Mixed Cellulose Ester Membrane Filters Research Articles

Microbial communities in aerosol generated from cyanobacterial bloom-affected freshwater bodies: an exploratory study in Nakdong River, South Korea.

Toxic blooms of cyanobacteria, which can produce cyanotoxins, are prevalent in freshwater, especially in South Korea. Exposure to cyanotoxins via ingestion, inhalation, and dermal contact may cause severe diseases. Particularly, toxic cyanobacteria and their cyanotoxins can be aerosolized by a bubble-bursting process associated with a wind-driven wave mechanism. A fundamental question remains regarding the aerosolization of toxic cyanobacteria and cyanotoxins emitted from freshwater bodies during bloom seasons. To evaluate the potential health risk of the aerosolization of toxic cyanobacteria and cyanotoxins, the objectives of this study were as follows: 1) to quantify levels of microcystin in the water and air samples, and 2) to monitor microbial communities, including toxic cyanobacteria in the water and air samples. Water samples were collected from five sites in the Nakdong River, South Korea, from August to September 2022. Air samples were collected using an air pump with a mixed cellulose ester membrane filter. Concentrations of total microcystins were measured using enzyme-linked immunosorbent assay. Shotgun metagenomic sequencing was used to investigate microbial communities, including toxic cyanobacteria. Mean concentrations of microcystins were 960 μg/L ranging from 0.73 to 5,337 μg/L in the water samples and 2.48 ng/m3 ranging from 0.1 to 6.8 ng/m3 in the air samples. In addition, in both the water and air samples, predominant bacteria were Microcystis (PCC7914), which has a microcystin-producing gene, and Cyanobium. Particularly, abundance of Microcystis (PCC7914) comprised more than 1.5% of all bacteria in the air samples. This study demonstrates microbial communities with genes related with microcystin synthesis, antibiotic resistance gene, and virulence factors in aerosols generated from cyanobacterial bloom-affected freshwater body. In summary, aerosolization of toxic cyanobacteria and cyanotoxins is a critical concern as an emerging exposure route for potential risk to environmental and human health.

Measuring the Concentrations of Asbestos Fibers in Some Crowded Areas of Baghdad in The Summer of 2020

Aims of this research to determine asbestos fibers levels in surrounding air of some crowded sites of Baghdad city were monitored in summer 2020. Collection of samples was conducted by directing air flow to a mixed cellulose ester membrane filter mounted on an open‑faced filter holder using sniffer a low flow sampling pump, samples of air were collected from five studied areas selected in some heavy traffic areas of Baghdad city, (Al-Bayaa and Al-Shurta tunnel, Al-Jadriya, and Al-Meshin commercial complex, control), then analyzed to determine concentrations of asbestos fibers. Counting of asbestos on the filters was carried out through using both scanning electron microscope SEM and an energy dispersive X‑ray system EDS to count and determine asbestos fibers. The results of this research appeared that the levels of asbestos fibers which recorded minimum value in control site was 0.018±0.001 f/ml and maximum value in Al-Gadriya was 0.121±0.006 f/ml. The concentrations of asbestos fibers in all studied areas were more than standards of world health organization WHO for air was 0.0022 f/ml. This may be because the presence of crowded traffic, occurrence of industries near studied areas. Therefore, effective plans like management of traffic, changing of industrial locations, and products substitution replacement can be effective in reduce concentrations of asbestos fibers. Keywords: Asbestos Fibers, SEM, Crowded Areas, Ambient Air, Summer.

Simplified ex-vivo drug evaluation in ocular surface cells: Culture on cellulose filters of cells obtained by impression cytology

