Comparative photodegradation study of atrazine and desethylatrazine in water samples containing titanium dioxide/hydrogen peroxide and ferric chloride/hydrogen peroxide

Results are reported for a comparative photodegradation study of atrazine and desethylatrazine in water using TiO2/H2O2, FeCl3/H2O2, and photolysis. Deionized water and ground water spiked with atrazine or desethylatrazine at 36 micrograms/L were irradiated by using a xenon arc lamp and/or sunlight. After irradiation, the water samples containing the spiked pesticides were preconcentrated by using C18 solid-phase extraction disks and analyzed by gas chromatography with nitrogen-phosphorus and mass spectrometric detection. A relative percentage of 7% desethylatrazine was detected in samples removed after 20 and 4 min of sensitized photodegradation with TiO2 and Fe3+, respectively. Atrazine and desethylatrazine did not degrade when solar irradiation (in winter) and deionized water were used. Atrazine degraded faster than desethylatrazine when a xenon arc lamp or sunlight plus FeCl3 was used, with half-lives varying from 5 to 11 min and from 19 to 26 min, respectively. In other photodegradation experiments, the degradation of atrazine was slightly higher than that of desethylatrazine. This study shows that desethylatrazine has slightly higher stability than atrazine in environmental water samples; this stability accounts for the frequent detection of desethylatrazine together with atrazine in natural waters.     

The Occurrence of Pesticides in Groundwater—Results of Case-studies

Abstract

A comparative review of pesticide survey endosing 16 waterworks in the FRG tries to increase the understanding about interferences of pesticide utilization and pesticide occurrence in ground- and drinkingwater, which includes characterization of sampling points, subsurface situation, land use and pesticide application. Between 1986 and 1991, 5772 samples were measured and led to 219094 data about the occurrence of various pesticides. 5% of these analyses showed pesticide or metabolite concentrations above the particular detection limits. This result does not vary in large extent considering groups of different characterized sampling points like groundwater dominated or surface water sampling points. As the herbicide atrazine and its metabolite desethylatrazine as well as the herbicide simazine were detected most often in all samples independent whether considering groundwater und surface water samples, this fact confirms the FRG-application ban for atrazine as well as the application restriction for simazine.     

Compound-specific stable isotope analysis of organic contaminants in natural environments: a critical review of the state of the art,prospects, and future challenges

Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L^–1 range, and the development of methods for CSIA of other elements are reviewed. Furthermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.Abbreviations BTEX benzene, toluene, ethylbenzene, xylenes - MTBE methyl tert-butyl ether - PAHs polycyclic aromatic hydrocarbons - VOCs volatile compounds - PCBs polychlorinated biphenyls - CSIA compound-specific (stable) isotope (ratio) analysis - GC-IRMS, GC/IRMS or GCIRMS gas chromatography-isotope ratio mass spectrometry - GC-C-IRMS, GC/C/IRMS or GCC-IRMS gas chromatography-combustion-isotope ratio mass spectrometry - irmGC/MS isotope ratio monitoring gas chromatograph-mass spectrometry - GC/P/IRMS gas chromatography-pyrolysis-isotope ratio mass spectrometry (used for D/H) - KIE kinetic isotope effect - PSIA position-specific isotope analysis (for intramolecular isotope distribution) - SNIF-NMR site-specific natural isotopic fractionation by nuclear magnetic resonance spectroscopy     

Comparison of different sorbents for multiresidue solid-phase extraction of 16 pesticides from groundwater coupled with high-performance liquid chromatography

A procedure based on solid-phase extraction (SPE) followed by high-performance liquid chromatography (HPLC) with diode array detection has been developed for the simultaneous analysis of 16 widely used pesticides in groundwater samples. The compounds analysed were: aldicarb, atrazine, desethylatrazine, desysopropylatrazine, carbofuran, 2,4-D, dicloran, fenitrothion, iprodione, linuron, metalaxyl, metazachlor, phenmedipham, procymidone, simazine and vinclozolin. Five different SPE sorbents, C₁₈ bonded silica (Isolute SPE C18 (EC)), graphitised carbon black (Superclean Envi-Carb), highly cross-linked polystyrene-divinylbenzene (Lichrolut EN), divinylbenzene-N-vinylpyrrolidone (Oasis HLB) and surface modified styrene-divinylbenzene (Strata X), were compared. HPLC separation and quantification of the selected pesticides was carried out under isocratic conditions by means of a new reversed-phase column (Gemini from Phenomenex) based on C₁₈ bonded to organic-silica particles. Oasis HLB and Strata X provided the best results in the preconcentration of 1-l samples, yielding average recoveries higher than 70%, except for phenmedipham that rapidly degrades in groundwater. Detection limits of the target pesticides provided by the proposed SPE-HPLC procedure were between 0.003 and 0.04 μg l⁻¹.     

