A new spectrophotometric method for the determination of formaldehyde in air

A new spectrophotometric method for the determination of formaldehyde is described, based on a colour reaction with oxalyidihydrazide and copper(II). The optimum reaction conditions, and other analytical parameters such as interferences, Beer's law, sensitivity, collection efficiency, etc. have been studied.     

Spectrophotometric determination of traces of formaldehyde

Summary A comparative study of various colorimetric methods for determining and detecting traces of formaldehyde has been made. Chromotropic acid and 2,7-duiydroxynaphthalene were found to be the best reagents and were subjected to a thorough study. Precise and accurate methods for determining formaldehyde using either chromotropic acid or 2,7-dihydroxynaphthalene are described. The color system produced by following the standard procedure obeys Beer's law. Using chromotropic acid 0.05 g to 2.0 g of formaldehyde per ml can be determined quite accurately. Acrolein seems to be the only seriously interfering substance, and its interference can be much diminished by slightly modifying the standard procedure. The reagent solutions are perfectly stable.     

HPLC-method for the determination of cytarabin in plasma

Conclusion This method is characterized by a minimal sample requirement (1 ml of blood) which also facilitates its use in pediatrics. The simple but effective preparation of sample (combination of ultrafiltration with precolumn switching technique) prolongs the life of the analytical column. The low detection limit, linearity of the calibration curve over a wide range of concentration, good recovery and the absence of interference indicates that this method is suitable for routine analysis. A major disadvantage is the relatively long analysis time (30 min).

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HPLC-Methode zur Bestimmung von Cytarabin im Plasma

     

Spectrophotometric determination of formaldehyde in air

A spectrophotometric method for the determination of formaldehyde in air is described, based on the colour reaction of formaldehyde, p-aminoazobenzene and sulphur dioxide in hydrochloric acid medium. Beer's law is obeyed at 505 nm in the range 2-12 mug of formaldehyde per 25ml of final solution (0.08-0.48 ppm). Optimum conditions for colour development, and possible interferences, have been studied.     

Piezoelectric crystal sensor for the determination of formaldehyde in air

Formaldehyde in air was detected and assayed with a piezoelectric quartz crystal coated with a 7,10-dioxa-3,4-diaza-1,5,12,16-hexadecatetrol/chromotropic acid solution. Water vapor and several gaseous interferents were removed by passing the sampling stream through a column of anhydrous magnesium perchlorate. The response curves were linear in the concentration ranges 0.4-4.5 and 0.4-3.6 ppm v/v CH(2)O with and without the scrubber column, respectively. A single coating was used for 12 days (500 assays) without significant loss in sensitivity. With a single-point daily recalibration, the useful lifetime of the coating is about 2 months.     

HPLC-method for the determination of a low molecular weight trypsin inhibitor in urine

Summary A method to analyse a low molecular weight trypsin inhibitor (UTI-L, apparent molecular weight: 6200) in human urine is described. The procedure consists of an enrichment step and a separation by RP-HPLC. The urine sample with aprotinin as internal standard is adjusted to pH 8.3 and percolated through a trypsin-Sepharose 4B column; the inhibitors are eluted with acid solution. This eluate is analysed by RP-HPLC with ultraviolet detector (200 nm). Starting with a known sample volume (ca. 200 ml) the detection limit of the whole analytical procedure is 0.02 IU _bapna 1^–1 of urine.

