Separation of Chlorinated Phenols by Isocratic High-Performance Liquid Chromatography on Reverse Phase Column

Abstract

A method is described for isocratic highperformance liquid chromatographic separation of chlorinated phenols using methanol : phosphate buffer - pH 7.20 (50:50) solvent system. 13 out of 15 congeners of chlorophenols and phenol have been separated in 32 minutes at a flow rate of 0.8 ml per minute. The system is found to be useful for the separation of chlorophenols extracted from mouse liver fed with hexachlorocyclohexane.     

Trace Enrichment and HPLC Analysis of Chlorophenols in Environmental Samples,Using Precolumn Sample Preconcentration and Electrochemical Detection

Abstract

A HPLC method has been developed for trace analysis of chlorophenols in the 0.2–2 ppb range from spiked water samples. Simple liquid-liquid extraction followed by on-line preconcentration of total mono- and dichlorophenols has been performed using a divinylbenzene-styrene copolymeric sorbent (PRP₁) as packing material for the precolumn. The chlorophenols have been eluted from the precolumn on an analytical column (5μm LiChrosorb RP-18, 12.5 cm × 4 mm) by use of a switching valve system followed by separation. Detection was carried out with an electrochemical detector. The linearity of the detector response has been proved over two orders of magnitude. The detection limit of chlorophenols by means of the electrochemical method is in the lower picogram range. The recoveries of the isomeric chlorophenols from spiked river water samples having initial concentrations of 2ppb are usually 70–90%. The procedure has been applied to drinking water and river water.     

Rapid determination of nineteen chlorophenols in wood, paper, cardboard, fruits, and fruit juices by gas chromatography/mass spectrometry.

Although the use of pentachlorophenol (PCP) is prohibited in most countries, it is still widely found in the wood of pallets, containers, crates and in cardboard, paper, etc. Such material may contain not only PCP but other chlorophenols as well. Wooden crates and cardboard boxes are often used to store and transport fresh fruits. Consequently, chlorophenols present in the wood may contaminate the stored fruits by migration. To ascertain that packaging, storage material, and fruit raw materials are free from chlorophenol residues, we developed a rapid and sensitive method for the detection of 19 chlorophenols by gas chromatography/mass spectrometry (GC/MS). The test portions are directly extracted and acetylated in a solution of sodium carbonate in the presence of acetic anhydride and hexane. The hexane layer is analyzed, without further purification, by GC/MS in the selective-ion monitoring mode. The method allows the analysis of >40 samples/day with detection limits of <20 microg/kg for chlorophenols in wood, cardboard, and paper, and <2 microg/kg for chlorophenols in fruits. Typical recoveries of all chlorophenols were 94% from paper, 115% from cardboard, 51% from wood (depending on the size of the chips or shavings), and 93% from fruit puree.     

Vertical Mobility of Soil Contaminants: Preliminary Results of a Survey on the Herbicide Atrazine

Abstract

Atrazine is considered a potential contaminant of water bodies, where it has been repeatedly detected. Its use in Italy is almost limited to the Northern part of the country where corn monocultures are common. Northern Italy is characterized by the presence of an area with soil quite permeable and where ground waters are often present at not very deep levels. In this area well waters, which represent the main source of drinking water, have been frequently found contaminated by atrazine. A program has been started aimed at studying the role of soil nature and local factors in the process of groundwater contamination. Two atrazine application rates were used at two sites with loamy and loamy-sandy soils. Results clearly show a different mobility of atrazine in the two soil types. Since the two sites have similar organic carbon levels, the major proportion of clay to sand and the lower pH of loamy soil may explain the lower vertical mobility of atrazine in this soil. Work is in progress to study atrazine behaviour to a soil depth of 30cm and the effect of repeated atrazine applications on ground water pollution.     

