Filter Discs Research Articles

Abnormalities in Uridine Homeostatic Regulation and Pyrimidine Nucleotide Metabolism as a Consequence of the Deletion of the Uridine Phosphorylase Gene

We report in the present study the critical role of uridine phosphorylase (UPase) in uridine homeostatic regulation and pyrimidine nucleotide metabolism, employing newly developed UPase-/- mice. Our data demonstrate that the abrogation of UPase activity led to greater than a 6-fold increase in uridine concentrations in plasma, a 5-6-fold increase in lung and gut, and a 2-3-fold increase in liver and kidney, as compared with wild type mice. Urine uridine levels increased 24-fold normal in UPase-/- mice. Uridine half-life and the plasma retention of pharmacological doses of uridine were significantly prolonged. Further, in these UPase-/- mice, abnormal uridine metabolism led to disorders of various nucleotide metabolisms. In the liver, gut, kidney, and lung of UPase-/- mice, total uridine ribonucleotide concentrations increased 2-3 times as compared with control mice. Cytidine ribonucleotides and adenosine and guanosine ribonucleotides also increased, although to a lesser extent, in these organs. Most significant deoxyribonucleotide changes were present in the gut and lung of UPase-/- mice. In these tissues, dTTP concentration increased more than 4-fold normal, and dCTP, dGTP, and dATP concentrations rose 1-2 times normal. In kidney, dTTP concentration increased 2-fold normal, and dCTP and dGTP concentrations rose less than 1-fold normal. In addition, the accumulated uridine in plasma and tissues efficiently reduced 5-fluorouracil host toxicity and altered the anesthetic effect of pentobarbital. These data indicate that UPase is a critical enzyme in the regulation of uridine homeostasis and pyrimidine nucleotide metabolism, and 5-fluorouracil activity.

A simple solid phase assay for the detection of 2,4-D in soil

Contaminated soils are usually characterized using chemical analyses. However, these do not assess the bioavailability of pollutants, a factor which may be important in estimating the risks associated with contamination. Thus there is a need to support chemical analyses with information on biological effects to determine the potential risks a pollutant may pose in the soil. Although bacterial bioreporters have been used to detect the presence of contaminants in soils, in general these studies have been carried out in slurries or soil extracts rather than soil itself. The following study presents the development of a simple solid-phase bioassay for the direct detection of the herbicide 2,4-dichlorophenoxy acetic acid (2,4-D) in soil using Ralstonia eutropha JMP 134-32, a luxCDABE-based 2,4-D whole cell bioreporter. The bioreporter was spotted onto glass microfibre filter discs that allowed its retrieval and analysis after exposure to 2,4-D amended soils. These disc-fixed cells responded in a concentration dependent manner to 2,4-D in solution (0–25 mg/L) and in spiked soil (0–50 mg/kg). The influence of environmental factors on bioavailability was demonstrated in soil with a low moisture content which prevented 2,4-D-induced bioluminescence but which did not affect bioluminescence from already induced cells. This rapid and low cost bioassay provides a proof of concept demonstrating that retrievable disk-fixed cells can be induced in soil, thus providing a measure of solid-phase bioavailability. This method overcomes some of the limitations associated with the inoculation and monitoring of bioreporters directly in soil. Additionally, this simple system should be amenable to use with other bioreporters.

Transcriptional Responses of Escherichia coli to S-Nitrosoglutathione under Defined Chemostat Conditions Reveal Major Changes in Methionine Biosynthesis

Nitric oxide and nitrosating agents exert powerful antimicrobial effects and are central to host defense and signal transduction. Nitric oxide and S-nitrosothiols can be metabolized by bacteria, but only a few enzymes have been shown to be important in responses to such stresses. Glycerol-limited chemostat cultures in defined medium of Escherichia coli MG1655 were used to provide bacteria in defined physiological states before applying nitrosative stress by addition of S-nitrosoglutathione (GSNO). Exposure to 200 microm GSNO for 5 min was sufficient to elicit an adaptive response as judged by the development of NO-insensitive respiration. Transcriptome profiling experiments were used to investigate the transcriptional basis of the observed adaptation to the presence of GSNO. In aerobic cultures, only 17 genes were significantly up-regulated, including genes known to be involved in NO tolerance, particularly hmp (encoding the NO-consuming flavohemoglobin Hmp) and norV (encoding flavorubredoxin). Significantly, none of the up-regulated genes were members of the Fur regulon. Six genes involved in methionine biosynthesis or regulation were significantly up-regulated; metN, metI, and metR were shown to be important for GSNO tolerance, because mutants in these genes exhibited GSNO growth sensitivity. Furthermore, exogenous methionine abrogated the toxicity of GSNO supporting the hypothesis that GSNO nitrosates homocysteine, thereby withdrawing this intermediate from the methionine biosynthetic pathway. Anaerobically, 10 genes showed significant up-regulation, of which norV, hcp, metR, and metB were also up-regulated aerobically. The data presented here reveal new genes important for nitrosative stress tolerance and demonstrate that methionine biosynthesis is a casualty of nitrosative stress.

