Sampling and determination of gas phase divalent mercury in the air using a KCl coated denuder

KCl coated denuders were employed for the measurement of divalent mercury (Hg²⁺) species in the air. Laboratory tests show that gaseous Hg²⁺ can be collected by the denuder with an average efficiency of 98% and elemental Hg will pass through it freely. Hg²⁺ trapped in the denuder can be quantitatively extracted by 1 mol/L HCl and analyzed by the method of SnCl₂ reduction-CVAFS determination. Hg²⁺ concentrations of 0.04–0.15 ng m^–3 corresponding to about 2–9% of the total gaseous mercury in the ambient air were determined at several sampling locations. Received: 24 September 1996 / Revised: 14 January 1997 / Accepted: 18 January 1997     

Improved determination of gaseous divalent mercury in ambient air using KCl coated denuders

An improved method for the determination of gaseous divalent mercury (GDM) in ambient air using KCl coated denuders has been developed and tested. GDM collected in the KCl coated denuders can be quantitatively desorbed at 450 degrees C in 10 min. After being complete thermally reduced to Hg0 at 900 degrees C, all mercury released from the denuder is pre-concentrated on the analytical Au trap, and detected by cold vapor atomic fluorescence spectrometry (CVAFS). The absolute detection limit of the method is less than 3 pg. Preliminary data of GDM concentration in ambient air from different sampling stations show that GDM concentrations in the urban air of G?teborg are much higher than in rural air (R?rvik and Sasetta), which indicates the anthropogenic origin of GDM.     

Improved determination of gaseous divalent mercury in ambient air using KCl coated denuders

An improved method for the determination of gaseous divalent mercury (GDM) in ambient air using KCl coated denuders has been developed and tested. GDM collected in the KCl coated denuders can be quantitatively desorbed at 450?°C in 10 min. After being complete thermally reduced to Hg⁰ at 900?°C, all mercury released from the denuder is pre-concentrated on the analytical Au trap, and detected by cold vapor atomic fluorescence spectrometry (CVAFS). The absolute detection limit of the method is less than 3 pg. Preliminary data of GDM concentration in ambient air from different sampling stations show that GDM concentrations in the urban air of Göteborg are much higher than in rural air (Rörvik and Sasetta), which indicates the anthropogenic origin of GDM.     

Performance of a 2,4-DNPH coated annular denuder/HPLC system for formaldehyde monitoring in air

Summary The performance of annular denuders coated with 2,4-dinitrophenylhydrazine for collection of atmospheric HCHO has been evaluated by HPLC/UV analysis of samples coming from laboratory tests and field experiments. A number of parameters, such as collection efficiency at varying air humidity, detection limit, operative capacity and temporal self-consistency have been investigated to optimize the denuder behaviour under different weather conditions and to obtain short-term concentration profiles of HCHO. Deviations between measurements made simultaneously by the DNPH denuder method and differential optical absorption spectrometry (DOAS) have been found to average approximately 30% in the 0–5 ppb HCHO concentration range.     

Determination of nitric acid in ambient air using diffusion denuder tubes

A method has been developed for the determination of gaseous nitric acid in air based on its separation from particulate nitrate aerosol using diffusion denuder tubes. An integrated value of nitric acid concentration in air is obtained. The experimentally derived absorption efficiencies of the diffusion denuder tubes ranged from 87.6 to 96.9%. The standard deviation of the method was calculated as 0.10 mug/m(3) for nitric acid concentrations in the range 0.54-1.72 mug/m(3). A correction procedure, using two diffusion denuders in series, should be applied if measurements are made in the presence of high levels of nitrogen oxides.     