Trace enrichment of chlorophenols in human urine by C18 reversed-phase adsorption and by n-hexane extraction

Summary The efficiency and sensitivity of C₁₈ reversed-phase adsorption of free chlorophenols and of n-hexane extraction of either free or acetylated chlorophenols from human urine were compared. All procedures were found to be efficient for the trace enrichment of 2,4-dichlorophenol, 2,4,6- and 2,4,5-trichlorophenols, 2,3,4,6- and 2,3,4,5-tetrachlorophenols and pentachlorophenol. The recoveries of chlorophenols from non-hydrolysed and acid hydrolysed urine samples were comparable. By treatment of 1 ml urine sample detection limits of 1–2 ng/ml were achieved, while the treatment of 5 ml samples enhanced the detection sensitivity to less than 1 ng/ml. The n-hexane extraction of acetylated chlorophenols from 1 ml urine samples is the simplest and fastest procedure because the acetylation and extraction of chlorophenols are performed simultaneously in one step. The C₁₈ adsorption seems to be more suitable than n-hexane extraction for accumulation of chlorophenols from a urine volume of 5 ml and higher because the elution is performed always with the same small volume of acetone. Both C₁₈ adsorption and n-hexane extraction procedures were applied for analysis of chlorophenols in general population and in persons with possible occupational exposure to organochlorine compounds.     

New Cleanup Procedure for Determining Polychlorinated Dibenzo-P-Dioxins and Dibenzofurans in Lipophilic Matrices

Abstract

A new cleanup procedure for determining polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in naturally occurring adipose matrices is suggested. The procedure can be used for analyzing butter, human and cow's milk, eggs, and meat. Quality of sample purification is better than that in the standard procedure, and the recovery of PCDD and PCDF internal standards is within the range 50–80%. The time it takes for sample preparation is shortened, and the consumption of solvents and sorbents is decreased. The FAS-MD activated carbon, which was especially prepared for the extraction of dioxins and related compounds, was used in this work.     

Application of a Deconvolutive Procedure to Analyze Several Chlorophenol Species in Natural Waters by Square‐Wave Voltammetry on the Boron‐Doped Diamond Electrode

Abstract

The anodic voltammetric behavior of 4‐chlorophenol (4‐CP) on a boron‐doped diamond electrode (BDD) in aqueous solution was studied by square‐wave voltammetry. After optimization of the experimental conditions, 4‐CP was determined in a Britton‐Robinson buffer solution with pH 6.0, prepared with pure water. Moreover, mixtures of some different chlorophenols were also investigated and an analytical method was developed for the simultaneous determination of these compounds in natural waters. The oxidation of 4‐CP on BDD was used for analytical purposes and quantification limits as low as 9.2 µg L^?1 were obtained. This result illustrates the advantage of using oxidation process currents on BDD electrodes as the analytical signal, even in contaminated matrices. In order to compare the results found here with the conventional methodology to determine chlorophenols, HPLC‐UV‐vis measurements were also performed and were in good agreement with the analytical values obtained by SWV.     

Anaerobic Degradation of PCB in Soils

Abstract

The anaerobic degradation of PCB in loamy and clayey soils containing indigeneous microflora was studied. The anaerobic conditions were created by an argon atmosphere in the flasks containing soil flooded by a liquid medium with glucose. GC-ECD analysis of soil extracts after 40 day incubation showed, in addition to the concentration changes of the less chlorinated PCB congeners, a significant decrease in the concentration of highly chlorinated congeners in both soils. The results indicate that in both soil types reductive dehalogenation of PCB congeners was encountered.     

Rapid, one-pot derivatization and distillation of chlorophenols from solid samples with their on-line enrichment

A microwave-assisted steam distillation (MASD) sample preparation technique for extracting chlorophenols from solid samples was studied. This open vessel microwave system based study developed as an integrated method since it has incorporated extractive distillation, derivatization and on-line enrichment. Gas chromatography (GC) with electron-capture detection was used for the analysis. The study involved optimization of MASD parameters and on-line enrichments using spiked solid samples. MASD achieved recoveries for spiked soil samples in the range of 94-101% within 20min with a collection of only 20ml distillate facilitating on-line enrichment. Some real samples were analyzed that included soil, wood, leather, textiles, dyes and certified reference materials of soil and wood samples. Limit of detection values of 12ng/g for pentachlorophenol and 194ng/g for monochlorophenol were found. Recoveries of 96.6% in the case of soil certified reference material (CRM) with RSD 2.7% and 80.6% in the case of wood CRM with RSD 3.3% were observed in this study. MASD studied found to produce very clean extracts in comparison to reference techniques.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for determination of chlorophenols in water and body fluid samples

