Evaluation of double solid-phase extraction system for determining triazine herbicides in milk

Summary High-performance liquid chromatography with UV detection was used to determine eight triazine herbicides in milk. Solid-phase extraction was performed using a double trap; first, a nonspecific adsorbent (Carbograph), and then a cation exchanger (SCX). Eluate from the SCX was evaporated to dryness under reduced pressure and redissolved in mobile phase. An aliquot was injected into the chromatograph, which was operated isocratically in the reverse-phase mode with UV detection at 225 nm. Analytical recoveries for the eight triazines ranged from 73.0 % to 92.4 %. The limit of sensitivity of this method was about 0.09 ng mL⁻¹ of milk. The method was validated and evaluated by comparison with a method reported in literature.     

Rapid method for determination of phenylurea herbicides in milk

Summary A method has been developed for the determination of thirteen phenylurea herbicide residues in milk. It involves one-step solvent extraction of the milk with methanol by ultrasonication. The extract is cleaned up on an Amberchrom resin cartridge. Reversed-phase, gradient elution, high-performance liquid chromatography with UV detection at 242 nm is used to analyse the residues. The recovery of thirteen phenylurea pesticides is quantitative, ranging from 71.4% to 97.9% for the individual herbicides investigated at concentrations around 0.05 mg kg^–1 and from 65.1% to 95.6% around 0.005 mg kg^–1. The method is not associated with any of the emulsion problems common to conventional solvent extraction, which considerably reduce the sample clean-up process compared with existing methods.     

High-performance-liquid chromatographic separation of 1,3,5-trizine herbicides

Summary A number of 11 triazine herbicides and 7 of their corresponding metabolites were separated in a single HPLC run. The separation was achieved on a reversed-phase column using gradient elution with acetonitrile/buffer. Detection was by UV absorption at a wave-length of 220 nm.     

Determination of triazine herbicides in human body fluids by solid-phase microextraction and capillary gas chromatography

Summary Eight triazine herbicides, prometon, propazine, atrazine, simazine, prometryn, ametryn, metribuzin, and cyanazine, have been extracted from human whole blood and urine samples by headspace solid-phase microextraction (SPME) with a polydimethylsiloxane-coated fiber and quantified by capillary gas chromatography with nitrogen-phosphorus detection. Extraction efficiencies for all compounds were 0.21–0.99% for whole blood, except for cyanazine (0.06%). For urine, the extraction efficiencies for prometon, propazine, atrazine, prometryn and ametryn were 13.6–38.1%, and those of simazine, metribuzin and cyanazine were 1.35–8.73%. The regression equations for the compounds extracted from whole blood were linear within the concentration ranged 0.01–1 μg (0.5 mL)⁻¹ for prometon, propazine, atrazine, prometryn, and ametryn, and 0.02–1 μg (0.5 mL)⁻¹ for simazine, metribuzin, and cyanazine. For urine, regression equations for all compounds were linear within the concentration range 0.005–0.25 μg mL⁻¹. Compound detection limits were 2.8–9.0 ng (0.5 mL)⁻¹ and 0.4–2.0 ng mL⁻¹ for whole blood and urine, respectively. The coefficients of within-day and day-to-day variation were satisfactory for all the compounds, and not greater than 10.3 and 14.2%, respectively. Data obtained from determination of atrazine in rat whole blood after oral administration of the compound are also presented.     

Analysis of triazine in water samples by solid-phase microextraction coupled with high-performance liquid chromatography

