A simple diffuse reflectance Fourier transform infrared spectroscopic determination of sulfur dioxide in ambient air using potassium tetrachloromercurate as the absorbing reagent

This paper presents development of a simple, rapid, and precise analytical method for determination of sulfur dioxide in ambient air by a gas to solid-phase conversion method. Sulfur dioxide is determined in the form of sulfite (SO3(2-)) because the absorbing reagent, potassium tetrachloromercurate (TCM), used in this method absorbs sulfur dioxide from the atmosphere in the form of sulfite. Determination of submicrogram levels of sulfur dioxide was based on the selection of a quantitative analytical peak at 495 cm(-1) among the 3 observed vibrational peaks for the dichlorosulfitomercurate complex formed after reaction of sulfur dioxide with TCM and measurement of absorbance using diffuse reflectance Fourier transform infrared spectroscopy. The limits of detection and quantification of the method were found to be 0.09 and 0.4 microg/g SO3(2-), respectively. The precision in terms of standard deviation and relative standard deviation (RSD) at a level of 2 microg SO3(2-)/10.1 g KBr for n = 10 was found to be 0.036 microg SO3(2-) and 1.8%, respectively. The RSD (n = 10) for determination of sulfur dioxide in ambient air was observed to be in the range of 2.7-4.2%. The method proposed is time saving and eliminates the slow and cumbersome steps of pH maintenance of the reaction mixture and color formation of the U.S. Environmental Protection Agency recommended West and Gaeke spectrophotometric method and other methods for quantitative determination of sulfur dioxide.     

A new indirect spectrophotometric procedure for determination of sulphur dioxide

An operationally inexpensive and sensitive spectrophotometric procedure for sulphur dioxide is proposed. The reagent 5,5-dimethyl-1,2,3-cyclohexanetrione-1,2-dioxime-3-thiosemicarbaz one is used to determine trace amounts of sulphur dioxide indirectly by means of the reduction of Fe(III) to Fe(II). The method can determine down to 0.032 microg/ml of sulphur dioxide in the final solution and recoveries are better than 98%. The method can be applied to the determination of atmospheric SO(2) provided that interfering gases such as nitrogen dioxide and hydrogen sulphide are eliminated.     

Development of passive sampler technique for ozone monitoring. Estimation of indoor and outdoor ozone concentration

A passive sampler method has been developed for ozone monitoring. The method involves a badge type passive sampler and is applied to the analysis of ozone exposure as an indoor and outdoor air pollutants. The passive sampler used in this experiment consists of glass fiber filter coated with NaNO(2), Na(2)CO(3) and ethylene glycol, and diffusion filter to remove the wind effects and several spacer effects. The principle component of coating is nitrite ion, which in the presence of ozone is oxidized to nitrate ion on the filter medium and then analyzed by ion chromatography. The results from laboratory and field tests show excellent correlation between the passive method and standard ozone monitoring system, integrated over the same time period. The wind tunnel parameters that were examined show that determination of relative humidity (ranging from 30 to 80%), temperature (ranging from 10 to 20 degrees C) and wind velocity ( ranging from 0.5 to 1.5 m s(-1)) at typical ozone levels (1-40 ppb) do not influence sampler performance. The detection limit attained 0.1 ppb is adequate for the determination of ozone in indoor and outdoor areas. A statistical comparison with a reference method was done in order to demonstrate the validation of the developed method. The accuracy of the proposed method, expressed as a percent relative error, when compared with a standard reference method, is found to be better than about +/-3.5%. The standard errors of the difference was measured in terms of relative standard deviation (R.S.D.) and it was found that the R.S.D. of the passive sampler for O(3) sampler ranged from 2.0 to 6.0%.     

Determination of sulphite in wine by flow injection analysis with indirect electrochemical detection

A flow-injection method has been developed for the determination of total sulphite in wine samples. After hydrolysis of bound sulphite, sulphur dioxide is separated from the matrix by means of an in-line gas diffusion module. For detection indirect amperometry is used, with iodine as oxidizing reagent. The iodine can be generated in-line by merging and mixing iodate and iodide solutions, or alternatively, electrochemically from iodide. With the latter method the best results were obtained. The reproducibility of the peak heights is better than 2%. The linear range of the method can be regulated by adaptation of the current applied to generate the iodine reagent. Due to the low detection limits obtained (0.05 mg L^–1), wine samples can be strongly diluted before injection, which makes the sample pretreatment fast and simple. Good agreement has been found with the results obtained for the total sulphite concentration in different wine samples by titration.     