A new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP), in tap water, river water and human urine samples, is described. The derivatization conditions with acetic acid anhydride and the SBSE conditions such as extraction time are investigated. Then, the stir bar is subjected to TD followed by GC-MS. The detection limits of the chlorophenols in tap water, river water and human urine samples are 1-2, 1-2, and 10-20 pg ml⁻¹ (ppt), respectively. The calibration curves for the chlorophenols are linear and have correlation coefficients higher than 0.99. The average recoveries of the chlorophenols in all the samples are higher than 95% (R.S.D. < 10%) with correction using added surrogate standards, 2,4-dichlorophenol-d₅, 2,4,6-trichlorophenol-¹³C₆, 2,3,4,6-tetrachlorophenol-¹³C₆ and pentachlorophenol-¹³C₆. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of chlorophenols in liquid samples.     

Microwave-assisted extraction combined with dispersive liquid-liquid microextraction as a new approach to determination of chlorophenols in soil and sediments

A new method was applied for extraction of five chlorophenols from soil and marine sediment samples. Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction followed by semi-automated in-syringe back-extraction technique was used as an extraction technique. Microwave-assisted extraction was performed by using 2.0 mL of alkaline water at pH 10.0. After extraction, the pH of extraction solution was adjusted at 6.0 and dispersive liquid-liquid microextraction procedure was done using 1.0 mL of acetone as a disperser solvent and 37.0 μL of chlorobenzene as extraction solvent. About 20.0 ± 0.5 μL sedimented phase was collected after centrifugation step. Then, chlorophenols were back extracted into 20 μL of alkaline water at pH 12.0 within the microsyringe. Finally, 20.0 μL of aqueous solution was injected into high performance liquid chromatography with ultra violet detection for analysis. The obtained recovery and preconcentration factors for the analytes were in the range of 68.0-82.0% and 25-30, respectively, with relative standard deviations ≤7.6%. The limits of the detection were found in the range of 0.0005-0.002 mg/kg. The method provides a simple and fast procedure for the extraction and determination of chlorophenols in soil and marine sediment samples.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Field Study on Mobility and Persistence of Linuron and Monolinuron in Agricultural Soil

Abstract

A field site equipped with suction cup lysimeters was installed at Treviglio (BG) to assess the migration capacity of the herbicides linuron and monolinuron from topsoil to groundwater and to verify the appearance of their relevant transformation products in soil and water samples. A constant hydraulic head was applied in order to develop water saturation conditions in the upper layers. KCl was used as a tracer to evaluate water infiltration velocity through the vertical soil profile. The constant hydraulic head accelerated infiltration rates, while herbicide concentrations reached maximum contamination because soil adsorption capacity was underdeveloped. The results indicated two main processes of pesticide transport: firstly transport due mainly to water infiltration through macropores; secondly the transport driven by matrix flow. Linuron was found to be the most mobile herbicide, while chloroanilines were found to be the major transformation products of the herbicides considered.     

Evaluation of carbon nanocones/disks as sorbent material for solid-phase extraction

The potential of carbon nanocones/disks as sorbent material in solid-phase extraction (SPE) procedures has been evaluated. For this aim, a model analytical problem, the determination of chlorophenols in water samples, was selected. An accurately weighed amount of 20 mg of purified carbon nanocones/disks was packed in 3 mL commercial SPE cartridges. Once conditioned, up to 8 mL of water samples can be preconcentrated without analyte losses. The chlorophenols were eluted by using 200 μL of hexane. Aliquots of 2 μL of the organic extract were injected in the gas chromatograph–mass spectrometer for separation and quantification. The purification of the commercial nanocones/disks to reduce the presence of amorphous carbon has been successfully achieved by heating the carbon nanocones/disks at 450 °C for 20 min. Detection limits of chlorophenols were in the range 0.3–8 ng mL⁻¹ by using 2 mL of sample. Moreover, excellent average recovery values (98.8–100.9%) have been obtained after the analysis of water samples from different nature. Finally, the performance of the carbon nanocones/disks as sorbent material has been compared with that of multiwalled carbon nanotubes, providing the former better results under the experimental conditions assayed.     

