Deionized Water Samples Research Articles

Hollow fiber-protected liquid-phase microextraction of triazine herbicides.

A new microextraction technique termed hollow fiber-protected liquid-phase microextraction (LPME) was developed. Triazines were employed as model compounds to assess the extraction procedure and were determined by gas chromatography/mass spectrometry. Toluene functioned as both the extraction solvent and the impregnation solvent. Some important extraction parameters, such as effect of salt, agitation, pH, and exposure time were optimized. The new method provided good average enrichment factors of > 150 for eight analytes, good repeatability (RSDs <3.50%, n = 7), and good linearity (r2 > or = 0.9995) for spiked deionized water samples. The limits of detection (LODs) were in the range of 0.007-0.063 microg/L (S/N = 3) under selected ion monitoring mode. In addition to enrichment, hollow fiber-protected LPME also served as a technique for sample cleanup because of the selectivity of the membrane, which prevented large molecules and extraneous materials, such as humic acids in solution, from being extracted. The utilization of this procedure in the extraction of a slurry sample (mixture of soil and water) also gave good precision (RSDs <5.00%, n = 3) and LODs (0.04-0.18 microg/L, S/N = 3). Finally, the comparison of the new method with the static solvent drop LPME and solid-phase microextraction was performed. The results demonstrated that hollow fiber-protected LPME was a fast, accurate, and stable sample pretreatment method that gave very good enrichment factors for the extraction of triazine herbicides from aqueous or slurry samples.

Recovery of Atrazine, Bromacil, Chlorpyrifos, and Metolachlor from Water Samples after Concentration on Solid-Phase Extraction Disks: Interlaboratory Study

An interlaboratory comparison was conducted in 1997 and 1998 to examine the feasibility of using C18 solid-phase extraction disks (Empore) to simultaneously determine the herbicides atrazine, bromacil, and metolachlor and the insecticide chlorpyrifos in water samples. A common fortification source and sample processing procedure were used to minimize variation in initial concentrations and operator inconsistencies. The protocol consisted of paired laboratories in different locations coordinating their activities and shipping fortified water samples (deionized or local surface water) or Empore disks on which the pesticides had been retained and then quantitating the analytes by a variety of gas chromatographic methods. Average recoveries from all laboratories were >80% for atrazine, bromacil, and metolachlor, and >70% for chlorpyrifos. Detection of bromacil was unachievable at some locations because of chromatographic problems. Shipping samples between cooperating laboratories did not affect the recovery of atrazine, chlorpyrifos, or metolachlor in either matrix. Recoveries tended to be higher from disks shipped to cooperating laboratories compared with those from fortified water. Shipping disks eliminated many problems associated with the shipment of water samples, such as bottle breakage, higher shipping cost, and possible pesticide degradation. Recoveries of bromacil and metolachlor were lower from fortified surface water samples than from fortified deionized water samples. This collaborative research demonstrated that pesticides in water samples can be concentrated on solid-phase extraction disks at one location and quantitated under diverse analytical conditions at another location. The extraction efficiencies of the disks were comparable with or better than the recoveries obtained from the shipped water samples, and the problems associated with shipping water samples were eliminated by using the disks.

Identification of New Photodegradation Byproducts of the Antifouling Agent Irgarol in Seawater Samples

A photodegradation study for Irgarol was carried out in order to investigate several products of degradation formed in different environmental matrices and under different conditions. Deionized water, groundwater and seawater samples, spiked at 30–100 μg/L with Irgarol, were irradiated using a xenon are lamp and/or sunlight. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by means of solid-phase extraction (SPE) using either C18 or PLRP-s cartridges. Separation and detection of the compounds was accomplished by several analytical methodologies such as liquid chromatography-diode array detection (LC-DAD), liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS) and gas chromatography-mass spectrometry (GC-MS). Four new byproducts, with molecular weights of 167, 197, 207 and 213, were identified in this photodegradation study. When the photolysis was carried out with xenon lamp, half-lives of Irgarol were 103.8, 125.4 and 107.5 minutes in deionized water, groundwater and seawater, respectively. In seawater samples, a 98% of degradation was observed for Irgarol, after 217 hours of solar irradiation, being the main byproduct formed that corresponding to Mw = 213. On the other hand, the use of two different sensitizers -(TiO2/H2O2), (FeCI3/H2O2)- was also evaluated in deionized water samples containing Irgarol. These experiments were carried out in order to evaluate the use of these two sensitizers for decontamination of polluted waters.

