Graphitized Carbon Black Cartridge Research Articles

Using stable carbon isotope ratio analysis to detect adulteration in red yeast rice dietary supplements

Red yeast rice (RYR) is marketed as a dietary supplement because it contains natural 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), including monacolin K. However, there is concern that some RYR supplements may be adulterated with the pharmaceutical drug lovastatin to enhance health claims. We have developed an optimized method to isolate monacolin K/lovastatin from complex RYR dietary supplement matrices to then test for adulteration in RYR supplements using stable carbon isotope (δ13C) analysis. Samples were initially screened for monacolin K/lovastatin using liquid chromatography with mass spectrometric detection (LC-MS). To ensure the extraction process did not affect the measured isotopic values (i.e., isotopic fractionation effects), neat lovastatin standards were spiked into two types of blank RYR matrices (powder and gel). The monacolin K/lovastatin peaks were detected using high performance liquid chromatography with ultraviolet detection (HPLC-UV) and isolated using fraction collection. Residual matrix components were removed from targeted fractions by solid phase extraction (SPE) using graphitized carbon black cartridges. The resulting isolates were then analyzed using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) to measure δ13C values. The δ13C values of the extracted lovastatin standards were compared to their respective neat lovastatin δ13C values and demonstrated negligible isotopic fractionation effects. Using this optimized clean up method and carbon isotope analysis, thirty-one samples were screened. Eight RYR dietary supplement samples had >0.8 mg/g of monacolin K/lovastatin, our minimum threshold for analyzing samples using this method. Four of these eight samples had δ13C values greater than −28.3‰, a previously proposed cutoff value for natural monacolin K, indicating likely adulteration. Additionally, five RYR powder samples were analyzed as part of a collaborative study using in-house methods from two laboratories and the data shows acceptable agreement in the δ13C values of monacolin K/lovastatin (differences ranging from ±0.02‰ to ±0.76‰). This optimized method represents a robust, reproducible procedure for detecting lovastatin adulteration in dietary supplements with minimal isotopic fractionation.

Multiresidue pesticide analysis in tomato using GC-MS/MS using modified QuEChERS method with titanium-coated graphite with CNT-ABS nanocomposite as dispersive solid-phase extraction materials

Abstract The presence of pesticide residues in food and vegetables is a growing concern for consumers. To monitor these residues reliably, a selective and sensitive multiresidue system has been developed and validated in tomato by gas chromatography–tandem mass spectrometry (GC-MS/MS). Titanium-coated graphite with carbon nanotube (CNT) in acrylonitrile–butadiene–styrene (ABS) used as reversed-dispersive solid-phase (extraction materials with modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method. Titanium-coated graphite with CNT-ABS is synthesized, characterized by X-ray diffraction and scanning electron microscopy. The clean-up performance of titanium-coated graphite with CNT-ABS was demonstrated to be better to primary secondary amine and graphitized carbon black cartridges. The processing of two multiple reaction monitoring transformations for each analyte is done using GC-MS/MS in electron impact mode. Satisfactory purification and recovery effects (74%–100%) of 35 pesticides were achieved in tomato matrices when using 5 mg of titanium-coated graphite ABS-CNT nanocomposite. It was observed that quinolphos and deltamethrin are present above the maximum residue limit. The technique proved to be reliable and sensitive in tomato samples for the routine testing of 35 pesticides.

Development and validation of sensitive methods for simultaneous determination of 9 antiviral drugs in different various environmental matrices by UPLC-MS/MS

