Specific method for spectrophotometric determination of molybdenum in soil

A new, simple and specific spectrophotometric method for the determination of Mo in the soil extracts is described. Mo(VI) is reduced to Mo(V) with sodium borohydride and allowed to react with SCN^– ions in the presence of cationic and neutral surfactants e.g. CPC and TX-100 in the acidic aqueous solution. The molar absorptivity of the complex in both the aqueous, and toluene solutions is (2.30) × 10⁴ 1mol^–1 cm^–1 at absorption maximum, 460 nm. The extraction-procedure preconcentrated Mo at least 3-folds. the detection limit is 125ng Mo/g soil. The analytical variables of the method have been optimised and composition of the complex is proposed. None of the tested foreign ion interfered in the determination of Mo up to a large amount. An attempt for the removal of Fe-interference in the determination of Mo in soil extract has been described. The method has been found to be satisfactorily applicable for the determination of Mo in hot water leachates and acid digested soil solutions at lower ppm levels.     

Capillary electrophoresis as a method for ozone determination in atmospheres

Capillary electrophoresis (CE) is used to quantify nitrate and nitrite extracted from nitrite-impregnated glass fiber filters (IGFF) that are used to monitor ozone in atmospheres. The amount of nitrate produced from conversion of nitrite in the filters is directly related to the amount of ozone passed over the filter. The limit of detection for ozone using the CE method is 1.17 ppml and the method is linear over two orders of magnitude. The effect of the excess nitrite in the IGFF on the limits of detection is discussed. Results from CE analyses of both active and passive filters are presented. The active filter results are compared to ion chromatographic analyses.     

A new fluorescence method for determination of ozone in ambient air

A new simple method for determination of ozone in ambient air is presented. The reaction employed is based on the known ozonolysis of indigo dye. The indigotrisulfonate molecule contains one carbon–carbon double bond (C═C), which reacts with ozone and generates isatinsulfonates and sulfoanthranilate. The quantitatively formed sulfoanthranilate presents fluorescence (λ_ex 245 nm, λ_em 400 nm). Ozone was collected using two cellulose filters coated with 40 μL of 1.0 × 10^{− 3} mol L^{− 1} of indigotrisulfonate. The analytical response was linear in the range 0–150 ppbv ozone, and a detection limit of 7 ppbv was achieved using a sampling time of 15 min and an optimum sampling air flow rate of 0.4 L min^{− 1}. There was no interference from sulfur dioxide, formaldehyde or nitrogen dioxide. The ozonolysis mechanism and the reaction products are discussed.     

A permeation method for the determination of average concentrations of carbon monoxide in the atmosphere

A simple, inexpensive and reliable method for the determination of average concentrations of carbon monoxide in the atmosphere is described. Silver p-sulfa-moylbenzoic acid is used as the colorimetric reagent in a specially designed permeation device. The calibration graphs are linear up to 80 p.p.m. carbon monoxide, and the limit of detection is 2 p.p.m. for a 24-h exposure. Tests under field conditions are discussed.     

Development and validation of a method for the determination of trace alkylphenols and phthalates in the atmosphere

An analytical method has been developed for the simultaneous extraction and determination of trace tertiary octylphenol (t-OP), technical nonylphenol isomers (NP), nonylphenol monoethoxylate isomers (NP1EO) and seven phthalates in the atmosphere using gas chromatography-mass spectrometry (GC-MS). High volume samples were collected using a high-volume pump equipped with a PUF/XAD-2 column for air and glass fiber filter for particles. The detection limits of the method for alkylphenols (APs) and the phthalates ranged from 0.0006 to 0.034 ng m⁻³ in air. The recoveries of t-OP, NP, NP1EO and the phthalates for the entire procedure were satisfactory (>69%). The method was successfully applied to the determination of the analytes in the atmosphere samples collected over land and the ocean. The concentrations of t-OP, NP, NP1EO showed decline trends from land to the open sea, and the phthalates present over land and the North Sea were comparable. It is suggested that the atmosphere is a significant pathway for the transport of alkylphenols and the phthalates in the environment.     