Silicalite-1 crystallization on glass fiber filter discs

Silicalite-1 was in situ crystallized from clear synthesis solutions onto commercial millipore glass fiber filters. The filters with diameter 2.5 cm were soaked in the precursor mixtures and hydrothermally treated at 80 °C or 150 °C for time up to 150 h. After the synthesis, the filters were treated in an ultrasonic bath for 15 min with a 0.1 M ammonia solution. The disc composites prepared at 80 °C swelled during synthesis, were easy to disintegrate upon subsequent manipulations and wrinkled when dried. The calcined materials were brittle with a porcelain-like appearance. The filters synthesized at 150 °C, both as synthesized and calcined, seemed identical in shape and mechanical characteristics to the initial glass fiber filters. Prolongation of the treatment at 150 °C up to 100 h led to densified fiber discs according to the SEM study but without visual changes in their mechanical strength. The difference in crystallization at the two different temperatures was attributed to the slower nucleation process at 80 °C, which resulted in greater dissolution of the fiber units and a certain inhibition of the crystallization process caused by the changed chemical environment at the fiber–synthesis solution interface. The silicalite-1/filter composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), chemical analysis and N 2 adsorption measurements.

GC/MSによる室内環境中の防蟻剤の一斉分析

We have established a method for simultaneously analyzing termiticides (13 kinds) in indoor air based on collection by combination of quartz filter and C18 Empore extraction disks, and measurement using gas chromatography mass spectrometry (GC/MS). The lower limit of determination for each substance was 0.02 microg/m3 when 2 m3 of air was sampled. The recovery was 66-100%, and the relative standard deviation was 3.7-14.2%. In experiments using a model box with commercial termiticides, we verified that emissions of bis (2, 3, 3, 3-tetrachloropropyl) ether (S421) increased with a rise in temperature from 10 degrees C to 20 degrees C to 40 degrees C, whereas almost no etofenprox was released into the air regardless of temperature. In addition, decanal, nonanal and alkanes (C13 and C14), which are major components of termiticides, were detected in relatively high concentrations. In the present study, regardless of low vapor pressure of the termiticides, several compounds were detected with the model box experiment. The conclusion that can be drawn is that it is necessary to survey the indoor environmental pollution.

Recent Developments in the Analysis of Techetium-99

In recent years the use of extraction chromatography has grown significantly in methodologies for technetium-99 measurement. An aliphatic quaternary amine, impregnated on a polymeric support, trade named TEVA Resin has become a standard in separating and pre-concentrating pertechnetate prior to technetium-99 measurement by liquid scintillation or ICP-MS. TEVA Resin has a very high affinity for pertechnetate anion from low acid and even basic solutions. Figure 1 shows the uptake of TcO4 as a function of nitric acid and HCl concentration. It can be seen that the TcO4 uptake increases with decreasing acid concentration, while all the actinide elements show declining retention. This behavior indicates that the TEVA Resin can be used to separate pertechnetate anion from a wide variety of potentially interfering radionuclides. The k’ values in the range of 10–10 show that the resin can be used to pre-concentrate pertechnetate from very large volume samples (e.g. up to 4 liters of water.) The technique has been applied to a variety of matrices including water, soil, urine and waste samples. It has also been applied to process control samples in nuclear fuel reprocessing and waste treatment applications. TEVA Resin has been used in several formats: slurry-packed columns for gravity flow use, dry packed cartridges for us in vacuum manifold systems, and glass fiber filter discs to process very large liquid samples with fast flow rate (~100 mL/min.) As this methodology has been applied to broader and broader sample types, several challenging matrix interferences have been encountered that have made accurate measurements difficult. One example of a matrix challenge is the effect of high levels of Th-234 present in natural uranium samples on the quantitation of Tc-99 in the sample. In this case, the beta emissions from the interfering isotope are measured in the Tc99 window of the LSC. This can lead to a bias in the measurement of Tc-99.