Trace antiviral drug contamination in aquatic ecosystems is becoming a significant environmental concern that requires an urgent efficient determination method. Here we developed sensitive and robust multi-residue determination methods to simultaneously extract and analyze 9 commonly used antiviral drugs (abacavir, zidovudine, efavirenz, nevirapine, ritonavir, lopinavir, lamivudine, telbivudine and entecavir) in surface water, wastewater, sediment, and sludge. Water samples were extracted with solid-phase extraction (SPE) technique using tandem hydrophilic–lipophilic balance and graphitized carbon black cartridges, while sediment and sludge samples were extracted using QuEChERS (quick, easy, cheap, effective, rugged, and safe) method. The extraction conditions of SPE (pH and cartridge type) and QuEChERS (acetic acid content, salts reagent, and purification sorbent) methods were carefully optimized. We observed that under optimum conditions, the method quantification limits of the 9 antiviral drugs in water and solid samples ranged from 0.05 to 19.23 ng L−1 and from 0.02 to 7.38 ng g−1, respectively. For environmental samples spiking 3 different concentrations, the recovery values for the most targeted antiviral drugs ranged from 70 to 130%, except for efavirenz. All targeted antiviral drugs were detected in wastewater samples except for entecavir. We also found abacavir, efavirenz, ritonavir, lopinavir, and telbivudine in sediment and sludge samples. Notably, telbivudine was identified in all environmental matrices, with a high concentration of 127 ng L−1 and 222 ng g−1 in water and sediment samples, respectively.

Determination of atmospheric organochlorine pesticides using isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry

建立了测定大气中25种有机氯农药(OCPs)的同位素稀释-高分辨气相色谱/高分辨质谱法(ID-HRGC/HRMS)。样品用正己烷/二氯甲烷(1:1, v/v)进行加速溶剂萃取(ASE)。通过柱洗脱实验、单柱和组合柱净化实验,最终确定样品的净化方案为弗罗里硅土固相萃取柱和石墨化炭黑固相萃取柱组合净化。样品萃取液净化后进行HRGC/HRMS分析。采用平均相对响应因子(RRF)法对样品中目标物进行定量,6点校准溶液RRF的相对标准偏差(RSD)均≤20%。线性范围为0.4~800 μg/L,相关系数R2均>0.992。对空白样品依次进行100 pg、400 pg和15 ng水平下的加标试验,各添加水平下OCPs测定值的RSD为0.64%~16%,加标回收率为67.2%~135%。穿透试验表明,滤膜+聚氨酯泡沫/聚氨酯泡沫作为吸附介质的大体积主动大气采样器(AAS)在采集环境空气时,五氯苯极易发生穿透,有效采样模式待进一步研究。在上述采样模式下,六氯苯的有效采样体积较小,标准状态(101.325 kPa, 273 K)采样体积应≤30 m3,其他OCPs应≤1200 m3。以上述体积计算,25种目标化合物的检出限为0.002~0.7 pg/m3。对北京环境空气样品分析测定,结果显示除反式-环氧七氯、异狄氏剂、顺式-九氯和4,4'-滴滴滴在部分样品中未检出外,其他OCPs均为100%检出;六氯苯浓度在514~563 pg/m3之间,其他OCPs的浓度在0.01~18.9 pg/m3之间;替代标回收率为33.9%~155%。由于现有相关监测标准的仪器灵敏度较低、方法检出限较高,已无法满足目前空气中痕量OCPs的测定需求,因此亟待修订新的高灵敏度监测方法标准。该方法适用于目前大气中OCPs的超痕量水平分析,为新标准的制订奠定基础,也为国家履行相关国际公约提供有力技术指导。

Investigation of aromatic impurities in liquefied petroleum gas by solid-phase extraction sampling coupled with gas chromatography-mass spectrometry

A dynamic solid-phase extraction system for sampling and synchronous preconcentration of aromatic impurities from liquefied petroleum gas (LPG) with graphitized carbon black (GCB) sorbents was constructed. The target aromatics (benzene, toluene, xylenes, styrene and naphthalene) were rapidly collected from LPG flow and analyzed with gas chromatography-mass spectrometry. Compared with C18 and poly (styrene-divinylbenzene) copolymer sorbents, the tandem packed GCB cartridges presented the highest extraction efficiency for capturing aromatics from LPG. The sampling efficiency, reproducibility and storage stability of aromatics on the adsorption GCB cartridge were evaluated. The quantification curves of eight aromatics in nitrogen simulative gas flow were linear in the range of 15-1000 μ g/m 3 . The developed sampling method presented good advantages of high recoveries (92.9%-109.0%), low method detection limits (1.0-6.2 μg/m 3 ), together with excellent precision (relative standard deviations:0.6%-5.8%) and accuracy (relative errors:0.8%-8.2%), respectively.

