High Efficiency Annular Denuder for Formaldehyde Monitoring

Abstract

A practical and correct methodology for evaluating CH₂O in air without sampling artifact formation is presented. Formaldehyde is collected on an annular denuder coated with bisulfite-triethanolamine. The sorbent layer is extracted with water and the solution analyzed by the chromotropic acid (CTA) procedure. Sorption efficiency and loading capacity have been investigated along with storage stability.

Results of laboratory validation studies have indicated that a small annular denuder was able to sample about 300 μg CH₂O without an appreciable decrease in the initial collection efficiency (99% at 2.5 1 min^?1).

Tests on storage stability before and after exposure have also demonstrated that both oxidation of bisulfite and release of CH₂O did not occur for time periods as long as 1 month.     

Annular diffusion denuder for simultaneous removal of gaseous organic compounds and air oxidants during sampling of carbonaceous aerosols

A specially designed annular diffusion denuder for simultaneous removal of organic gaseous compounds and atmospheric oxidants in carbonaceous aerosol sampling is presented. Various kinds of denuder coatings were compared with respect to the collection efficiency of both organic gaseous compounds and NO₂ and ozone. The optimum sorbent is a mixture of activated charcoal and sulfite on molecular sieve. To ensure high collection efficiency over long-term field operation, two annular diffusion denuders are combined in series. The first half of the first denuder is filled with Na₂SO₃ on molecular sieve (23 cm long layer) while the second half of the first denuder and the whole second denuder are filled with activated charcoal (the total length of the charcoal section is 67 cm).     

Feinreinigung von Radiostrontiumproben mittels Ionen-Chromatographie

Summary An annular denuder system for simultaneous determination of gaseous and particulate pollutants in ambient air was developed. Inorganic acids (HCl, HNO₃) were collected in a NaF-coated denuder, while organic acids (HCOOH, CH₃COOH) were trapped in one coated with KOH. NH₃ was sampled with a H₃PO₄-coated denuder tube. Particulate H₂SO₄ was evaporated at elevated temperature (145°–155°C) and deposited on a NaF-coating together with HCl and HNO₃ originating from thermal decomposition of NH₄Cl and NH₄NO₃. NH₃ resulting from deammoniation of (NH₄)₂SO₄ as well as NH₃ remaining from NH₄Cl and NH₄NO₃ were collected in a H₃PO₄-coated denuder. The practical collection capacity of the tubes ranged from 0.35 to 1.0 mol calculated from an experimentally determined sorption efficiency of at least 90%. The precision, expressed as relative standard deviation, of sampling and analytical procedures was determined from duplicate measurements in ambient air. The reproducibility varied from 9% to 14% for the gaseous components, while that of the particulate compounds ranged from 12% to 23%. Aqueous extracts of the denuder coatings were analysed for ionic components by ion chromatography using conductivity detection. The minimum detectable concentration in air was found to be 1.5 to 14 nmol/m³ for the different compounds calculated for 1.6 m³ sample volume, based on 3-h measurements at a flow of 9 l/min.

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Bestimmung der atmosphärischen Konzentrationen von anorganischen und organischen gasförmigen Säuren, NH₃, teilchenförmigem SO ₄ ^2– , NO ₃ ^2– und Cl^– mit einem Ringspaltrohr-Diffusionsdenudersystem

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On leave from the Institute of Occupational Health, Helsinki, Finland     

Use Of Diffusion Controlled Preconcentration Systems With Chemically Immobilized Coatings For The Determination Of Atmospheric Nitric Acid

Abstract

A new coating procedure for different diffusion controlled preconcentration methods (tubular denuder, annular denuder, diffusion screen) is described for the determination of nitric acid in air. In this study, a silanization reaction is applied to obtain a chemically fixed coating with an end placed functional NH₂-group, which can be used as a sink to collect acidic compounds from air. This coating must be carried out only once and can be used for a long time. The denuders, coated with this procedures, were compared with conventionally coated NaF denuders.     