Antitermitic Quinones from Diospyros sylvatica

AbstractFor Abstract see ChemInform Abstract in Full Text.

Biocontrol of Rhizoctonia Damping‐off of Tomato by Bacillus subtilis Combined with Burkholderia cepacia

Abstract Bacillus subtilis strain RB14‐C and Burkholderia cepacia strain BY were used in combination to control damping‐off of tomato plants caused by Rhizoctonia solani. Microcosm tests showed complete inhibition of R. solani growth on filter disks buried in soil added with the mixture of both bacteria. Single BY inhibited the fungus, but not completely, and RB14‐C had only slight inhibitory effect on pathogen growth. The efficacy of this combining treatment was checked in pot experiments, where bacteria were applied to the soil in several combinations: RB14‐C and BY together 4 days before seed planting, RB14‐C 4 days and BY 2 days before seed planting, RB14‐C 4 days and BY immediately before seeds. The effect of these treatments on population of R. solani in soil and infection of plants was compared with the activity of single application of each agent. All bacterial treatments significantly decreased damping‐off of tomato plants. The best control was obtained when BY was added 2 days after RB14‐C. In this treatment plant protection was significantly higher than that obtained in other combined applications and obtained by single strains, except BY added to the soil 4 days before seed planting. The lowest suppression indicated BY introduced to the soil before seed planting. RB14‐C only slightly decreased number of R. solani in the soil. In contrast, BY drastically reduced population of the pathogen. However, there was not a clear relation between decrease of pathogen density in soil and the rate of plant infection. The results show that combination of B. subtilis RB14‐C with B. cepacia BY can lead to greater damping‐off suppression than biocontrol exhibited by these strains used separately, but the effect of combining bacterial agents was clearly related to the order in which both agents were introduced.

Methylene-bridged carbosilanes and polycarbosilanes as precursors to silicon carbide—from ceramic composites to SiC nanomaterials

Polymeric and oligomeric carbosilanes having Si atoms linked by methylene ( CH 2 ) groups were used to prepare nano-sized tubules and bamboo-like SiC structures by both CVD and liquid precursor infiltration and pyrolysis inside of nanoporous alumina filter disks, followed by dissolution of the alumina template in HF (aq). These initially amorphous SiC structures were characterized by SEM, EMPA, TEM, and XRD. Typical outer diameters of the SiC nanotubes (NTs) were 200–300 nm with 20–40 nm wall thicknesses and lengths up to the thickness of the original alumina templates, ca. 60 μm. In the case of the CVD-derived SiC NTs, annealing these structures up to 1600 °C in an Ar atmosphere yielded a nanocrystalline β-SiC or β-SiC/C composite in the shape of the original NTs, while in the case of the liquid precursor-derived nanostructures, conversion to a collection of single crystal SiC nanofibers and other small particles was observed.

Novel Mechanism of Inhibition of HIV-1 Reverse Transcriptase by a New Non-nucleoside Analog, KM-1

2-Naphthalenesulfonic acid (4-hydroxy-7-[[[[5-hydroxy-6-[(4 cinnamylphenyl)azo]-7-sulfo-2-naphthalenyl]amino]-carbonyl]amino]-3-[(4-cinnamylphenyl)]azo (KM-1)) is a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) that was designed to bind at an unconventional site on human immunodeficiency virus type 1 reverse transcriptase (RT) (Skillman, A. G., Maurer, K. W., Roe, D. C., Stauber, M. J., Eargle, D., Ewing, T. J., Muscate, A., Davioud-Charvet, E., Medaglia, M. V., Fisher, R. J., Arnold, E., Gao, H. Q., Buckheit, R., Boyer, P. L., Hughes, S. H., Kuntz, I. D., and Kenyon, G. L. (2002) Bioorg. Chem. 30, 443-458). We have investigated the mechanism by which KM-1 inhibits wild-type human immunodeficiency virus type 1 RT by using pre-steady state kinetic methods to examine the effect of KM-1 on the parameters governing the single nucleotide incorporation catalyzed by RT. Analysis of the pre-steady-state burst phase of dATP incorporation showed that KM-1 decreased the amplitude of the reaction as previously shown for other NNRTIs, because of the slow equilibration of the inhibitor with RT. In the ternary enzyme-DNA-KM-1 complex (E-DNA-I), incorporation of the next nucleotide onto the primer is blocked. However, unlike conventional NNRTIs, the inhibitory effect was caused primarily by weakening the DNA binding affinity and displacing DNA from the enzyme. Wild-type RT binds a 25/45-mer DNA duplex with an apparent K(d) of 3 nm, which was increased to 400 nm upon saturation with KM-1. Likewise, the apparent K(d) for KM-1 binding to RT increased at higher DNA concentrations. We therefore conclude that KM-1 represents a new class of inhibitor distinct from nevirapine and related NNRTIs. KM-1 can bind to RT in both the absence and presence of DNA but weakens the affinity for DNA 140-fold so that it favors DNA dissociation. The data suggest that KM-1 distorts RT conformation and misaligns DNA at the active site.