Development of a Rapid LC-MS/MS Method for the Determination of Emerging Fusarium mycotoxins Enniatins and Beauvericin in Human Biological Fluids.

A novel method for the simultaneous determination of enniatins A, A1, B and B1 and beauvericin, both in human urine and plasma samples, was developed and validated. The method consisted of a simple and easy pretreatment, specific for each matrix, followed by solid phase extraction (SPE) and detection by high performance liquid chromatography-tandem mass spectrometry with an electrospray ion source. The optimized SPE method was performed on graphitized carbon black cartridges after suitable dilution of the extracts, which allowed high mycotoxin absolute recoveries (76%–103%) and the removal of the major interferences from the matrix. The method was extensively evaluated for plasma and urine samples separately, providing satisfactory results in terms of linearity (R2 of 0.991–0.999), process efficiency (>81%), trueness (recoveries between 85% and 120%), intra-day precision (relative standard deviation, RSD < 18%), inter-day precision (RSD < 21%) and method quantification limits (ranging between 20 ng·L−1 and 40 ng·L−1 in plasma and between 5 ng·L−1 and 20 ng·L−1 in urine). Finally, the highly sensitive validated method was applied to some urine and plasma samples from different donors.

Determination of tetrodotoxin in seafood using graphitized carbon black clean-up with hilic ultra performance liquid chromatography-triple quadrupole mass spectrometry

To develop a rapid hilic ultra performance liquid chromatography (UPLC)-mass spectrum (MS)/MS method for determination of tetrodotoxin in seafood. The sample of muscle and liver of puffer fish and nassarius were extracted with aqueous solution containing 0.2% (V/V) acetic acid (the extract of liver must be purified through HLB cartridge), and then cleanup of extract was accomplished by solid-phase extraction with a graphitized carbon black cartridge. The analysis of tetrodotoxin was carried out on a chromatographic column (Acquity UPLC BEH Amide, 100 mm×2.1 mm×1.7 µm) with gradient elution of 95% (V/V) acetonitrile-H2O both containing 0.1% (V/V) formic acid and 2.0 mmol/L ammonium formate, and detected by positive electrospray ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode, and quantified by matrix-match standard solution. The calibration curves were linear in the range of 30 - 10 000, 50 - 10 000 and 30 - 10 000 µg/kg of tetradotoxin in muscle and liver of puffer fish and in muscle of nassarius, respectively. The correlation coefficients were within 0.9963 - 0.9990. The limits of detection were 10, 20 and 10 µg/kg, and that of quantitation were 30, 50 and 30 µg/kg for muscle and liver of puffer fish and muscle of nassarius, respectively. The average recoveries were 81.5% - 93.1%, 82.3% - 106.0% and 83.5% - 95.2% for tetrodotoxin spiked in muscle and liver of puffer fish and in muscle of nassarius, respectively, with relative standard deviation (RSD) of 2.3% - 11%, 4.3% - 14.0% and 3.5% - 13.0% (n = 6). The method was simple, accurate and sensitive, and could be successfully applied to the measurement of tetrodotoxin in puffer fish and nassarius.

Simultaneous determination of multiresidual phenyl acetanilide pesticides in different food commodities by solid‐phase cleanup and gas chromatography‐mass spectrometry

An efficient and sensitive multiresidue method has been developed for quantification and confirmation of 25 phenyl acetanilide pesticides in a wide variety of food commodities including maize, spinach, mushroom, apple, soybean, chestnut, tea, beef, cattle liver, chicken, fish, and milk. Analytes were extracted with acetone-n-hexane (1:2, v/v) followed by cleanup using SPE. Several types of adsorbents were evaluated. Neutral aluminum and graphitized carbon black cartridge showed good cleanup efficiency. The extract was determined by GC-MS in the selected ion monitoring mode using one target and two qualitative ions for each analyte. The limits of detection were 0.01 mg/kg for all analytes. The average recoveries ranged from 66.9 to 110.6% (mean 88.8%) and RSDs were in the range 2.0-19% (mean 10.5%) across three fortification levels. The proposed method was successfully applied to real samples in routine analysis and a satisfactory result was obtained.