Drug development, resource- and time-intensive, extensively employs cell-based assays to assess the efficacy and safety of candidate drugs. The widely used immortalized cell lines, experimentally convenient, have limited predictive value. In contrast, ex-vivo models more faithfully reproduce diseases but are technically challenging to establish. To address this need, we developed a simplified process for ex-vivo cell culture, demonstrating its feasibility in ocular surface cells. Conjunctival cells were harvested by impression cytology and grown on mixed cellulose ester membrane filters (MCFs). Human and rabbit conjunctival cells cultured on MCFs are 100% viable at 24 h, and 43% viable at 72 h. A gene expression study evaluating 84 genes involved in ocular inflammation demonstrated that ex-vivo culturing maintains intact the expression of two thirds of these genes in human cells. That these cells are suitable for the assessment of ocular drugs was demonstrated by studying the effect of phosphosulindac (PS), a small molecule under development for the treatment of dry eye disease, in both human and rabbit conjunctival cells. PS, for example, suppressed the expression of CXCL10, a cytokine participating in the pathogenesis of dry eye disease, in human and in rabbit conjunctival cells cultured ex-vivo by 32% and 70%, respectively. Conjunctival cells cultured ex-vivo can be transfected to evaluate mechanistic questions. We successfully transfected such cells with a plasmid expressing luciferase under the control of an IFN-γ-responsive promoter or its control plasmid. IFN-γ stimulated luciferase expression by 85% in cells with the responsive plasmid but not in controls; PS significantly suppressed this induction by 37% without affecting the control plasmid. These findings demonstrate that human and rabbit conjunctival cells cultured ex-vivo with our method are viable and maintain their biological integrity; respond to biological and pharmacological agents; and are transfectable with informative plasmids. The unique advantage of this method is to potentially accelerate the development of novel drugs for the treatment of ocular surface diseases, and to advance our understanding of ocular surface pathophysiology.

Air Pollution with Asbestos Fibers in Some Heavy Traffic Areas of Baghdad

This research was conducted to measure the levels of asbestos fibers in the air of some dense sites of Baghdad city, which were monitored in autumn 2019. Samples collection was conducted via directing air flow to a mixed cellulose ester membrane filter mounted on an open‑faced filter holder using sniffer with a low flow sampling pump. Air samples were collected from four studied areas selected in some high traffic areas of Baghdad city, two of them were located in Karkh (Al-Bayaa and Al-Shurta tunnel) and two in Rusafa (Al-Jadriya and Al-Meshin complex), then analyzed to determine concentrations of asbestos. Measuring of levels of asbestos fibers on the filters was carried out via using scanning electron microscope SEM together with an energy dispersive X‑ray system (EDS). The results showed that the lowest level was recorded in Al-Jadriya intersection (0.0352 fiber/ml), while the maximum concentration was in Al-Bayaa (0.156 f/ml). Asbestos average concentration in the ambient air of the four studied areas was 0.0718 f/ml, which exceeded the standards of world health organization (WHO) for air which is equal to 0.0022 f/ml. This may be due to the presence of crowded traffic and the occurrence of industries near the city. Therefore, plans such as management of traffic, changing locations of industrial sites, and products substitution can be effective in minimizing the concentrations of airborne fibers.

Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only recently have microplastics in freshwater systems, such as rivers and lakes, been quantified. Microplastic sampling at the surface usually consists of deploying drift nets behind either a stationary or moving boat, which limits the sampling to environments with low levels of suspended sediments and floating or submerged debris. Previous studies that employed drift nets to collect microplastic debris typically used nets with ≥300 µm mesh size, allowing plastic debris (particles and fibers) below this size to pass through the net and elude quantification. The protocol detailed here enables: 1) sample collection in environments with high suspended loads and floating or submerged debris and 2) the capture and quantification of microplastic particles and fibers <300 µm. Water samples were collected using a peristaltic pump in low-density polyethylene (PE) containers to be stored before filtering and analysis in the lab. Filtration was done with a custom-made microplastic filtration device containing detachable union joints that housed nylon mesh sieves and mixed cellulose ester membrane filters. Mesh sieves and membrane filters were examined with a stereomicroscope to quantify and separate microplastic particulates and fibers. These materials were then examined using a micro-attenuated total reflectance Fourier transform infrared spectrometer (micro ATR-FTIR) to determine microplastic polymer type. Recovery was measured by spiking samples using blue PE particulates and green nylon fibers; percent recovery was determined to be 100% for particulates and 92% for fibers. This protocol will guide similar studies on microplastics in high velocity rivers with high concentrations of sediment. With simple modifications to the peristaltic pump and filtration device, users can collect and analyze various sample volumes and particulate sizes.

On-site Determination of Trace Arsenic by Reflection-Absorption Colorimetry of Molybdenum Blue Collected on a Membrane Filter.

