacetic acids as biomarkers of exposure, the method was applied in a human experimental oral exposure to MCPA, 2,4-D and 2,4,5-T. Two healthy volunteers received 200 microg of each phenoxyacetic acid in a single oral dose followed by urine sampling for 72 h post-exposure. After exposure, between 90 and 101% of the dose was recovered in the urine. In the female subject, 23%, and in the male subject 17%, of MCPA was excreted as HMCPA.     

Micellar-enhanced photochemically induced fluorescence detection of chlorophenoxyacid herbicides. Flow injection analysis of mecoprop and 2,4-dichlorophenoxyacetic acid

In this paper, a combination of a flow injection analysis (FIA) system with micellar-enhanced photochemically induced fluorescence (MEPIF) detection is presented as a powerful alternative for the rapid and sensitive analysis of chlorophenoxyacid herbicides. These compounds do not show native fluorescence but they can be photolysed into strongly fluorescence photoproducts after direct irradiation with ultraviolet light. The use of a cationic surfactant such as cetyltrimethylammonium chloride (CTAC) provides a considerable enhancement of photochemically induced fluorescence intensity and the nature of the technique allows a possible and easy adaptation to a FIA system. In this sense, parameters related to the nature of the analytical signal (pH, irradiation times, surfactant concentration) and to the FIA manifold (injection volume, flow rate and reactor length) have been optimised. Linear calibration graphs, with three replicates for each concentration value were established in the range of 0.2-5.0 mug ml(-1) for 2,4-Dichlorophenoxyacetic acid (2,4-D) and 0.1-5.0 mug ml(-1) for Mecoprop (MCPP). The IUPAC detection limits were 73.2 and 33.5 ng ml(-1) for 2,4-D and MCPP, respectively. Satisfactory recoveries were obtained in the analysis of these herbicides in spiked waters.