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the determination of triazine is described. Carbowax/templated resin (CW/TPR, 50 μm), polydimethylsiloxane/divinylbenzene (PDMS/DVB, 60 μm), polydimethylsiloxane (PDMS, 100 μm), and polyacrylate (PA, 85 μm) fibers were evaluated for extraction of the triazines. CW/TPR and PDMS/DVB fibers were selected for further study. Several parameters of the extraction and desorption procedure were studied and optimized (such as types of fibers, desorption mode, desorption time, compositions of solvent for desorption, soaking periods and the flow rate during desorption period, extraction time, temperature, pH, and ionic strength of samples). Both CW/TPR and PDMS/DVB fibers are acceptable; a simple calibration-curve method based on simple aqueous standards can be used. The linearity of this method for analyzing standard solution has been investigated over the range 5-1000 ng mL⁻¹ for both PDMS/DVB and CW/TPR fibers. All the correlation coefficients in the range 5-1000 ng mL⁻¹ were better than 0.995 except Simazine and Atratone by CW/TPR fiber. The R.S.D.s range from 4.4% to 8.8 % (PDMS/DVB fiber) and from 2.4% to 7.2% (CW/TPR fiber). Method-detection limits (MDL) are in the range 1.2-2.6 and 2.8-3.4 ng mL⁻¹ for the two fibers. These methods were applied to the determination of trazines in environmental water samples (lake water).     

基于混合固定相色谱柱的SPE-HPLC法检测环境水体中三嗪类除草剂

利用混合固定相色谱柱(Optimix SCX/C8)分析了8种三嗪类化合物,在0.01 mol/L乙酸钠缓冲溶液(pH4.2)-CH3CN(75：25,V/V)等度洗脱的流动相条件下,实现了利用液相色谱方法分离同分异构体敌草净和西草净,并对比了相同色谱条件下8种目标物在C8色谱柱上的分离效果;比较了PEP和C18固相萃...     

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.     

Hollow fiber membrane-protected solid-phase microextraction of triazine herbicides in bovine milk and sewage sludge samples

A porous polypropylene hollow fiber membrane (HFM)-protected solid-phase microextraction (HFM-SPME) procedure in conjunction with gas chromatography/mass spectrometric analysis for use in the determination of triazine herbicides in bovine milk samples is described. A 65-microm polydimethylsiloxane-divinylbenzne (PDMS-DVB) SPME fiber was protected by an HFM. HFM-SPME experimental parameters such as fiber type, extraction time, extraction temperature and salt concentration were investigated and optimized. The relative standard deviations for the reproducibility of the optimized HFM-SPME method varied from 4.30 to 12.37%. The correlation coefficients of the calibration curves were between 0.9799 and 0.9965 across a concentration range of 0-200 microg l(-1). The method detection limits for triazines in bovine milk were in the range of 0.003-0.013 microg l(-1) and limits of quantification were in the range of 0.006-0.021 microg l(-1). The suitability of HFM-SPME was extended to the analysis of the herbicides in sewage sludge samples. The results demonstrate that HFM-SPME was an efficient pretreatment and enrichment procedure for complex matrices.     

Supercritical fluid extraction of triazine herbicides from solid matrices

Summary Several investigations were performed to optimise the extraction of polar triazine herbicides using supercritical fluid extraction from two different solid matrices: C₁₈-silica and soil samples. Supercritical CO₂ modified with methanol [10% (VV)] at 250 bars and 50°C was required to quantitatively extract Atrazine and 2-Hydroxyatrazine from spiked C₁₈-silica. Extraction of Desisopropyl-desethyl-2-hydroxyatrazine (MET) attained only 52%, even following addition of water to the polar modifier. Extractions of spiked soil samples (20 ppm of each pesticide) were successful at 300 bars and 65°C. A non polar wash improved the recoveries of the three target analytes [i.e. atrazine: 88%; 2-hydroxyatrazine: 96%; MET: 41%]. The extraction parameters employed are discussed in this paper.     

Pressurized-liquid extraction for determination of imidazolinone herbicides in soil

Summary A rapid and simple method has been developed for determination of imidazolinone (IMI) residues in soil. Extraction of the analytes from the soil matrix was performed with a pressurized-liquid-extraction apparatus built in this laboratory. Four different types of soil sample (clay, clay loam, sandy clay loam, and silty loam) were fortified with target compounds at levels of 10 and 50 ng g⁻¹ by a procedure which can mimic weathered soils. The samples were then dried and packed in a 25 cm×4.6 mm i. d. stainless steel column; this was placed inside a GC oven and extracted by passing an aqueous solution of KCl (0.1m, 20 mL) through the column at 90°C. Quantification of the analytes in the final extract (50-μL injection) was performed by reversed-phase liquid chromatography-mass spectrometry with a TurbolonSpray interface. Recoveries of the analytes were greater than 83% andRSD less than 7%. The method detection limit was in the 1–2.5ng g⁻¹ range in analysis by time-scheduled selected-ion monitoring (SIM).     