Atrazine and Parathion-Methyl Removal by UV And UV/O3 in Drinking Water Treatment

Abstract

The degradation of atrazine and parathion-methyl by UV-light in the presence of O₂(UV/O₂) and by a combination of UV-light and ozone in the presence of O₂(UV/O₂/O₃) was studied at a pilot plant for drinking water treatment. The photolysis rate of parathion-methyl increased with UV/O₂/O₃ compared to the treatment with UV/O₂ only, while the photodecomposition rate of atrazine was not enhanced by the UV/O₂/O₃ combination under the working conditions applied.

In field experiments with a large-scale plant the degradation of atrazine and desethylatrazine was studied at a drinking water supply. The applied ozone dose rates were smaller and the residence time of the liquid phase in the UV-reaction unit was shorter than in the pilot plant. The degradation rate of both atrazine and desethylatrazine increased with increasing ozone dose rates and increasing radiant power. At a continuous flow rate of 70 m³/h of contaminated raw water atrazine could be degraded below the threshold limit for pesticides (0.1[ugrave]g/L) at optimum operation conditions, whereas the resulting desethylatrazine concentration exceeded this limit. At a continuous flow rate of 30 m³/h desethylatrazine could be degraded below the threshold limit, too.     

Optimization of Liquid Chromatography and Micellar Electrokinetic Chromatography for the Determination of Atrazine and its First Degradation Products in Humic Waters Without Sample Preparation

Liquid chromatographic method and micellar electrokinetic chromatographic method were optimized for determination of atrazine, desethylatrazine, desisopropylatrazine, hydroxyatrazine and their polar degradation products in solutions with humic acid without previous sample preparation step. Reversed-phase HPLC method was satisfactory in terms of repeatability and detection limits, which were ± 1.7–12.5% (RSD) and 0.1–0.5 mg L^?1, respectively. However, the most polar products could not be separated from the front peak pertaining to humic acid. With MEKC, excellent separation of both chloro and hydroxy degradation products and parent compounds was achieved in a single analysis, and possible interferences of humic acid were successfully avoided by its retention at the anode. Drawbacks were detection limits, estimated to be 2–4 mg L^?1, and RSD of the migration times was 20% compared to 0.5% with HPLC method. HPLC method was used to monitor degradation of atrazine and its first degradation products in the presence of humic acids, and MEKC was used for confirmation purposes.     

Current challenges in compound-specific stable isotope analysis of environmental organic contaminants

Compound-specific stable-isotope analysis (CSIA) has greatly facilitated assessment of sources and transformation processes of organic pollutants. Multielement isotope analysis is one of the most promising applications of CSIA because it even enables distinction of different transformation pathways. This review introduces the essential features of continuous-flow isotope-ratio mass spectrometry (IRMS) and highlights current challenges in environmental analysis as exemplified for the isotopes of nitrogen, hydrogen, chlorine, and oxygen. Strategies and recent advances to enable isotopic measurements of polar contaminants, for example pesticides or pharmaceuticals, are discussed with special emphasis on possible solutions for analysis of low concentrations of contaminants in environmental matrices. Finally, we discuss different levels of calibration and referencing and point out the urgent need for compound-specific isotope standards for gas chromatography-isotope-ratio mass spectrometry (GC-IRMS) of organic pollutants.     