An on-site determination method for trace arsenic has been developed by collecting it as molybdenum blue (MB) in the presence of tetradecyldimethylbenzylammonium chloride on a mixed cellulose ester membrane filter and by measuring reflection absorbance (RA) of MB on the filter using a laboratory-made palm-top size reflection-absorbance colorimeter with a red light-emitting diode. The value of RA was proportional to the amount of arsenic up to 0.5 μg with a detection limit of 0.01 μg. The proposed method was successfully applied to soil extract and hot-spring water samples.

Measurement of airborne asbestos levels in high traffic areas of Shiraz, Iran, in winter 2014

Aims: Levels of asbestos fibers in ambient air of dense areas of Shiraz, Iran, were monitored in winter 2014. Materials and Methods: Sampling was carried out by directing air flow to a mixed cellulose ester membrane filter mounted on an open-faced filter holder using a low flow sampling pump. Fiber counting on the filters was conducted using both phase contrast microscopy (PCM) method to determine total fibers and scanning electron microscopy (SEM) method to identify nonasbestos from asbestos fibers. Results: The average concentration of asbestos fibers in the ambient air of the study in different areas of Shiraz were 1.18 ± 0.28 PCM f/L and 13.64 ± 2.87 SEM f/L, in which a maximum level was measured in Valiasr square (1.89 ± 0.54 PCM f/L [20.37 ± 5.55 SEM f/L]), and that of in Moallem square was in minimum (1.05 ± 0.47 PCM f/L [12.24 ± 3.04 SEM f/L]). Conclusions: The averages of asbestos fibers in all sampling points were higher than the WHO suggested standards for ambient air (0.05 PCM f/L, 2.2 SEM f/L). This may be attributed to the frequent occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Therefore, immediate courses of action such as product substitution, traffic smoothing, and industrial sites relocating should be taken to eliminate asbestos fibers emission.

Comparison of a Wipe Method With and Without a Rinse to Recover Wall Losses in Closed Face 37-mm Cassettes used for Sampling Lead Dust Particulates

Closed-face 37-mm polystyrene cassettes are often used for exposure monitoring of metal particulates. Several methods have been proposed to account for the wall loss in air sampling cassettes, including rinsing, wiping, within-cassette dissolution, and an internal capsule fused to the filter that could be digested with the filter. Until internal capsules replace filters, other methods for assessing wall losses may be considered. To determine if rinsing and wiping or wiping alone is adequate to determine wall losses on cassettes, we collected 54 full-shift area air samples at a battery recycling facility. We collected six replicate samples at three locations within the facility for three consecutive days. The wall losses of three replicate cassettes from each day-location were analyzed following a rinse and two consecutive wipes. The wall losses of the other three replicates from each day-location were analyzed following two consecutive wipes only. Mixed-cellulose ester membrane filter, rinse, and wipes were analyzed separately following NIOSH Method 7303. We found an average of 29% (range: 8–54%) recovered lead from the cassette walls for all samples. We also found that rinsing prior to wiping the interior cassette walls did not substantially improve recovery of wall losses compared to wiping alone. A rinse plus one wipe recovered on average 23% (range: 13–33%) of the lead, while one wipe alone recovered on average 21% (range: 16–22%). Similarly, we determined that a second wipe did not provide substantial additional recovery of lead (average: 4%, range: 0.4–19%) compared to the first wipe disregarding the rinse (average: 18%, range: 4–39%). We concluded that when an internal capsule is not used, wall losses of lead dust in air sampling cassettes can be adequately recovered by wiping the internal wall surfaces of the cassette with a single wipe.

Proposal of reference values of microbiological environment monitoring in foodservice establishments

To propose a new reference of microbiological environment monitoring in foodservice establishments. The present work shows the determination and evaluation of the microbiological contamination generated in a foodservice establishment Method: It is based on surface sampling (microbial build-up) using mixed cellulose ester membrane filters and on air sampling (hourly microbial adhesion) using Petri dishes. Limits of contamination are established before and during the food elaboration, by means of the microbiological analysis of the environment, surfaces and equipment systems, until reliable limits and levels of acceptance are established of each selected point. Finally, a program of environmental microbiological monitoring was established including the evaluation of all parameters that compose and are implicit in the area, thus assuring and supporting its continuity with the documentation and registers developed for a safety area. Samples for microbiological examination were collected over a period of one moth on ten different days, at two different times. Twelve selected points having previously been identified as hazardous were monitored. Furthermore, foods though to be of high risk were periodically collected for microbiological analysis. The possibility to use of an ample range of selective media, well over the limited number used in this study, allows the analysis of many single microbial species.

