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.

     

Bestimmung von Coffein,Theobromin und Theophyllin in Tee,Kaffee, Kakao und Getränken durch Hochdruckflüssigkeitschromatographie mit elektrochemischem Detektor

Zusammenfassung Eine Methode zur quantitativen Bestimmung von Coffein, Theobromin und Theophyllin wurde ausgearbeitet. Nach Untersuchung des voltammetrischen Verhaltens dieser Verbindungen an einer glasartigen Kohlenstoffelektrode zeigte sich, daß eine gleichzeitige voltammetrische Bestimmung infolge der ähnlichen Halb-Peakpotentiale nicht möglich ist. Daher wurden die Methylxanthine durch Hochdruckflüssigkeitschromatographie getrennt und mit einem amperometrischen Detektor angezeigt.Angewandt wurde die Methode zur Bestimmung des Coffeins, Theobromins und des Theophyllins in Tee, Kaffee, Kakao und Getränken. Nach Extraktion mit Wasser wurden störende Substanzen an Polyamid gebunden und die Methylxanthine durch reversed phase chromatography getrennt. Die Identifizierung und die quantitative Bestimmung erfolgte mit dem elektrochemischen Detektor. Die Nachweisgrenze liegt für Coffein bei 4 ng, für Theobromin bei 1,5 ng und für Theophyllin bei 0,7 ng.

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Determination of caffeine, theobromine and theophylline in tea, coffee, cocoa and beverages by high fressure liquid chromatography with electrochemical detection

Summary A method for quantitative determination of caffeine, theobromine and theophylline was developed. By investigation of the voltammetric behaviour of these substances at a glassy carbon electrode it was found, that a simultaneous voltammetric determination is impossible because the half-peak potentials of theobromine and caffeine are nearly identical. Therefore the methylxanthines were separated by HPLC and detected with an amperometric detector.This method was applied to the determination of caffeine, theobromine and theophylline in tea, coffee, cocoa and in beverages. After extraction with water interfering substances were removed on a polyamide column and the extract was separated by reversed phase chromatography. For identification and quantitative determination the electrochemical detector was used. The detection limit for caffeine is 4 ng, for theobromine 1,5 ng and for theophylline 0,7 ng.

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Vorgetragen beim 8. Internationalen Mikrochemischen Symposium in Graz, 28. August 1980.     

Quantitative Determination of Formaldehyde In Air Using the Acetylacetone Method

Abstract

The quantitative determination of formaldehyde in air using the fluorimetric acetylacetone method is described. Known concentrations of formaldehyde were generated and collected in water using abosorbers. The sampling rate was 0.5 1/min, and the sampling volumes varied from 2 to 20 1, depending on the concentration level. Under these conditions the entire sampling and the analytical method were evaluated over a range of 0.2–1.7 mg formaldehyde per m³ of air.

The precision of the method expressed as a mean value of the relative standard deviation of 7 independent measurements (6 single determinations each) was (3.4 ± 1.6) % (SD). The accuracy was (101 ± 5) % (SD). The detection limit of the method was estimated to be 0.040 mg formaldehyde per m³ of air (5 liter air sample).     

Determination of digitalis-glycosides by HPLC and reaction-detection

Summary A reference method for the determination of digoxin in serum has been developed. The method consists of RP-HPLC, reaction detection and fluorimetric measurement. Characteristics of the method for the analysis in serum are: detection limit of 100 pg/ml; reproducibility of VC= ±2.9% and linearity up to 5 ng.The sample preparation consists of serum injection on a clean-up column and purge injections.

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Bestimmung von Digitalis-Glykosiden durch HPLC und ReaktionsdetektionAnwendung zur Digoxinbestimmung in Humanserum

Zusammenfassung Eine Referenzmethode zur Bestimmung von Digoxin in Humanserum wird vorgestellt. Die Einzelschritte bestehen aus einer RP-HPLC, dem Einsatz eines Reaktionsdetektors und der anschließenden Fluorescenzdetektion. Verfahrenscharakteristica für die Analyse von Serumproben sind: Nachweisgrenze von 100 pg/ml; Reproduzierbarkeit von VK=±2,9% und Linearität bis 5 ng.Die Probenvorbereitung besteht lediglich aus der Seruminjektion auf eine Injektionskartusche und Spülinjektionen.

