Determination of endotoxins by gas chromatography: evaluation of electron-capture and negative-ion chemical-ionization mass spectrometric detection of halogenated derivatives of beta-hydroxymyristic acid

The sensitivity and selectivity of gas chromatography for analysing several halogenated ester derivatives of beta-hydroxymyristic acid were studied using both selected-ion monitoring detection with negative-ion chemical-ionization mass spectrometry and electron-capture detection. Six different derivatization methods were compared with respect to yield, chemical stability and formation of by-products. Procedures for removal of excess reagents using disposable silica columns and thin-layer chromatography were elaborated. The 3-O-pentafluorobenzoyl-methyl ester was the preferred derivative since it provided high sensitivity and had the molecular ion as the base peak in the mass spectrum. The detection limit was 0.5 pg with electron-capture detection and 0.3 pg with the mass spectrometric system. Using beta-hydroxymyristic acid as a chemical marker it was possible to detect Escherichia coli endotoxin in aqueous solution at a level of 1 ng/ml.     

Analysis of medazepam, diazepam, and metabolites in plasma by gas-liquid chromatography with electrolytic conductivity detection.

An improved electrolytic conductivity detector allowed the gas-liquid chromatographic analysis of medazepam, diazepam, and major metabolites in 2 ml plasma at concentrations of 20 microgram/l. The detector had a sensitivity limit of less than 1 ng (or 100 pg nitrogen) when operated in the nitrogen-selective mode and a nitrogen/carbon elemental selectivity ratio of greater than 100,000 compared to octadecane and cholesterol. Detector response when operated in various element-selective chemical modes was investigated, and its application to the analysis of the title compounds was compared to electron capture and flame ionization detection systems.     

Gas--liquid chromatographic evaluation of lofemizole in biological samples for pharmacokinetic investigations. Comparison of two analytical methods

The present paper reports the analytical conditions allowing lofemizole, a new non-steroidal anti-inflammatory drug, to be evaluated in biological fluids for pharmacokinetic and bioavailability investigations. The first approach led to an N-methyl derivative of lofemizole which could be successfully analysed by gas--chromatography employing a flame-ionization detector, reaching a sensitivity of 2 micrograms/ml. The second approach led to the N-(2-chlorobenzoyl) derivative of lofemizole which was suitable for pharmacokinetic investigation using gas--liquid chromatography with electron-capture detection, and reaching a much higher sensitivity of 10 ng/ml of plasma. Recovery of the extraction, reproducibility and specificity were all satisfactory with both methods. Since the first method employing flame-ionization detection was suitable for pharmacokinetic investigations in animal species, this paper describes both methods on a comparative basis.     

Schnelle Methode zur gas-chromatographischen Bestimmung von 5-Brom-5-nitro-1,3-dioxan in Shampoos und Badepr?paraten

Zusammenfassung Zur Bestimmung von 5-Brom-5-nitro-1,3-dioxan in tensidhaltigen nicht-emulsionsartigen Cosmetica wie Shampoos, Schaum- und Duschbädern wurde — unter Berücksichtigung eines zu erwartenden Konzentrationsbereichs von 0,001–0,1% sowie der allgemein bekannten Problematik der Abtrennung von Wirkstoffen aus Tensidmatrices 3- eine schnelle und einfach durchzuführende, für die Routine geeignete Analysenmethode entwickelt. Die qualitative und quantitative Bestimmung erfolgt gas-chromatographisch mittels Electron-Capture Detector (ECD) nach säulen-chromatographischer Isolierung. Aufgrund der hohen Elektronenaffinität des Moleküls und der daraus resultierenden Selektivität des ECD's wird 5-Brom-5-nitro-1,3-dioxan äußerst empfindlich registriert, so daß die Nachweisgrenze 2 pg absolut beträgt. Die durchschnittlichen Wiederfindungsraten wurden im angegebenen Konzentrationsbereich zu 96% ermittelt. Die Standardabweichung beträgt ±0,14 mg/100 g bei einem mittleren Gehalt von 2 mg/100 g. Der Zeitaufwand für parallel durchgeführte Doppelanalysen beträgt etwa 60 min. An einer Auswahl von Handelsproben wurde die Methode geprüft. Danach enthielten von 18 untersuchten Proben acht 5-Brom-5-nitro-1,3-dioxan zwischen 0,002 und 0,04%.