Syntheses,crystal structures,and magnetic properties of a series of Fe2Ln complexes

A family of phenoxo-bridged heterometallic Schiff base trinuclear complexes, [Fe₂LnL₂(C₃H₇COO)(H₂O)]·CH₃OH·CH₃CN·H₂O (Ln = Sm, 1; Gd, 2; Tb, 3; Dy, 4) is reported. Those complexes were afforded by “one-pot” reaction of a polydentate Schiff base ligand 2-hydroxy-3-methoxy-phenylsalicylaldimine (H₂L) with Fe(NO₃)₃·9H₂O, Ln(NO₃)₃·6H₂O and sodium butyrate (C₃H₇COONa) in a mixture of methanol and acetonitrile in the presence of triethylamine as a base. Single-crystal X-ray diffraction analysis reveals that the structures of the four complexes are isomorphic. In each complex, two anionic [FeL₂]^? units coordinate to the central lanthanide ion as a tetradentate ligand using its four phenoxo oxygens, forming a two-blade propeller-like molecular shape. Magnetic properties of 1–4 were investigated using variable temperature magnetic susceptibility, and weak ferromagnetic exchange between the Fe^III and Ln^III ions has been established for the Gd derivative. The Tb and Dy complexes show no evidence of slow relaxation behavior above 2.0 K.     

C–H···Onitrate synthon assisted molecular assembly of hydrogen bonded Ni(II) and Cu(II) complexes

Two Schiff base metal complexes [Cu–SPETN·NO₃ (1) and Ni–SPETN·NO₃ (2) [SPETN?=?2,2′-[propane,1,3-diylbis(nitrilomethyldyne)pyridyl,phenolate]] with hydrogen bonding groups have been synthesized and characterized by single-crystal X-ray diffraction. In both of the compounds nitrates occupy a crystallographic general position. In 1 the lattice nitrates are on the 2₁ screw axis while in 2 they are at the crystallographic inversion center. C–H···O_nitrate synthons (formed by the nitrate anions and peripheral hydrogen bonding groups of the metal complexes) are non-covalent building blocks in molecular-assembly and packing of the cationic Schiff base metal complexes (M?=?Ni²⁺, Cu²⁺), resulting in 2-D hydrogen bonded networks. The Cu···Cu non-bonding contact in 1 is 3.268?Å while the Ni–Ni bonding distance in 2 is 3.437?Å.     

Simultaneous measurements of formaldehyde and ozone in air by annular denuder-HPLC techniques

Summary A denuder sampling method combined with HPLC analysis for the simultaneous determination of formaldehyde and ozone in ambient air is described. It is based on the reactions of CH₂O and O₃ with 2,4-dinitrophenylhydrazine (DNPH) and 4-allyl-2-methoxyphenol (eugenol)_respectively, both acting as coatings of two annular denuders connected in series. Formaldehyde released from the ozonolysis of eugenol is quantitatively collected on a third downstream DNPH-coated denuder. The two DNPH denuders are then extracted and analyzed as hydrazone derivative by HPLC with UV absorbance detection.The stoichiometric factor of the eugenol-ozone reaction was found to be 2.0±0.1 moles of O₃ per mole of CH₂O. The limits of detection are 0.8gm^–3 CH₂O and 3gm^–3 O₃ for 100l air sampled, corresponding to 1-h sampling at 1.7l min^–1.     

Nitration of Simple Aromatics with NO2 under Air Atmosphere in the Presence of Novel Brønsted Acidic Ionic Liquids

Abstract

Aromatics nitrate with NO₂/air catalyzed by novel Brønsted acidic ionic liquids (ILs) without any volatile chlorinated organic solvent under mild conditions. The ILs employed were caprolactam based, [Caprolactam]X (X^?=pTSO^?, BSO^?, BF₄ ^?, NO₃ ^?), which are of relatively lower cost and lower toxicity than traditional imidazolium‐based ILs. The nitration reactions were carried out at ?15 to ?0°C first, then at room temperature for a longer time with a little excessive NO₂ (ca. 1.4 eqv.) for moderate yield (for toluene). The IL could be reused four times.     

Synthesis,crystal structures and NIR luminescence of sandwich-like tetradentate salophen phenoxo-bridged heterotrinuclear metal complexes

Six phenoxo-bridged tetradentate salophen heterotrinuclear Zn₂Ln complexes, [Ln(ZnL)₂(NO₃)₃(CH₃OH)₂]·CH₃OH·CH₂Cl₂ [Ln?=?Pr (1), Nd (2)] and [Ln(ZnL)₂(NO₃)₃(CH₃OH)]·CH₃OH·CH₂Cl₂ [Ln?=?Eu (3), Ho (4), Er (5), and Yb (6)], have been isolated from reactions of N,N′-bis(salicylidene)-1,2-(phenylene-diamine) with Ln(NO₃)₃6H₂O and Zn(OAc)₂2H₂O. X-ray diffraction analysis reveals that 1–6 are isomorphic with phenoxo-bridged, sandwich-like {Zn₂Ln} core. Near infrared (NIR) luminescence spectra show that 6 exhibits typical emission of Yb³⁺ upon excitation at the ligand-centered absorption band at 357?nm.     

