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     

Photopolymerization of methyl methacrylate using a morpholine–sulfur dioxide charge-transfer complex as the photoinitiator

Photopolymerization of the vinyl monomer (M) of methyl methacrylate (MMA) was kinetically studied by using near-UV/visible light at 40°C and employing a morpholine (MOR)–sulfur dioxide (SO₂) charge-transfer (C-T) complex as the photoinitiator. The rate of polymerization (R_P) was found to be dependent on the morpholine: sulfur dioxide mole ratio; the 1 : 2 (MOR–SO₂) complex acted as the latent initiator complex C which underwent further complexation with the monomer molecules to give the actual initiating complex I. Using the 1 : 2 (MOR–SO₂) C-T complex as the latent initiator, the observed kinetics may be expressed as R_P [MOR–SO₂]^0.27[M]^1.10. Benzoquinone behaved as a strong inhibitor. Polymers obtained tested positive for the incorporation of a sulphonate-type end group. Polymerization followed a radical mechanism. Kinetic nonideality as revealed by a low initiator exponent and monomer exponent of greater than unity was explained on the basis of a prominent primary radical termination effect. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1973–1979, 1998     

Multifunctional substances — Determination of pKa-values in overlapping ranges using an iteration procedure

Summary In multifunctional substances, pK_a-values from different functional groups may overlap. Therefore, systematically wrong results are obtained, if pK_a-values are used from titration charts without appropriate corrections. The iteration procedure presented in this article starts with the pK_a-values at the half-way neutralisation points. From these preliminary values, new positions in the charts are calculated, from which better approximations of the pK_a-values are obtained. These steps are repeated several times, until the results converge. Cefodizime (HR 221) with three acid/base functional groups was used as model substance. The disodium salt was titrated using three molar equivalents of 0.1 mol/l hydrochloric acid. Using the iteration procedure, three pK_a-values were obtained from the titration chart: 1. The amino-function: pK₁=2.85; 2. the first carboxyl-function: pK₂=3.37; 3. the second carboxyl-function: pK₃=4.18.     

An optical chemical sensor based on functional polymer films for controlling sulfur dioxide in the air of the working area: Acrylonitrile and alkyl methacrylate copolymers with brilliant green styrene sulfonate

The effects of the chemical and phase composition of acrylonitrile and alkyl methacrylate (Alkyl-MA) copolymers with styrene sulfonates (SS) of triphenylmethane dye cations on the gas permeability and sensing properties of their films were studied for developing an optical chemical sensor (OCS) for sulfur dioxide (SO₂) on the basis of functional polymers. Of the three triphenylmethane dyes tested, namely, fuchsine, Crystal Violet, and Brilliant Green (BG), only the last dye was selected for molecular design. It was shown that the copolymer of Decyl-MA with SS—BG with the degree of modification DM = 0.10 is the best material among the studied ones from the viewpoints of sensitivity, response time, and time stability of sensor characteristics. The conditions for fabricating polymer films and the parameters of their functioning in OCSs for SO₂ were optimized. The effect of annealing conditions on the sensitivity of spectra to SO₂ was studied. Working temperature, working wavelength, and the conditions for the regeneration of the initial spectral parameters were optimized. Calibration characteristics of OCSs for the dynamic admittance of SO₂—air mixtures were obtained. The calculated detection limit for SO₂ in an air flow for a sensor with a sensing film fabricated of the decyl-MA—SS—BG copolymer with DM = 0.10 was 0.16 vol %, or 4160 mg/m³. This points to the necessity of searching for more sensitive sensing materials among other classes of functional polymers.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 307–315.Original Russian Text Copyright © 2005 by Soborover, Tverskoi, Tokarev.     

Indirect Spectrophotometric Method for Determination of Sulfur Dioxide

Abstract

An operationally inexpensive and satisfactory analytical procedure for sulfur dioxide is proposed. The reagent 3-methyl-1,2-cyclopentanodione dithiosemicarbazone has been used to determine trace amounts of sulfur dioxide indirectly using the reduction of Fe(III) to Fe(II) principle. In order to find the optimal conditions for SO₂ determination, properties of 3-Me-CPDT-Fe(II) complex such as its composition, stability and free energy change of formation have been determined. The best conditions for the complex formation such as standing time, pH, wavelength and the effect of interfering ions are described. The complex has been used with success in spectrophotometric determination of SO₂. The procedure can determine down to 0.63 μg and recoveries are better than 97.5%. The method is also suitable for determination of sulfur dioxide in the air provided that interfering gases such as H₂S and NO₂ are removed.     

