Determination of atrazine and simazine in environmental water samples using multiwalled carbon nanotubes as the adsorbents for preconcentration prior to high performance liquid chromatography with diode array detector

Multiwalled carbon nanotubes, a new nanoscale material, has been gained many interests for use in various fields, and has exhibited exceptional merit as SPE absorbents for enrichment of environmental pollutants. This paper focused on the enriching power of atrazine and simazine, two important widely used triazine herbicides and described a novel and sensitive method for determination of these two herbicides based on SPE using multiwalled carbon nanotubes as solid phase absorbents followed by high performance liquid chromatography with diode array detector. Factors that maybe affect the enrichment efficiency of multiwalled carbon nanotubes such as the volume of eluent, sample flow rate, sample pH, and volume of the water samples were optimized. Under the optimal procedures, multiwalled carbon nanotubes as the absorbents have obtained excellent enrichment efficiency for atrazine and simazine. The detection limits of the atrazine and simazine were 33 and 9 ng l⁻¹, respectively. The spiked recoveries of the two analytes were over the range of 82.6-103.7% in most cases. Good analytical performance was achieved from real-world water samples such as river water, reservoir water, tap water and wastewater after primary pretreatment with proposed method. All these experimental results indicated that the developed method could be used as an alternative for the routine analysis of atrazine and simazine in many real water samples.     

Preconcentration of atrazine and simazine with multiwalled carbon nanotubes as solid-phase extraction disk

A sensitive and selective preconcentration method using solid-phase extraction (SPE) disk, namely multiwalled carbon nanotubes (MWCNTs) disk, is proposed for the determination of atrazine and simazine in water samples. Atrazine and simazine were extracted on MWCNTs disk and then determined by gas chromatography–mass spectrometry (GC/MS). Several parameters on the enrichment factor of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 5 using 200 mL of validation solution containing 0.1 μg of triazines and 5 mL of acetone as an eluent. The maximum enrichment factors for atrazine and simazine were 3900 ± 250 and 4000 ± 110, respectively when 200 mL of sample solution volume was used. Relative standard deviations for seven determinations were 6.9% (atrazine) and 3.0% (simazine) under optimum conditions. The linear range of calibration curves were 0.1 to 1 ng mL^{− 1} for each analyte with good correlation coefficients. The detection limits (3S/N) were 2.5 and 5.0 pg mL^{− 1} for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of atrazine and simazine in environmental water samples with high precision and accuracy.     

Preconcentration of atrazine and simazine with multiwalled carbon nanotubes as solid-phase extraction disk

A sensitive and selective preconcentration method using solid-phase extraction (SPE) disk, namely multiwalled carbon nanotubes (MWCNTs) disk, is proposed for the determination of atrazine and simazine in water samples. Atrazine and simazine were extracted on MWCNTs disk and then determined by gas chromatography–mass spectrometry (GC/MS). Several parameters on the enrichment factor of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 5 using 200 mL of validation solution containing 0.1 μg of triazines and 5 mL of acetone as an eluent. The maximum enrichment factors for atrazine and simazine were 3900 ± 250 and 4000 ± 110, respectively when 200 mL of sample solution volume was used. Relative standard deviations for seven determinations were 6.9% (atrazine) and 3.0% (simazine) under optimum conditions. The linear range of calibration curves were 0.1 to 1 ng mL^− 1 for each analyte with good correlation coefficients. The detection limits (3S/N) were 2.5 and 5.0 pg mL^− 1 for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of atrazine and simazine in environmental water samples with high precision and accuracy.     

Ultrasound-assisted emulsification-microextraction coupled to ion mobility spectrometry for monitoring of atrazine and simazine in environmental water

Triazine herbicides and some of their transformation products are considered as one of the most important classes of chemical pollutants owing to their widespread use and toxicity. Triazines and their degradation products have caused concern because they are toxic and persistent in water, soil, and organisms. The present paper describes the validation of ultrasound-assisted emulsification-microextraction (USAEME) method for determination of atrazine and simazine using ion mobility spectrometry (IMS) in environmental water. The parameters influencing the extraction efficiency such as sonication time, extraction solvent, extraction volume and salt concentration were investigated. Under the optimum conditions, enrichment factors was 170 and 150 with corresponding LOD of 8 and 12 μg/L for atrazine and simazine respectively . Linearity with a coefficient of estimation (r²) were >0.99 in the concentration level range of 15–1500 μg/L and 20–1700 μg/L for extraction of atrazine and simazine in water samples. The proposed method successfully was applied to screen of atrazine and simazine in environmental water.     