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HPLC-Methode zur Bestimmung eines niedermolekularen Trypsin-Inhibitors in Harn

     

A new fluorimetric method for the determination of formaldehyde in air based on the liquid droplet sampling technique

A new, simple, sensitive, selective and in-field fluorimetric method for the determination of formaldehyde is proposed. The reaction of formaldehyde with hydralazine in acidic medium, heating on a boiling water-bath for 25 min, produces s-triazolo[3,4-a]phthalazine (Tri-P). The fluorescence intensity of the product formed (Tri-P) was determined at lambda em = 389 nm with lambda ex = 236 nm. The fluorescence intensity is linear over a formaldehyde concentration range of 1.2-33.0 micrograms l-1. The proposed method was applied successfully to the determination of formaldehyde sampled from the atmosphere using the liquid droplet technique. Formaldehyde vapour in a wind tunnel was produced by a mean of permeater. A linear curve was obtained between the concentration in the wind tunnel and that in the droplet. The detection limit for formaldehyde was 2.0 micrograms l-1 with RSDs varying from 3 to 12% in ambient air, using a droplet correction solution (boric acid and hydralazine). The effect of interfering substances on the determination shows that most cations and anions did not interfere. The results obtained were satisfactory compared with a reference method.     

Some new aspects in air pollutants analysis of hydrocarbons by automatic gas-chromatography

Summary Ambient measurement of hydrocarbons is gaining in importance. The value of a total measurement of hydrocarbons, as it is usually performed, is slight since the characteristics of organic compounds are different. Total measurement of hydrocarbons can only be of interest in less polluted regions, provided that the harmless methane which occurs in relatively high concentrations in nature is not to be included in the measurement. In toxicological evaluation of air the concentrations of particular components (e.g. ethylene, toluene, acetylene, propylene, butadiene, vinylchloride, benzene or xylene) are of interest and the concentrations of these components can lie at a few g/m³, i.e. in the ppb-range. These values can only be measured with a selective equipment. An automatic analyzer combined with a concentrating unit, which fully satisfies the requirements of selective measurement of hydrocarbons in air in the ppb-range, and as an example of the application of this equipment, the measurement of C₁-C₆ hydrocarbons (paraffins, olefins) and aromatics (benzene, toluene, ethylbenzene, xylene) are described. Complete measuring setups within automatic measuring stations are projected.

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Einige neue Aspekte bei der Analyse von Kohlenwasserstoffverunreinigungen in Luft mit Hilfe automatischer Gas-Chromatographie

Zusammenfassung Immissionsmessungen von Kohlenwasserstoffspuren gewinnen immer mehr an Bedeutung. Die Messung der Kohlenwasserstoffe als Summe, wie gewöhnlich durchgeführt, ist ungenügend, da organische Verbindungen unterschiedliche Wirkungscharakteristik aufweisen. Sie kann daher nur in Gebieten mit kleinen Kohlenwasserstoffverunreinigungen sinnvoll sein, vorausgesetzt, daß das ungefährliche Methan, welches überall in der Natur vorkommt, von der Messung ausgeschlossen wird. Bei der toxikologischen Bewertung der Luft interessieren die Konzentrationen bestimmter Komponenten wie Äthylen, Acetylen, Propylen, Butadien, Vinylchlorid, Benzol, Toluol oder Xylole. Die Konzentrationen dieser Komponenten können bei wenigen g/m³, d. h. im ppb-Bereich, liegen. Diese Werte können nur mit einer selektiven Meßeinrichtung erfaßt werden. Ein automatischer Gas-Chromatograph mit Speichersäule, der die Forderung der selektiven Messung von Kohlenwasserstoffen in Luft im ppb-Bereich erfüllt, wird beschrieben. Als Applikationsbeispiel dieser Meßeinrichtung wird die Messung von C₂-C₆-Kohlenwasserstoffen (Paraffine, Olefine) und Aromaten (Benzol, Toluol, Äthylbenzol, Xylol) erwähnt. Der Einsatz dieses Gerätes in automatischen Luftmeßstationen wird derzeit projektiert.

Presented at the 6th Chemical Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria.     

Some observations on the dimedone method for the gravimetric determination of formaldehyde

Tables are provided which give the dependence on the temperature and the pH of solution of the second order rate constant for the reaction between dimedone and formaldehyde.These, together with the relevant rate equations, enable calculations to be made of the optimum conditions of analysis of formaldehyde solutions by the dimedone method.     