Multiresidue analysis of atrazine, diuron and their degradation products in sewage sludge by liquid chromatography tandem mass spectrometry

A multiresidue method has been developed to analyze atrazine (ATZ), diuron (DIU), and their major degradation products, desethylatrazine (DEA), desisopropylatrazine (DIA), and dichlorophenylmethylurea in sewage sludge. Liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI-MS–MS) allowed, in the multiple-reaction monitoring mode, the simultaneous analysis of these pesticides in only one run after their extraction with ethyl acetate–dichloromethane 90:10 (v/v) and a cleanup on a Florisil column. Stable isotopically labeled ATZ and DIU were used as internal standards to overcome matrix effects during the pesticide quantification. Using fortified samples, the method gave rise to 86–115% as mean recovery values depending on the analyte. Limits of detection (LODs) and of quantification (LOQs) ranging from 0.3 (DIA) to 1.5 (DEA) μg kg⁻¹ dw and from 0.4 (DIA) to 2.0 (DEA) μg kg⁻¹ dw, respectively, were sufficient to achieve the monitoring of these molecules in sludge from wastewater treatment plants of the Ile-de-France region.     

New competitive dendrimer-based and highly selective immunosensor for determination of atrazine in environmental,feed and food samples: The importance of antibody selectivity for discrimination among related triazinic metabolites

A new voltammetric competitive immunosensor selective for atrazine, based on the immobilization of a conjugate atrazine-bovine serum albumine on a nanostructured gold substrate previously functionalized with poliamidoaminic dendrimers, was realized, characterized, and validated in different real samples of environmental and food concern. Response of the sensor was reliable, highly selective and suitable for the detection and quantification of atrazine at trace levels in complex matrices such as territorial waters, corn-cultivated soils, corn-containing poultry and bovine feeds and corn flakes for human use. Selectivity studies were focused on desethylatrazine, the principal metabolite generated by long-term microbiological degradation of atrazine, terbutylazine-2-hydroxy and simazine as potential interferents. The response of the developed immunosensor for atrazine was explored over the 10⁻²–10³ ng mL⁻¹ range. Good sensitivity was proved, as limit of detection and limit of quantitation of 1.2 and 5 ng mL⁻¹, respectively, were estimated for atrazine. RSD values <5% over the entire explored range attested a good precision of the device.     

Quantification of atrazine and its metabolites in urine by on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry

We have developed a method using on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry (SPE-HPLC-MS/MS) and isotope dilution quantification to measure atrazine and seven atrazine metabolites in urine. The metabolites measured were hydroxyatrazine, diaminochloroatrazine, desisopropylatrazine, desethylatrazine, desethylatrazine mercapturate, atrazine mercaturate and atrazine itself. Our method has good precision (relative standard deviations ranging from 4 to 20% at 5, 10 and 50 ng/mL), extraction efficiencies of 67 to 102% at 5 and 25 ng/mL, relative recoveries of 87 to 112% at 5, 25, 50 and 100 ng/mL limits of detection (LOD) ranging from 0.03 to 2.80 ng/mL. The linear range of our method spans from the analyte LOD to 100 ng/mL (40 ng/mL for atrazine and atrazine mercapturate) with R ² values of greater than 0.999 and errors about the slope of less than 3%. Our method is rapid, cost-effective and suitable for large-scale sample analyses and is easily adaptable to other biological matrices. More importantly, this method will allow us to better assess human exposure to atrazine-related chemicals. Figure A schematic representation showing the elution of the analytes from the solid-phase extraction cartridge onto the analytical column for chromatographic separation prior to MS/MS analysis     

Rapid selective accelerated solvent extraction and simultaneous determination of herbicide atrazine and its metabolites in fruit by ultra high performance liquid chromatography

A selective accelerated solvent extraction procedure achieved one step extraction and cleanup for analysis of herbicide atrazine and its metabolites in fruit. Using a BEH C18 analytical column and the gradient mode with 2 mM ammonium acetate aqueous solution/acetonitrile as a mobile phase achieved effective chromatographic separation of the five analytes within 4 min. The calibration curves were linear over two orders of magnitude of concentration with correlation coefficients (r) of 0.9996?0.9999. The method limit of quantification was 1, 2, 1.5, 3, and 2 μg/kg for atrazine, desethylatrazine, desisopropylatrazine, desethyldesisopropylatrazine, and hydroxyatrazine, respectively, in the case of atrazine it is at least two orders of magnitude lower than the maximum residue limit (0.25 mg/kg). The intra‐day and inter‐day precisions of the five analytes were in the range of 2.1–3.5 and 3.1–4.8 %, respectively. The recoveries of the five analytes at three spiked levels varied from 85.9 to 107% with a relative standard deviation of 1.8–4.9% for pear and apple samples. The ultra high performance liquid chromatography with diode array detection method was proved to be fast, inexpensive, selective, sensitive, and accurate for the quantification of the analytes in pear and apple samples.     