Comparison of supercritical fluid extraction and liquid-liquid extraction for isolation of selected pesticides stored in freeze-dried water samples

Summary The stability of freeze-dried water samples spiked with eight agrochemicals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samples. In addition, two different extraction procedures, liquid-liquid and supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen phosphorus detection and electronic impact mass spectrometry, and by liquid chromatography-diode array detection. The whole methodology developed in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 g L^–1.     

Development of ultrasound-assisted emulsification microextraction for the determination of triazine herbicides in environmental water samples by high-performance liquid chromatography

A simple, rapid, efficient, and environmentally friendly method for the determination of some triazine herbicides (simazine, atrazine, prometone, ametryn and prometryne) in water samples was developed by ultrasound-assisted emulsification microextraction (USAEME) coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD). The main parameters that affect the extraction efficiencies, such as the kind and volume of the extraction solvent, ultrasound emulsification time and salt addition, were investigated and optimized. Under the optimum conditions, the method was sensitive and showed a good linearity within a range of 0.5 to 200?ngm?L^?1 for simazine, atrazine, prometone, ametryn and prometryne, with the correlation coefficients (r) varying from 0.9993 to 0.9998. High enrichment factors were obtained ranging from 148 to 225. The limits of detection (LODs) were in the range between 0.06 and 0.1?ngm?L^?1 and the limits of quantification (LOQs) were in the range between 0.2 and 0.3?ngm?L^?1. The recoveries of the analytes from water samples at spiking levels of 5.0 and 50.0?ngm?L^?1 were ranged from 82.4% to 107.0%. The relative standard deviations (RSDs) varied from 3.0% to 4.6%. The results demonstrated that the USAEME-HPLC-DAD method was an ef?cient pretreatment and enrichment procedure for the determination of triazine pesticides in real water samples.     

Screening method for phthalate esters in water using liquid-phase microextraction based on the solidification of a floating organic microdrop combined with gas chromatography-mass spectrometry

A simple and efficient liquid-phase microextraction (LPME) technique was developed using directly suspended organic microdrop coupled with gas chromatography–mass spectrometry (GC–MS), for the extraction and the determination of phthalate esters (dimethyl phthalate, diethyl phthalate, diallyl phthalate, di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBP), dicyclohexyl phthalate and di-2-ethylhexyl phthalate (DEHP)) in water samples. Microextraction efficiency factors, such as nature and volume of the organic solvent, temperature, salt effect, stirring rate and the extraction time were investigated and optimized. Under the optimized extraction conditions (extraction solvent: 1-dodecanol; extraction temperature: 60 °C; microdrop volume: 7 μL; stirring rate: 750 rpm, without salt addition and extraction time: 25 min), figures of merit of the proposed method were evaluated. The values of the detection limit were in the range of 0.02–0.05 μg L⁻¹, while the R.S.D.% value for the analysis of 5.0 μg L⁻¹ of the analytes was below 7.7% (n = 4). A good linearity (r² ≥ 0.9940) and a broad linear range (0.05–100 μg L⁻¹) were obtained. The method exhibited enrichment factor values ranging from 307 to 412. Finally, the designed method was successfully applied for the preconcentration and determination of the studied phthalate esters in different real water samples and satisfactory results were attained.     

Determination of atrazine, deethylatrazine and simazine in water at parts-per-trillion levels using solid-phase extraction and gas chromatography/ion trap mass spectrometry

Methods for trace analysis of atrazine and simazine in water have been developed by using stable-isotope dilution with detection by gas chromatography/mass spectrometry. D(5)-Atrazine was used as the internal standard for the determination of atrazine and deethylatrazine, while (13)C(3)-simazine was used for simazine analysis. Water samples were fortified with known amounts of the internal standards and submitted to solid-phase extraction with a C(18) bonded-silica cartridge. A gas chromatograph coupled with an ion-trap mass spectrometer was used to analyze the water sample extracts. Method detection limits were 38 parts-per-trillion (ppt) for atrazine and deethylatrazine and 75 ppt for simazine. The accuracy of the method, represented by relative analytical errors, was less than 15%, and the method precision was less than 5% (relative standard deviation, n = 9). The method was successfully applied to analyze surface water samples collected from a reservoir and a river at ppt levels.     