Raman spectroscopy of selected arsenates--implications for soil remediation

The contamination of soils with heavy metals such as As, Cr and Cu is of great importance; the remediation of such soils even more so. Arsenic compounds are prevalent in soils either through leaching of mine tailings, the use of Cu/Cr/As as a wood preservative or through the use of arsenic in cattle dips. The arsenic compounds in soils and leachates can be highly reactive and mobile, resulting in the formation of metal arsenate compounds. Of these compounds, one such set of minerals that can be formed is the vivianite arsenate minerals. Raman spectroscopy has been used to characterise the vivianite arsenates and to identify arsenic contaminants in a soil.     

A Rapid,Simple, and Sensitive Spectrophotometric Determination of Traces of Vanadium (V) in Foodstuffs,Alloy Steels,and Pharmaceutical,Water, Soil,and Urine Samples

Abstract

A rapid, simple, sensitive, and selective spectrophotometric method is investigated for the determination of traces of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples in aqueous DMF medium. The metal ion forms a green colored complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) in an acidic buffer of pH 6.0. The green colored solution, having an absorbance maximum at 380 nm, is stable for more than 72 hours. Beer's law is obeyed in the range of 0.051–2.037 µg ml^?1. The molar absorptivity and Sandell's sensitivity of the method are found as 2.75 × 10⁴ l mol^?1 cm^?1 and 0.0018 µg cm^?2, respectively. The green colored complex has 1:2 [V(V)-HMBATSC] stoichiometry. The stability constant of the complex is determined as 3.267 × 10¹¹ by Job's method. The optimum reaction conditions and other analytical parameters are studied. A sensitive and selective second-order derivative spectrophotometry has also been proposed for the determination of V(V). The interference of various cations and anions are studied. The present method is successfully applied to the determination of vanadium (V) in foodstuffs, alloy steels, and pharmaceutical, water, soil, and urine samples.     

固相萃取-气相色谱-质谱法测定木制家具中氯酚类及菊酯类防腐剂

建立了固相萃取-气相色谱-质谱(SPE-GC-MS)检测含氯酚类化合物(2,4-二氯苯酚、2,4,6-三氯苯酚、2,4,5-三氯苯酚、2,3,4,6-四氯苯酚、五氯苯酚、林丹)和菊酯类化合物(氯菊酯、氟氯氰菊酯、氯氰菊酯、溴氰菊酯)等10种木材防腐剂的方法。对家具样品采用超声萃取法、以甲醇为提取剂在室温下反复提取2次,提取液经浓缩后,加入碳酸钾和乙酰酐衍生化,将衍生化后的溶液通过Oasis HLB固相萃取柱净化,用乙酸乙酯洗脱并收集检测。采用该方法实现了家具中10种木材防腐剂的分离检测,该方法中氯酚类防腐剂定量限为1 mg/kg、菊酯类防腐剂定量限为5 mg/kg,平均回收率为76.0%～108.8%。应用该方法对市场上销售的木制家具进行了检测,在部分家具中检出含有少量林丹。实验结果证明,该方法准确、灵敏,可有效地应用于木制家具中防腐剂的实际检验工作中。     

氯酚为前生体生成二噁英类的研究进展

评述了氯酚作为前生体生成二噁英类的问题，总结了热过程、光转化、酶反应三种途径中氯酚生成二噁英类的条件及机制。热过程中氯酚缩合成二Wu英的主要影响因素为：温度、热解时间、含氧量和催化剂；而光转化过程中光强、溶剂种类、光敏物质的存在对氯酚生成Wu英有影响，热过程和光转化的反应机制均是通过自由基来完成的。     

Implementation of depth-dependent soil concentrations in multimedia mass balance models

In standard multimedia mass balance models, the soil compartment is modeled as a box with uniform concentrations, which often does not correspond with actual field situations. Therefore, the theoretically expected decrease of soil concentrations with depth was implemented in the multimedia model SimpleBox 3.0. The effects of this implementation on the model outcomes were explored for nine compounds in four environmental compartments. For compounds with a low penetration depth, the new model predicts substantially higher or lower concentrations in the vegetation compartment than the old model. For those compounds, predicted concentrations in surface water and air were higher in the new model, but the deviations from the old model were smaller than in the vegetation compartment. For compounds with a large penetration depth, the model adaptations show little effect. No field study was carried out to validate the results of the model calculations, but we did collect measured data on concentrations in vertical soil profiles from literature. According to those data, we concluded that the implementation of depth dependent soil concentrations might be a useful extension for steady state multimedia mass balance models. More field study has to be carried out to validate the model outcomes.