Simultaneous determination of neutral, basic and acidic pesticides in aquatic environmental matrices by solid-phase extraction and liquid chromatography electrospray ionization mass spectrometry

Simultaneous determination of a wide variety of pesticides and herbicides in environmental waters by liquid chromatography electrospray-ionization mass spectrometry (LC-ESI-MS) has been a challenging task due to matrix interferences. In this study, deuterated analogues and graphitized carbon black (GCB) solid-phase extraction (SPE) were investigated to compensate for and eliminate sample matrix interferences. Significant ion suppression and enhancement were observed when deuterated pesticides were used as internal standards. GCB cartridges can well retain neutral, basic and acidic pesticides and herbicides but the complete elution requires a combination of different characteristics of the solvent. A new procedure for SPE extraction and sample preparation was developed for simultaneous determination of neutral, basic pesticides and phenoxy acid herbicides in environmental waters by LC-ESI-MS. The proposed method was validated by examining the limit of detection and range of linearity and testing river water samples. The limit of detection ranged between 0.005 and 2 μg L−1 and the correlation coefficient for 5–5000 μg L−1 calibration standards was greater than 0.995. The recoveries of 79–121% from river water samples and relative standard deviations of 2–21% were obtained at the concentrations of 0.4–500 μg L−1 for 37 pesticides and herbicides.

Pressurized Liquid Extraction and Cleanup Procedure for the Determination of Pyrethroids in Soils Using Gas Chromatography/Tandem Mass Spectrometry

An analytical method for the simultaneous determination of 12 pyrethroids in soil samples was developed using gas chromatography tandem quadrupole mass spectrometry. Pyrethroids were extracted by pressurized liquid extraction with optimized parameters such as solvent, temperature and extraction time. Then the graphitized carbon black cartridges were used for further purification. The method showed good linearity (R(2) > 0.9931) and good repeatability (RSD < or = 12.6%) for all compounds, with the method detection limits ranging from 0.26 ng g(-1) for transfluthrin to 0.87 ng g(-1) for prallethrin. The recoveries of all compounds were 75-120%.

Evaluation and interlaboratory validation of a GC-MS method for analysis of pesticide residues in teas

AbstractA method was described for simultaneous determination of nine organic heterocyclic pesticide residues by gas chromatography-mass spectrometry-selected ion monitoring. Atrazine, vinclozolin, procymidone, triflumizole, imazalil, buprofezin, propiconazole, fenarimol, and pyridaben were clearly separated from each other, extracted with acetone—hexane mixture, purified with graphitized carbon black cartridge and neutral Al2O3 cartridge, eluted with acetone—hexane mixture, simultaneously determined by GC-MS, and then quantified with an external standard method. Recoveries of pesticides ranged from 73 % to 116 % at the spiked level of 0.01–30 mg kg−1, while the relative standard deviation was between 3 % and 27 %. In addition, the limits of determination (0.01 mg kg−1 to 5.0 mg kg−1) and linearity (0.02–40 μg mL−1) revealed that simultaneous determination of multi-residues in Chinese teas (like Oolong tea, green tea, red tea, etc.) was possible. Furthermore, an interlaboratory study among 5 labs was conducted to further validate the method, and the results were satisfactory.

Application of combination column of macroporous diatomaceous earth and graphitized carbon black for pesticide residue analysis

An analytical method for pesticide residue for agricultural products was developed using combination column of macroporous diatomaceous earth (MDE) and graphitized carbon black (GCB). The on-column liquid–liquid partition was performed by the following procedure. The concentrated sample extract was diluted with an equal volume of acetonitrile and transferred into the MDE column, and the residue pesticides were eluted with hexane. It was possible to elute the non-polar pesticides (log POW>4.3) from the MDE column by using a smaller volume of organic solvent. One hundred-seventy-three of 238 pesticides were recovered at more than 70% with hexane from the MDE columns when applied in acetonitrile–water (1 : 1, v/v) solution. After eluting from the MDE column, the elution profiles with the GCB cartridge indicated that the majority of pesticides could be eluted with common organic solvents such as hexane, ethyl acetate and acetone. The applicability of this method was evaluated by the recovery from 5 fortified agricultural products (cucumber, spinach, tomato, carrot and chinese cabbage) at 0.02 and 2.0 μg/g. The recovery of 2 synthetic pyrethroid insecticides and 7 organic chlorine pesticides ranged from 81% to 113%, and the limit of detection was 0.005 μg/g.