Quantification of trovafloxacin in serum by high-performance liquid chromatography with on-line solid-phase extraction

Summary A rapid, simple, accurate and sensitive liquid chromatographic assay with on-line solid-phase extraction is described for determination of trovafloxacin in human serum. Samples were deproteinized with acetonitrile and injected on to an NH₂ extraction column for sample clean-up. Thereafter, an on-line column-switching system was used for quantitative transfer of the drug to a C₁₈ analytical column. Separation was performed by ion-pair chromatography and detection was by ultraviolet absorbance at 275 nm. Recovery was 98.5%. The linear range was from 0.25 to 20μg mL⁻¹, with a correlation coefficient of 0.999. Detection limit was 0.1 μg mL⁻¹ from extraction of 25 μL serum.     

Determination of benzoic acid in milk by solid-phase extraction and ion chromatography with conductivity detection

A simple, fast, precise and eco-friendly method, based on ion chromatography (IC) with a suppressed conductivity detector, was proposed for the determination of benzoic acid (BA) inmilk in this paper. The chromatographic separation was accomplished by using an anion exchange column eluted with 3.2 μmol/L aqueous Na2CO3 and 1.0 mmol/L aqueous NaHCO3 at a flow-rate of 0.7 mL/min. Themethod validation experiment provided excellent results with respect to linearity (correlation coefficient up to 0.9997), limit of detection (0.1 μg/L), recovery values (ranging from 88.0% to 93.0%) and relative standard deviation (RSD) (below 2.2%, n = 7).     

Preparation and binding study of solid-phase microextraction fiber on the basis of ametryn-imprinted polymer: Application to the selective extraction of persistent triazine herbicides in tap water,rice, maize and onion

A monolithic ametryn molecular-imprinted polymer based on a simple polymerization method was fabricated for use as new solid-phase microextraction (SPME) fiber, which can be coupled with GC and GC/MS for selective extraction and analysis of triazine herbicides. Methacrylic acid (MAA), ethylene glycol dimethacrylate (EDMA) and ametryn bear role of functional monomer, cross-linker and template, respectively. In the optimized conditions the fabricated fiber showed better molecular recognition abilities for methylthiotriazine herbicides than chloro-triazine herbicides. By use of bi-Langmuir isotherm model the evaluated equilibrium constants for ametryn were 0.01 and 890.69 μM⁻¹, and the numbers of binding sites were 129.98 and 5.82 nmol g⁻¹, respectively. The high extraction efficiency was obtained for ametryn, prometryn, terbutryn, atrazine, simazine, propazine, and cyanazine, yielding the detection limits of 14, 28, 45, 56, 85, 95 and 74 ng mL⁻¹, respectively by GC with flame ionization detection. The reliability of the prepared fiber for extraction of ametryn and other analogues in real samples has been investigated and proved by using spiked samples such as tap water, rice, maize, and onion.     

Determination of triazine herbicides in surface and drinking waters by off-line combination of liquid chromatography and gas chromatography-mass spectrometry

Summary Mass spectra of 12 triazines were obtained by electron impact (EI), positive-ion chemical ionization (PCI) and negative-ion chemical ionization (NCI) using methane and isobutane as reagent gases. EI mass spectrometry is more sensitive than PCI and NCI, although the chemical ionization modes increase selectivity markedly. A pre-column packed with polymer stationary phase was employed to preconcentrate surface and drinking water samples. After desorption of the analytes with ethyl acetate, an aliquot was injected directly into the GC-MS system. Atrazine and simizine were found in these samples at 10–80 ppt levels. The limits of detection for both herbicides were below 10 ppt in drinking water.     