Occupational Exposure to Manganese‐containing Welding Fumes and Pulmonary Function Indices among Natural Gas Transmission Pipeline Welders

The objectives of this study were to evaluate manganese (Mn)-containing welding fumes' exposure, assess urinary Mn as a biomarker for Mn exposure and investigate the correlation of Mn in air, total fumes and urinary Mn with pulmonary function indices in 118 welders and 37 unexposed controls from two regions in Iran, Assaluyeh and Borujen. Air samples were collected on mixed cellulose ester membrane filters in personal air samplers and then analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) (NIOSH Method 7300). For all participants, urine samples were collected during the entire work shift, and Mn in urine was determined by graphite furnace atomic absorption spectroscopy according to NIOSH Method 8310. Spirometric measurements were also done for participants. The maximum exposures to airborne Mn and total fumes were 0.304 ± 0.256 mg/m(3) and 21.52 ± 9.40 mg/m(3), respectively. The urine Mn levels in the various groups ranged between 0.77 to 7.58 μg/l. The correlation between airborne Mn and urinary Mn was significant for total whole participants. Some values of spirometric indices were statistically lower in welders rather than controls. Our results indicate that many welders have been exposed to higher concentrations of Mn-containing welding fumes. Urinary Mn can be used as a biomarker for Mn exposure. There were weak inverse correlations between Mn-containing welding fumes and pulmonary function indices, and the inverse correlation between urinary Mn with forced vital capacities (FVC) and forced expiratory volume in 1 s (FEV1) was significant.

Effects of Voltage and Wire Feed Speed on Weld Fume Characteristics

Welding generates high concentrations of ultrafine particles, which research suggests may be more toxic than larger particles. Fume characteristics were measured in a controlled apparatus as a function of voltage level and wire feed speed. Particles were sampled close to the welding process on mixed cellulose ester membrane filters and analyzed for iron, manganese, and total particulate matter at an accredited industrial hygiene laboratory. An ultrafine condensation particle counter measured the particle number concentration, and an optical particle counter measured the particle size distribution. Submicrometer particle number concentrations and iron, manganese, and total particle mass concentrations all depended on voltage levels but not on wire feed speed at a constant voltage. Ultrafine particle concentrations were more than three times greater at 23.5 V than at 16 V. Particles 0.5–0.7 μ m in diameter counted by the optical particle counter increased from 9800 particles/cm 3 at 16 V to 82,800 particles/cm 3 at 23.5 V. Manganese concentration was 1.7 mg/m 3 at 16 V vs. 6.4 mg/m 3 at 23.5 V. The data suggest that welders should use lower voltage levels whenever possible.

Evaluation of two portable lead-monitoring methods at mining sites

Two methods for measuring airborne lead using field-portable instruments have been developed by the National Institute for Occupational Safety and Health (NIOSH): Method 7702 uses X-ray fluorescence (XRF), and Method 7701 employs ultrasonic extraction (UE) followed by anodic stripping voltammetry (ASV). The two portable methods were evaluated at mining sites. Area air samples were collected throughout two mills where ore from nearby mines was processed; the primary constituent of the ore was lead sulfide (galena). The air samples were collected on 37 mm mixed cellulose ester membrane filters housed within plastic filter cassettes. At the end of the work shift, the cassettes were collected and taken to a room off-site for analysis by the two portable methods. The filter samples were first analyzed by XRF and then by UE/ASV. Calibration was verified on both instruments according to standard procedures. The samples were then sent for confirmatory analysis via flame atomic absorption spectrometry (FAAS) according to NIOSH Method 7082. Pairwise comparisons between the methods using the paired t-test showed no statistically significant differences between ASV and FAAS ( P>0.05); however, the comparison between XRF and FAAS was statistically significant ( P<0.05). The elevated lead concentrations reported by XRF relative to FAAS were likely the result of the ability of XRF to report total lead, including lead silicates. This form of lead is not liberated in the digestion process prior to FAAS analysis, and is therefore not detected by this method. Despite this discrepancy, lead concentrations measured by both portable technologies were found to be highly correlated with the laboratory method ( R 2>0.96), suggesting that they are suitable as screening methods for airborne lead at mining sites.