Detection of traces of formaldehyde in pure air by gas chromatography and helium ionization detection

The sensitive helium ionization detector (HID) was used for the direct determination of ppm to ppb levels of formaldehyde in air. Two methods to generate formaldehyde in an air stream were evaluated. The first method utilized a paraformaldehyde permeation tube and the second utilized a motor driven syringe and a dilute solution of formaldehyde. The two methods were evaluated using gas chromatography with HID and spectrophotometry. The paraformaldehyde permeation tube generates only about 60% of the theoretical value, while the motor driven syringe was accurate for levels below 2 ppm; however, at a concentration of 13 ppm or above, oligomers or other chemical forms of CH2O are formed to decrease the concentration of gaseous CH2O produced.     

A portable gas chromatograph with air carrier gas for the determination of explosive traces

A three-step scheme for a miniature air purification filter for a gas chromatograph has been proposed. A method for controlling the selectivity of a new ion gas chromatography detector has been considered using a simulating model. The possibility of determining explosive traces by a gas chromatograph with air as a carrier gas has been demonstrated.     

A new contamination-free method for the determination of traces of anthropogenic silver in freshwaters

The use of different products containing silver in anthropic activities has caused the increase of silver concentrations in many water courses. To establish their toxic effects, both precise and accurate analytical methods are needed to quantify silver at very low concentrations. Although different methods may be found in the literature, in practice, most chemists or other environmentalists use solvent extraction methodology in a Clean Lab, which is tedious and with high risk of sample contamination during manipulation. In this work, the applicability of a liquid membrane-based method was studied as an alternative for the analysis of silver in freshwaters using triisobutylphosphine sulphide, TIBPS (Cyanex 471X^©), as a carrier. Transport conditions were studied and optimised; including pH and co-ion (nitrate) concentration in sample, the influence of anionic species present in freshwaters, and concentrations of carrier and stripping reagent. Under optimum conditions an extraction efficiency of 59.5% was achieved after a 4-hours operation time. Since both extraction and back-extraction processes are carried out simultaneously and without sample manipulation, this system offers a clean alternative (avoiding contamination) for determination of traces and ultra-traces of silver in freshwaters. The system was successfully applied to the preconcentration of silver, in tap and freshwater samples, before their quantification by flame atomic absorption spectroscopy (FAAS) at a ppb-level or by inductively coupled plasma-mass spectrometry (ICP-MS) at the ppt-level.     

Some peculiar aspects of a new catalyst for propene polymerization

An investigation was carried out on the preparation of highly disordered samples of MgCl₂ (in delta -form), starting from different Mg-alkyls and chlorinating agents. Successively we studied which kind of silica carrier had to be preferred and which treatment was strictly' necessary to achieve a qualified catalyst precursor showing outstanding performance. Different routes were investigated to support the active, disordered MgCl₂ on the silica carrier and then some following ways to complete the catalyst. The final result of this investigation was the synthesis of a catalyst showing the best performance with reference to the parameters of use in every polymerization process. It has to be e.g. mentioned: — high yield, referred to the residual content of Mg, Ti and Cl; — no activity decrease when operating at a very high hydrogen concentration; — possibility to polymerize also at elevated temperatures; — very high isotactic index and stereoregular structure, as measured by the NMR technique; — possibility to reach high MFR (Melt Flow Rate) (up to 400 g IPP/10 min at 230°C, 2,16 kg, ASTM D 1238L); — outstanding morphology and flowability.     