Triazinic herbicide determination by gas chromatography–mass spectrometry in breast milk

A solid-phase extraction procedure using a graphitized carbon black cartridge for extraction and cleaning of a series of five triazines (atrazine, deethylatrazine, deisopropylatrazine, ametryne and prometryne) from breast milk samples was developed. Using a chemometric methodology, the optimisation of both the analysis time and the triazinic herbicide separation by gas chromatography–mass spectrometry (GC–MS) was then carried out with only 18 experiments. Detection and quantification limits for 1 ml breast milk sample were, respectively, 0.3 and 1 ppb for each studied compound. The variation coefficients were less than 5% over the concentration range from 1 to 100 ppb. The accuracy was between 98.63 and 104.62% for each triazinic herbicide. The recovery was between 58.64 and 63.22% for the concentration range from 1 to 100 ppb for each triazinic herbicide. The assay was successfully applied to the analysis of several breast milk samples.

Sample Preparation for Determination of Macrocyclic Lactone Mycotoxins in Fish Tissue, Based on On-Line Matrix Solid-Phase Dispersion and Solid-Phase Extraction Cleanup Followed by Liquid Chromatography/Tandem Mass Spectrometry

A new method based on matrix solid-phase dispersion (MSPD) on-line with a solid-phase extraction (SPE) cleanup process followed by liquid chromatography with tandem mass spectrometry (LC/MS/MS) is presented for the determination of 3 macrocyclic lactone mycotoxins in fish tissues: zearalenone, alpha-zearalenol, and beta-zearalenol. The sample was prepared in a device that used a reversed-phase material (C18) or a normal-phase material (neutral alumina) as a matrix dispersing agent, and a graphitized carbon black cartridge was used for sequential cleanup by SPE. LC/MS/MS was used for selective determination. Isocratic elution with acetonitrile-methanol-water was used for LC separation; for MS/MS, 2 types of interfaces (a pneumatically assisted electrospray ionization interface or an atmospheric pressure chemical ionization interface) were evaluated and compared in terms of the intensity of the total ion current produced by each analyte. The use of highly selective MSPD on-line with SPE for sample preparation before analysis allowed the removal of interfering matrix compounds present in tissue extracts that would otherwise cause severe ionization suppression of zearalenone and its metabolites during the ionization process. Average recoveries at 100 ng/g were between 83 and 103% with C18 and > or = 67% with neutral alumina; the relative standard deviations were < 11% with C18 and < 18% with alumina. The limits of detection ranged from 0.1 to 1.0 ng/g. Sample preparation is simple to perform, no special technical equipment is required, and solvent volumes are minimal.

Stability of herbicides and their degradation products on graphitized carbon black extraction cartridges used for large volumes of surface water

The stability of 18 herbicides (ten organonitrogens and eight phenylureas, including four degradation products), selected for the frequency of their detection in the environment, was evaluated under a variety of storage conditions. Large volumes of s ur- face water (4 L) were extracted using large-particle-size graphitized carbon black cartridges (Carbopack B 60-80 mesh). The effe cts of temperature, matrix type, drying and solvent-washing of cartridges on the recovery of these contaminants, after different stora ge periods, were studied and compared to the conservation of surface water in bottles. After two months, there was no significant di ffer- ence between the conserved surface water and the stored cartridges for the selected compounds. Cartridges kept at -20 °C were be t- ter than those stored at 4 °C and 20 °C. The type of matrix water selected, in this case St. Lawrence surface water, appears to hav e a minor effect on the recovery of the target pesticides after cartridge storage. No improvement was observed in the recovery of a ny of the chemicals when the cartridges were dried or washed and stored in a solvent. After immediate surface-water extraction, the mo st practical storage condition for the target herbicides was found to be storage on cartridges in the dark at - 20 °C, with no solven t dry- ing or washing of the Carbopack B material.

