Experimental study on isotope fractionation of evaporating water of different initial isotopic composition

The studies of evaporative isotopic fractionation in controlled conditions are of particular importance for understanding the mechanism of evaporation fractionation in natural conditions. We present the measurements of the average isotopic fractionation factors during the evaporation of water having different initial isotopic compositions at constant temperature. The results show that the isotopic composition of residual water become more enriched over the time and the initial isotopic composition of evaporating water has considerable effect on the average isotopic fractionation factors. The average isotopic fractionation factors in evaporation of Water A and Water B under the present experimental conditions were found to be 0.9817 ± 0.0044 and 0.9887 ± 0.0031 for oxygen and 0.9178 ± 0.0182 and 0.9437 ± 0.0169 for hydrogen, respectively. The findings of this work should lead to a better understanding and use of stable isotope techniques in isotope hydrology by using a simple technique of evaporation pan.     

Nanofiltration and electrodialysis: alternatives in heavy metal containing high salinity process water treatment

Desalination is priority in process water treatment and several different technologies can be applied to minimize the total salinity of water. Our aim was to study desalination and simultaneous elimination of heavy metal residues from process waters. Nanofiltration (NF) and electrodialysis (ED) treatment technologies were applied for high salinity model solutions and high salinity, heavy metal containing real process waters originating from electroplating industry. Efficiencies of two technologies were compared in respect to salt and heavy metal removal both for model solutions (NaCl and Na₂SO₄) and three real process water samples. Initial concentrations of model solutions chosen accordingly the most common process water salt composition. Both technologies showed similar efficiency of heavy metal (Ni²⁺ and Cu²⁺) removal; however, they provide different demineralization rates, rejection, and extraction percentage for sodium and chloride ions. ED experiments of model solutions showed complete desalination after 1 h operating time at 6 V applied voltage; on the other hand, the increasing conductivities of NF permeates verified the selectivity of NF membrane, therefore, representing partial desalination. These phenomena were confirmed by demineralisation rate values as well (NF: for NaCl: 41.5–66.6%, for Na₂SO₄: > 96.6%; ED: both for NaCl and Na₂SO₄ > 98%). Significantly. higher demineralisation rates were achieved by ED (37.3–99.2%) than NF (20.2–62.3%) during the treatment of real process waters. We successfully demonstrated that ED is more efficient for simultaneous salt and heavy metal removal for process waters originating of electroplating industry.     

A novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry based on sample mixing with a non-enriched standard

In this work, a novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ⁶⁵Cu, δ⁵⁶Fe, and δ⁵⁷Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ⁶⁵Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ⁶⁵Cu value obtained using the conventional approach (bias ≤0.15?‰).     

Determination of the Concentrations of Binary Mixtures of Glycerine and Water by a Transient Method

The conductivities of binary mixtures of glycerine and water were measured at 20°C by means of a transient method. The equation describing the correlation between concentration and thermal conductivity was determined. The equation can be used for determining concentrations in mixtures. The results show that (1) the error in the determination of the molar concentration of water in mixtures is less than 1%, (2) the time of measurement is 1 s, (3) this method can be used for on-line analysis in production control. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of desorption and sorption of water on the purity of perfluorooctanoic acid

The composition of impurities in perfluorooctanoic acid (PFOA) was measured and determined to be notably different between lots. Since the purity of PFOA varied, the accuracy of prepared calibration solution concentrations was reduced. In this study, factors influencing the purity were investigated using a Karl Fischer titrator and a LC/MS to support the development of reference materials. The results showed variances of water and isomer/homologue contents under different ambient conditions during sample handling. Moreover, these variances, especially for water, greatly affected the purity of PFOA (0.95–0.99 kg kg^?1). Therefore, PFOA of reliable purity should be used for the preparation of calibration solutions.     

Rapid monitoring and sensitive determination of DDT and its metabolites in water sample using solid-phase extraction followed by ion mobility spectrometry

Dichlorodiphenyl trichloroethane (DDT) as an organochlorine compound has been globally used as a pesticide for controlling soil-dwelling insects and treating diseases such as malaria and typhus. The degradation products of DDT and its metabolites have also negative effects on the environment. The present study has investigated the determination of DDT and its metabolites in water sample using ion mobility spectrometry (IMS) as a rapid and sensitive detection technique. For this purpose, DDT and its metabolites were extracted using reverse phase solid-phase extraction (SPE) from water samples. The samples were then recovered by eluting with methanol and finally, quantified using the corona discharge IMS technique. Injection and oven temperatures and the effect of dopant were optimized as experimental parameters influencing both detection and determination efficiencies. Degradation of DDT in IMS drift tube was studied and reduced mobility values of DDT and its metabolites were calculated. The developed method was validated using water sample to obtain good results for the determination of DDT at low levels (1 ng ml^?1) while spiked recoveries were obtained to be between 95.0–96.7%. The proposed method based on IMS proved to be a simple, inexpensive, rapid and sensitive procedure for the fast monitoring and determination of DDT and its main metabolites in water sample.     