Validation of the Willems badge diffusive sampler for nitrogen dioxide determinations in occupational environments

The Willems badge, a diffusive sampler for nitrogen dioxide, has previously been validated for ambient air measurements. This paper describes the laboratory and field validation of the Willems badge for personal sampling under working environment conditions. The mean sampling rate in the laboratory tests was 46 ml min(-1), with an RSD of 12%. No statistically significant effects on sampling rate of the sampling time, concentration of NO2 or relative humidity were found. A slightly decreased sampling rate was observed at low wind velocity. This was also confirmed during static sampling, which makes the sampler less appropriate for static sampling indoors. No back diffusion was observed. Storage of the samplers for two weeks before or after exposure did not affect the sampling rate. Our analysis is based on a modified colorimetric method, performed by FIA (flow injection analysis). This technique was compared to ion chromatography analysis. The use of ion chromatography lowered the detection limit from 11 to 2 microg m(-3) for an 8 h sample, and furthermore enabled the detection of other anions. In conclusion, the diffusive sampler was found to perform well for personal measurements in industrial environments.     

Evaluation of a passive air sampler for measuring indoor formaldehyde.

A passive air sampler, using 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, was evaluated for the determination of formaldehyde in indoor environments. Chromatography paper cleaned using a 3% hydrogen peroxide solution was experimentally determined as being the optimum absorption filter for the collection of formaldehyde (0.05 microg cm(-2) formaldehyde). From a linear-regression analysis between the mass of formaldehyde time-collected on a passive air sampler and the formaldehyde concentration measured by an active sampler, the sampling rate of the passive air sampler was 1.52 L h(-1). The sampling rate, determined for the passive air sampler in relation to the temperature (19 - 28 degrees C) and the relative humidity (30 - 90%), were 1.56 +/- 0.04 and 1.58 +/- 0.07 L h(-1), respectively. The relationship between the sampling rate and the air velocity was a linear-regression within the observed range. In the case of exposed samplers, the stability of the collected formaldehyde decreased with increasing storage time (decrease of ca. 25% after 22 days); but with the unexposed samplers the stability of the blank remained relatively unchanged for 7 days (decrease of ca. 37% after 22 days). The detection limits for the passive air sampler with an exposure time of 1 day and 7 days were 10.4 and 1.48 microg m(-3), respectively.     

Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air

Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NO_x-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO₂/m³. The detection limit for the passive sampler is 1 μg NO₂/m³ (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NO_x-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO₂/m³, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%.     

Modification of Amaya-Sugiura passive sampling spectrophotometric method of nitrogen dioxide determination in ambient air

Summary On the example of the previously tested method of nitrogen dioxide determination in ambient air two aspects of wind influence on the badge-type sampler performance were discussed: an appropriate design of the sampler eliminating any open recess over the face of the sampler and so called starvation effect i.e. decrease in the mass of analyte absorbed by the sampler at wind velocities below 20 cm/s. The wind effect on the performance of the passive sampler has been diminished from about 150% to maximum 20%.     

Colorimetric Determination of Sulphur Dioxide and Sulphites in Various Environmental Samples

Rhodamine‐B has been proposed as a simple and sensitive colorimetric reagent for the estimation of sulphur dioxide in air. The air sample containing sulphur dioxide is passed through the absorbing solution of aqueous potassium iodate and N‐chlorosuccinimide to liberate iodine. The liberated iodine bleaches the pinkish red coloured rhodamine‐B dye, which measured at 555 nm. Beer's law was obeyed in the range of 0.5–5.0 μg, of sulphite per 25 mL (0.02–0.2 ppm) equivalent to 0.4–4.0 μg of sulphur dioxide (0.016–0.16 ppm). The molar absorptivity and Sandell's sensitivity were found to be 4.56 × 10⁵ l mol^?1 cm^?1 and 0.00017 μg cm^?2, respectively. The method has been suitably modified and successfully applied to the determination of sulphites in water after liberation of sulphur dioxide in acidic medium.     