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Rapid method for the gas-chromatographic determination of 5-Bromo-5-nitro-1,3-dioxane in shampoos and bath preparations

Summary A simple and rapid method suitable for routine analysis was developed to determine 5-bromo-5-nitro-1,3-dioxane in non-emulsified cosmetics containing surfactants. Its concentration in shampoos, foam baths and shower bath preparations was expected between 0.001 and 0.1%. The qualitative and quantitative determination was made by gas chromatography with an electron-capture detector (ECD) after column-chromatographic separation. The sensitive recording of 5-bromo-5-nitro-1,3-dioxane is due to the intensive electron affinity of the molecule and the selectivity of the ECD. The detection limit is 2 pg. The average recovery rate in the given concentration range was ascertained to be 96%. The standard deviation is ±0.14mg/100g for an average content of 2mg/100g. The expenditure of time for a duplicate determination is about 60 min. A selection of 18 commercial products was examined. Eight samples contained 0.002–0.04% of 5-bromo-5-nitro-1,3-dioxane.

     

Determination of sulphhydryl compounds in physiological fluids by liquid chromatography with polarographic detection

Summary A polarographic detector with a horizontal, fast dropping mercury electrode has been applied for the determination of thiols in physiological fluids. To establish suitable detection conditions first some basic studies on the polarographic behaviour of penicillamine, glutathione and cysteine were performed. This type of detection shows a high selectivity and reasonably low detection limits for sulphhydryl compounds. Detection limits of 6×10^–7 mol l^–1 for penicillamine and cysteine and 8×10^–7 mol l^–1 for glutathione were found. A good linearity has been observed over a concentration range of three orders. The detector has successfully been applied to the determination of penicillamine in urine and serum samples.

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Bestimmung von Sulfhydrylverbindungen in physiologischen Flüssigkeiten durch Flüssigkeits-Chromatographie mit polarographischer Detektion

Zusammenfassung Ein polarographischer Detektor mit horizontaler, schnell tropfender Quecksilberelektrode wurde zur Bestimmung von Thiolen in physiologischen Flüssigkeiten angewendet. Zur Feststellung geeigneter Bedingungen wurden zunächst grundlegende Untersuchungen zum polarographischen Verhalten von Penicillamin, Glutathion und Cystein durchgeführt. Das Verfahren bietet hohe Selektivität und niedrige Nachweisgrenzen (6 · 10^–7 mol/l für Penicillamin und Cystein, 8 · 10^–7 mol/l für Glutathion). Linearität besteht über drei Größenordnungen. Der Detektor wurde mit gutem Erfolg für die Penicillaminbestimmung in Harn und Serum verwendet.

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

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On leave from the Technical University of Gdansk     

Photometrische Borbestimmung im Picogramm-Bereich

Zusammenfassung Eine Methode zur qualitativen und quantitativen Erfassung sehr kleiner Absolutmengen Bor als Bor-Curcumin-Komplex wird beschrieben. Der Komplex wird auf einem Silberblech in einer Salzsäure-Eisessigmischung entwickelt und in Aceton gelöst auf Chromatographiepapier übertragen. Zum qualitativen Nachweis wird das überschüssige Reagens chromatographisch abgetrennt. Die Erfassungsgrenze beträgt 200 pg B (= 2 · 10^–10g). Zur quantitativen Erfassung wird in einer einfachen Vorrichtung der Komplex unmittelbar auf dem Papier photometrisch bestimmt. Bestimmungsgrenze 200–1000 pg; Standardabweichung s=60 pg B; Zeitdauer der Bestimmung etwa 1 Std.

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Summary A method has been developed for the qualitative and quantitative detection of very small amounts of boron. A boron curcumin complex ist produced on a sheet of silver in a hydrochloric-acetic acid mixture, solved in acetone, and transferred on chromatographic paper. For the qualitative detection the excess reagent is separated by paper chromatography. Limit of detection is 200 pg of boron (= 2 · 10^–10 g). A simple experimental device has been developed for the quantitative photometric determination of the complex; the absorbancy is measured directly on the paper in transmission. Limit of detection: 200–1000 pg; standard deviation: s=60 pg of B; operating time: about 1 hour.

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Herrn Prof. Dr. C. Mahr zum 65. Geburtstag gewidmet.

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Der Deutschen Forschungsgemeinschaft und dem Verband der Chemischen Industrie (Fonds der Chemischen Industrie) danken wir für finanzielle Förderung der Arbeit.     