Spectrophotometric determination of trace ionic and non-ionic surfactants based on a collection on a membrane filter as the ion associate of the surfactant with Erythrosine B

The spectrophotometric method for the determination of trace surfactants with Erythrosine B (EB) based on the aqueous reaction and the collection on a membrane filter by filtration was studied. Cationic surfactants (CS +), such as a quaternary ammonium ion, and polyoxyethylene non-ionic surfactants (NS) in the presence of potassium ion, containing a long-chain alkyl group associate with EB buffered at pH 5.5. CS + associates with anionic surfactants (AS −). For the determination of CS +, four methods were employed: the collection of the ion associate of CS + with EB on a mixed cellulose ester (MCE) or PTFE membrane filter, the collection of the ion associate of CS + with AS − on a PTFE membrane filter followed by the ion exchange of AS − with EB, and the first collection of CS + followed by the second collection of EB on a PTFE membrane filter. For the determination of AS −, the collection of the ion associate of AS − with CS + on a PTFE membrane filter followed by the ion exchange of AS − with EB was done. For the determination of NS, the ion associate of NS with EB was collected on a MCE membrane filter. The MCE membrane filter with the analyte was dissolved in methyl cellosolve. The analyte on the PTFE membrane filter was eluted with ethanol. The CS + up to 5×10 −7 M can be determined by the absorbance at 542 nm of the methyl cellosolve solution or the absorbance at 535 nm of the ethanol solution. The AS − up to 5×10 −7 M can be determined by the absorbance at 536 nm of the ethanol solution. The NS up to 2.53×10 −6 M can be determined by the absorbance at 537 nm of the methyl cellosolve solution. This is the sensitive method for the determination of 10 −8 to 10 −7 M order of ionic surfactants and 10 −7 to 10 −6 M order of NS without toxic organic solvents.

Application of Membrane Filters for Spectrophotometric Determination of Cationic Surfactants in River Water and Sediment

Cationic surfactant (CS+) in urban river water and sediment was extracted and determined spectrophotometrically with 2 membrane filters. The CS+ in the water samples, mostly in the form of an ion associate with the coexisting anionic surfactant (AS), was collected on a polytetrafluoroethylene (PTFE) membrane filter and eluted with methanol. Bromphenol blue (BPB), hydrochloric acid, and water were added to the methanol solution successively, and the mixed solution was filtered through a mixed cellulose ester membrane filter. The CS+-BPB- ion associate, formed by a counter ion exchange, was collected on the filter and dissolved into N,N-dimethylformamide (DMF) together with the mixed cellulose ester membrane filter. After addition of 2 drops of triethanolamine, the absorbance of the DMF solution was measured. The CS+ in sediment samples was extracted with methanol by ultrasonic irradiation; the methanol solution was then passed through a PTFE membrane filter and evaporated to dryness. The CS+ was redissolved in a small amount of methanol. For water samples, recoveries and relative standard deviations for 0.30 microM benzyldimethyl-tetradecylammonium ion, a standard material, were > or =93 and < or =5%, with a detection limit of 0.02 microM. Concentrations of CS+ in sediments were much higher than those in water samples, indicating that CS+ is adsorbed on the surface of the sediment.

