Simultaneous differential pulse-polarographic determination of CS2 and COS gases and its application in the analysis of dithiocarbamate fungicide residues in foods

The differential pulse-polarographic (DPP) determination of both CS₂ and COS gases, after their absorption in a methanolic piperidine reagent and the subsequent application of this technique to the residue analysis of dithiocarbamate fungicides is described. Rectilinear calibration curves for both CS₂ and COS in the respective regions of 1.5–9.2 and 2.1–12.6 μmol/l were obtained. The DPP method has been successfully applied to the determination of thiram residues on apples after a hot acid hydrolysis of the fruits.     

Simultaneous UV-spectrophotometric determination of CS2 and COS using the piperidine, pyrrolidine, ethylenediamine or morpholine reagent

Summary The success of a spectrophotometric method for the determination of dithiocarbamate or tetramethylthiuram disulphide (thiram) fungicide residues based on the quantification of the evolved CS₂ after an acid hydrolysis of the fungicide depends on the sensitivity and selectivity of the CS₂ absorbing reagent. In the present study piperidine, pyrrolidine, ethylenediamine and morpholine and their corresponding optimum reaction conditions with CS₂ and COS were spectrophotometrically investigated for their suitability as CS₂ and COS absorbing reagents. The CS₂-amine and COS-amine adducts, formed after the absorption of the CS₂ and COS gases in an alcoholic amine, exhibit different UV-absorption spectra which facilitated the quantification of both CS₂ and COS. The sensitivity of the amines to CS₂ and COS and the stability of the CS₂-amine and COS-amine adducts were found to be dependent on the reaction time between the CS₂ and COS with the amine, the concentration and the temperature of the alcoholic amine reagent. Under optimized conditions, ethylenediamine, pyrrolidine and morpholine proved to be equally sensitive to both CS₂ and COS just as the previously reported piperidine. Furthermore, the sensitivity of piperidine to COS was improved. The sensitivity optimized amine reagents, dissolved in methanol instead of ethanol and with detection limits for both CS₂ and COS down to 0.3 g/ml, should provide new and cheaper means in the residue analysis of dithiocarbamate and tetramethylthiuram disulphide (thiram) fungicides based on the evolved CS₂ and COS after an acid hydrolysis.     

Al_(2)O_(3)-Zn-K催化水解COS和CS_(2)的研究北大核心CSCD

以活性氧化铝为载体,浸渍负载Zn、K活性组分,制备优选Al_(2)O_(3)-Zn-K催化剂.考察了反应工艺条件对COS、CS_(2)脱除精度的影响,并对失活的催化剂进行表征,分析催化剂的失活原因.结果表明,负载Zn、K活性组分后,催化剂的弱碱性中心显著提高,负载量为4%时催化剂具有最优的水解活性.在180℃催化水解过程中,工艺条件对CS_(2)脱除精度的影响较COS更为明显.无氧条件下,反应过程中生成的硫酸盐和表面活性物质发生迁移导致催化剂碱性中心减少是催化剂失活的主要原因.     

Steady state activity of acidic, basic and amphoteric oxides in the CO2+CS2=2COS reaction

Under steady state conditions also La₂O₃ and ThO₂, both having strong ionic character, unfilled d- and f-orbitals and a large metal ion radius proved to be order(s) of magnitude more active than oxides of s, sp and d-metals.     

Initial activity of acidic, basic and amphoteric oxides in the reaction of CO2 with CS2 to form COS

Among various acidic, basic and amphoteric oxides La₂O₃ and ThO₂, both having strong ionic character and peculiar acid-base properties, exhibited outstanding initial catalytic activity in the CO₂+CS₂=2COS reaction.     

A sensitive spectrophotometric method for the determination of dithiocarbamate fungicide and its application in environmental samples

A sensitive spectrophotometric method based on the evolution of CS₂ and colour development by leuco crystal violet is described for the determination of dithiocarbamate fungicides, e.g. thiram, ziram and zineb. Dithiocarbamate fungicides release CS₂ on acid hydrolysis. This CS₂ is absorbed in ethanolic sodium hydroxide and forms xanthate. The xanthate formed is subsequently treated with potassium iodate and N-chlorosuccinimide, during which free iodine is liberated. Crystal violet dye was formed through selective oxidation of leuco crystal violet by liberated iodine, which has an absorbance maxima at 595 nm. The colour systems obey Beer's law in the range of 0.02–0.20, 0.02–0.24 and 0.04–0.32 ppm for thiram, ziram and zineb respectively. The molar absorptivity of the colour system were found to be 9.6×10⁵, 1.1×10⁶ and 6.8×10⁵±100 l mol⁻¹ cm⁻¹ for thiram, ziram and zineb respectively. The method has been successfully applied to the determination of these dithiocarbamate fungicides in various environmental samples.     

A re-examination of the CS2 laser

Wavelength measurements on an optically pumped CS₂ laser are reported. The lasing lines are assigned to the 00°1 → 10°0 transition.     

Photochemical decomposition of the CS2N3 ion

The pseudo-halide 1, 2, 3, 4-thiatriazol-5-thiolate, in the anion and acid forms, undergoes photochemical decomposition with the formation of sulfur, nitrogen and the thiocyanate anion, with quantum yields (θ₃₁₃) of 0.13 and 0.26 for the acid and anion forms, respectively.     