Analysis of nicotine as a trichloroethyl carbamate by gas chromatography with electron-capture detection

Nicotine was subjected to reaction at 90 degrees with trichloroethyl chloroformate in the presence of pyridine to form a carbamate in which the pyrrolidine ring was opened. Upon heat treatment, this carbamate partially formed the corresponding olefin. About 10 pg could be detected with an electron-capture detector and 60 pg with an alkali flame-ionization detector. The extraction was studied with 14C-labelled nicotine. Methylene chloride was suitable for extraction from diluted plasma, whereas toluene containing 5% of heptafluorobutanol was used in a re-extraction step and also as the chloroformate reaction medium. Due to a nicotine blank the limit for quantitative determinations was 10 ng/ml in plasma (sample volume 1 ml). N-n-Propylnornicotine was used as an internal standard. The precision at the 30 ng/ml level was +/- 8.8% (n = 7).     

Gas-Chromatographic Determination of Butanol and Butyl Acrylate in Aqueous Solutions with the Use of Headspace Analysis

A procedure has been developed for the determination of the concentration of butanol and butyl acrylate in aqueous solutions in the range of 0.5–20 MPC. The procedure is based on static headspace gas-chromatographic analysis on a column filled with the Chromaton N-AW-HMDS sorbent containing 15 wt % of polyethylene glycol adipate with detection by a flame-ionization detector.     

Gas chromatography of epinephrine and norepinephrine after derivatization with chloroformates in aqueous media

Optimal conditions for the reaction of alkyl chloroformates with epinephrine and norepinephrine in aqueous solution have been evaluated. The maximal yield with 0.06 M methyl chloroformate was in the pH range 7.0–8.5. The derivatives formed are isolated by extraction with methylene chloride and gas chromatographed on 3% QF-1 with a nitrogen-selective detector after trimethylsilylation of the alcohol group.     

Hydride generation-graphite furnace atomic absorption spectrometry: new prospects

Summary Methods are described for the interference free determination of As and Se in seawater as well as marine tissues and sediments based on the generation of AsH₃, and SeH₂ using NaBH₄ with subsequent trapping in a graphite furnace at 600° C. Calibration is achieved with simple aqueous working curves having sensitivities of 24±4 and 72±17 pg/0.0044 A for As and Se, respectively. Absolute detection limits of 30 pg As and 70 pg Se are estimated. Precision of determination is 2–3% for As and 5–10% for Se.

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Graphitofen-AAS mit Hydriderzeugung: neue Entwicklungen

Zusammenfassung Verfahren werden beschrieben zur störungsfreien Bestimmung von As und Se in Meereswasser sowie marinen Geweben und Sedimenten, die auf der Erzeugung von AsH₃ und SeH₂ mit Hilfe von NaBH₄ und anschließender Graphitofen-AAS (600° C) beruhen. Die Eichung erfolgt mit einfachen Eichkurven, die mit wässrigen Lösungen hergestellt werden (Empfindlichkeit: 24±4 bzw. 72±17 pg/0,0044 A für As bzw. Se). Die absoluten Nachweisgrenzen liegen bei 30 pg As und 70 pg Se. Die Präzision beträgt 2–3% für As und 5–10% für Se.

     

Ein empfindlicher Entladungsdetektor für die Gaschromatographie

Zusammenfassung Ein Detektor wird beschrieben, der durch elektrische Funkenentladung in Edelgasatmosphäre weniger als 10^–8 g flüchtiger Substanzen wie Hexan oder Benzol nachzuweisen gestattet.

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A sensitive discharge detector for gaschromatography

Summary The detector described allowes the detection of less than 10^–8 g of volatile substances like hexane or benzene by means of electric spark discharge in noble gas atmosphere (Argon).

     

Multiresidue analysis of phenylurea herbicides in environmental waters by capillary electrophoresis using electrochemical detection

A rapid multiresidue method has been developed for the analysis of seven phenylurea herbicides in the presence of two s-triazines in environmental waters. A simple end-column electrochemical detector was used in combination with a commercially-available capillary electrophoresis instrument with UV detection. The determination of phenylurea pesticides using micellar electrokinetic capillary chromatography with electrochemical detection represents the first such determination that has been reported. In both detection systems, linear ranges were obtained for the seven phenylurea herbicides at concentrations lower than 2.0×10^–5 mol l^–1, in 0.020 mol l^–1 phosphoric acid at pH 7.0 and containing 0.020 mol l^–1 of sodium dodecylsulfate, in order to obtain selectivity in the additional separation by a micellar distribution process. Under these conditions a detection limit lower than 5.0×10^–6 mol l^–1 (0.25 pmol of pesticide) was achieved for most of them. The pesticides were resolved in less than 30 min.     