Determination of atrazine and simazine in water samples by high-performance liquid chromatography after preconcentration with heat-treated diatomaceous earth

A sensitive and selective column adsorption method is proposed for the preconcentration and determination of atrazine and simazine. Atrazine and simazine were preconcentrated on heat-treated diatomaceous earth as an adsorbent and then determined by high-performance liquid chromatography (HPLC). Several parameters on the recoveries of the analytes were investigated. The experimental results showed that it was possible to obtain quantitative analysis when the solution pH was 2 using 100 mL of validation solution containing 1.5 μg of triazines and 5 mL of ethanol as an eluent. Recoveries of atrazine and simazine were 95.7 ± 4.2% and 75.0 ± 1.9% with a relative standard deviation for seven determinations of 4.7% and 2.7% under optimum conditions. The maximum preconcentration factor was 100 for triazines when 500 mL of sample solution volume was used. The linear ranges of calibration curves for atrazine and simazine were 1-150 ng mL⁻¹ and 1-300 ng mL⁻¹, respectively, with correlation coefficients of 0.999 and the detection limits (3Signal-to-Noise) were 0.24 ng mL⁻¹ and 0.21 ng mL⁻¹ for atrazine and simazine. The capacity of the adsorbent was also examined and found to be 0.8 mg g⁻¹ and 1.3 mg g⁻¹ for atrazine and simazine, respectively. The proposed method was successfully applied to the determination of triazines in river water and tap water samples with high precision and accuracy.     

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.     

Determination of Atrazine,Simazine, Alachlor,and Metolachlor in Surface Water Using Dispersive Pipette Extraction and Gas Chromatography–Mass Spectrometry

Four commonly found pesticides (alachlor, atrazine, metolachlor, and simazine) in surface water were determined using dispersive pipette extraction followed by gas chromatography–mass spectrometry. The rapid mixing and equilibrium between the dispersive pipette extraction adsorbent and water sample resulted in fast and efficient extraction. Using only 5?mL of water sample, the estimated time consumption for extraction of each sample was less than 5?min. Method validation was performed to evaluate accuracy, precision, linearity, the limits of detection, and the limits of quantitation. Average recovery of above 90% was obtained with relative standard deviations below 10%, which indicated good accuracy and precision of the dispersive pipette extraction method. Coefficients of determination were all above 0.9901 and showed good linearity. For the four pesticides studied using the current method, the limits of detection ranged from 7 to 40?ng?L^?1, and limits of quantitation were from 20 to 130?ng?L^?1. Method validation results supported the application of the current method for drinking water safety monitoring per National Primary Drinking Water Regulations established by the US Environmental Protection Agency. Water samples from Lake Lanier and Stone Mountain Lake (Georgia, USS) were analyzed with this method as a preliminary work for a larger scale drinking water quality study in the future. Trace amounts of simazine and atrazine were found in lake water samples, but both were below the regulation levels of the US Environmental Protection Agency.     

A simple approach for the preparation of simazine molecularly imprinted nanofibers via self-polycondensation for selective solid-phase microextraction

A novel molecularly imprinted sol-gel material based on polysiloxane nanofiber was introduced as a solid-phase microextraction coating on a stainless steel wire for the extraction of simazine. The nanostructured molecularly imprinted fiber was prepared by a simple single step method at room temperature, using methyltriethoxysilane as the sol-gel precursor and simazine as the template molecule. The fiber was applied for the extraction of simazine in different water samples followed by gas chromatography and mass spectrometry detection. The extraction capacity of the molecularly imprinted fiber was 8 ng, and it had better extraction efficiency than the non-imprinted fiber and commercial fibers (PDMS and PA). The fiber had also a good selectivity for simazine and its analogous compounds. Important parameters affecting the extraction and desorption efficiency, such as salt concentration, stirring rate, pH of sample solution, extraction time and temperature, temperature and time of desorption, were investigated. The intra- and inter-day relative standard deviations were in the range of 4.3–7.6%. The fiber-to-fiber reproducibility was 7.7–8.5%. The method showed a good linearity (r²> 0.9980) in the range of 0.02–20 μg L⁻¹ with the detection limit of 0.005 μg L⁻¹. The relative recoveries were also in the range of 94–97% for different water samples.     