Strong correlation effects in the ionisation of CS2

The Hell photoelectron spectrum of CS₂ is presented. This spectrum is investigated by two different Green's function calculations. For the outer valence region the origin and assignment of satellite lines of significant intensity is clarified. Strong final state correlation effects are found for the inner valence region showing the so-called breakdown of single-particle picture of ionisation.     

Simultaneous determination of aflatoxins B2 and G2 in peanuts using spectrofluorescence coupled with parallel factor analysis

In the present study a method for the simultaneous determination of aflatoxins B₂ and G₂ in peanuts has been developed. The method uses second order standard addition method and excitation–emission fluorescence data together with parallel factor analysis (PARAFAC). The aflatoxin analysis was based on extraction with methanol–water and carried out using immunoaffinity clean-up. The results of PARAFAC on a set of spiked and naturally contaminated peanuts indicated that the two aflatoxins could be successfully determined. The method was validated and analytical figures of merit were obtained for both analytes. The limits of detection (LOD) were 0.05 and 0.04 μg kg⁻¹ for aflatoxins B₂ and G₂, respectively. The limits of quantification (LOQ) were 0.16 and 0.12 μg kg⁻¹ for aflatoxins B₂ and G₂, respectively. Coupling of spectrofluorimetry with PARAFAC can be considered as an alternative method for quantification of aflatoxins in the presence of unknown interferences obtained through analysis of highly complex matrix of peanuts samples at a reduced cost per analysis.     

Bestimmung von Schwefeldioxid im Ein- und Austrittsgas einer Claus-Ofenanlage nach gas-chromatographischer Trennung von CS2, COS, H2S, CO2 und Inertgas

Ohne Zusammenfassung     

Laser induced aerosol formation in CS2 vapour

We observed the formation of aerosol particles in CS₂ vapour irradiated by 337 nm nitrogen laser light. Various interesting features of the kinetics of the formation process are reported. The chemical nature of the photoreaction products giving rise to the formation of aerosol particles is also discussed.     

OCS formation in the reaction of OH with CS2

A steady-state system involving photolysis of HONO as a source of OH was used to investigate the reaction of OH with CS₂ at 1 atm and 295 K. In the presence of O₂ ( > 40 Torr) a rapid reaction of OH with CS₂ occurs giving OCS. At lower O₂ concentrations, OCS formation ceases. In air the overall rate constant for OH + CS₂ → OCS was (1.7 ± 0.9) × 10^?12 cm³ molecule^?1 s^?1.     

Comparison of the sulfurization of CoMoK/Al2O3 catalyst with H2S and CS2

Only H₂S consumption and H₂O formation was found in the sulfurization of CoMoK/Al₂O₃ water gas shift catalyst with H₂S/H₂, but CO₂ was formed first, then CH₄, H₂O and H₂S appeared in the later part of TPS with CS₂/H₂. Carbon deposition on the catalyst during the sulfurization with CS₂/H₂ caused a lower activity than the catalyst sulfurized with H₂S but could be removed in the run of WGS reaction.

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, CoMoK/Al₂O₃, H₂S/H₂ H₂S H₂O, CS₂/H₂ CO₂ CH₄, H₂O H₂S. CS₂/H₂ H₂S, , .

     

Simultaneous determination of NH3, SO2, NO and NO2 by direct UV-absorption in ambient air

Summary Direct spectroscopic methods are not hampered by wall losses, are highly specific, have a potential for real time detection and offer the possibility to measure several species simultaneously in one experiment. This is demonstrated for the determination of NH₃, NO and SO₂ in ambient air by a differential optical a2bs orption spectroscopy (DOAS) technique in the spectral region 207–221 nm. Detection limits were 1 ng/g or better.     

The forbidden raman (v2, πu) transition in crystalline CS2

Raman spectra associated with the v₂(π_u) bending vibration of CS₂, which is forbidden for an isolated molecule, are presented The spectra are assigned to combination bands with phonons and show well-resolved critical point structure.     

Comments on a modified tutwiler method for the determination of H2S and SO2 in gases

A modified form of the Tutwiler analysis which was proposed a few years ago and has to some extent, been used as a method for controlling the Claus sulphur recovery process, has been examined as to its exactitude for this purpose, viz. for, determining both H₂S and SO₂ in gas mixtures.It has been found suitable for the determination of H₂S alone, and also (with a small modification) of SO₂ alone, but not for both compounds if they occur together.These disadvantages are not possessed by an alternative method of analysis, recently published.     

Entanglement and Energy for Vibrationally Localized States in Molecule CS2

The dynamics of quantum entanglement described by the von Neumann entropy is studied for the localized states of Fermi-resonance coupling vibrations in molecule CS₂, where the interacting energy between the stretching and the bending modes is considered to establish a connection between entanglement and energy. It is shown that entanglement reveals dominant anti-correlation with the interacting energy for the stretch-localized state, while that exhibits dominantly positive correlation for the bend-localized state. The entanglement and the energy for the dislocalized states are discussed as well. Those are useful for molecular quantum computing and quantum information in high dimensional states.