The determination of hydrogen chloride in ambient air with diffusion/denuder tubes

A manual method for the determination of hydrogen chloride in air, based on diffusion/denuder tube separation from particulate chloride aerosol is described. When air is drawn through a tube coated with a selective absorbent (sodium fluoride), separation is achieved because gaseous hydrogen chloride diffuses much more rapidly to the tube walls than particulate chloride aerosol, which passes through virtually unabsorbed. After the sampling period (the length of which depends on the concentration of gaseous hydrogen chloride expected), the sorbed hydrogen chloride is washed from the tube and measured with a highly sensitive chloride ion-selective electrode with a mercury (I) chloride membrane. The method is examined theoretically and experimentally. The experimentally derived absorption efficiencies of the diffusion/denuder tubes were > 90% and the standard deviation of the method was 0.023 μg m^?3 for hydrogen chloride concentrations of 0.16–0.55 μg m^?3. Interference from particulate chloride salts was negligible; this was confirmed by tests with artificially generated aerosol particles from an aerosol generator. The diffusion/denuder tubes have high capacity; level as high as 330 μg m^?3 hydrogen chloride can be sampled for 60 min without affecting performance. A detection limit of (50/t) μg m^?3 can be achieved, where t is the sampling rime (min); e.g., 1μg m^?3 hydrogen chloride can be detected with a sampling period of 50 min.     

Development and laboratory investigation of a denuder sampling system for the determination of carbonyl compounds in stack gas

A method for sampling and detection of low volatile carbonyl concentrations (aldehydes and ketones) in stack gas is proposed. For this purpose, a novel fourfold glass annular-denuder, coated with acidified 2,4-dinitrophenylhydrazine (DNPH) has been developed for the sampling of carbonyl compounds under high temperature and high humidity emission conditions. After sampling, the hydrazones are eluted with acetonitrile and analyzed using RP-HPLC. They are detected by UV-absorbance, with maximum sensitivity obtained between 350 and 380 nm. The sampling efficiency has been investigated for different flow rates, temperatures and relative humidities. The influence of other trace gases (ozone, nitrogen dioxide) on the sampling system was investigated as well.     

DPASV determination of mercury in plant material after a preliminary separation via gas phase and gold trap

A new separation procedure was developed which solves problems of organic interferences in the analysis of mercury traces in environmental matrices using differential pulse anodic stripping voltammetry (DPASV). The separation combines the volatilization of metallic mercury and its absorption on Au-wool, followed by a quantitative anodic dissolution of the mercury into a pure electrolyte solution. This procedure prolongs the analysis time for about 2 min, but offers an interference-free determination of mercury using the standard DPASV method without deterioration of sensitivity and precision. The method was tested with plant reference material olive leaves (BCR No 62).     

Development and laboratory investigation of a denuder sampling system for the determination of carbonyl compounds in stack gas

A method for sampling and detection of low volatile carbonyl concentrations (aldehydes and ketones) in stack gas is proposed. For this purpose, a novel fourfold glass annular-denuder, coated with acidified 2,4-dinitrophenylhydrazine (DNPH) has been developed for the sampling of carbonyl compounds under high temperature and high humidity emission conditions. After sampling, the hydrazones are eluted with acetonitrile and analyzed using RP-HPLC. They are detected by UV-absorbance, with maximum sensitivity obtained between 350 and 380 nm. The sampling efficiency has been investigated for different flow rates, temperatures and relative humidities. The influence of other trace gases (ozone, nitrogen dioxide) on the sampling system was investigated as well. Received: 25 November 1996 / Revised: 19 February 1997 / Accepted: 22 February 1997     

The determination of free ammonia in ambient air with diffusion/denuder tubes

Ammonia is important in atmospheric chemistry because it neutralises acidic species and increases the pH of cloud droplets. Data on the concentration of free ammonia in the atmosphere are sparse because it is difficult to separate free ammonia from particulate ammonium salt aerosol. A manual method for the determination of free ammonia in air is described based on diffusion/denuder tube separation of ammonia from ammonium salt aerosol. When air is drawn through a tube coated with a selective absorbent (here oxalic acid) separation is achieved because the gaseous species diffuses much more rapidly to the tube wall than the particles. After the sampling period (usually 1–4 h, depending on the free ammonia concentration expected), the sorbed ammonia is washed from the tube and measured potentiometrically with an ammonia probe. The method is tested theoretically and experimentally. The absorption efficiency of the coated tubes is ca. 90%. In samples of room air containing 12–28 μg m^?3, the standard deviation is estimated as 1.0 μg m^?3. In field use, ammonia contents were in the range 0.53–5.0 μg m^?3.     