Enzyme sensor for L-lactate using differential pulse amperometric detection

An enzyme sensor using differential pulse (DP) amperometric detection has been developed based on the measurement of the reduction current of the oxidized form of -nicotinamide adenine dinucleotide (NAD⁺) consumed by an enzyme reaction. This biosensor has the definite advantage to prevent interference caused by electrooxidative species such as ascorbate and uric acid and exhibits higher sensitivity and selectivity in comparison to the classical DC amperometric detector. The linear detection range of this biosensor was 5.0×10^–5 — 5.0×10^–4 mol/l and the relative standard deviation (R.S.D.) at 2.5×10^–4 mol/l was 5.0%.     

Determination of traces of bismuth in copper by anodic stripping voltammetry

Summary Procedures are described for the determination of bismuth impurities in. copper using anodic stripping voltammetry on a hanging mercury drop electrode. Bismuth was previously separated from copper by cation or anion exchange in hydrochloric acid. The method was applied to the analysis of commercially available high purity copper, showing satisfactory sensitivity and accuracy. The detection limit was about 2×10^–9 M bismuth in solution for a pre-electrolysis time of 15 min (–0.5 V vs. Ag/AgCl); this corresponds to 0.004 ppm of bismuth for a 1 g sample and a final volume of 10 ml after separation.

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Bestimmung von Wismutspuren in Kupfer durch anodische Amalgamvoltammetrie

Zusammenfassung Mit hängendem Quecksilbertropfen. Wismut wird vor der Bestimmung durch Kationen oder Anionenaustausch aus salzsaurer Lösung vom Kupfer abgetrennt. Das Verfahren wurde zur Analyse von handelsüblichem hochreinem Kupfer angewendet. Mit einer Vorelektrolysedauer von 15 min (–0,5 V gegen Ag/AgCl) konnten noch 2×10^–9 M Bi bestimmt werden; das entspricht 0,004 ppm Bi für eine 1 g-Probe bei einem Endvolumen von 10 ml nach der Trennung.

     

Electron-capture determination of metoclopramide in biological fluids using fused silica capillary columns. Application to placental transport studies in sheep and humans

An electron-capture gas-liquid chromatographic assay for metoclopramide using cross-linked fused silica capillary columns which provides improved selectivity and sensitivity is reported. A 25 m X 0.31 mm fused silica capillary column was used for all analyses. Linearity was observed in the range of 4--40 ng of metoclopramide base per 0.25--0.5 ml of plasma. This represents from ca. 0.9--9.0 pg at the detector employing a split ratio of 30:1 and an injection volume of 2 microliters. Applicability of the method is demonstrated by the analysis of human and sheep plasma (maternal, fetal and neonatal) from metoclopramide placental transfer studies.     

Retention Time Locking in the Determination of Narcotic Drugs by Chromatography and Chromatography–Mass Spectrometry

The use of retention time locking (RTL) in the development of unified procedures for the detection and quantitative determination of drugs in biological fluids was considered. With consideration for the use of RTL, a chromatographic procedure with flame-ionization and mass-selective detection was developed for the detection and quantitative determination of opiates and their synthetic analogs; phenylalkylamine derivatives; cocaine; ketamine; and other narcotic drugs, their derivatives, and metabolites in urine. The analytical ranges for chromatography–mass spectrometry were 0.05–1000 and 0.005–1000 g/mL under the conditions of total ion current (TIC) scanning and selected ion monitoring (SIM), respectively. With flame-ionization detection (GC–FID), the analytical range was 0.5–1000 g/mL.     

Optimization of the two-phase separation process in flow-injection analysis with an electron-capture detection system

A liquid-gas-phase tubing separator was designed and its operation studied in comparison with a PTFE tape-based separator. The relative efficiencies of the two separators were compared after injection into the carrier solution of a sample containing free chlorine using a chromatographic electron-capture detector for detection in the gaseous phase. The membrane separator contained porous PTFE tape whereas the tubular separator consisted of microporous PTFE membrane tubing. The two separators were compared with respect to sensitivity and reproducibility, simplicity of design and liability to interferences. Linear ranges and free chlorine detection limits were established for each of the two separators, that of the PTFE tape-based separator being 100 μg 1^?1 and that of the tubing device 50 μg 1^?1.     