Extraction and Separation of Cationic Surfactants from River Sediments: Application to a Spectrophotometric Determination of Cationic Surfactant in an Aquatic Environment Using Membrane Filters

The quantitative extraction of cationic surfactant (CS+) in river sediments was studied. Further, the developed method was applied to the spectrophotometric determination of CS+ in urban river sediment samples by solid-phase extraction with membranes. A mixture of methanol and hydrochloric acid was proposed as an eluent. Dried sediment was digested in the eluent under ultrasonic irradiation. After elution, the eluent was evaporated to almost dryness. The residue was dissolved in a small volume of methanol and diluted to a certain volume with water. The pH of the solution was adjusted to 4-5 to separate iron and some other metals as precipitates of hydroxides. The solution was passed through two-piled membranes: first glass-fiber and then polytetrafluoroethylene (PTFE) membranes. A small volume of methanol was passed through the membranes to elute any CS+ retaining on the membranes. After passing the methanol solution through a cationic exchange resin column, the retained CS+ was eluted with methanol containing a high concentration of sodium chloride. Water, Bromophenol Blue (BPB) and hydrochloric acid were added to the solution. The solution was passed through a mixed cellulose ester membrane filter to retain an ion associate of CS+.BPB-. The retained ion associate was dissolved in a small volume of N,N-dimethylformamide together with the membrane filter, followed by the addition of triethanolamine to make the solution alkaline. The absorbance due to BPB2- was measured at 603 nm against a reagent blank. This method was applied to the determination of CS+ in river water and sediment. A cationic surfactant in sediments at 10(-5) mol kg-1 levels was detected with satisfactory precision. It was found that CS+ was about 500-fold enriched in the sediment from water at the place where domestic wastewater was discharged.

X-ray fluorescence spectrometric determination of sulfur-containing anionic surfactants in water after their enrichment on a membrane filter as an ion-pair complex with a cationic surfactant.

Anionic surfactants containing sulfur in their structure were enriched on a mixed cellulose ester membrane filter (MF) by filtration as an ion-pair complex with a cationic surfactant. After their enrichment, the anionic surfactants were determined by X-ray fluorescence spectrometry of the sulfur enriched on the MF. A linear calibration was obtained over a concentration range from 0.05 to 0.8 mg L(-1) of sodium dodecyl sulfate as a standard material with less than 6% RSD. The detection limit based on 3s for the reagent blank was 2 microg L(-1). This method is very simple, rapid and highly selective for sulfur-containing surfactants, and does not require any organic solvent extraction. This method was applied to the determination of anionic surfactant in some urban river waters where domestic wastewater was discharged. The results were compared with those obtained by conventional solvent extraction-spectrophotometry. The distribution of the analyte complexes within the MF where the ion-pair was retained is also discussed.

Evaluation of a portable X-ray fluorescence instrument for the determination of lead in workplace air samples.

Occupational Safety and Health Administration (OSHA) regulations for worker exposure to lead specify worker protection levels based upon airborne concentrations of lead dust. The rapid, on-site determination of lead in air filter samples using a portable x-ray fluorescence (XRF) instrument with an attachment to hold the filter would expedite the exposure assessment process and facilitate compliance with the OSHA standards. A total of 65 lead in air filter samples were collected at bridge blasting lead-abatement projects using closed-faced, 37-mm cassettes with pre-loaded 0.8 micron pore size mixed cellulose ester membrane filters. The lead loading range of the data set was 0.1-1514.6 micrograms (micrograms) of lead/sample. Samples were initially analyzed with a field portable XRF (NITON 700) using an experimental non-destructive XRF method. Samples were subsequently analyzed using National Institute for Occupational Safety and Health (NIOSH) Method 7105 (Graphite Furnace AA) as a reference analytical method. The paired data were not normally distributed; therefore, the non-parametric Wilcoxon signed rank test was used for statistical analysis. There was no statistically significant difference between data from the field portable XRF method and the NIOSH method (p-value = 0.72). Linear regression of the data resulted in a slope of 0.959, a y-intercept of 5.20 micrograms, and an r2 of 0.985. The XRF limit of detection and limit of quantitation were determined to be 6.2 and 17 micrograms of lead/sample, respectively. The XRF method accuracy was +/- 16.4% (7.1%-27%, 90% confidence interval). The data presented in this study indicate that field-portable XRF can be used for the analysis of lead air filter samples over the range of 17 to 1500 micrograms of lead/sample. The practicing industrial hygienist can use field-portable XRF to produce a rapid, on-site determination of lead exposure that can immediately be communicated to workers and help identify appropriate levels of personal protection. As the method is non-destructive, samples can subsequently be sent to a laboratory for confirmation. Confirmation would be recommended when greater than 16.4 percent accuracy from an analytical method is required. This study provided data of suitable quality for the development of NIOSH Method 7702, "Lead by Field Portable XRF."