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Herrn Prof. Dr. H. Monien mit herzlichen Grüßen zum 60. Geburtstag gewidmet     

Quantitative determination of ultra-traces of chlorinated compounds in high-volume air samples from the Arctic using polyurethane foam as collection medium

Summary A method has been developed for the determination of very low concentrations (pg/m³) of organic chlorinated compounds in air. Chlorinated benzenes, hexachlorocyclohexanes, polychlorinated biphenyls and the DDT group. Since most of the atmospheric burden of such compounds occurs in the gas phase, a high volume sampling method has been developed using carefully precleaned polyurethane foam as collection medium. Samples of 2000–4000 m³ were taken at different sites in the Arctic. The foam quality as well as the precleaning procedure of the foam and the clean-up of the sample are described in detail. The recovery of both the extraction and sample pretreatment was in the range of 80–115% for nanogram amounts. Sampling efficiency for the first foam plug was 80–100%.The sampling efficiency is influenced by different factors (temperature, air humidity, sampling volume). For quantification and identification, the highly selective methods of negative ion chemical ionization mass spectrometry and electron capture detection were combined with high resolution gas chromatography. The detection limit of the method was for most compounds less than a few pg/m³. Some preliminary data from the Arctic measurements are presented and are briefly discussed.

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Quantitative Bestimmung von Ultraspuren chlorierter Verbindungen in großvolumigen Luftproben aus der Arktis mit Hilfe von Polyurethanschaum als Sammelmedium

Zusammenfassung Das beschriebene Verfahren dient zur Bestimmung von chlorierten Verbindungen (chlorierte Benzole, Hexachlorcyclohexane, polychlorierte Biphenyle, DDT-Gruppe) in niedrigen Konzentrationen (pg/m³) in Luft. Da die meisten dieser Verbindungen gasförmig vorkommen, wurde eine Probenahmemethode für große Volumina unter Verwendung von sorgfältig vorgereinigtem Polyurethanschaum als Adsorptionsmedium entwickelt. Proben von 2000–4000 m³ wurden an verschiedenen Stellen der Arktis genommen. Die Vorbehandlung des Schaums und der Probe wird ausführlich beschrieben. Bei ng-Mengen lag die Wiederfindung bei 80–115%. Die Leistungsfähigkeit der ersten Schaumschicht lag bei 80–100%. Durch Temperatur, Luftfeuchtigkeit und Probenahmevolumen wird die Leistungsfähigkeit beeinflußt. Zur Identifizierung und quantitativen Bestimmung wurde die Negativionen-Massenspektrometrie mit chemischer Ionisation und die EC-Detektion mit der Hochleistungs-Gas-Chromatographie kombiniert. Die Nachweisgrenze lag für die meisten Verbindungen bei weniger als einigen pg/m³. Einige Daten der arktischen Messungen werden vorgestellt und kurz diskutiert.

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Partly presented at the Fourth European Conference on Analytical Chemistry, Helsinki/Espoo, Finland 1981     

Gas chromatographic determination of alkali metal O,O-diethyl phosphorodithioate present in trace amounts

Summary A gas Chromatographic determination of traces of alkali metal O,O-diethyl phosphorodithioates is described. The salts were converted into a volatile derivative by alkylation with diazomethane. The product was identified by gas chromatography-mass spectrometry. With aqueous samples a linear relationship of peak height to amount of salt was obtained in the range 0.04–1 ng and for urine samples a calibration curve was constructed. The detection limit (signal to noise ratio 4/1) was 40 pg of salt. The procedure was successfully used for monitoring phosalone absorption by occupationally exposed persons.

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Zusammenfassung Eine gaschromatographische Bestimmung von Spuren Alkalisalz des Diäthyldithiophosphorsäureesters wurde beschrieben. Die Salze wurden durch Alkylieren mit Diazomethan in ein flüchtiges Derivat übergeführt. Dessen Identifizierung erfolgte mittels eines gaschromatographisch-massenspektrometrischen Systems. In Wasserproben wurde ein lineares Verhältnis der Peakhöhen und der Salzmenge festgestellt und für Urinproben wurde eine Eichkurve ermittelt. Die Nachweisgrenze (Signal zu Rausch 41) wurde bei 40 pg Salz festgestellt. Die Methode wurde für die Kontrolle der Absorption von Phosalon bei beruflich exponierten Personen erfolgreich angewendet.