Ozone mass transfer in water and wastewater treatment: experimental observations using a 2D laser particle dynamics analyzer

Ozone mass transfer in water and wastewater was studied by using a 2D laser particle dynamics analyzer (PDA) to simultaneously measure bubble size distribution and mixing intensity. Three types of water samples, including deionized water, tap water and pulp mill effluents were tested to demonstrate the enhancement of ozone absorption with the presence of chemical reactions. Bubble size distribution and apparent mass transfer rates were used to estimate individual mass transfer parameters and examine the effects of operating conditions and selected gas spargers. It was shown that gas bubbles in ozonation systems varied over a broad range of sizes and their distributions usually deviated from a simple normal distribution. Among the factors examined, the gas sparger and water types were identified as the most important factors affecting mean bubble size, whereas the impacts of ozone dose and gas flow rate on bubble size distribution were minor. Due to the higher gas holdup, however, the specific surface area was strongly dependent on the gas flow rate as well. Consequently, the mass transfer coefficient increased as the gas flow rate increased. A further enhancement of mass transfer was observed for pulp mill wastewaters as compared to tap and deionized water samples, because the occurrence of chemical reactions depleted the dissolved ozone within the gas–liquid film.

Stability of inorganic arsenic (III) and arsenic (V) in water samples

The objective of this study was to formulate a protocol for the collection and preservation of natural water samples (lakes and streams) to be analysed for the inorganic species As(III) and As(V). The analytical technique employed was HPLC-ICP-MS, using a proprietary anion exchange resin (ANX-1606-AS from Cetac) as the basis for separation of the two species. Initial experiments carried out at room temperature, where de-ionised water and Ottawa River water samples were spiked at low (0.5-20) µg l –1 concentrations of As(III) and As(V), demonstrated that As(V) is actually reduced to As(III) within a few days. This reduction is matrix and concentration dependent and was confirmed by independent analysis using HGAAS with hydride generation at pH 4.5 and <1. Such conversion of As(V) to As(III) does not occur in spiked deionised water maintained at 5 °C but is evident in the Ottawa River sample at this temperature. A time and temperature study of a filtered (0.45 µm) natural water sample, with a total As concentration of 21 µg l –1 , showed that immediate storage in a filled bottle at about 5 °C will preserve As (III) and As(V) concentrations for about 30 d. If kept at room temperature, changes for this particular sample occur after about 5 d, with As(V) becoming the dominant species via oxidation and gradually declining thereafter. Although acidification to 0.1% HNO 3 stabilises the As species for at least 15 d at 22 °C, its effect is immediately to alter the species distribution. With the natural water sample, this effect was to increase the concentration of As(III) substantially and, to a lesser extent, that of As(V), at the expense of other forms of the element. Acidification to 0.1% HCl also produced these results. The study of spiked de-ionised water and Ottawa River samples at 0.1 and 0.4% in HNO 3 and HCl demonstrated that both acids cause the oxidation of As(III) to As(V) but HNO 3 showed a higher degree of oxidation with greater acid strength, as expected.

Recovery of 137Cs by a bioaccumulation system using Rhodococcus erythropolis CS98

With a bioaccumulation system using Rhodococcus erythropolis CS98 for recovery of cesium-137, we found that 137Cs accumulated when a carbon source was added for energy supply. With the addition of ammonium acetate as the carbon source, almost all the 137Cs from deionized water was recovered using a cell suspension of 1 g/ l with incubation for 24 h. Cell damage by radioactivity was not detected during the 24 h period. 137Cs recovery from river water samples was lower than that from deionized water, especially from river water with a very high potassium concentration (the lower reaches of the Sakura River: potassium concentration=4.3 mg/ l). When 3.9 mg/ l of potassium was added to a deionized water sample, 137Cs recovery decreased to 35% of that without potassium addition, suggesting that the potassium concentration is a critical factor for 137Cs recovery. We conclude that a bioaccumulation system with a semipermeable membrane tube, such as is described in this paper, is feasible for the recovery of radioactive cesium from fresh waters.