Penetration of Candida biofilms by antifungal agents.

A filter disk assay was used to investigate the penetration of antifungal agents through biofilms containing single and mixed-species biofilms containing Candida. Fluconazole permeated all single-species Candida biofilms more rapidly than flucytosine. The rates of diffusion of either drug through biofilms of three strains of Candida albicans were similar. However, the rates of drug diffusion through biofilms of C. glabrata or C. krusei were faster than those through biofilms of C. parapsilosis or C. tropicalis. In all cases, after 3 to 6 h the drug concentration at the distal edge of the biofilm was very high (many times the MIC). Nevertheless, drug penetration failed to produce complete killing of biofilm cells. These results indicate that poor antifungal penetration is not a major drug resistance mechanism for Candida biofilms. The abilities of flucytosine, fluconazole, amphotericin B, and voriconazole to penetrate mixed-species biofilms containing C. albicans and Staphylococcus epidermidis (a slime-producing wild-type strain, RP62A, and a slime-negative mutant, M7) were also investigated. All four antifungal agents diffused very slowly through these mixed-species biofilms. In most cases, diffusion was slower with biofilms containing S. epidermidis RP62A, but amphotericin B penetrated biofilms containing the M7 mutant more slowly. However, the drug concentrations reaching the distal edges of the biofilms always substantially exceeded the MIC. Thus, although the presence of bacteria and bacterial matrix material undoubtedly retarded the diffusion of the antifungal agents, poor penetration does not account for the drug resistance of Candida biofilm cells, even in these mixed-species biofilms.

Yeast hygromycin sensitivity as a functional assay of cyclic nucleotide gated cation channels

Cyclic nucleotide gated cation channels (CNGCs) are a large (20 genes in Arabidopsis thaliana) family of plant ligand gated (i.e. cyclic nucleotides activate currents) ion channels, however, little is known about their functional properties. One reason for this is the recalcitrance of plant CNGC expression in heterologous systems amenable to patch clamp studies. Here, we show results demonstrating the efficacy of using growth of a K + uptake-deficient yeast ( trk1,2) as a functional assay of CNGCs as inwardly-conducting cell membrane cation (K +) transporters. Prior work demonstrated that trk1,2 is hypersensitive to the antibiotic hygromycin (hyg) and that expression of an inwardly conducting K + transporter suppresses hyg hypersensitivity. We find that increasing [hyg] in solid YPD medium inhibits trk1,2 growth around a filter disk saturated with 3 M K +. Northern analysis indicated that message is transcribed in trk1,2 transformed with the CNGC coding sequences. Confocal imaging of yeast expressing CNGC-fluorescent fusion proteins indicated channel targeting to the cell membrane. Trk1,2 expressing several plant CNGCs grown in the presence of hyg demonstrated (a) greater growth than trk1,2 transformed with empty plasmid, and (b) enhanced growth when cAMP was added to the medium. Alternatively, cAMP inhibited growth of yeast transformed with either the empty plasmid, or the plant K + channel KAT1; this channel is not a CNGC. Growth of trk1,2 was dependent on filter disk [K +]; suggesting that complementation of hyg hypersensitivity due to presence of a functional plant CNGC was dependent on K + movement into the cytosol. We conclude that plant CNGC functional characterization can be facilitated by this assay system.

Antitermitic quinones from Diospyros sylvatica

Six quinones were isolated from the chloroform extract of the roots of Diospyros sylvatica and identified as 2-methyl-anthraquinone, plumbagin, diosindigo, diospyrin, isodiospyrin and microphyllone. The effect of the root extract on the orientation and survival of the subterranean termite, Odontotermes obesus was tested. In addition, four of these quinones were tested on the survival of the subterranean termite. In a direct-choice experiment, exposure to an extract-treated filter disc had a significantly repellent effect over the solvent-treated filter disc. The no-choice experiment revealed the toxic property of the extract as well as the tested quinones and showed high mortality of the O. obesus workers after 48 h on forced exposure. The major termiticidal components identified were plumbagin, isodiospyrin and microphyllone while diospyrin was not toxic to termites at the concentration tested. All the quinones are reported for the first time from D. sylvatica.