Analysis of chlorophenoxy acid herbicides in water by large-volume on-line derivatization and gas chromatography–mass spectrometry

This work presents a modified method to analyze chlorophenoxy acid herbicides in water samples. The herbicides 2,4-D (2,4-dichlorophenoxyacetic acid), Silvex (2,4,5-trichlorophenoxypropionic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) were used to evaluate the method. The method involves extraction of samples by a graphitized carbon black cartridge, and on-line derivatization in the GC injection port using a large-volume (10–20 μl) direct sample introduction (DSI) device with tetraalkylammonium salts. The analytes were then identified and quantitated by ion-trap gas chromatography–mass spectrometry. The large-volume DSI injection-port derivatization technique provides sensitivity, fast and reproducible results for chlorophenoxy acid herbicides residues, to quantitation at 0.1 to 0.2 μg/l in 500-ml water samples. An enhanced characteristic mass chromatogram of molecular ions of butylated chlorophenoxy acid herbicides with a significant chlorine isotope pattern by electron impact ionization MS allows us to determine herbicides residues at trace levels in aqueous samples. Recovery of the herbicide residues in spiked various water samples ranged from 70 to 99% while RSDs ranged from 1 to 13%.

Analysis of Atrazine and Four Degradation Products in the Pore Water of the Vadose Zone, Central Indiana

A new method is described for the analysis of atrazine and four of its degradation products (desethylatrazine, deisopropylatrazine, didealkylatrazine, and hydroxyatrazine) in water. This method uses solid-phase extraction on a graphitized carbon black cartridge, derivatization of the eluate with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA), and analysis by gas chromatography/mass spectrometry (GC/MS). This method was used to analyze lysimeter samples collected from a field in central Indiana in 1994 and 1995. Atrazine and its degradation products were transported rapidly through the vadose zone. Maximum values of atrazine ranged from 2.61 to 8.44 μg/L and occurred from 15 to 57 days after application. Maximum concentrations of the degradation products occurred from 11 to 140 days after atrazine application. The degradation products were more persistent than atrazine in pore water. Desethylatrazine was the dominant degradation product detected in the first year, and didealkylatrazine was the dominant degradation product detected in the second year. Concentrations of atrazine and the degradation products sorbed onto soil were estimated; maximum concentrations ranged from 7.3 to 24 μg/kg for atrazine and were less than 5 μg/kg for all degradation products. Degradation of atrazine and transport of all five compounds were simulated by the vadose zone flow model LEACHM. LEACHM was run as a Darcian-flow model and as a non-Darcian-flow model.

Stability of organophosphorus insecticides on graphitized carbon black extraction cartridges used for large volumes of surface water

The stability of nine organophosphorus insecticides (azinphos-ethyl, azinphos-methyl, diazinon, EPN, ethion, fonofos, malathion, phosmet and parathion-methyl) was evaluated under a variety of storage conditions. Large volumes of surface water (4 l) were extracted using large-particle-size graphitized carbon black cartridges (Carbopack B 60–80 mesh). The effects of temperature, matrix type and drying of cartridges on the recovery of these contaminants, after different storage periods, were studied and compared to the conservation of surface water in bottles. After a 2-month period, all the chemicals stored on cartridges and kept at −20°C remained stable, with recoveries ranging from 70 to 134%. By contrast, phosmet and EPN could no longer be recovered from the bottled surface water. Cartridges kept at −20°C fared better than did those stored at 4°C and 20°C. The type of matrix water selected appears to have kept the target pesticides stored on cartridges from degrading, compared to the Milli-Q water, in which malathion and phosmet were unstable. The effect of the cartridges being either wet or dry made no difference in terms of improving the recovery of chemicals. After immediate surface water extraction, the most practical storage condition for the target insecticides was found to be storage on cartridges in the dark at −20°C, with no drying or solvent washing of the Carbopack B material.