Comparison of the Enrichment Efficiency of Multiwalled Carbon Nanotubes, C18 Silica, and Activated Carbon as the Adsorbents for the Solid Phase Extraction of Atrazine and Simazine in Water Samples

Multiwalled carbon nanotubes with exceptional merits as SPE adsorbents for enrichment of environmental pollutants have absorbed much attention. The goal of this paper was to make a comparison with it and regular adsorbents such as C18 silica and activated carbon in the extraction capacity of atrazine and simazine. The results indicated that multiwalled carbon nanotubes were very suitable for determination of atrazine and simazine because of an enrichment performance similar to that of C18 silica. In contrast, the spiked recovery of simazine was higher than that of atrazine using multiwalled carbon nanotubes as packing material for SPE. However, reverse results were obtained when the extraction was performed with packing of C18 silica. Moreover, as the extraction of simazine was concerned, multiwalled carbon nanotubes were much better than C18 silica. As for the enrichment of atrazine, C18 silica achieved greater extraction factor than multiwalled carbon nanotubes. Activated carbon did not give the expected extraction efficiency because of its large size and blank volume and less active sites for adsorption. All these experimental results indicated that multiwalled carbon nanotubes could be used as a valuable alternative adsorbent for SPE of atrazine and simazine in many real water samples.     

Determination of some selected polycyclic aromatic hydrocarbons in environmental samples by high-performance liquid chromatography with fluorescence detection

Summary Analytical methods for the determination in environmental samples, of some selected Polycyclic Aromatic Hydrocarbons (PAH's), which are included on the EPA Priority Pollutant list, have been developed and evaluated. The methodology involves the extraction of PAH's from water samples by solvent extraction with dichloromethane. Solid samples were ultrasonically extracted with acetone/hexane and the extract was cleaned up on a silica gel/alumina column. The concentrated and cleaned up extracts were analysed by HPLC on a polymeric C₁₈ column using a gradient of acetonitrile/water as the mobile phase and fluorescence detection. Typical detection limits lie in the range of 1–30 ng ml^–1 of the analytes, but after sample pretreatment detection limits of 10–300 ng l^–1 were obtained. The extraction, clean-up and HPLC methodology was applied to the determination of selected PAH's in coal washings samples and the method was validated by the quantification of PAH's in a natural contaminated and a spiked sediment.     

Interference modelling, experimental design and pre-concentration steps in validation of the Fenton's reagent for pesticides determination

The determination of atrazine in real samples (commercial pesticide preparations and water matrices) shows how the Fenton's reagent can be used with analytical purposes when kinetic methodology and multivariate calibration methods are applied. Also, binary mixtures of atrazine-alachlor and atrazine-bentazone in pesticide preparations have been resolved. The work shows the way in which interferences and the matrix effect can be modelled. Experimental design has been used to optimize experimental conditions, including the effect of solvent (methanol) used for extraction of atrazine from the sample. The determination of pesticides in commercial preparations was accomplished without any pre-treatment of sample apart from evaporation of solvent; the calibration model was developed for concentration ranges between 0.46 and 11.6 × 10⁻⁵ mol L⁻¹ with mean relative errors under 4%. Solid-phase extraction is used for pre-concentration of atrazine in water samples through C₁₈ disks, and the concentration range for determination was established between 4 and 115 μg L⁻¹approximately. Satisfactory results for recuperation of atrazine were always obtained.     

Combination of ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the determination of triazine herbicides in water samples

A temperature-controlled ionic liquid dispersive liquid-phase microextraction in combination with high performance liquid chromatography was developed for the enrichment and determination of triazine herbicides such as cyanazine,simazine,and atrazine in water samples.1-Octyl-3-methylimidazolium hexafluorophosphate([C8MIM][PF6]) was selected as the extraction solvent.Several experimental parameters were optimized.Under the optimal conditions,the linear range for cyanazine was in the concentration range of 0.5–80 mg/L and the linear range for simazine and atrazine was in the range of1.0–100 mg/L.The limit of detection(LOD,S/N = 3) was in the ranges of 0.05–0.06 mg/L,and the intra day and inter day precision(RSDs,n = 6) was in the ranges of 3.2%–6.6% and 4.8%–8.9%,respectively.Four real water samples were analyzed with the developed method,and the experimental results showed that the spiked recoveries were satisfactory.All these exhibited that the developed method was a valuable tool for monitoring such pollutants.     