Effect of SO2 on the catalytic activity of SnO2 and CeO2 in methane oxidation

The variation of the catalytic activity of tin and cerium dioxides in the combustion of SO₂-containing methane has been investigated at SO₂ concentrations of 50 to 1000 ppm in the gas stream. The catalytic activity of SnO₂ decreases dramatically upon the introduction of SO₂, but it returns rapidly to its initial level and then remains invariable (95% conversion, operating temperature of 600°C). Cerium dioxide is much less resistant to poisoning with sulfur dioxide: the higher the SO₂ concentration in the gas stream, the larger the decrease in its activity. After sulfur dioxide is cut off, CeO₂ regains its initial activity at 750°C. The behaviors of SnO₂ and CeO₂ are in agreement with the thermal stabilities of the corresponding sulfates and oxosulfates.     

The Protonation and Deprotonation Equilibria of Hypericin Revisited

 The protonation and deprotonation behaviour and the assignment of pK _a values of hypericin are reviewed and discussed. Three experiments (electrospray MS, ¹H NMR, acid–base indicator equilibria) provided additional evidences for the assignment of pK _a values of −5 and −6 to mono- and diprotonation at the carbonyl groups of hypericin, of pK _a = 2 to monodeprotonation at the bay-region, and of pK _a = 11 to dideprotonation at the bay- and peri-regions.     

二氧化硫溶于水和酸性溶液的化学状态研究

采用拉曼光谱技术，对SO₂溶于水和酸性溶液的化学状态进行了研究。测定出SO₂的特征拉曼光谱(1147 cm^-1)，表明SO₂是以SO₂·nH₂O形式存在于水和酸性溶液里。     

The Protonation and Deprotonation Equilibria of Hypericin Revisited

Summary.  The protonation and deprotonation behaviour and the assignment of pK _a values of hypericin are reviewed and discussed. Three experiments (electrospray MS, ¹H NMR, acid–base indicator equilibria) provided additional evidences for the assignment of pK _a values of −5 and −6 to mono- and diprotonation at the carbonyl groups of hypericin, of pK _a = 2 to monodeprotonation at the bay-region, and of pK _a = 11 to dideprotonation at the bay- and peri-regions. Received September 26, 2001. Accepted October 1, 2001     

Nafion-like thin film plasma-polymerized from perfluorobenzene/SO2 mixture

Plasma polymerization of perfluorobenzene/sulfur dioxide (PFB/SO₂) mixture was investigated by elemental analysis, infrared spectroscopy, and XPS. Plasma polymer films like Nafion were obtained from the plasma polymerization of PFB/SO₂ mixture. The plasma polymerization deposited fluoropolymers with sulfur moieties including sulfonate and sulfonic acid groups. The elemental composition, F/C, and S/C atomic ratio of the formed plasma polymers were 0.65–0.67 and 0.24–0.27, respectively, which were independent of the starting mixture composition. The polymers showed cation-exchange ability of which the capacity was 0.49 meq/g polymer, and initiated the polymerization of pyrrole.     

Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration

The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl₄ at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO₄ ^2– without evolving H₂S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO₄, and the remaining Ba²⁺ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur. Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998     

Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration

The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl₄ at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO₄ ^2– without evolving H₂S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO₄, and the remaining Ba²⁺ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur. Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998     

An Optical Chemical Sensor Based on Functional Polymer Films for Controlling Sulfur Dioxide in the Air of the Working Area: Polydimethylsiloxane Copolymers with Ionically Bound Brilliant Green Cations

The search for functional polymers for an optical chemical sensor (OCS) for sulfur dioxide was continued. Copolymers of polyamides, methyl methacrylate (PMMA), and poly(dimethylsiloxanes) (PDMSs) were examined. It was shown that the sensitivity of the spectral parameters of polymers in absorption spectra of their films upon the action of SO₂ in vacuum depends on the chemical and phase composition of polymers. For a sensor with a sensing layer based on PDMSs, linear calibration graphs on logarithmic coordinates were obtained in a wide range of SO₂ concentrations in an air flow (5–6200 mg/m³). It was found that the slope of the calibration graph depends on the thickness of the sensing layer, other conditions being the same. The calculated detection limit is of about 3 mg/m³, which points to the possibility of using the proposed OCS for controlling the air of the working area.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 5, 2005, pp. 507–513.Original Russian Text Copyright © 2005 by Soborover, Tverskoi, Tokarev.     

High-field NMR of ethylene—sulfur dioxide copolymers

Copolymers of ethylene and sulfur dioxide containing 40–60 wt-% sulfur dioxide have been analyzed by using 220 MHz high-resolution NMR, and it has been shown that they contain structures of the form, ? SO₂? (CH₂? CH₂)_n? SO₂? , where n is 1, 2, 3, 4, … The relative numbers of structures with n = 1, 2, 3, or 4 and above can be calculated from the NMR spectra. The fraction of ethylenes in longer blocks and the sulfur dioxide contents of the polymers can also be determined from the NMR data. The NMR results indicate that the distribution of ethylenes among the different structures is not that expected for a random copolymerization of ethylene and sulfur dioxide but that the arrangement of these structures within the copolymer is random.     