The photodissociation of vibrationally excited ozone in the upper atmosphere

The photodissociation of vibrationally excited O₃ in the sunlit mesosphere is investigated. Dissociation rate coefficients for specific vibrationally excited states of O₃ are calculated for the conditions of an overhead sun. Possible vibrational enhancements of the O(¹D) and O₂(a¹Δ_g) production rates are assessed. It is shown that such enhancements should make only minor contributions to the daytime production of these species in the mesosphere and lower thermosphere.     

Automized procedures for the determination of ozone and ammonia contents in air by using the chromatomembrane method for gas-liquid extraction

Chromatomembrane cells (CMC) operate as unique manifolds for extraction and preconcentration procedures in computer controlled flow-injection-analysis (FIA). By coupling to an ion chromatograph and to a conductometer, respectively, instrumentation is obtained that allows the pretreatment and the detection of ozone- and ammonia-containing samples after absorption of the gaseous constituents of air inside a chromatomembrane cell. The analysis of air even in the presence of liquid aerosols is discussed.     

Automized procedures for the determination of ozone and ammonia contents in air by using the chromatomembrane method for gas-liquid extraction

Chromatomembrane cells (CMC) operate as unique manifolds for extraction and preconcentration procedures in computer controlled flow-injection-analysis (FIA). By coupling to an ion chromatograph and to a conductometer, respectively, instrumentation is obtained that allows the pretreatment and the detection of ozone- and ammonia-containing samples after absorption of the gaseous constituents of air inside a chromatomembrane cell. The analysis of air even in the presence of liquid aerosols is discussed.     

Cluster mechanism of the atmosphere ozone destruction by bromine ions

Interaction of bromine ions absorbed by water cluster with adsorbed oxygen and ozone molecules has been investigated by the molecular dynamics method. It was shown that the part of O₂ molecules was removed from the system by evaporating Br⁻ ions, while all O₃ molecules and Br ions were kept in the system during 25 ps. The increase the concentration of the Br⁻ ions in the clusters resulted in a reduction of the absorption intensity and emission in IR spectra at the presence of oxygen, whereas the absorption intensity in the appropriate IR spectra of ozone-containing systems increased with the growth of a number of the Br⁻ ions. Raman spectra of oxygen-containing systems were poorly sensitive to the concentration of the Br⁻ ions but the absorption intensity of Raman spectra for systems with ozone considerably decreased with the growth of a number of bromine ions.     

Development of a gas chromatography-mass spectrometry method for the determination of pesticides in gaseous and particulate phases in the atmosphere

A reliable multi-residue method for determining gaseous and particulate phase pesticides in atmospheric samples has been developed. This method, based on full scan gas chromatography–mass spectrometry (GC–MS), allowed the proper determination of sixteen relevant pesticides, in a wide range of concentrations and without the influence of interferences. The pesticides were benfluralin, bitertanol, buprofezin, chlorfenvinphos, chlorpyrifos, chlorpyrifos-methyl, ethalfluralin, fenthion, lindane, malathion, methidathion, propachlor, propanil, pyriproxifen, tebuconazol and trifluralin. Comparisons of two types of sampling filters (quartz and glass fibre) and four types of solid-phase cartridges (XAD-2, XAD-4, Florisil and Orbo-49P) showed that the most suitable supports were glass fibre filter for particulate pesticides and XAD-2 and XAD-4 cartridges for gaseous pesticides (>95% recovery). Evaluations of elution solvents for ultrasonic-assisted extraction demonstrated that isooctane is better than ethylacetate, dichloromethane, methanol or a mixture of acetone:hexane (1:1).Recovery assays and the standard addition method were performed to validate the proposed methodology. Moreover, large simulator chamber experiments allowed the best study of the gas-particle partitioning of pesticides for testing the sampling efficiency for the validation of an analytical multiresidue method for pesticides in air. Satisfactory analytical parameters were obtained, with a repeatability of 5 ± 1%, a reproducibility of 13 ± 3% and detection limits of 0.05–0.18 pg m⁻³ for the particulate phase and 26–88 pg m⁻³ for the gaseous phase. Finally, the methodology was successfully applied to rural and agricultural samples in the Mediterranean area.     