Membrane sphingolipid-ergosterol interactions are important determinants of multidrug resistance in Candida albicans.

In this study, we examined the importance of membrane ergosterol and sphingolipids in the drug susceptibilities of Candida albicans. We used three independent methods to test the drug susceptibilities of erg mutant cells, which were defective in ergosterol biosynthesis. While spot and filter disk assays revealed that erg2 and erg16 mutant cells of C. albicans became hypersensitive to almost all of the drugs tested (i.e., 4-nitroquinoline oxide, terbinafine, o-phenanthroline, itraconazole, and ketoconazole), determination of the MIC at which 80% of the cells were inhibited revealed more than fourfold increase in susceptibility to ketoconazole and terbinafine. Treatment of wild-type C. albicans cells with fumonisin B1 resulted in 45% inhibition of sphingolipid biosynthesis and caused cells to become hypersensitive to the above drugs. Although erg mutants displayed enhanced membrane fluidity and passive diffusion, these changes alone were not sufficient to elicit the observed hypersusceptibility phenotype of erg mutants. For example, the induction in vitro of a 12% change in the membrane fluidity of C. albicans cells by a membrane fluidizer, benzyl alcohol, did not affect the drug susceptibilities of Candida cells. Additionally, the surface localization of green fluorescent protein-tagged Cdr1p, a major drug efflux pump protein of C. albicans, revealed that any disruption in ergosterol and sphingolipid interactions also interfered with its proper surface localization and functioning. A 50% reduction in the efflux of the Cdr1p substrate, rhodamine 6G, in erg mutant cells or in cells with a reduced sphingolipid content suggested a strong correlation between these membrane lipid components and this major efflux pump protein. Taken together, the results of our study demonstrate for the first time that there is an interaction between membrane ergosterol and sphingolipids, that a reduction in the content of either of these two components results in a disruption of this interaction, and that this disruption has deleterious effects on the drug susceptibilities of C. albicans cells.

Comparative Study of Antibacterial Activities of the Fresh and Dried Fruit of <i>Capsicum</i> Species

The fresh and dried fruit extracts of Capsicum species were screened for antibacterial activities against Staph. aureus, S. typhi and B. subtilis using two assay methods. The filter disk and agar plate diffusion were the assay methods employed in the study. The results of the study revealed that the extracts obtained from the fresh tissue of C. annuum and C. longum more potently inhibited the growth of Staph. aureus and S. typhi. Furthermore, they were more active against these pathogenic organisms when the filter disc was used as the assay method. However, the extracts obtained from either the dried or fresh tissue of C. frustescens, C. pubescens and C. grossum demonstrated no activities against the tested organisms in the two assay methods used. Key Words: Fresh fruit, Capsicum species, antibacterial spectrum. Nig. J. Health and Biomed. Sciences Vol.2(2) 2003: 90-93

A LC/MS method for the determination of cyanobacteria toxins in water.

The cyanobacteria toxins anatoxin-a, microcystin-LR, microcystin-RR, microcystin-YR, and nodularin were separated in less than 30 min on several 1 mm x 15 cm reversed-phase liquid chromatography (LC) columns, and their electrospray mass spectra were measured using injections of 50 ng or less with a benchtop time-of-flight (TOF) mass spectrometer. New data from this work include the following: (a) the impact of acetic acid concentrations in the methanol-water mobile phase on measured ion abundances; (b) the performance of the electrospray-TOF mass spectrometer as an LC detector; (c) the accuracy and precision of exact m/z measurements after LC separation with a routinely used mass spectrometer resolving power of 5000; and (d) recoveries of the five toxins from reagent water, river waters, and sewage treatment plant effluent samples extracted with C-18 silica particles enmeshed in thin Teflon membrane filter disks. This technique has the potential of providing a relatively simple and reasonable-cost sample preparation and LC/MS method that provides the sensitivity, selectivity, reliability, and information content needed for source and drinking water occurrence and human exposure studies.