Application of liquid chromatography with mass spectrometry combined with photodiode array detection and tandem mass spectrometry for monitoring pesticides in surface waters

Liquid chromatography with photodiode array detection (LC–DAD) and liquid chromatography with mass spectrometry (LC–MS) are two techniques that have been widely used in monitoring pesticides and their degradation products in the environment. However, the application of liquid chromatography with tandem mass spectrometry (LC–MS–MS) for such purposes, once considered too costly, is now gaining considerable ground. In this study, we compare these methods for the multi-residue analysis of pesticides in surface waters collected from the central and southeastern regions of France, and from the St. Lawrence River in Canada. Forty-eight pesticides belonging to eight different classes (triazine, amide, phenylurea, triazole, triazinone, benzimidazole, morpholine, phenoxyalkanoic), along with some of their degradation products, were monitored on a regular basis in the surface waters. For LC–MS, we used the electrospray ionization (ESI) interface in the negative ionization mode on acidic pesticides (phenoxyalkanoic, sulfonylurea), and the atmospheric pressure chemical ionization (APCI) interface in the positive ionization mode on the remaining chemicals. Different extraction techniques were employed, including liquid–liquid extraction with dichloromethane, and solid-phase extraction using C 18-bonded silica and graphitized carbon black cartridges. Eleven of the target chemicals (desethylatrazine, desisopropylatrazine, atrazine, simazine, terbuthylazine, metolachlor, carbendazime, bentazone, penconazole, diuron and isoproturon) were detected by LC–MS at concentrations ranging from 20 to 900 ng/l in the surface waters from France, and six pesticides (atrazine, desethylatrazine, desisopropylatrazine, cyanazine, simazine and metolachlor) were detected by LC–MS and LC–MS–MS at concentrations ranging from 3 to 52 ng/l in the samples drawn from the St. Lawrence River. There was good correlation between the LC–DAD and LC–MS techniques for 60 samples. The slope of the curves expressing the relationship between the results obtained with LC–DAD versus those obtained by LC–MS was near 1, with a correlation coefficient ( r) of over 0.93. The identification potential of the LC–MS technique, however, was greater than that of the LC–DAD; its mass spectra, mainly reflecting the pseudomolecular ion resulting from a protonation or a deprotonation of the molecule, was rich in information. The LC–MS–MS technique with ion trap detectors, tested against the LC–MS on 10 surface water samples, gave results that correlated well with the LC–MS results, albeit generating mass spectra that yielded far more information about the structure of unknown substances. The sensitivity of the LC–MS–MS was equivalent to the selected ion monitoring (SIM) acquisition mode in LC–MS. The detection limits of the target pesticides ranged from 20 to 100 ng/l for the LC–MS technique (under full scan acquisition), and from 2 to 6 ng/l for LC–MS–MS. These limits were improved by a factor of almost 10 by increasing the sample volume to 10 l.

Part-per-trillion level determination of antifouling pesticides and their byproducts in seawater samples by off-line solid-phase extraction followed by high-performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry

A new method for the simultaneous determination of antifouling pesticides and some of their byproducts such as dichlofluanid, diuron and its byproducts [demethyldiuron and 1-(3,4-dichlorophenyl)urea], (2-thiocyanomethylthio)benzothiazole, chlorothalonil, Sea-nine 211, Irgarol 1051 and one of its byproducts (2-methylthio-4- tert.-butylamino- s-triazine) in seawater was developed. The extraction of these compounds from the filtered seawater samples was performed off-line with different solid-phase extraction sorbents using (I) a 500 mg graphitized carbon black cartridge (ENVI-Carb) and (II) 200 mg polymeric cartridges (LiChrolut EN and Isolute ENV+) and passing 500 ml of the sample through these cartridges. The detection was carried out by reversed-phase high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry both in the negative and positive ion modes. The recovery ranged from 76 to 96% for the whole antifouling group with the ENVI-Carb cartridges and the detection limit was at the part-per-trillion level except for TCMTB. The method utilizing the polymeric cartridge proved to be very useful, time saving and with good recoveries when only Irgarol and its byproduct, Sea-nine 211 and diuron and its byproducts, have to be analyzed. The different cartridges were applied to the analysis of these pesticides in different marinas of the Catalan coast; diuron, dichlofluanid, Sea-nine 211, Irgarol as well as demethyldiuron and the Irgarol byproduct being the must ubiquitous pollutants. Maximum concentration levels were 2–3.5 μg/l of diuron and Sea-nine 211, respectively.