Radio-release determination of mercury vapour in air using radioactive kryptonate of selenium sulfide

Radioactive kryptonate of selenium sulfide is suggested for the determination of the concentration of mercury vapour in air. Selenium sulfide was applied as a coating to paper; upon the exposure to an atmosphere containing mercury vapor, a black color of mercuric sulfide and mercuric selenide developed. The fractional decrease in the radioactivity of the paper (related to the original specific activity) was found to be proportional to the concentration of mercury vapor and time of exposure. Other factors which can be controlled were found to be affecting the determination significantly.     

Wet effluent diffusion denuder technique and the determination of volatile organic compounds in air. II. Monoterpenes

In this work, a comparative study for the fractionation of Trichoderma reesei cellulases on five different hydrophobic interaction chromatography adsorbents (Butyl-Sepharose 4 FF, Phenyl-Sepharose 6 FF, Octyl-Sepharose 4 FF, Epoxy-Sepharose CL-6B and Polypropylene glycol-Sepharose CL-6B) is shown. The influence of the mobile phase composition on the chromatographic behaviour of T. reesei cellulases complex was evaluated using different concentrations of ammonium sulphate in the eluent buffer. A selective separation of beta-glucosidase with two-fold increase in specific activity and good recoveries of cellobiase activity were obtained with Butyl-Sepharose 4 FF and Phenyl-Sepharose 6 FF using 7% (w/v) ammonium sulphate in the eluent buffer. A beta-glucosidase fractionation was also obtained with Epoxy-Sepharose CL-6B, using 13% (w/v) of the salt in the mobile phase.     

Sampling procedure and a radio-indicator study of mercury determination in whole blood by using an AMA 254 atomic absorption spectrometer

A sampling procedure appropriate for the determination of mercury in whole blood was tested by using both inactive controls and a ¹⁹⁷Hg mercury radio-indicator. To exclude the influence of the instrumental device (an AMA 254 single-purpose mercury atomic absorption spectrometer) on the determination of mercury in whole blood, the function of the instrument was checked by using rat blood with metabolised ¹⁹⁷Hg. The measurement procedure was found to be free of errors. However, the study showed that the material used for the sampling vessels is a crucial parameter for obtaining accurate analytical results. The stability of solutions and samples was tested towards polyethylene (PE) and polypropylene (PP) vessels. PE displayed a time-dependent increase in the mercury content both in the samples and in the blood control material. The probable cause of this increase was direct contamination from the material of the vessel and/or diffusion of mercury from the environment through the vessel walls related to a strong complexing affinity of the sample matrix. This assumption was confirmed by supplying the vessels with the complexing agent Na₂EDTA (0.05 mol L^–1). Commercial PP vessels for blood sampling (Sarstedt S-Monovette Metall Analytik) did not give rise to statistically significant variations in mercury content in the samples and blood control material over a 30-day period.     

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L^–1 HCl solution containing 0.02 mol L^–1 KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at –0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about –0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I^– remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10^–10–5×10^–7 mol L^–1. The lowest detectable concentration of Hg²⁺ is 2×10^–10 mol L^–1 at 5 min accumulation. The relative standard deviation (RSD) at 1×10^–8 mol L^–1 Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.     

Anodic stripping determination of mercury in air with a glassy carbon electrode

A technique for stripping determination of mercury traces in air employing a glassy carbon electrode is described. The sample is passed at 2 liters min^?1 for 2 hr through an absorber containing 0.2 M potassium permanganate and 10% $\text{w}\text{v}$ sulfuric acid (1:1). After reduction with hydroxylamine hydrochloride, the determination is carried out in 0.12 M potassium thiocyanate at pH 2.0 ± 0.2 in the presence of 0.2 ppm of cupric ions. Calibration curves were found to be linear in the range 20 ppb-1 ppm Hg(II) in the cell. The accuracy of the method was tested over simulated samples and it was found to be better than 95%; the relative standard deviation was 5% or less. The limit of detection of mercury in air was approximately 10 μg m^?3.     

Kinetics of gas phase hydrochlorination of acetylene over a mercury catalyst

The kinetics of gas phase hydrochlorination of acetylene over a mercury catalyst has been studied. The kinetic equation is in agreement with the experimental data of various authors.