Application of pentafluorophenyl hydrazine derivatives to the analysis of nabumetone and testosterone in human plasma by liquid chromatography–atmospheric pressure chemical ionization–tandem mass spectrometry

Two carbonyl compounds, nabumetone and testosterone, were derivatized with pentafluorophenyl hydrazine (PFPH) and analyzed by atmospheric-pressure chemical-ionization mass spectrometry. The PFPH derivatives underwent dissociative electron capture in negative-ion APCI (ECAPCI) and gave intense [M–20]^– ions in the mass spectra. In positive-ion APCI, the PFPH derivatives underwent efficient protonation and gave intense [M+H]⁺ ions in the mass spectra. In CID, the major product ions of the [M–20]^– ions in ECAPCI corresponded to the partial moiety of PFPH. In contrast, the major product ions of [M+H]⁺ corresponded to the partial moiety of the analyte. By using selected reaction monitoring (SRM) detection, low pg of nabumetone (1 pg) and testosterone (7 pg) could be detected in both ECAPCI and positive-ion APCI. In comparison with the detection limits (SRM) of the underivatized analytes, use of the PFPH derivatives resulted in 2500-fold and 35-fold sensitivity enhancements for nabumetone and testosterone, respectively. The PFPH derivatives were applied to the analysis of nabumetone and testosterone in human plasma by both ECAPCI and positive-ion APCI and were found to enable detection of 0.1 ng mL^–1 nabumetone in spiked plasma. For testosterone, endogenous testosterone in female plasma was detected in both ECAPCI and positive-ion APCI.     

Determination of particle-bound trace metals in high purity hydrogen chloride

Summary Two analytical procedures for the determination of particle-bound trace metals in high purity hydrogen chloride are described. Polycarbonate membrane filters with a pore diameter of 0.05 m were used for sampling. Membrane filtration with subsequent instrumental neutron activation analysis (using irradiation with a thermal neutron flux of 10¹³ n cm^–2 s^–1 and irradiation and measurement times of either 20 min) has made it possible to determine the elements Br, Mg, Mn, Na, Sb, Sn, Te, Ti and Zn. For a gas sample volume of 500 l the detection limits determined are in the range of 0.86 ng l^–1 for Zn to 0.30 pg l^–1 for Mn.The elements Cr, Cu, Fe, Mn and Ni were determined by membrane filtration with subsequent graphite tube furnace atomic absorption spectrometry. In this case the detection limits achieved are (for a gas sample volume of 500 l and 4 ml digestion solution) between 8.4 pg l^–1 for Fe and 2.1 pg l^–1 for Cu. The analytical procedures were applied for the characterisation of high purity hydrogen chloride, which is used in the manufacture of highly integrated semiconductor components, by trace analysis, both directly on the gas cylinder and at the 'point of use after passing through the supply system. A review of the status of element determination in high purity process gases is given.

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Bestimmung von partikelgebundenen Metallspuren in hochreinem Chlorwasserstoff

     

Gas-chromatographische Bestimmung von Wasser mit dem Elektronen-Einfang-Detektor im Nanogramm-Bereich

Zusammenfassung Wasser ist in organischen Lösungsmitteln im ng-Bereich gas-chromatographisch ohne Derivatisierung mittels eines linearisierten Elektroneneinfangdetektors (ECD) nach Abtrennung auf einer Porapak QS-Säule bestimmbar. Ausreichend wasserfreie Lösungsmittel ließen sich durch Trocknen mit aktivierten 4 Å-Molekularsieben oder superaktiven Aluminiumoxiden W 200, Woelm Pharma, Eschwege, herstellen. Um Wasserblindwerte aus der Raumluft auszuschließen, ist es notwendig, sämtliche Operationen in einer Box mit Umlauftrocknung durchzuführen. Wassermengen bis zu 15 ng absolut sind bestimmbar. Im Konzentrationsbereich 7–150 g/ml ist die Detektoranzeige für Wasser linear.

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Gas-chromatographic determination of water with the electron-capture-detector in the nanogram range

Summary Water can be determined directly in organic solvents in the ng range after separation on a porapak-QS column using a linear electron-capture detector (ECD). Organic solvents can be dried by activated 4 Å molecular sieves to a water content of 5 g/ml, about 0.3×10^–3 molar. To exclude water contamination all operations, storage of solvents and standards included, were made in a glove box with permanent drying of the inside atmosphere. The EC-detector allows to determine 15 ng of water absolute. In the range of 7–150 g/ml a linear response for water by the ECD has been found.