Photo-induced flow-injection determination of nitrate in water

A sensitive flow-injection method for the chemiluminescent determination of ultra-low concentration of nitrate in water is presented. Nitrate is on-line photolytically converted to peroxynitrite by absorption of UV light inside of 60 mm long quartz capillary (i.d. 530 µm, o.d. 720 µm). Peroxynitrite is subsequently determined by the chemiluminescent reaction with luminol. The detection limit of nitrate is 7 × 10^?10 M (S/N = 3). The linear range of the method is 2 × 10^?9–1 × 10^?5 M nitrate. The interference of nitrite is eliminated by its conversion to nitrogen after mixing of sample with a solution of sulfamidic acid. Other common anions do not interfere. The interference of cations is eliminated by passing the sample through a cation-exchange column. The FIA procedure allows analysing of 15 samples per hour. The method was applied to the determination of nitrate in various real water samples. The results are in good agreement with a reference ion chromatographic method.     

The use of LA-SF-ICP-MS for nuclear forensics purposes: uranium isotope ratio analysis

This work describes the utilization of the laser ablation sector field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS) technique for the determination of uranium isotopic composition in a highly enriched uranium sample. The measurements were performed on a continuous ablation with low energy density and defocusing, which demonstrated to be the optimum to reach the best signal stability. The measurements were improved by adjusting the following parameters: RF power, laser beam diameter, defocusing of laser beam, laser energy, laser energy density, auxiliary gas and sample gas. The ²³⁵U/²³⁸U isotope ratio with its respective uncertainty was 16.36 ± 0.15 and its precision was 1.12 % relative standard deviation. The uncertainties were estimated following the ISO GUM, with a confidence level of 95.45 % (k = 2.00). When compared the isotope abundances to the Round Robin Exercise Number 3’s average results a difference of 0.46 % has been found and when compared to supplier’s value, the difference was 0.41 %. The results presented by the measurements revealed that the LA-ICP-MS technique offers a rapid and accurate alternative to measure uranium isotope ratios without any sample preparation, since it allows carrying out the measurements straight on the sample. Moreover, it preserves the testimony—very important for safeguards and nuclear forensics purposes.     

Spectrophotometric determination of trace-level bromate in drinking water after post-column reaction with pararosaniline based on multi-walled carbon nanotubes

A simple and sensitive spectrophotometric method is described for low level determinationof bromate in drinking water. This method is based on the reduction of bromate ions into bromine in the presence of pararosaniline by sodium metabisulphite to form a highly stable pink-red complex measured at 540 nm. Maximum colour formation was obtained at about 45 min. Multi-walled carbon nanotubes, a solid phase extraction sorbent, has been described for the removal of cationic interferences of major elements and heavy metals from water samples prior to conducting the assay. Bear’s law is obeyed in the range of 5–80 µg.L^?1 with limit of detection of 0.44 µg.L^?1 and correlation coefficient of 0.998 (n = 5). The mean relative standard deviation (RSD%) of the results within-day precision and accuracy were ≤1.2% which confirmed the reproducibility of the assay technique. The optimum assay conditions and their applicability to the determination of water samples are described. The method was successfully applied for the determination of bromate in water samples with satisfactory results and recommended to be applied in all desalination plant samples.     

Performance of laser ablation: quadrupole-based ICP-MS coupling for the analysis of single micrometric uranium particles

In this paper we describe the application of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) coupling to particle analysis, i.e., the determination of the isotopic composition of micrometric uranium particles. The performances of this analysis technique are compared with those of the two reference particle analysis techniques: secondary ion mass spectrometry (SIMS) and fission track-thermo-ionization mass spectrometry (FT-TIMS), based on the measurement of the isotopic ratios of ²³⁵U/²³⁸U in particles present in an inter-comparison particulate sample. The agreement of the results obtained using LA-ICP-MS with target values and with the results obtained using FT-TIMS and SIMS was good. Accuracy was equivalent to that of the other two techniques (±3 % deviation). However, relative experimental uncertainties present with LA-ICP-MS (7 %) were higher than those present with FT-TIMS (4.5 %) and SIMS (3 %). Furthermore, measurement yield of LA-ICP-MS coupling was close to that obtained with the same quadrupole ICP-MS for the measurement of a liquid sample (~10^?4), but lower than that obtained with FT-TIMS and SIMS, respectively, by a factor of 10 and 20, although the particles analyzed using LA-ICP-MS were most likely smaller (diameter ~0.6 μm, containing 4–7 fg of ²³⁵U). Nevertheless, thanks to the brevity of the signals obtained, the detection capacity for low isotopic concentrations by LA-ICP-MS coupling is equivalent to that of FT-TIMS, although it remains well below that of SIMS (×15). However, with more sensitive double focusing ICP-MS, performances equivalent to those achieved using SIMS could be obtained.     