Reaction rates between water and the Karl Fischer reagent

Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.     

Determination of hydrogen sulphide and sulphur dioxide in a mixture

A method has been proposed for the determination of hydrogen sulphide and sulphur dioxide in a mixture. The method is based upon the quantitative oxidation of sulphide and sulphite with an excess of radiochloramine-T in alkaline medium /0.1N NaOH/. The released chloride activity is proportional to the total amount of sulphide and sulphite present. Addition of 1% CdSO₄ solution to the mixture of sulphide and sulphite precipitates sulphide, and sulphite in the filtrate determined by the reagent. From the difference in activities, the amount of sulphide can be calculated. This method can be employed for the determination of hydrogen sulphide and sulphur dioxide in air samples.     

Spectrophotometric determination of carbon monoxide with ruthenium(II) octaethylporphyrin

A novel spectrophotometric method for the estimation of carbon monoxide at levels from 2 to 250 ppm is presented. The method is empirical and based on formation of a carbonyl complex of ruthenium(II) octaethylporphyrin and measurement of the difference in absorbance at 393.5 nm between this complex and the porphyrin reagent. Oxygen and nitrogen do not interfere and up to 300 ppm of sulphur dioxide and about 1500 ppm of carbon dioxide can be tolerated in determination of carbon monoxide at the 4 and 10 ppm levels. Hydrogen sulphide interferes and must be removed before the determination. The method has been tested over the range 2-45 ppm of carbon monoxide with 16 synthetic and 2 commercial standard air samples. The average error was +/- 3%. Application to urban-air samples and car-exhaust gases yielded acceptable results. The main disadvantages are the tedious preparation of the initial ruthenium(III)-porphyrin compound and the decomposition of the reagent in the presence of hydrazine.     

In Process Citation

The method for the determination of sulphur in organic compounds (E. Debal and R. Levy, Bull. Soc. Chim. France, 1968, 426; 1971, 3374) by combustion in oxygen at 1310-1320 degrees C and coulometric titration of the sulphur dioxide formed is improved. Silver and 8-hydroxy-quinoline are successfully used to remove halogens (fluorine included) from combustion products. A new glass cell for the acidimetric titration of sulphur dioxide with an automatic coulometer is devised, with a water-jacket for its cathodic and reference compartments. The constant-temperature water-flow makes this determination easy to carry out with no drawbacks, even in varying ambient temperature.     

Fluorimetric determination of nitrogen oxides in the air by a novel red-region fluorescent reagent

A sensitive fluorimetric method for the determination of nitrogen oxides (NO(x): NO+NO(2)) in air is described. Nitrogen dioxide (nitrogen monoxide was previously converted to nitrogen dioxide in oxide tubes) was aspirated through a fritted glass bubble at a flow rate of 500 ml min(-1) for 120 min and fixed as nitrite, using 0.1 N NaOH as a trapping solution with the empirical absorption efficiency 0.74 and the stoichiometric factor 0.5. The method is based on the fluorescence quenching of a red-region fluorescent reagent, tetra-substituted amino aluminum phthalocyanine (TAAlPc), after being diazotized by nitrite. Under optimal conditions the linear range of the calibration curve for nitrite is 1-40 ng ml(-1) (NO(2) 0.24-9.6 ppb, v/v). The detection limit is 0.34 ng ml(-1) for nitrite (NO(2) 0.08 ppb, v/v) and the relative standard deviation for six replicate measurements of 15 ng ml(-1) nitrite is 3.2%. The method has been applied to the determination of nitrogen oxides in the air with satisfactory results. Typical gaseous co-pollutants such as SO(2), H(2)S and HCHO did not interference the determination.     