Synthesis,structure, magnetic properties and kinetics of formation of a cluster containing a {Cu3(μ3-OH)} core supported by a triazole-based ligand

The trinuclear copper complex, [Cu₃(μ₃-OH)(CTMB)₃(NO₃)₂(CH₃CN)₂]·5CH₃CN·H₂O (1) {CTMB = cyclohexotriazole-3-(4-methoxybenzamide)}, has been prepared by mixing Cu(NO₃)₂·2.5H₂O and CHMBH {CHMBH = N,N′-cyclohexane-1,2-diylidene-bis(4-methoxybenzoylhydrazide)} in acetonitrile under ambient conditions. Compound 1 was characterized by IR and UV–visible spectroscopies as well as elemental analyses. X-ray crystallography shows that the cluster contains a {Cu₃(μ₃-OH)} core supported by three triazole-based Schiff base ligands. Each Cu is bound to the 2-N of one triazole ring and the 1-N of another. However, the coordination sphere of each Cu is different, one is five-coordinate and the other two are six-coordinate and bridged by a NO₃ group. The six-coordinate sites are different, one has a terminal NO₃ and the other a MeCN ligand. Magnetic measurements revealed the presence of isotropic and antisymmetric exchange between the copper(II) centers. The data were analyzed using the Hamiltonian containing isotropic exchange for an isosceles triangle together with antisymmetric exchange: H = –J₁(S₁S₂ + S₂S₃)?J₂S₁S₃ + G[S₁ × S₂ + S₂ × S₃ + S₃ × S₁]. Compound 1 exhibits strong antiferromagnetic coupling with J₁ = ?180 and J₂ = ?118 cm^?1 and antisymmetric exchange with G_z = 15 cm^?1. Stopped flow spectrophotometric studies show that the formation of 1 occurs in three distinct phases and the kinetics of each phase has been determined.     

Four 3d–4f heteromultinuclear zinc(II)–lanthanide(III) complexes constructed from a distinct hexadentate N2O2-type ligand: syntheses,structures and luminescence properties

Four 3d–4f heteronuclear complexes, [(ZnL)₂La(OAc)₂]·ClO₄·2CHCl₃ (1), [(ZnL)₂La(OAc)₂]·CF₃SO₃·H₂O (2), [ZnNd(L)(Py)(NO₃)₃] (3), and [ZnGd(L)(OAc)(NO₃)₂] (4) (Py = pyridine; H₂L = 6,6′-dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), have been prepared by one-pot reaction of H₂L with zinc(II) acetate, lanthanide(III) ions and Py. Although the heterobinuclear complexes 1–4 are prepared in the same reaction condition, the Py does not coordinate to Zn(II) of 1, 2, and 4. Instead, the bridging μ-acetato ligand is present. The coordination of the Py in 3 leads to smaller distortion of square pyramidal coordination site of Zn(II), the higher coplanarity between the planes of ZnO(phenoxo)₂ and LnO(phenoxo)₂, and the longer Zn?Ln distance compared with 4. The luminescence properties of 1–4 have been discussed. The ligand (L^2?) can sensitize NIR luminescence of Nd(III) ions.     

苯并咪唑基Ir(Ⅲ)配合物的合成、结构和发光行为的调控或转换

合成了2个新的铱配合物[Ir(ppy)(qbiH)]NO_3(1·NO_3)和[Ir(ppy)(qbi)](2)。晶体结构分析表明,配合物1·NO_3和2中的[Ir(ppy)2]+单元分别与苯并咪唑基的中性配体qbiH与阴离子配体qbi-螯合。在溶液以及在固态条件下,2个配合物表现出明显不同的发光行为。1·NO_3和2在CH_2Cl_2溶液中的磷光发射波长分别为581和574 nm。在固态,1·NO_3和2分别发红色(616 nm)与桔色(598 nm)的磷光。有趣的是,1·NO_3和2在Et3N或TFA蒸汽的作用下,表现出红光发射与桔光发射之间的转换,这是因为它们的配体qbiH和qbi-发生了酸碱诱导的结构转换。此外,还讨论了配合物1·NO_3和2的结构与发光行为之间的关系。     