Gas chromatographic determination of formaldehyde in air using solid-phase microextraction sampling

Summary The optimization of in situ derivatization and preconcentration of formaldehyde in air using solid phase microextraction with gas chromatographic determination was investigated. A dimethylpolysiloxane coating (7 μm) solid-phase microextraction needle was used in the final procedure as a support for derivatizing reagents such as 2,4-dinitrophenylhydrazine and acetylacetone. Standard concentrations of formaldehyde in air were obtained using a headspace technique and equilibrium concentrations of formaldehyde in air were calculated using Henry's law. After derivatization on the fiber, the derivative was thermally desorbed in the injector of a gas chromatograph and analyzed using an electron capture detector. A detection limit of 0.17 mg m⁻³ was obtained. Calibration was done at 296 K. Reproducibility of the method was 9.6%. Some real air samples were also analyzed. The method is very convenient and ideal for the rapid determination of formaldehyde in air. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Continuous chemiluminescence determination of formaldehyde in air based on Trautz-Schorigin reaction

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5 L min⁻¹ (absorption liquid flow rate of 336 μL min⁻¹). The limit of detection (S/N = 3) is 0.60 μg m⁻³ HCHO (0.49 ppb). The calibration graph is linear up to 300 μg m⁻³ HCHO (244 ppb). The relative standard deviations of chemiluminescence method for 1 × 10⁻⁶ and 5 × 10⁻⁶ M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.     

Spectrophotometric determination of traces of formic acid and formaldehyde in effluent waters with or without preconcentration

Formic acid plus formaldehyde are determined after reducing the acid with nascent hydrogen; formaldehyde alone is determined without reduction. The chromotropic acid method is used in 6–7.5 M sulfuric acid. The limit of determination is 0.05 μg ml^-1 without preconcentration and 0.05 ng ml^-1 with preconcentration by extraction with diethyl ether. Analysis time is 30 min by the direct method and 1 h with preconcentration.     

Method for determination of formaldehyde in air in the pptv-range by HPLC after extraction as 2,4-dinitrophenyl-hydrazone

Summary The derivatization of formaldehyde with 2,4-dinitrophenylhydrazine and the extraction of the product formalhydrazone is studied. The determination is carried out by HPLC. Applying a cryogenic sampling technique and a sampling volume of 300 l of air the detection limit of formaldehyde in air is 30 pptv and this is suitable for measurements of formaldehyde in the atmosphere.

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Bestimmung von Formaldehyd in Luft im pptv-Bereich mit Hilfe von HPLC nach Extraktion als 2,4-Dinitrophenylhydrazon

Zusammenfassung Die Derivatisierung des Formaldehyds mit 2,4-Dinitrophenylhydrazin und die Extraktion des gebildeten Formylhydrazons wurde untersucht. Die Bestimmung erfolgte mit der HPLC. Mit Hilfe kryogener Sammelverfahren können bei einem Sammelvolumen von 300 l Luft noch Formaldehyd-Mischungsverhältnisse von 30 pptv nachgewiesen werden. Das Verfahren verfügt damit über eine für Messungen des Formaldehyds in der Atmosphäre ausreichende Nachweisgrenze.

     

Preconcentration with membrane cell and adsorptive polarographic determination of formaldehyde in air

The present paper describes a procedure that formaldehyde in air was preconcentrated in a membrane cell and its content was determined by adsorptive polarography. First the formaldehyde in air samples was preconcentrated in a membrane cell using water, then the formaldehyde reacted with 2,4-dinitrophenyl hydrazine to form 2,4-dinitrophenyl hydrazone, which can be adsorbed at the mercury electrode and yields a sensitive adsorptive polarographic wave. Over the range 6.0x10(-10)-5.0x10(-6) M, the peak currents are linearly proportional to the concentration of formaldehyde, the detection limit is 2.0x10(-10) M.     

Separation and determination of traces of ammonia in air by means of chromatomembrane cells

Chromatomembrane cells are new devices for gaseous/liquid and liquid/liquid extractions consisting of porous hydrophobic material (PTFE) with two types of pores, i.e., micropores and macropores. Their application benefits from established procedures of preconcentration and continuous extraction being used at the present to automate sample preparation in analytical chemistry. A method is reported to separate traces of ammonia from air by means of a chromatomembrane cell with subsequent potentiometric determination. The measuring system responds proportionally to both gas phase concentration of ammonia and preconcentration time.     