离子色谱法在城市和背景区域SO2监测中的应用

介绍用无动力采样技术采集样品、离子色谱法分析SO2污染物浓度的监测方法。国际实验室间分析结果的比对实验表明，离子色谱法具有快捷、准确及自动化程度较高等优点。该方法在城市和背景区域环境空气背景值研究，如SO2污染物迁移规律、空气质量预测预报模型验证及远距离传输等方面具有很大的实用价值。     

Laboratory and field measurements of a badge type passive sampler for the determination of ambient sulfur dioxide concentrations

The performance of a badge type passive sampler for the determination of sulfur dioxide is described. The trapping agent is triethanolamine. Analysis is performed by ion chromatography. Thus, the method allows the simultaneous detection of sulfur dioxide and nitrogen dioxide. The sampler was tested in the laboratory and in the field. The intercomparison with independent methods in the field showed very good agreement against two active sampling methods. Regression analyses (the results of the passive sampler always represent the y-axes) gave r² = 0.81 and k = 1.07 ± 0.01 for the intercomparison with an annular denuder technique and r² = 0.92 and k = 0.96 ± 0.01 for the intercomparison with a commercial fluorescence sulfur dioxide analyzer. The average reproducibility in the field was 7% (RSD). The detection limit was 0.18 μg SO₂/m³ for an exposure time of two weeks. Received: 9 February 1998 / Revised: 22 June 1998 / Accepted: 26 June 1998     

Laboratory and field measurements of a badge type passive sampler for the determination of ambient sulfur dioxide concentrations

The performance of a badge type passive sampler for the determination of sulfur dioxide is described. The trapping agent is triethanolamine. Analysis is performed by ion chromatography. Thus, the method allows the simultaneous detection of sulfur dioxide and nitrogen dioxide. The sampler was tested in the laboratory and in the field. The intercomparison with independent methods in the field showed very good agreement against two active sampling methods. Regression analyses (the results of the passive sampler always represent the y-axes) gave r² = 0.81 and k = 1.07 ± 0.01 for the intercomparison with an annular denuder technique and r² = 0.92 and k = 0.96 ± 0.01 for the intercomparison with a commercial fluorescence sulfur dioxide analyzer. The average reproducibility in the field was 7% (RSD). The detection limit was 0.18 μg SO₂/m³ for an exposure time of two weeks. Received: 9 February 1998 / Revised: 22 June 1998 / Accepted: 26 June 1998     

On-line collection/concentration and detection of sulfur dioxide in air by flow-injection spectrophotometry coupled with a chromatomembrane cell.

A simple and rapid procedure for SO2 determination in air was developed by using a flow injection analysis (FIA) system coupled with a 3-hole chromatomembrane cell (CMC). The CMC was applied for the on-line collection/concentration of SO2 from air into a solution of 2 g l(-1) triethanolamine (TEA) solution as an absorbing solution: SO2 was converted to SO3(2-) in the alkaline absorbing solution. The solution containing absorbed SO2 was introduced into the carrier stream of the FIA system. The amount of SO3(2-) in the absorbing solution was measured by spectrophotometry with a mixed reagent of pararosaniline and formaldehyde, and was converted to the concentration of SO2 in the air sample. A calibration graph prepared by using standard sodium sulfite aqueous solutions was adopted for the determination of SO3(2-) in the absorbing solution. The SO2 concentration in indoor air examined was found to be 22.7 +/- 0.2 ppbv using 20 ml of air sample with the air flow rate of 5 ml min(-1), where the relative standard deviation was 1.7%. The detection limit for aqueous solutions and air samples were 6.9 x 10(-8) M and 0.48 ppbv, respectively. The measuring time for one sample was about 10 min when a 20 ml air sample was used. The interferences from common anionic species, formaldehyde and acetaldehyde, were also examined.     

A comparative study using HPLC and packed column supercritical fluid chromatography for the assay of three anti-psychotic dosage forms

A reproducible and selective method was developed for the analysis of three anti-pschycotics, i.e. haloperidol, trifluoperazine and trihexyphenidyl in bulk and dosage forms using packed column supercritical fluid chromatography (SFC). The analytes were resolved by elution with supercritical fluid carbon dioxide doped with 16.67% (v/v) methanol containing 0.8% isopropylamine. Parallel studies were performed by HPLC using ion pairing reagent and a comparison is discussed. The method was successfully used for the assay of three formulations containing a combination of: (1) haloperidol-trihexyphenidyl; (2) haloperidol-trifluoperazine; (3) trifluoperazine-trihexyphenidyl.     

A gas chromatographic analysis for SO2 oxidation

Summary An improved method of determining yields of sulphur trioxide in sulphur dioxide oxidations is reported. The method relies on the absorption of SO₃ from the reaction gases. An all-teflon system incorporating a gas density balance is used. Separation of SO₂ and O₂ is effected on a Porapak PS column at ambient temperature.