Cytokines, matrix metalloproteinases and tissue inhibitor of metalloproteinases‐1 in gingival crevicular fluid from patients with Papillon‐Lefèvre syndrome

The aim of the present study was to compare concentrations of cytokines, matrix metalloproteinases (MMPs) and a metalloproteinase inhibitor (TIMP‐1) in gingival crevicular fluids (GCF) from sites with gingival inflammation in 28 young patients with Papillon‐Lefèvre syndrome (PLS), and in age‐ and gender‐matched controls. Each group consisted of 17 females and 11 males with a mean age of 11.0 years (range 4–22 years). In both groups, anterior upper sites with a clinical diagnosis of gingival inflammation and with pockets ≤3 mm were selected for sampling of GCF, which was carried out with filter disks inserted into the gingival crevice until saturated. The concentrations of cytokines (IL‐1α, IL‐1β, TNF‐α, and IL‐8), matrix metalloproteinases (MMP‐1, MMP‐3, MMP‐8, and MMP‐9), and their tissue inhibitor (TIMP‐1) were analysed using commercial ELISA kits. Significantly higher levels of IL‐1β (P < 0.001) and MMP‐8 (P < 0.05) were disclosed among the PLS patients compared with their controls, while the opposite was found for IL‐8 (P < 0.05) and MMP‐1 (P < 0.001). The individual variations were considerable in both groups. When comparing the expression of cytokines, MMPs, and TIMP‐1 in PLS patients with clinically active and non‐active periodontitis, the non‐active PLS patients showed significantly higher values of IL‐1β than the patients with active periodontal disease (ANOVA, P < 0.01). In conclusion, this study was unable to demonstrate a clear‐cut pathognomonic expression of cytokines or MMPs in patients with PLS, but further studies on cytokine and MMP output are warranted.

Effects of Acidity on Some Physiological Parameters of Laboratory Re-Synthesized Lichen Cladonia cristatella and Its Isolated Mycobiont

Abstract Cellulose-acetate filter disks were found convenient for the cultivation of lichen mycobionts and artificial re-synthesis of lichens, and using this method of culture we tested the effects of acidification on Cladonia cristatella Tuck. Mycobionts subjected to short-term strongly acidic conditions showed decreased formazan production compared to colonies grown at optimal pH 5.0. Disk-supported synthetic lichens grown at pH 3.0 or 5.0 exhibited no significant differences in pigment chemistry or photosynthetic efficiency compared to those at pH 7.0, but all of these parameters changed at pH 1.5. Chlorophyll a integrity significantly decreased under all treatments involving acidified water, with the highest amount of degradation at pH 1.5. At pH 1.5, significantly decreased concentrations of both β-carotene and total carotenoids were observed. A significant decrease in chlorophyll a fluorescence was also shown at pH 1.5.

Simultaneous determination of semivolatile organic compounds in indoor air by gas chromatography–mass spectrometry after solid-phase extraction

A method is described for simultaneous determination of semivolatile organic compounds (SVOCs) in indoor air by gas chromatography–mass spectrometry (GC–MS). The selected 73 SVOCs were collected using combined adsorbents (quartz fiber filter disk and Empore disk) for 24 h at a 5.0 l/min flow rate. The SVOCs collected were extracted with acetone, concentrated, then analyzed by an internal standard method. Forty compounds (19 plasticizers and flame retardants; 19 insecticides; 1 synergist; and 1 fungicide) among the target SVOCs were determined accurately and precisely. The method of detection limits for these compounds were approximately 0.5 ng/m 3 for most of the SVOCs. The collected SVOC samples could be stored for up to 1 month at 4 °C in the refrigerator.

New Arsenic standard Spurs Search for Cost‐Effective Removal Techniques

The new maximum contaminant level for arsenic in drinking water will require many water authorities to add unit operations for arsenic removal. A recent study conducted on groundwater from a small rural city in Colorado investigated removing arsenic by modified coagulation/filtration. On the basis of the results of the study, modified coagulation/filtration was proven to be a practical process for removing arsenic from groundwater. Coagulation by ferric chloride and ferric sulfate produced similar residual arsenic concentrations, although ferric sulfate gave a lower residual turbidity. Adjustment of the pH of the groundwater is likely to be necessary. A ferric ion dose of 6 mg/L and an initial pH of 6.8 gave a residual arsenic concentration of 2 μg/L or less, depending on the pore size of the membrane filter disks. These results are in agreement with previous studies conducted using carefully prepared arsenic solutions. However, the level of arsenic removal from groundwater is highly dependent on the water quality.