Composition of Coexisting Liquid Phases Determined by Rayleigh Interferometry

Rayleigh interferometry is a precise macroscopic gradient technique that has been utilized for the determination of multicomponent diffusion coefficients. Because concentration gradients in multicomponent systems drive a diffusion-based partial separation of different solutes, this interferometric technique may be potentially used for the determination of solute concentrations. We have therefore theoretically examined how Rayleigh interferometry can be applied for the determination of composition of ternary aqueous mixtures. The effect of cross-term diffusion coefficients on the accuracy of this method is also discussed. Furthermore, since the poly(vinyl)alcohol+poly(ethylene)glycol+water system undergoes liquid–liquid phase separation (LLPS), we have experimentally characterized its LLPS boundary at 25 °C. The corresponding tie-lines were characterized by determining the composition of the two coexisting liquid phases using Rayleigh interferometry.     

Semi-automated continuous sample drop flow microextraction with swift preconcentration and atomic absorption spectrometry determination of lead in water and apple leaves

In this paper, we present novel developments to our recently developed method so-called “continuous sample drop flow microextraction (CSDF-ME)” technique. Previously, we showed that the CSDF-ME technique offers several advantages, including stability of extraction solvent, no need for holder device, and easy to operate. The merit of current study is to make the extraction steps faster with sample required for the analysis. The key novelty of proposed method includes usage of a solvent mixture (i.e., methanol and carbon disulfide), allowing to pump aqueous samples with a higher flow rate than the former technique which led to reduce the extraction time. Results show that the technique is cable to become faster by five times with an enrichment factor of 93 for 4.0 mL of aqueous sample. The linear range and limit of detection for Pb are found to be 0.1–6.0 and 0.03 µg L^?1, respectively. The relative standard deviation for determination of 1.0 µg L^?1 of Pb in a sample is 2.9% (n?=?5). Furthermore, the relative recoveries of the developed CSDF-ME method for Pb in tap water, mineral water, and Standard Reference Material for apple leaves (1515) are shown to be 98, 100, and 94%, respectively.     

Cyanopropyl Bonded-Phase Cartridges for Trace Enrichment of Dioxins and Chlorinated Pesticides from Water Samples

Gas chromatography of dioxins and chlorinated pesticides in water samples has been performed after adsorption from 50 to 100 mL sample on to a cartridge containing 100 mg cyanopropyl-bonded porous silica. The dioxins and chlorinated pesticides were desorbed with 2 mL carbon disulfide, which is concentrated and analysed by gas chromatography coupled with an electron-capture detector. The average recovery of 0.20 ng mL^?1 of each chlorinated pesticide and of 0.50 ng mL^?1 of each dioxin from distilled water and river water samples (50 mL) is ≥97.2% with a standard deviation (SD) ≤ 2.6. In the dioxin separation from chlorinated pesticides the recovery of dioxins at levels of 0.1–0.5 ng mL^?1 is ≥97.9% with a SD ≤ 1.3, with traces of aldrin, heptachlorepoxide and 4,4′-DDD (≤1.7%) by the CN-Sep-Pak cartridge, while the recovery of chlorinated pesticides at levels of 0.05–0.2 ng mL^?1 is ≥97.4% with a SD ≤ 1.5, with traces of hep-dioxin (2.4%) and penta-dioxin (1.0%) by the C₁₈-Sep-Pak cartridge connected “in series” to the CN-Sep-Pak cartridge.     

Conductivity and Dielectric Behavior Studies of Carboxymethyl Cellulose from Kenaf Bast Fiber Incorporated with Ammonium Acetate-BMATFSI Biopolymer Electrolytes

This work was undertaken to study the conductivity and dielectric behavior of a biopolymer electrolyte based on carboxymethyl cellulose that was synthesized from kenaf fiber. Biopolymer electrolytes comprised of various weight percentage ratios of the host polymer, ammonium acetate salt, and butyl-trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid were prepared by the solution casting technique. The conductivity values were determined by impedance spectroscopy. The highest conductivity found was 2.18 × 10^?3 S cm^?1 at ambient temperature for the film incorporated with 20 wt.% salt and 20 wt.% ionic liquid. In order to understand the conductivity behavior, a dielectric study was carried out. The results showed that the system obeys the Arrhenius rule and confirmed non-Debye behavior in the sample.     