Evaluation of C18 solid‐phase extraction cartridges for the isolation of select pesticides and metabolites

Nine different C18 solid‐phase extraction (SPE) cartridges were evaluated for their efficiency at extracting nine pesticides and two s‐triazine metabolites from spiked deionized water samples. The SPE cartridges were found to contain nitrogen (N) and/or phosphorus (P) contaminants and varied in their extraction efficiency for certain pesticides and metabolites. Four of the nine SPE cartridges gave acceptable (70 to 120%) pesticide and metabolite recovery percentages, while five cartridges had marginal (50 to 70%) to poor (< 50%) recoveries. Statistical analyses showed that the poor to marginal recoveries found for three compounds could not be explained by considering several indigenous chemical and physical traits of the cartridge. It is suggested that proper SPE cartridge selection for pesticide recovery should be evaluated using several different cartridges.

Artifact formation of methyl mercury during aqueous distillation and alternative techniques for the extraction of methyl mercury from environmental samples

Aqueous distillation as a pre-extraction step for monomethyl mercury (MMHg) in waters and sediments is the most common method because it eliminates negative interferences in the aqueous ethylation procedure. However, the distillation procedure generates a positive MMHg artifact as a result of the action of naturally occurring organic substances on inorganic Hg in the sample. Methylation of Hg(II) does not occur in deionized water samples, indicating that the artifact is not due to the distillation itself or the reagents added (ammonium pyrrolidine dithiocarbamate, HCl), but rather to naturally occurring organic matter. Methylation of Hg(II) spikes ranged from 0.001% for rainwater and oligotrophic lake water to 0.08% for brown, humic-rich water. Methylation of Hg(II) spikes in sediments ranged from 0.005 to 0.1%, with the highest conversions in wetland peat. In most water samples, the artifact is not significant, as the ambient concentration of MMHg is 1–10% of the total, well above the contribution due to the artifact. The artifact may be significant in sediments and in Hg-contaminated water samples, where the measured fraction of MMHg is less than 1% of the total. The best of six alternative techniques involves leaching with KBr/H2SO4/CuSO4 and extraction into CH2Cl2, followed by back extraction into water, and subsequent ethylation.

Influence of concentrations of elements upon technetium preconcentration in deposition samples during heating

Technetium volatilization during preconcentration of deposition samples (containing rain and solid matter) with different concentrations of elements was studied by tracer experiments. During evaporation of the samples to dryness, hardly and Tc contained in them was volatilized. However, when the same evaporation experiment was carried out with a deionized water sample, unexpected behaviour of Tc was observed, i.e. a part of the Tc was lost during preparation of the dried-up sample. The major elements, which are present in large amounts in deposition samples, affected Tc stability.

Electron beam irradiation of n-type porous silicon obtained by photoelectrochemical etching

The effects of electron beam irradiation on luminescence and microstructure of n-type porous silicon (PS) have been investigated, using cathodoluminescence (CL) in the scanning electron microscope (SEM), and electron energy loss spectroscopy in the transmission electron microscope (TEM). In the SEM, the CL rapidly decreased with irradiation. It could be fully restored by boiling the samples in de-ionized water. In the TEM, freshly restored PS emerged as Si nano-crystallites embedded in an unstable silicon oxide. The effect of irradiation was to suppress the oxide, and also, in the case of proximity of carbon from the foil holding the sample, to change the crystallite composition to β-SiC.

Determination of didealkylatrazine in water by graphitized carbon black extraction followed by gas chromatography-high resolution mass spectrometry

A highly specific and sensitive method has been developed for determining trace levels of didealkylatrazine (DDA), one of the dealkylated products of atrazine degradation occurring in ground and surface waters. The analyte was isolated efficiently from deionized water and ground water by liquid-solid extraction via a graphitized carbon black cartridge, and the recoveries are greater than 80%. These recoveries are an order of magnitude greater than those achieved by liquid-liquid extraction (dichloromethane) and solid-phase extraction with a C 18 bonded silica cartridge. Analysis was performed by gas chromatography-high resolution mass spectrometry; mass profiles were acquired in the selected ion monitoring mode. A precision of < 20% (relative standard deviation) was obtained for six deionized water samples fortified with DDA at the 500 ppt level. The average accuracy is 85% of the true amount for the deionized water samples. The detection limit for a 200-ml sample is 2 ppt. The method has been successfully applied to determine DDA in ground water.