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.     

Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction techniques for sample clean-up

Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 g/ml concentration range; the limit of detection was 5 ng/mL.     

Determination of biogenic amines in wine after clean-up by solid-phase extraction

Summary A suitable method for the determination of 16 biogenic amines in wine has been developed. The method involves clean-up of wine samples using ion-exchange cartridges and a preconcentration step, under controlled vacuum, before derivatization of the amines by treatment with phthalaldehyde (PA) and reversedphase HPLC with gradient elution and fluorimetric detection. Linearity of response was obtained for all the biogenic amines from 100 g L^–1 to mg L^–1. Limits of detection for the amines were similar for all PA-derivatives (25–50 g L^–1) and the quantitation limits were about 0.1 mg L^–1. After clean-up and preconcentration, the concentration levels increased 10-fold for all amines except putrescine and cadaverine, which gave poor recovery by this method unlike the rest which gave recoveries of almost 90%. The overall process was successfully applied to identify and quantify biogenic amines in several red wines from the Tarragona region.     

Determination of triazine herbicides using membrane-protected carbon nanotubes solid phase membrane tip extraction prior to micro-liquid chromatography

A novel microextraction technique termed solid phase membrane tip extraction (SPMTE) was developed. Selected triazine herbicides were employed as model compounds to evaluate the extraction performance and multiwall carbon nanotubes (MWCNTs) were used as the adsorbent enclosed in SPMTE device. The SPMTE procedure was performed in semi-automated dynamic mode and several important extraction parameters were comprehensively optimized. Under the optimum extraction conditions, the method showed good linearity in the range of 1–100 μg/L, acceptable reproducibility (RSD 6–8%, n = 5), low limits of detection (0.2–0.5 μg/L), and satisfactory relative recoveries (95–101%). The SPMTE device could be regenerated and reused up to 15 analyses with no analyte carry-over effects observed. Comparison was made with commercially available solid phase extraction-molecular imprinted polymer cartridge (SPE-MIP) for triazine herbicides as the reference method. The new developed method showed comparable or even better results against reference method and is a simple, feasible, and cost effective microextraction technique.     

Determination of momordicoside A in bitter melon by high-performance liquid chromatography after solid-phase extraction

Summary Momordicoside A has been determined by solid-phase extraction (SPE) on a Envi Carb cartridge (3 mL, 250mg) then high-performance liquid chromatography (HPLC) on a C₁₈ column (4.6 mm×250 mm, 5 μm particle) with acetonitrile-methanol-50mm potassium dihydrogen phosphate buffer, 25:20:60 (v/v), as mobile phase, at a flow rate of 0.8 mL min⁻¹, and UV detection at 208 nm. The analytical method was shown to be highly reproducible, with precision (asRSD) and accuracy (asRME)<10%, both intra-day and inter-day. Absolute recoveries were >90%. The method was applied to the determination of momordicoside A in various tissues from different varieties of bitter melon from different producing areas.     

Improvement of on-line solid-phase extraction for determining phenolic compounds in water

Summary Modifying the most common design for the on-line coupling of a precolumn to reversed phase LC with diode array detection has resulted in reduction of the broadening of the peaks which results when the compounds of interest are strongly retained by a highly hydrophobic sorbent. The modification consists of the desorption of the analytes trapped on the precolumn solely by the organic solvent used to modify the solvent strength of the mobile phase. Results obtained using this design were compared with those obtained with the conventional design, with C₁₈ and PLRP-S precolumns. The performance of the system was also tested with a highly cross-linked styrene-divinylbenzene copolymer (ENVI-chrom P) precolumn for the determination of phenolic compounds in real samples. The advantages and disadvantages are discussed. Ion-pair solid phase extraction is used in order to increase the breakthrough volumes of more polar compounds, mainly phenol. The use of the new design enables phenolic compounds to be determined at the low μg L⁻¹ level with limits of detection ranging between 0.1 and 2 μg L⁻¹ in tap water when a 10 mL sample was analyzed.