Pitfalls in compound-specific isotope analysis of environmental samples

In the last decade compound-specific stable isotope analysis (CSIA) has evolved as a valuable technique in the field of environmental science, especially in contaminated site assessment. Instrumentation and methods exist for highly precise measurements of the isotopic composition of organic contaminants even in a very low concentration range. Nevertheless, the determination of precise and accurate isotope data of environmental samples can be a challenge. Since CSIA is gaining more and more popularity in the assessment of in situ biodegradation of organic contaminants, an increasing number of authorities and environmental consulting offices are interested in the application of the method for contaminated site remediation. Because of this, it is important to demonstrate the problems and limitations associated with compound-specific isotope measurements of environmental samples. In this review, potential pitfalls of the analytical procedure are critically discussed and strategies to avoid possible sources of error are provided. In order to maintain the analytical quality and to ensure the basis for reliable stable isotope data, recommendations on groundwater sampling, and sample preservation and storage are given. Important aspects of sample preparation and preconcentration techniques to improve sensitivity are highlighted. Problems related to chromatographic resolution and matrix interference are discussed that have to be considered in order to achieve accurate gas chromatography/isotope ratio mass spectrometry measurements. As a result, the need for a thorough investigation of compound-specific isotope fractionation effects introduced by any step of the overall analytical method by standards with known isotopic composition is emphasized. Finally, we address some important points that have to be considered when interpreting data from field investigations. Figure CSIA Principal (Carbon)     

Degradation of atrazine by Fenton and modified Fenton reactions

Abstract  

For 50 years, farmers around the world have relied on the herbicide atrazine—one of the triazine family of herbicides—to fight weeds in corn, grain sorghum, sugar cane, and other crops. Although prohibited in the European Union because of widespread contamination of waterways and drinking water supplies, it is still one of the most widely used herbicides in the world. Atrazine and some of its degradation products are among the most commonly found xenobiotics in groundwater and soils in the world. It is also an endocrine disruptor that causes abnormal reproductive development and immune suppression in wildlife. The purpose of this study was to identify the degradation products of atrazine. Fenton reaction treatment, a hydroxyl radical oxidation process recently developed for the degradation of aqueous pesticide waste, was applied to the degradation of atrazine. Classical and modified Fenton reactions have been used as Advanced Oxidation Process treatment methods. A HPLC method was developed and optimized for the identification of resulting degradation products. In general, very good atrazine degradation efficiencies were achieved by both of the methods used. The degradation products, such as oxalic acid, urea, formic acid, acetic acid, and acetone, were identified by HPLC with a photodiode array detector.     

Precise and accurate compound-specific carbon and nitrogen isotope analysis of RDX by GC-IRMS

A new analytical method is presented for the compound-specific carbon and nitrogen isotope ratio analysis of a thermo-labile nitramine explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by gas chromatograph coupled to an isotope ratio mass spectrometer (GC-IRMS). Two main approaches were used to minimise thermal decomposition of the compound during gas chromatographic separation: programmed temperature vaporisation (PTV) as an injection technique and a high-temperature ramp rate during the GC run. δ¹⁵N and δ¹³C values of RDX measured by GC-IRMS and elemental analyser (EA)-IRMS were in good agreement within a standard deviation of 0.3‰ and 0.4‰ for nitrogen and carbon, respectively. Application of the method for the isotope analysis of RDX during alkaline hydrolysis at 50°C revealed isotope fractionation factors ε _carbon?=??7.8‰ and ε _nitrogen?=??5.3‰.     