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Presented at the Fourth International Congress of Pesticide Chemistry (IUPAC), Zürich, July 24–28, 1978.     

Die Bestimmung von Schwermetallen in nativer Nierenmatrix mittels Feststoffanalytik und Atomabsorptionsspektrometrie

Summary Solid sample analysis by Zeeman AAS is a method which allows rapid determination of lead and cadmium in small amounts of fresh renal tissue without time consuming chemical digestion. The renal cortex is preferable to other tissues or the whole kidney to optimize standardization of sampling, homogeneity, element concentration and microsampling. The analytical quality is sufficient to detect limit concentrations of Pb and Cd in the kidney and normal levels as well.

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Teil I: Fresenius Z Anal Chem 328:370     

Determination of clotiazepam by HPLC with spectrophotometric and amperometric detection

Summary Spectrophotometric and amperometric detectors were compared for the determination of clotiazepam by HPLC. Methanol-water (6040) containing 0.01 mol/l ammonium acetate and methanol-water (7030) containing 0.01 mol/l acetate buffer pH 4 were used as mobile phase in the spectrophotometric and amperometric detection, respectively. The minimum detectability for the spectrophotometric detection was 20 ng injected and the method was applied for the determination of clotiazepam in serum, whereas for the amperometric detection a limit of detection of 2.5 g injected was obtained, using this technique for clotizepam determination in tablets.

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Bestimmung von Clotiazepam durch HPLC mit spektralphotometrischer und amperometrischer Detektion

     

Analysis of 5-methyl-deoxycytidine in DNA by micro-HPLC

Summary A method for the quantitative analysis of 5-methyl-deoxycytidine (5dmC) in DNA based on enzymatic hydrolysis to nucleosides, separation by Micro-HPLC and quantification with external calibration has been developed. The method was applied to DNA from calf thymus, drosophila and yeast; the fully sequenced DNA from the Phage X174 has been used to establish the accuracy of the procedure. The detection limit is 0.4 pmol 5dmC absolute; the content of modified nucleoside in DNA of drosophila and yeast was shown to be lower than the current detection limit, which means that less than one methylated cytosine per 14000 (12000 resp.) unmodified nucleobases are to be found in the genomes.

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Bestimmung von 5-Methyl-desoxycytidin in DNA mit Mikro-HPLC

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

Study of the conditions for the determination of metamitron by differential pulse polarography

Summary The electrochemical behaviour of the herbicide 4-amino-3-methyl-6-phenyl-1,2,4 triazine-5(4H)-on (Metamitron) is studied in aqueous medium using voltammetric techniques, with the ionic strength adjusted to 0.1 mol/l in sodium perchlorate and using a Britton-Robinson buffer. Two reduction waves on the mercury drop electrode appear, at –0.49 V the first and the second folded at –0.95 V and –1.05 V. The system is identified as irreversible and fundamentally controlled by diffusion. Using differential pulse polarography the detection limit reached was 0.02 mg · l^–1 for the first wave with an error of less than 2%. Thus a method is proposed for the determination of Metamitron in soil, with a detection limit of up to 0.02 g/g.

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Untersuchung der Bedingungen zur Metamitronbestimmung durch Differential-Puls-Polarographie

     

Amperometric flow injection technique for determination of hydrogen peroxide and sulfur(IV) in atmospheric liquid water

Summary A sensitive, selective and fast method for the determination of hydrogen peroxide and sulfur(IV) present in atmospheric liquid phase is described and discussed. The flow injection system used contains a specially designed electrochemical micro-cell. The necessary selectivity is achieved using an alkaline carrier flow for the oxidative determination of H₂O₂ and an acidic one for the bisulfite oxidation, and employing differential measurements before and after addition of catalase or sulfite oxidase, respectively. Samples of 200 l volume can be injected at a rate of 30 per hour and the electroactive species be determined in the range from millimolar level down to the detection limit of 2 · 10^–8mol/l. The S(IV) present as hydroxymethanesulfonate or in form of other carbonyl adducts is determined after a previous alkalinization of the sample to liberate the sulfite. The method has been tested with rain, snow, fog and cryo-sampled atmospheric water vapor. The time resolution is adequate to follow precipitation events.