Detection of Infectious Tomato Mosaic Tobamovirus in Fog and Clouds

Tomato mosaic tobamovirus (ToMV) was detected by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction-blot hybridization (RT-PCR-BH) in cloud samples collected from the summit of Whiteface Mountain, NY, and in fog samples from two collection sites along the coast of Maine. The virus was subsequently transmitted to Chenopodium quinoa from a composite of RT-PCR-BH-positive concentrates. There was no apparent relationship between the presence of ToMV and sample collection date, volume, or pH. The RT-PCR products of three cloud and fog samples and one deionized water sample were identical to one another and to a stream water isolate of ToMV from Whiteface Mountain based on nucleotide sequencing of a 347-bp fragment within the coat protein gene and 99.1 and 72.9% similarity to ToMV-L and tobacco mosaic virus-vulgare, respectivelv.

Validation of an automated fluorescein method for determining bromide in water

Surface, atmospheric precipitation and deionized water samples were spiked with μg l−1 concentrations of bromide, and the solutions stored in polyethylene and polytetrafluoroethylene bottles. Bromide was determined periodically for 30 days. Automated fluorescein and ion chromatography methods were used to determine bromide in these prepared samples. Analysis of the data by the paired t-test indicates that the two methods are not significantly different at a probability of 95% for samples containing from 0.015 to 0.5 mg l−1 of bromide. The correlation coefficient for the same sets of paired data is 0.9987. Recovery data, except for the surface water samples to which 0.005 mg l−1 of bromide was added, range from 89 to 112%. There appears to be no loss of bromide from solution in either type of container.

Automated Extraction Technique for Determination of Experimental Insecticide Nifluridide and Its Cyclized Product in Water by High Pressure Liquid Chromatography

A method is described for the simultaneous determination of the experimental insecticide nifluridide (N-(2-amino-3-nitro-5-(trifluoromethyl)phenyl)-2,2,3,3-tetrafluoropropanamide) and its cyclized product, EL-919 (7-nitro-2-(1,1,2,2-tetrafluoroethyl)-5-(trifluoromethyl)benzimidazole), in water. Both compounds are extracted by passage of up to 500 mL water through two Sep-Pak C18 cartridges joined in series. The extraction is automated by using vacuum. The compounds are eluted from the cartridges with acetonitrile. Both compounds are then separated and measured by high pressure liquid chromatography with UV detection at 235 nm. Recoveries were 91.2-97.1% nifluridide and 82.7-98.0% EL-919 for deionized water samples fortified with 0.001-0.1 ppm nifluridide and 0.005-0.1 ppm EL-919. Analysis of water samples (pH 8) from bluegill and rainbow trout toxicity studies with nifluridide resulted in a half-life determination of 10 h at 13 degrees C and 2.5 h at 20 degrees C with nearly quantitative conversion to EL-919 within 96 h.

Trace element contamination in blood-collecting devices

We have used proton-induced X-ray emission (PIXE) methods to determine the trace-element contamination from devices commonly used for blood collection. After a qualitative evaluation of the elemental composition of the devices, we have measured the contamination in de-ionized water and plasma samples following various experimental procedures. We have found that the Vacutainer tubes are the main source of contamination, but their effect in plasma elemental analysis is significant only in the case of zinc. Use of disposable syringes to collect blood samples seems to avoid this contamination.

Solution/air interfaces I. An oscillating jet relative method for determining dynamic surface tensions

The oscillating jet method has been investigated for the determination of the surface tension of water using horizontal jets from elliptical orifices in bell-shaped and uniform-channel tubes. Improved techniques have been developed for measuring the wave parameters, the flow rate and for extending the range of investigations to include the initial 80–90 msec of jet surface age. The surface tension values, calculated using the Bohr equation from measurements on successive waves of the water jets, were dependent on the characteristics of the orifice, its position, the flow rate and the wave serial number, but were within ±2 mN/m of the equilibrium value if the initial wave values were disregarded. An extension of the Bohr equation developed for vertical jets was found to be invalid for horizontal jets. Calculated surface tension versus surface age relationships for surfactant solutions also varied with the experimental conditions, but by fixing the position of the orifice tube, and standardizing with water, a relative method was developed for determining dynamic tensions that were independent of the tube used and of the flow rate. The validity of the method was illustrated by results obtained with two surfactant solutions using seven tubes (bell-shaped and uniform-channel) over an age range from 0.6 to 75 msec. The surface tensions of deionized water samples have been determined by the relative method and compared with those obtained by a static method. The true surface age along the jet surface is concluded to be close to the value derived from the mean axial velocity. Evidence is given indicating that, within the millisecond age range, water does not have a dynamic tension above the equilibrium value.