Chemistry of organic traces in air

Summary Chlorine, bromine and bromine-chlorine C₁- and C₂-hydrocarbons were determined in marine air and in air and rain from southern Germany. Marine sampling was done on board the German research vessel F.S. Polarstern near the coast of Portugal. A combination of analytical techniques like adsorption on Tenax TA, thermal desorption with cold trapping, high-resolution gas chromatography on DB1 (100% dimethyl-polysiloxane), BP10 (7% cyanopropyl, 7% phenyl-methyl-polysiloxane) and coupled fused-silica capillary columns and electron-capture detection were used. With these methods it is possible to determine organic trace compounds from 0.1 pptv up to 200 pptv in the air masses of the westwind drift.The concentration of tetrachloromethane in the troposphere of both hemispheres is nearly constant, its annual increase is in the range of the accuracy of determination. Therefore, tetrachloromethane can be taken as a built-in stable internal standard in tropospheric air.R _T(A)-value = conc. (A)conc. (CCl₄) in pptvpptv. (1)Calculating theR _T-value of a compound A is useful for the interpretation of the organohalogen burden of air masses and for discussing input, output and transport mechanisms.Air and rain of a fast moving rainfront coming from the North Atlantic was sampled in Ulm. The volatiles were purged out of the rainwater with clean air and trapped on Tenax TA. The analysis clearly shows the wash-out effect and the accumulation of the more polar bromine and bromine-chlorine compounds in the rain.

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Chemie organischer Spurenstoffe in Luft.V. Bestimmung von halogenierten C₁-C₂-Kohlenwasserstoffen in mariner Reinluft sowie kontinentaler Luft und in Regen mittels hochauflösender Capillar-Gas-Chromatographie auf verschiedenen stationären Phasen

Zusammenfassung Chlorierte, bromierte und gemischt halogenierte C₁- und C₂-Kohlenwasserstoffe wurden in marinen Reinluftproben und in Luft und Regen über Süddeutschland bestimmt. Die marine Luftprobenahme fand vor der Küste Portugals an Bord des deutschen Forschungsschiffes Polarstern statt. Die Kombination verschiedener analytischer Techniken wie Adsorption auf Tenax TA, thermische Desorption mit Kühlfallen-Zwischenkondensation, Trennung auf DB1 (100% dimethyl-polysiloxane), BP10 (7% cyanopropyl-, 7% phenylmethyl-polysiloxane) und auf gekoppelten Fused-silica-Capillaren und Elektronen-Einfang-Detektion ermöglicht die Identifizierung und Bestimmung von flüchtigen, halogenierten organischen Spurenstoffen in den Luftmassen des Westwindgürtels mit Gehalten von 0.1 pptv bis über 200 pptv.Zur Interpretation der gemessenen Belastung der Luftmassen mit organischen Halogen-Verbindungen wird die relative Konzentration bezogen auf den Tetrachlormethan-Gehalt in der freien Troposphäre eingeführt:R _T(A)-Wert = conc.(A)conc.(CCl₄) in pptvpptv. (1)Der Gehalt an Tetrachlormethan ist sowohl in der Nordwie in der Südhemisphäre nahezu konstant, seine zeitliche Änderung liegt im Bereich der derzeitigen Meßgenauigkeit. Tetrachlormethan kann daher als ein interner Standard für unbelastete Luft der unteren Troposphäre betrachtet werden.Regen einer schnell über Westeuropa ziehenden Niederschlagsfront wurde in Ulm gesammelt. Die Untersuchung auf flüchtige Organohalogen-Verbindungen erfolgt durch Ausblasen mit gereinigter Luft und nachfolgender Adsorption auf Tenax TA. Eine Anreicherung der polaren bromierten und gemischt halogenierten Methane im Regen gegenüber den Gehalten in Luft ist klar erkennbar.

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Part IV: Ballschmiter K, Mayer P, Class Th (1986) Fresenius Z Anal Chem 323:334–339

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Dedicated to Prof. Dr. H. Hartkamp on the occasion of his 60th birthday