Determination of pesticide residues and related compounds in water and industrial effluent by solid-phase extraction and gas chromatography coupled to triple quadrupole mass spectrometry

Pollution of drinking water supplies from industrial waste is a result of several industrial processes and disposal practices, and the establishment of analytical methods for monitoring organic compounds related to environmental and health problems is very important. In this work, a method using solid-phase extraction (SPE) and gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) was developed and validated for the simultaneous determination of pesticide residues and related compounds in drinking and surface water as well as in industrial effluent. Optimization of the method was achieved by using a central composite design approach on parameters such as the sample pH and SPE eluent composition. A single SPE consisting of the loading on a polymeric sorbent of 100 mL of sample adjusted to pH 3 and elution with methanol/methylene chloride (10:90, v/v) permitted the obtaining of acceptable recoveries in most cases. The concentration factor associated with sensitivity of the chromatographic analysis permitted the achievement of the method limit of detection values between 0.01 and 0.25 μg L^?1. Recovery assays presented mean recoveries between 70 and 120 % for most of the compounds with very good precision, despite the different chemical nature of the compounds analyzed. The selectivity of the method, evaluated through the relative intensity of quantification and qualification ions obtained by GC-QqQ-MS/MS, was considered adequate. The developed method was finally applied to the determination of target analytes in real samples. River water and treated industrial effluent samples presented residues of some compounds, but no detectable residues were found in the drinking water samples evaluated.     

Determination of aromatic amines in environmental water samples using solid-phase extraction modified with sodium dodecyl sulphate and micellar liquid chromatography

Extraction and determination of seven aromatic amines in environmental water samples were performed with solid-phase extraction (SPE) and micellar liquid chromatography (MLC) using experimental design. Extraction of aromatic amines was carried out with a C₁₈ cartridge modified with sodium dodecyl sulphate (SDS). The washing solution and elution solvent for extraction of aromatic amines were aqueous solution containing 5% (v/v) acetonitrile and 5% (v/v) acetone and 3 mL methanol, respectively. The chemometrics approach was applied for the separation optimisation of these compounds using MLC. Different mobile phase compositions were used for modelling based on retention times to obtain the best separation using central composite design. The optimum mobile phase composition for separation and determination of analytes in water samples was 69 mM SDS, 9% v/v 1-propanol and pH = 6.4. Recoveries were between 84.8–93.5% with relative standard deviation (RSD) less than 5.8% (n = 5). Limits of detection and linear range were 1–4.5 and 3.1–125.0 µg/L, respectively. The proposed method was applied to determine the aromatic amines in real samples (river and well waters). Amount of 4-nitroaniline and 3-nitroaniline in river water sample were 2.15 and 1.91 µg/L, respectively.     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements.     

Effect of water release on thermal properties of polyaniline

Conducting polyaniline (PANI) was studied by thermal expansion measurement, thermogravimetric analysis and by electrical conductivity measurement. Relative elongation and coefficient of thermal expansion (CTE) were determined from room temperature to 60 °C. Various temperature profiles were used. During heating, the treatment of samples at a constant temperature higher than the room temperature, or evacuation, water was released from the samples. Water release was detected by mass and thermogravimetric analysis. Water release was connected with shrinkage of the PANI samples and apparent negative CTE in the first thermal cycle. In the following thermal cycles, it increased and reached a positive value. CTE of PANI attained values in the range of ?30 × 10^?6 K^?1 up to 20 × 10^?6 K^?1 in dependence on water content in the sample before measurement and on experimental conditions of measurement. Irreversible shrinkage of the polymer was the largest in the first thermal cycle. Water release exhibited a strong time and temperature dependence, and it was only partially reversible. The electrical conductivity was measured by a four-point van der Pauw method. Relative electrical conductivity decreased with amounts of water release. Relative decrease of electrical conductivity reached as far as 20% after evacuation 7 h at the room temperature.     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements. Received: 5 January 1998 / Revised: 17 February 1998 / Accepted: 18 February 1998     

Morphologies of three-phase emulsions of the ternary nonionic amphiphile/oil/water systems and their determination by electrical method

Equations have been developed for the electrical and thermal conductivities of dispersions of two different phases of low conductivity in a third, conductive phase. These equations predict the conductivity of the dispersion from the volume fractions and conductivities of the constituent phases. Electrical conductivity measurements on dispersions of three liquid phases, i.e., three-phase emulsions, were made over a wide range of volume fractions of each dispersed phase and used to test the equations. The equations predict accurately dispersion conductivities from the measured volume fractions and conductivities of the constituent phases without any adjustable parameters. The predicted values are in excellent agreement with the measured conductivities of three-phase emulsions in the nonionic amphiphile/oil/water systems. This leads to the determination of three-phase emulsion morphologies. When the ratio Kd of the emulsion-drop conductivity to the continuous phase conductivity is O(10(-1)) 相似文献