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Lead sulphide as a sorbent for the preconcentration of mercury from air and determination of mercury by atomic emission spectroscopy

Summary Lead sulphide, if prepared by precipitation reaction between lead acetate and sodium sulphide, both in aqueous solution, and adjusted to pH 1, has been shown to be an efficient absorbent for mercury vapour from air. After a portion has been used to collect mercury from a measured volume of air, it is packed into a hollow iron electrode and the mercury is determined by emission spectrography with a dc arc and photographic recording of the spectra from samples and standards. The limit of detection is about 0.1 g, and the relative standard deviation 9% at the 1 g level.

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Bleisulfid als Sorbent für die Anreicherung von Quecksilber aus Luft und Bestimmung von Quecksilber mittels Atomemissionsspektrographie

Zusammenfassung Bleisulfid, synthetisiert durch Fällungsreaktion zwischen wäßrigen Lösungen von Bleiacetat und Natriumsulfid (pH 1), erwies sich als sehr wirksames Adsorptionsmittel für Quecksilberdampf aus Luft. Der Kollektor, der eine bestimme Menge Quecksilber aus einem bekannten Volumen absorbiert hat, wird in eine Eisenhohlelektrode eingebracht und das Quecksilber durch Emissions-spektrographie (Gleichstrombogen, photografische Registrierung der Spektren) von Proben und Standards bestimmt. Die Nachweisgrenze liegt bei ungefähr 0,1 g und die relative Standardabweichung beträgt 9% bei 1 g Quecksilber.

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Presented as a poster at Euroanalysis V, Cracow, August 26–31, 1984     

Direct measurement of the mercury content of exhaled air: a new approach for determination of the mercury dose received

A new rapid technique is presented for determination of the dose of mercury inhaled; it is based on direct measurement of the concentration of mercury in exhaled air by use of a Zeeman mercury spectrometer RA-915+. It has been demonstrated experimentally that the dose received during short-term exposure to mercury vapor is determined more reliably by this method rather than by conventional techniques based on measurement of the mercury content in blood or urine.     

Sampling and analysis of volatile organic compounds in air using a dualsorbent trap

Summary A dualsorbent trap containing graphitized carbon blacks was used for the collection of volatile and semi-volatile organic pollutants from the atmosphere of different workplaces and from an above-ground parking lot. The method proved to be sensitive, simple and reliable. Thermal desorption and solvent extraction methods followed by GC-MS analysis were employed.     

Development and complete validation of a method for the determination of dimethyl mercury in air and other media

The rigorous validation of a previously developed research method for the determination of dimethyl mercury ((CH₃)₂Hg) in environmental samples is presented. During atmospheric analysis, (CH₃)₂Hg was trapped on Carbotrap™ and analyzed by thermal desorption, isothermal GC separation, and cold vapor atomic fluorescence spectrometry (CVAFS). Water samples were analyzed after direct purging of 100 mL aliquots onto Carbotrap™, while sediment and tissue samples were digested with 10 mL of 25% KOH in methanol at 60 °C and diluted to 40 mL with methanol. An ambient air-spiking manifold, which allowed simultaneous replicate sampling, was constructed in a room controlled for temperature and humidity. (CH₃)₂Hg was introduced into the feed airflow (0.4 m³ min⁻¹) from a well-calibrated diffusion cell, to obtain a concentration of approximately 5.5 ng m⁻³ as Hg. Samples were collected onto Carbotrap™ columns, and the total volumes quantified by integrating mass flow meters. Trapping efficiency was investigated over a range of sampler flow rates (0.05-0.25 L min⁻¹), volumes (2-200 L), collection temperatures (15-42 °C) and relative humidity levels (10-70%). Method detection limits (MDLs), analytical precision and accuracy were quantified for all media. Carbotrap™ was found to be the best choice as a sampling media, whereas Tenax™ was found to be inadequate due to high breakthrough (>70%). This study verified that the method is sufficiently precise, accurate and robust for field sampling at mercury contaminated sites. No interferences were observed from elevated levels of potential co-contaminants, Hg⁰ (125 ng m⁻³) and H₂S (1.27 ppmv).