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Amperometrisches Fließinjektionsverfahren zur Bestimmung von Wasserstoffperoxid und Schwefel(IV) in atmosphärischem Flüssigwasser

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Multielement radiochemical neutron activation analysis of high purity aluminium

Summary A radiochemical neutron activation analysis technique for the determination of 51 elements in high purity aluminium via medium- and long-lived indicator radionuclides has been developed. It is based on a separation procedure involving the removal of ²⁴Na, produced via the reaction ²⁷Al(n,), on a hydrated antimony pentoxide column and further separation of the radionuclide mixture into 11 groups on two Dowex 1X8 columns and one Dowex 50X8 column from HCl/HF and HCl media as well as the extraction of copper with APDTC in chloroform. The indicator radionuclides for the significant impurities thorium and uranium, ²³³Pa and ²³⁹Np, were separated with satisfactory selectivity in one fraction. For 43 elements, the limits of detection are <10 ng/g, for thorium and uranium, they are 50 pg/g. The method was applied to the analysis of different high purity aluminium samples. For a number of elements, the results of this technique are compared with those of other techniques.

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Radiochemische Multielement-Neutronenaktivierungsanalyse von hochreinem Aluminium

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

Flameless atomic absorption determination of barium in natural waters using the technique of standard additions

Summary A simple method for the determination of barium in natural waters by flameless atomic absorption spectrometry using the carbon rod is proposed. Barium in highly salted waters is previously separated from the interfering ions by ion-exchange chromatography, using Dowex 50 W-X8 resin, and eluted with 0.1M EDTA solution. Mineral waters with low salinity are transferred directly to the furnace and the standard addition method is performed. The detection limit is 90 pg Ba for 10l injections. The method was applied to samples from the Atlantic Ocean and from Araruama Lake. Barium in commercially available waters was also determined.

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Bestimmung von Barium in natürlichen Wässern durch flammenlose Atomabsorptionsbestimmung unter Verwendung des Standard-Zugabe- Verfahrens

Zusammenfassung In salzreichen Wässern enthaltenes Barium wird von störenden Ionen durch Ionen-Austausch-Chromatographie über Dowex 50 W-X8 getrennt und mit 0,1M EDTA ausgewaschen. Mineralwässer mit geringem Salzge- halt werden unmittelbar in den Ofen eingebracht und die Standard-Zugabe- Methode angewendet. Die Nachweisgrenze liegt bei 90pg/10l. Die Methode wurde zur Untersuchung von Proben aus dem Atlantischen Ozean sowie aus dem Araruama-See angewendet. Außerdem wurde Barium in handelsüblichen Trinkwässern bestimmt.

     

Catalytic determination of traces of cobalt by the protocatechuic acid — Hydrogen peroxide reaction in a flow injection system

Summary A catalytic method in a flow injection system is proposed for the simple, rapid and sensitive determination of trace amounts of cobalt; the method is based on the cobalt-catalyzed oxidation of protocatechuic acid by hydrogen peroxide. The reported method has a limit of detection of 0.2 ppb by injecting 75l of sample, corresponding to 15 pg cobalt, and permitsca. 50 determinations per hour with a relative standard deviation of 1.5%. Relatively good selectivity is also obtained.

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Katalytische Bestimmung von Kobalt-Spuren mit der Protocatechusäure-Wasserstoffperoxid-Reaktion in einer Flie-Injektions-Vorrichtung

Zusammenfassung Eine einfache, schnelle und empfindliche Bestimmung von Kobaltspuren wurde beschrieben. Sie beruht auf der durch Kobalt katalysierbaren Oxydation von Protocatechusäure durch Wasserstoffperoxid. Bei Injektion von 75l Probe (entsprechend 15 pg Co) beträgt die Erfassungsgrenze des Verfahrens 0,2 ppb. 50 Bestimmungen sind pro Stunde durchführbar; die relative Standardabweichung beträgt 1,5%. Die Selektivität ist relativ gut.