TiO_2光催化失活复活特性与表面NO_3~-浓度的关系

以乙醛作为活性标的,通过人为控制表面附着NO3-浓度,检测TiO2对乙醛的吸附能力和光催化降解能力,得出了TiO2光催化失活复活特性和表面附着NO3-浓度的定量关系。结果表明,表面附着NO3-浓度达到4.24wt%时,光催化降解能力降低50%;表面附着NO3-浓度达到10.50wt%时,TiO2的吸附能力降低50%;通过溢流状态下水洗2h,可除去98%的表面附着NO3-,使TiO2光催化活性复活。     

Polymers to Selectively Remove Oxidizing Anions from Non-Oxidizing Anions and NO3 − and NO2 − and NO2 − From Polluted Waters

Abstract

A copolymer of 1-phenyl-2-diethylaminoethyl-p-aminobenzoate and polyvinyl-benzyl chloride was found to have a greater capacity for NO₃ ^? and NO₂ ^? than a previously reported nitron polymer but did not react as rapidly. The resin is readily regenerated with NH₄OH or NH₄Cl and is not affected by the pH of the water over the range of 4–10.

A copolymer of 1-(4′-nitrophenyl)-2-diethyl aminoethyl-p-nitrobenzoate and polyvinylbenzyl chloride was found to react nearly as fast as the nitron polymer and have a larger capacity for NO₃ ^? and NO₂ ^?.     

Silver(I) complexes with halo-substituted cyanoanilines: synthesis,characterization and antibacterial activity

Four Ag(I) complexes, [Ag(L₁)₂](NO₃) (1), [Ag(L₂)(NO₃)] (2), [Ag(L₃)₃](NO₃) (3), and [Ag(L₄)₂](NO₃) (4), with ligands derived from halo-containing cyanoanilines (L₁ = 4-amino-3fluorobenzonitrile, L₂ = 4-amino-3-chlorobenzonitrile, L₃ = 4-amino-3-bromobenzonitrile, L₄ = 4-amino-2-bromobenzonitrile) were synthesized and characterized by C, H, and N elemental analysis, IR and ¹H NMR spectroscopy and single crystal X-ray diffraction. Complexes 1–4 crystallized in the triclinic space group C2/c, P2(1)/n, P-1 and C2/c, respectively. In 1 and 4, Ag⁺ is four-coordinate with L₁ or L₄ to form 1-D _∞{[Ag(L₁/L₄)₂]⁺} polymeric cations. In 2, Ag⁺ is three-coordinate by two L₂ ligands and one NO₃^? ligand to form a 1-D _∞{[Ag(L₂)(NO₃)]} zigzag chain. In 3, Ag⁺ is four-coordinate by L₃ to form a dinuclear [Ag(L₃)₃]⁺ cation. The NO₃^? is a 4-connector bridging group in 1 and 3 and a 5-connector bridging group in 2 and 4. The intermolecular hydrogen bonds and Ag?O weak interactions play important roles in forming 3-D networks of 1–4. The antibacterial activities for 1–4 were evaluated against Bacillus subtilis, Staphylococcus aureus and Escherichia coli with MTT method. The antibacterial results indicated that 2 showed the best inhibitory activity against the test bacterial strains, and was as potent as chloramphenicol.     

NO2对Cu/SAPO-34分子筛催化剂上NH3选择性催化还原NO性能的影响

主要考察了NO₂对Cu/SAPO-34 分子筛催化剂在整个温度范围内（100-500 ℃）NH₃选择性催化还原（SCR）NO性能的影响. 研究所使用样品为新鲜Cu/SAPO-34 催化剂在750 ℃下水热处理4 h 的稳定期样品.通过X射线衍射（XRD）和扫描电子显微镜（SEM）对样品的结构以及形貌进行表征,采用SCR活性评价、动力学实验以及原位漫反射傅里叶变换红外光谱（in situ-DRIFTS）表征催化剂的性能以及催化剂表面物种的变化. 活性评价实验结果表明,NO₂会抑制催化剂的低温（100-280 ℃）活性,但其存在会提高催化剂的高温（280 ℃以上）活性. 与此同时,随着反应物中NO/NO₂的摩尔比例减少,由于NH₄NO₃物种的分解,副产物（N₂2O）的浓度增大. 动力学结果表明,Cu/SAPO-34 催化剂上快速SCR反应的表观活化能（E_a=64.02 kJ·mol^-1）比标准SCR反应的表观活化能（E_a=48.00 kJ·mol^-1）更大. In situ-DRIFTS实验结果表明NO比NO₂更容易在催化剂表面形成硝酸盐,并且NO₂更容易与吸附在Brønsted 酸性位上的NH₃物种反应生成NH₄NO₃. 低温下,催化剂表面的NH₄NO₃物种会覆盖SCR反应的活性位,造成活性降低,但在高温时,形成的NH₄NO₃物种一部分会被NO还原为N2,而另一部分会直接热分解为N₂O,造成催化剂的选择性降低.     