固液萃取-高效液相色谱-串联质谱法同时测定土壤中阿特拉津及其降解产物

建立了高效液相色谱-串联质谱法(HPLC-MS/MS)同时检测土壤中阿特拉津及其降解产物残留的分析方法。样品以甲醇-水(4∶1,V/V)作为提取溶剂,使用涡旋振荡提取,采用HPLC-MS/MS法进行测定,外标法定量。在0.01、0.2和5.0mg/kg三个添加浓度水平下,阿特拉津及其降解产物的平均回收率在73.7%~104.7%之间,相对标准偏差为0.4%~5.1%;阿特拉津,羟基阿特拉津在土壤样品中的方法检出限均0.045μg/kg,而脱乙基阿特拉津、脱乙基脱异丙基阿特拉津及脱异丙基阿特拉津在土壤样品中的方法检出限则分别为0.090、0.45和0.90μg/kg。本方法的灵敏度较高,且简便、快速,能较好的解决目标物极性差别大及样品基质对检测结果的干扰等问题,可以满足土壤中阿特拉津及其降解产物残留检测的需要。     

Gas chromatography/ion trap mass spectrometry applied for the analysis of triazine herbicides in environmental waters by an isotope dilution technique

A gas chromatography/ion trap mass spectrometry method was developed for the analysis of simazine, atrazine, cyanazine, as well as the degradation products of atrazine, such as deethylatrazine and deisopropylatrazine in environmental water samples. Isotope dilution technique was applied for the quantitative analysis of atrazine in water at low ng/l levels. One liter of water sample spiked with stable isotope internal standard atrazine-d₅ was extracted with a C₁₈ solid-phase extraction cartridge. The analysis was performed on an ion trap mass spectrometer operated in MS/MS method. The extraction recoveries were in the range of 83-94% for the triazine herbicides in water at the concentrations of 24, 200, and 1000 ng/l, while poor recoveries were obtained for the degradation products of atrazine. The relative standard deviation (R.S.D.) were within the range of 3.2-16.1%. The detection limits of the method were between 0.75 and 12 ng/l when 1 l of water was analyzed. The method was successfully applied to analyze environmental water samples collected from a reservoir and a river in Hong Kong for atrazine detected at concentrations between 3.4 and 26 ng/l.     

Enantioselective stable isotope analysis (ESIA) of polar herbicides

Assessing the environmental fate of chiral micropollutants such as herbicides is challenging. The complexity of aquatic systems often makes it difficult to obtain hydraulic mass balances, which is a prerequisite when assessing degradation based on concentration data. Elegant alternatives are concentration-independent approaches like compound-specific isotope analysis or enantiospecific concentration analysis. Both detect degradation-induced changes from ratios of molecular species, either isotopologues or enantiomers. A combination of both—enantioselective stable isotope analysis (ESIA)—provides information on ¹³C/¹²C ratios for each enantiomer separately. Recently, Badea et al. demonstrated for the first time ESIA for the insecticide α-hexachlorocyclohexane. The present study enlarges the applicability of ESIA to polar herbicides such as phenoxy acids: 4-CPP ((RS)-2-(4-chlorophenoxy)-propionic acid), mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid), and dichlorprop (2-(2,4-dichlorophenoxy)-propionic acid). Enantioselective gas chromatography–isotope ratio mass spectrometry was accomplished with derivatization prior to analysis. Precise carbon isotope analysis (2σ?≤?0.5‰) was obtained with ≥7 ng C on column. Microbial degradation of dichlorprop, 2-(2,4-dichlorophenoxy)-propionic acid by Delftia acidovorans MC1 showed pronounced enantiomer fractionation, but no isotope fractionation. In contrast, Badea et al. observed isotope fractionation, but no enantiomeric fractionation. Hence, the two lines of evidence appear to complement each other. They may provide enhanced insight when combined as ESIA.     

The use of stable carbon isotope analysis to detect the abuse of testosterone in cattle.

The use of stable carbon isotope analysis to detect the administration of anabolic steroids to cattle was investigated. Samples were extracted by solid-phase extraction on C18 cartridges. Stable isotope ratios (13C:12C) were measured by gas chromatography-isotope ratio mass spectrometry (GC-IRMS) of the underivatised extracts. A programmed temperature vaporiser (PTV) injector was installed in the GC-IRMS system, which conferred a number of advantages. First, it allowed large volumes of sample to be injected whilst the injector liner was cool. The solvent was subsequently vented to the atmosphere prior to transfer of the sample to the GC column. Thus a significantly greater amount of sample could be presented for analysis, thereby increasing the sensitivity. Second, by this means virtually all the solvent could be removed prior to analysis. This eliminates solvent peak tailing, which can be a major problem in GC-IRMS. Finally, the PTV allowed the use of higher initial GC oven temperatures, which in turn facilitated the analysis of underivatised steroids by reducing the GC run time and improving the chromatographic peak shape. The carbon isotope composition of 5 beta-androstane-3 alpha,17 alpha-diol, the major metabolite of testosterone found in bovine bile, was measured in bile samples from untreated cattle and from cattle injected intramuscularly with testosterone or a mixture of testosterone esters. There was considerable inter-animal variation in the values obtained and there was no significant difference between samples from treated and untreated animals. However, when the isotopic composition of the metabolite was normalised with respect to that of an endogenous reference compound (cholesterol) in the same sample, the difference between treated and untreated animals become statistically significant.     