     

Extraction, quantitative gas chromatographic determination and gas chromatographic/mass spectrometric detection of ecgonine for identification of cocaine and its metabolites in urine

Summary Quantitative extraction studies from urine were carried out by addition of cocaine, benzoylecgonine, ecgonine methyl ester and ecgonine to urine samples. After hydrolysis to ecgonine the compounds were analyzed together. Ecgonine was isolated by a cation-exchange resin and purified by an anion-exchange resin. The quantitative determination was performed by GC after silylation with MSTFA. The recovery was 77% at a concentration of 150 g ecgonine/ml urine. A qualitative determination of ecgonine by GC/MS was possible up to the detection limit of 20 ng/ ml. The method can be applied for the detection of cocaine abuse.

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Extraktion, quantitative gas-chromatographische Bestimmung und gas-chromatographischer massenspektrometrischer Nachweis von Ecgonin zur Identifizierung von Cocain und seinen Metaboliten in Urin

Zusammenfassung Es wurden quantitative Untersuchungen zur Extraktion von Urin durchgeführt, dem Cocain, Benzoylecgonin, Ecgoninmethylester und Ecgonin zugesetzt wurden. Die Summe dieser Verbindungen kann über eine vorgeschaltete Hydrolyse zu Ecgonin indirekt bestimmt werden. Nach Hydrolyse wird Ecgonin an einem Kationenaustauscher isoliert und der Extrakt an einem Anionenaustauscher gereinigt. Die quantitative Bestimmung erfolgt gaschromatographisch nach Silylierung mit MSTFA. Dabei beträgt die Wiederfindungsrate 77% bei Konzentrationen von 150 g Ecgonin/ml Urin. Der qualitative Nachweis von Ecgonin durch GC/MS ist bis zu einer Nachweisgrenze von 20 ng/ml möglich. Damit eignet sich die Methode zum Nachweis einer Cocain-Einnahme im Urin.

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From the dissertation by U. Zerell, University of Bonn, 1986 (in preparation)     

Determination of Uric Acid in Human Serum: Reversed-Phase Liquid Chromatography with Electrochemical Detection

Abstract

A method for the simultaneous determination of uric acid in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection has been developed. Human serum (0.5 ml) was mixed with 0.5 ml of 0.2 N perchloric acid solution and the mixture was centrifuged at 3,000 g for 20 min. An aliquot (10 μl) of the supernatant (deproteinized human serum) was injected into the chromatographic system employed in this study. The assay limit for quantitation was about 10 pg for uric acid. Complete separation of uric acid was achieved in about 8 min under the present chromatographic conditions.     

Feststoffanalytik mit Autoprobe-GFAAS

Summary A new graphite system has been developed for GFAAS combining the autoprobe technique and solid sampling analysis. Based on previous studies with D₂-background corrected solid sampling GFAAS it has been demonstrated that the determination of Pb, Cd, Zn, Mn and Cu in various matrices of mainly biological origin is possible and practicable by means of solid sampling autoprobe GFAAS. Accuracy and precision are comparable to known solid sampling GFAAS systems.

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Herrn Dr. A. Rosopulo gewidmet     

Determination of tin in environmental samples by graphite furnace atomic absorption and inductively coupled plasma-mass spectrometry

Summary Methods for the determination of total Sn in environmental samples (waters, animal tissue, plant material, sediments and coal fly ash), by graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS) have been developed and evaluated.Noble metals (Ag, Au, Pd, Pt, Rh) under reducing conditions were studied as matrix modifiers for the determination of Sn by GFAAS. The maximum ashing temperature (1400°C), highest sensitivity and the best absolute detection limit (4 pg) were achieved when Pd was used in the presence of hydroxylamine hydrochloride. The achievable sensitivity depended strongly on the chemical composition of the matrix.Both GFAAS and ICP-MS appeared to be equally sensitive techniques for the direct determination of Sn in waters, though ICP-MS was a more convenient and sensitive technique for the determination of Sn in digested biological and geological materials.

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Bestimmung von Zinn in Umweltproben durch Graphitrohr-AAS und ICP-MS