Preconcentration and Determination of Tin in Water Samples by Using Cloud Point Extraction and Graphite Furnace Atomic Absorption Spectrometry

A method based on cloud point extraction and graphite furnace atomic absorption spectrometry (GFAAS) was developed for the analysis of trace tin in water samples. After cloud point extraction, the tin in the water samples was preconcentrated and successfully separated from most interferents. During the procedure, 8-hydroxyquinoline (8-HQ) was used as chelating reagent, and Triton X-114 was added as surfactant. The parameters affecting the sensitivity and the extraction efficiency, such as solution pH, concentration of 8-HQ and Triton X-114, equilibration temperature and centrifuge time, were evaluated and optimized. Under the optimum conditions, a preconcentration factor of 96.2 was obtained for a 20 mL water sample. The detection limit (LOD) was as low as 0.012 ng mL⁻¹, and the analytical curve was linear in the range of 0.05–2.0 ng mL⁻¹ with satisfactory precision (RSD <4.1%). The proposed method was successfully applied to the determination of trace tin in water samples with recoveries in the range of 85.0–112.0%.     

磁性石墨烯纳米粒子固相萃取与气相色谱-质谱相结合测定环境水样中的三嗪类除草剂

将磁性石墨烯作为磁性固相萃取的吸附剂与气相色谱-质谱(GC-MS)相结合建立了环境水样中7种三嗪类除草剂残留的测定新方法。对影响萃取效率的一些因素如吸附剂用量、萃取时间、样品溶液的pH值、离子强度和解吸条件等进行了优化。在优化的实验条件下,7种三嗪类除草剂的富集倍数在574~968之间。测定西玛津、扑灭津、嗪草酮、西草净、氰草津的线性范围为0.01~10.0 μg/L,莠去津的线性范围为0.05~10.0 μg/L,扑灭净的线性范围为0.01~8.0 μg/L。线性相关系数为0.9968~0.9998,检出限(S/N=3)为1.0~5.0 ng/L。将本方法应用于井水、自来水和湖水等实际水样的分析,在0.5 μg/L和2.0 μg/L下的加标回收率为79.8%~118.3%,相对标准偏差为3.6%~10.5%。该法操作简单、富集倍数高,可满足水样中三嗪类除草剂残留的检测要求。     

Determination of triazine herbicide residues in water samples by on-line sweeping concentration in micellar electrokinetic chromatography

A new method for the determination of atrazine, simazine and prometryn in water samples by on-line sweeping concentration technique in micellar electrokinetic chromatography （MEKC） was developed. Various parameters affecting sample enrichment and separation efficiency were systematically studied. Compared with the conventional MEKC method, up to 60-200-fold improvement in concentration sensitivity was achieved in terms of peak height by using this sweeping injection technique. The compound strychnine was used as the internal standard for the improvement of the experimental reproducibility. The limits of detection （S/ N = 3：1） for atrazine, simazine and prometryn were 9, 10 and 0.5 ng mL-1, respectively. This method has been successfully applied to the analysis of atrazine, simazine and prometryn in lake, steam and ground water.     

Determination of Triazine Herbicides and Metabolites by Solid Phase Extraction with HPLC Analysis

An efficient solid phase extractive preconcentration/separation method was developed for the trace determination of herbicides in aqueous samples using Amberlite XAD-4 resin as the adsorbent. The retained herbicides were eluted with methanol at a flow rate of 1.0 mL min^?1 and determined by HPLC-DAD (wavelength of 220 nm) using water (pH:4.7, phosphoric acid) and methanol (ratio 35:65) as the mobile phase with a flow rate of 1.0 mL min^?1. Quantitative recoveries of simazine, atrazine and its metabolities were achieved at optimized analysis conditions that included 0.75 g of resin; a pH of 3.0; an eluent volume of 3.0 mL; an eluent flow rate of 1.0 mL min^?1; and a sample flow rate of 4.0 mL min^?1. The limits of detection, preconcentration factor, and linear ranges for the herbicides were 0.084–0.121 µgL^?1, 1000, and 0.5–20 mg L^?1, respectively. The performance of the method was evaluated by analysis of spiked water samples. The recoveries of simazine, atrazine and their metabolities were found to be quantitative (99.6–104.8%) with RSDs of 2.2–4.8% and 2.8–4.7% for intra-day and inter-day precision, respectively. The proposed method was successfully applied for trace determination of studied analytes in waste water, apple juice, and red wine samples.