Cyanine Polymersomes Inbreathe Gas Signaling Molecule: SO2-Driven Bilayer Tubular Deformation for Transmembrane Traffic Regulation

Fabricating nanoscale assemblies that can respond to gas signaling molecules has emerged as a field of growing interest owing to their unique biomedical applications in gas-guided delivery and gas therapeutics. Yet, among a variety of endogenous gaseous biosignals, exploiting sulfur dioxide (SO₂) as a cue for controllable self-assembly remains elusive, despite its crucial two-sided roles both in physiology and pathology. Here we show a SO₂-responsive polymersome system assembled from a novel class of cyanine-containing block copolymers. By intake of SO₂ gas, the tautomerism of cyanine drives such vesicles to continuously deform, and change into long nanotubes through axial stretching and anisotropic extrusion of the membranes. Unexpectedly, during this order-to-order phase transition, their membranes manifest well SO₂-dose-dependent permselectivity, which allows the cargos of different sizes loaded therein to be selectively transferred across the bilayers. This study would inspire us to better understand and mimic the function of gas signaling molecules in shifting biomembrane shape and managing transmembrane traffic.     

Monitoring of Atmospheric Sulfur Dioxide by Fluorescence Monitoring System

A fluorescence monitoring system was used to measure gaseous sulfur dioxide at Taoyuan Agricultural Farm. A gas-diluting system and gas chromatograph equipped with a sulfur chemiluminescence detector used to audit the accuracy of diluted sulfur dioxide are described. The accuracy was ?8% and ?2%, respectively, for the preparation of 10 and 50 ppb SO₂ standard gas. The pattern of variation of SO₂ concentration at Taoyuan Agricultural Farm is reported. In summer at Taoyuan Agricultural Farm, the concentration of SO₂ varied with a pattern of night concentration (15-20 ppb) greater than that in the afternoon (0–2 ppb). Computer-analyzed wind trajectories in Taiwan for this pattern are reported.     

Simple methods for the estimation of ionization constants of substituted pyridine N-oxides in polar aprotic solvents and water

A direct method for the determination of the pK _a values of acids conjugated to substituted pyridine N-oxides has been proposed which is based on the pH measurement of the solution of the basic salt. It has been experimentally shown that the method is reliable when applied to N-oxides of not too low basicity (pK _a >5). Correlation has been performed between the pK _a values in aqueous and aprotic media solutions which shows the great influence of the solvation effect on the acid-base equilibria. The good correlation between the pK _a values in aqueous and non-aqueous solutions enables the pK _a values in water to be estimated with sufficient accuracy, even in the cases when the experimental limitations make the determination impossible which is shown on the basis of selected examples.     

Acid-Base Properties of the Ground and Excited States of Ruthenium(II) Tris(4′-methyl-2,2′-bipyridine-4-carboxylic Acid)

The acid dissociation constant, pK_a, for the ground and excited states of ruthenium tris(4′-methyl-2,2′-bipyridine-4-carboxylic acid) complex have been measured. The ground state pK_a obtained from the pH titration curve of the complex absorption at 454 nm was 2.5. The lifetimes of the excited-state for deprotonated and protonated ruthenium complexes are 595 and 150 ns, respectively. The excited-state pK_a* is obtained from the emission titration curve at 630 nm and corrected for the excited-state lifetime to be 4.2. The increase of 1.7 pH units in the acid dissociation constant in the excited-state indicates that the ligand is much more basic in the excited-state. This result confirms the MLCT assignment for the lowest electronic transition of [Ru(mbpyCOOH)₃]²⁺.     

The relationship among pKa, pH, and binding constants in the interactions between boronic acids and diols—it is not as simple as it appears

In our continuing efforts into designing boronic acid-based sensors that recognize cell-surface carbohydrates, it has been necessary to examine various factors that affect the binding affinity between a boronic acid moiety and a diol. The current prevailing view is that the strongest boronic acid/diol complexes are generated by a combination of high solution pH and a low boronic acid pK_a. However, there has never been a systematic examination of the relationship among the binding constants, boronic acid pK_a, and the pH of the solution. Herein we report our findings with a series of 25 arylboronic acids with various substituents and their binding affinities with diols. We have found that (1) the relationship between the pK_a of monosubstituted phenylboronic acid and its substituents can be described using a Hammet plot; (2) the optimal pH for binding is not always above the pK_a of the boronic acid, and is affected by the pK_a values of the boronic acid and the diol, and other unknown factors; and (3) the general belief that boronic acids with lower pK_a values show greater binding affinities for diols is not always true.