"Cold" solid-phase microextraction method for the determination of volatile halocarbons present in the atmosphere at ultra-trace levels

Anthropogenic volatile halocarbons are compounds of great enviromnental concern because of their involvement in global change phenomena. They are present in the atmosphere at concentration levels in the order of parts per trillion by volume. The chosen analytical method for their determination is capillary gas chromatography coupled to mass spectrometry, preceded by an enrichment step on suitable adsorbent resins. The method here presented makes use of the solid-phase microextraction as a pre-analytical technique, using sub-ambient temperature in order to enhance the retention capability of the fiber coating. The proposed method was evaluated in terms of extraction efficiency, linearity, reproducibility, andlimits of detection. Results obtained showed that trace atmospheric halocarbons are detectable even when enriching very small air sample volumes. A good chromatographic resolution is obtained as a consequence of the extremely low injection volume. Finally a standard GC-MS instrumentation equipped with a simple split-splitless injector was employed, thus avoiding the use of expensive dedicated apparatus. The method was also applied to the analysis of actual samples collected both in remote, and in semi-remote sites.     

Specific thin-layer chromatographic method for the determination of theophylline in plasma in the presence of some other drugs.

A simple spectrodensitometric method for the direct determination of theophylline was developed from measurement of the absorbance of the compound on silica gel layers irradiated at 275 nm. Auantities as low as 0.010 mug can be detected and a linear relationship was obtained between peak area and the amount of the drug in the spots from 0.025-0.200 mug. The recovery over the usual range of plasma concentration (2.5-20 mug/ml) was 95-107%. The method is sufficiently sensitive and specific for clinical purposes and the time for the assay is about 2 h. Caffeine, frequently present in human plasma, was well separated from theophylline at all concentration levels as were several other drugs commonly used in respiratory problems.     

Analytical methods for the determination of emerging organic contaminants in the atmosphere

Concerns over the occurrence and transport of emerging organic contaminants (EOCs) from local sources to remote regions have resulted in wide developments in sampling strategy and analytical methodology for the determination of trace concentrations of EOCs in the atmosphere. This article discusses developments in the determination of EOCs in ambient air which includes polyfluorinated alkyl substances (PFASs), brominated-flame retardants (BFRs), synthesis musk fragrances, and alkylphenols (APs). References were mainly summarized from the past 5 years (2002 up to present) on new developments of sampling methods, extraction, separation/fractionation and/or applications of new technologies for sampling and determination.     

Potentiometrically indicated determination of trace amounts of ozone as an alternative to the photometric method

Summary The paper deals with the potentiometric indication as an alternative to the photometric indication in the determination of ozone contents in air between 0.01 and 0.1400 vpm. Using standard solutions (c=0.0001 mol/l) and a modern titrating processor, samples of 10 to 20 l of the loaded air were sufficient, depending on the ozone content.     

Early problems in the analysis and the determination of ozone

Schönbein’s correspondence with Berzelius (1836–1847) and with Faraday (1836–1862) are shown to be excellent accessible sources for his changing views as to the nature of ozone. Two of Schönbein’s qualitative tests for ozone, namely the reaction with neutral potassium iodide solution and that with indigo have current quantitative application. Andrew’s quantitative studies of the ozone reaction with potassium iodide (1856) and his work with Tait on the volumetric gas phase decomposition of ozone (1860) confirmed the allotropic nature of ozone but did not yield the structure which was first proposed by Odling (1861). Modern spectroscopic studies owe their origin to Hartley’s studies of 1881.     

Early problems in the analysis and the determination of ozone

Sch?nbein’s correspondence with Berzelius (1836–1847) and with Faraday (1836–1862) are shown to be excellent accessible sources for his changing views as to the nature of ozone. Two of Sch?nbein’s qualitative tests for ozone, namely the reaction with neutral potassium iodide solution and that with indigo have current quantitative application. Andrew’s quantitative studies of the ozone reaction with potassium iodide (1856) and his work with Tait on the volumetric gas phase decomposition of ozone (1860) confirmed the allotropic nature of ozone but did not yield the structure which was first proposed by Odling (1861). Modern spectroscopic studies owe their origin to Hartley’s studies of 1881. Received: 20 February 1996 / Accepted: 15 May 1996