Evaluation and applications of a gaseous mercuric chloride source

In this study, a diffusion-type device for generating gaseous mercuric chloride (HgCl₂) was systematically evaluated and applied to validate the annular denuder method for sampling gaseous HgCl₂ species in a synthetic gas stream. The results show that it takes at least 48 h for the system to reach a steady-state condition after the diffusion cell reaches the temperature set-point and the carrier gas is activated. The primary Hg species from the source was proven to be HgCl₂. In the temperature range from –5.00 to 11.80 °C, the Hg emission rates from the source vary from 1.8 to 14.2 pg min^–1. It is shown that, under the experimental conditions examined, KCl-coated annular quartz denuders designed for ambient reactive gaseous mercury (RGM) collection could quantitatively collect HgCl₂. It is also demonstrated that the impactors used to remove coarse airborne particulate matter could lead to a loss of up to one third of the HgCl₂ in the gas stream.     

High-capacity NO2 denuder systems operated at various temperatures (298–473?K)

In this study, we investigated several coatings for high-temperature, high-capacity, and high-efficiency denuder-based NO₂ removal, with the scope to face the harsh conditions and requirements of automotive exhaust gas sampling. As first coating, we propose a potassium iodide (KI)/polyethylene glycol coating with a high removal efficiency (ε?>?98?%) for about 2?h and 50?ppm NO₂ at room temperature (298?K). At elevated temperatures (423?K), the initial capacity (100?ppmh) is decreased to 15?ppmh. Furthermore, this is the first proposal of the ionic liquid methyl-butyl-imidazolium iodide ([BMIm⁺][I^?]) as denuder coating material. At room temperature, this ionic liquid exhibits far greater capacity (300?ppmh) and NO₂ removal efficiency (ε?>?99.9?%) than KI. Nevertheless, KI exhibits a slightly (~10?%) higher capacity at elevated temperatures than [BMIm⁺][I^?]. Both coatings presented are suitable for applications requiring selective denuding of NO₂ at temperatures up to 423?K.     

Determination of nitrous acid in air using wet effluent diffusion denuder-FIA technique

A sensitive and fast method for the determination of nitrous acid (HONO) in air is described. The method combines a continuous collection of nitrous acid into a thin film of absorption liquid in a cylindrical wet effluent diffusion denuder (CWEDD) and on-line analysis of collected nitrous acid at the denuder concentrate employing a flow-injection analysis (FIA) where nitrous acid is oxidized into peroxynitrous acid and a chemiluminescent light emitted during the reaction of peroxynitrite with luminol is detected. Various absorption solutions (carbonate, bicarbonate, phosphate) as well as deionized water were compared from point of view of collection efficiency of nitrous acid at the CWEDD and selectivity and sensitivity of nitrous acid determination in air.All tested liquids provide quantitative collection of HONO in the CWEDD at the air flow rate of 1 L min⁻¹. The detection limit of nitrous acid of 15 ppt (v/v) is the same for all tested liquids. Small positive interference of nitrogen dioxide and peroxyacetylnitrate has been found. The lowest interference of NO₂ was found for 1 × 10⁻⁴ M NaHCO₃ (pH 6.4; 0.18%) while for deionized water interference of NO₂ (0.28%) was slightly higher. The lowest interference of peroxyacetylnitrate was found for deionized water (1.46%). No enhanced formation of HONO inside the cylindrical wet effluent diffusion denuder was observed for simultaneous bringing of nitrogen dioxide together with phenol, p-cresol, guaiacol, catechol, o-nitrophenol as well as with n-octane, n-nonane, n-decane, isoprene, α-pinene, β-pinene, camphene, 3-carene, α-phellandrene, S-limonene, benzene, toluene or o-xylene in comparison with formation of HONO only in the presence NO₂.Deionized water was chosen as the optimum absorption liquid for the sampling of atmospheric nitrous acid at the CWEDD as well as for FIA chemiluminescent detection. The time resolution is 70 s and the response time is 164 s. The calibration curve is linear over 4 orders of magnitude (0.045-450 ppb HONO). The CWEDD-FIA technique has been applied to the measurement of nitrous acid in urban air.