Carbon and hydrogen isotope fractionation of benzene during biodegradation under sulfate‐reducing conditions: a laboratory to field site approach

The microbial carbon and hydrogen isotope fractionation of benzene under sulfate‐reducing conditions was investigated within systems of increasing complexity: (i) batch laboratory microcosms, (ii) a groundwater‐percolated column system, and (iii) an aquifer transect. Recent molecular biological studies indicate that, at least in the laboratory microcosms and the column system, benzene is degraded by similar bacterial communities. Carbon and hydrogen enrichment factors (ε_C, ε_H) obtained from laboratory microcosms and from the column study varied significantly although experiments were performed under similar redox and temperature conditions. Thus, enrichment factors for only a single element could not be used to distinguish benzene degradation under sulfate‐reducing conditions from other redox conditions. In contrast, using correlation of changes of hydrogen vs. carbon isotope ratios (Λ = Δδ²H/Δδ¹³C), similar Λ‐values were derived for the benzene biodegradation under sulfate‐reducing conditions in all three experimental systems (Λ_{laboratory microcosms} = 23 ± 5, Λ_column = 28 ± 3, Λ_aquifer = 24 ± 2), showing the robustness of the two‐dimensional compound‐specific stable isotope analysis (2D‐CSIA) for elucidating distinct biodegradation pathways. Comparing carbon and hydrogen isotope fractionation data from recent studies, an overlap in Λ‐values was observed for benzene biodegradation under sulfate‐reducing (Λ = 23 ± 5 to Λ = 29 ± 3) and methanogenic (Λ = 28 ± 1 to Λ = 39 ± 5) conditions, indicating a similar initial benzene reaction mechanism for both electron‐acceptor conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

Reconstructing bulk isotope ratios from compound‐specific isotope ratios

Carbon isotope analysis by bulk elemental analysis coupled with isotope ratio mass spectrometry has been the mainstay of δ¹³C analyses both at natural abundance and in tracer studies. More recently, compound‐specific isotope analysis (CSIA) has become established, whereby organic constituents are separated online by gas or liquid chromatography before oxidation and analysis of CO₂ for constituent δ¹³C. Theoretically, there should be concordance between bulk δ¹³C measurements and carbon‐weighted δ¹³C measurements of carbon‐containing constituents. To test the concordance between the bulk and CSIA, fish oil was chosen because the majority of carbon in fish oil is in the triacylglycerol form and ～95% of this carbon is amenable to CSIA in the form of fatty acids. Bulk isotope analysis was carried out on aliquots of oil extracted from 55 fish samples and δ¹³C values were obtained. Free fatty acids (FFAs) were produced from the oil samples by saponification and derivatised to fatty acid methyl esters (FAMEs) for CSIA by gas chromatography/combustion/isotope ratio mass spectrometry. A known amount of an internal standard (C15:0 FAME) was added to allow analyte quantitation. This internal standard was also isotopically calibrated in both its FFA (δ¹³C = ?34.30‰) and FAME (δ¹³C = ?34.94‰) form. This allowed reporting of FFA δ¹³C from measured FAME δ¹³C values. The bulk δ¹³C was reconstructed from CSIA data based on each FFA δ¹³C and the relative amount of CO₂ produced by each analyte. The measured bulk mean δ¹³C (SD) was ?23.75‰ (1.57‰) compared with the reconstructed bulk mean δ¹³C of ?23.76 (1.44‰) from CSIA and was not significantly different. Further analysis of the data by the Bland‐Altman method did not show particular bias in the data relative to the magnitude of the measurement. Good agreement between the methods was observed with the mean difference between methods (range) of 0.01‰ (?1.50 to 1.30). Copyright © 2010 John Wiley & Sons, Ltd.