Membrane solubilization with tetramethylammonium hydroxide for the preconcentration and electrothermal atomic absorption spectrometric determination of trace amounts of arsenic in water

Solubilization of a mixed cellulose ester membrane filter (MF) with tetramethylammonium hydroxide (TMAH) is proposed for the preconcentration and electrothermal atomic absorption spectrometric (ETAAS) determination of trace amounts of arsenic in water. Arsenic at not more than 0.4 µg in 100 ml of sample solution was retained on the MF by filtration as an ion associate of arsenomolybdate and tetraphenylphosphonium ions.The ion associate was dissolved in a small volume of TMAH together with the MF. After being made up to 2 ml with water, the arsenic in the concentrate was determined by ETAAS in the presence of zirconyl nitrate as a chemical modifier. This method is very simple and rapid. The detection limit, defined as three times the standard deviation of the blank, was 0.04 µg l–1. Inorganic matrix components in river waters, Na+, K+, Ca2+, Mg2+, SO42–, NO3– and silicate at high concentrations did not interfere with the determination. Trace components, phosphate at 0.3 mg l–1, dodecyl sulfate at 14 mg l–1 and aluminium at 5 mg l–1, also did not interfere with the determination. The proposed method was applied to the analysis of river water samples.

Ultrasonic extraction and field-portable anodic stripping voltammetry for the determination of lead in workplace air samples.

An on-site, field-portable analytical method for the determination of lead in workplace air samples, based on the use of ultrasonic extraction and anodic stripping voltammetry (ASV), was evaluated. Workplace air samples were obtained using a standard method involving particulate collection onto mixed cellulose ester membrane filters. Samples were collected at work sites where airborne particulates were generated from the abrasive blasting of lead-containing paint on highway bridges. Ultrasonic extraction (UE) of air filter samples in diluted nitric acid, followed by portable ASV, was used for the determination of lead. Also, performance evaluation samples consisting of reference materials of known lead concentration were subjected to the UE-ASV procedure for lead determination. Confirmatory analyses of the air filters and performance evaluation samples subjected to the UE-ASV lead measurement method were conducted by hotplate digestion in concentrated nitric acid and 30% hydrogen peroxide, followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination of lead. Recoveries of lead from performance evaluation materials (when using the UE-ASV method) were found to be quantitative. The performance of the UE-ASV method for lead in air filters was found to be acceptable, as evaluated by comparison with results from hotplate strong acid digestion followed by ICP-AES analysis. Based on the results of this study, the ultrasonic extraction/portable ASV procedure demonstrates potential for the on-site determination of lead in personal breathing zone and area air samples.

Ultrasonic Extraction and Field-Portable Anodic Stripping Voltammetry for the Determination of Lead in Workplace Air Samples

An on-site, field-portable analytical method for the determination of lead in workplace air samples, based on the use of ultrasonic extraction and anodic stripping voltammetry (ASV), was evaluated. Workplace air samples were obtained using a standard method involving particulate collection onto mixed cellulose ester membrane filters. Samples were collected at work sites where airborne particulates were generated from the abrasive blasting of lead-containing paint on highway bridges. Ultrasonic extraction (UE) of air filter samples in diluted nitric acid, followed by portable ASV, was used for the determination of lead. Also, performance evaluation samples consisting of reference materials of known lead concentration were subjected to the UE-ASV procedure for lead determination. Confirmatory analyses of the air filters and performance evaluation samples subjected to the UE-ASV lead measurement method were conducted by hotplate digestion in concentrated nitric acid and 30% hydrogen peroxide, followed by inductively coupled plasma-atomic emission spectrometric (ICP-AES) determination of lead. Recoveries of lead from performance evaluation materials (when using the UE-ASV method) were found to be quantitative. The performance of the UE-ASV method for lead in air filters was found to be acceptable, as evaluated by comparison with results from hotplate strong acid digestion followed by ICP-AES analysis. Based on the results of this study, the ultrasonic extraction/portable ASV procedure demonstrates potential for the on-site determination of lead in personal breathing zone and area air samples.