John F. Alder

Communication. An optical potassium ion sensor

An optical fibre sensor is described which is sensitive to potassium ions in aqueous solution in the concentration range 10–3–10–1M.

Denuder Tubes for Sampling of Gaseous Species A Review

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Arylethylamine psychotropic recreational drugs: a chemical perspective.

The arylethylamines substituted in the aryl ring, side-chain carbons and on the terminal amine, comprise a large number of human mood and behaviour altering chemicals. Some of these psychotropic drugs have been used since pre-history, but in many states are proscribed and are consequently subject to clandestine synthesis and illegal traffic world-wide in the forms particularly of amphetamines and to a lesser extent tryptamines. The chemistry employed in the synthesis of these compounds is dictated often by the available precursors and relies usually on relatively simple, unsophisticated conversion reactions to a suitable product. The internet web sites and documentation of the recreational drug culture have been studied alongside the professional scientific and regulatory literature. The review demonstrates the great complexity of the chemistry and neuro-pharmacology of these chemicals and the challenge faced by legislative bodies to control their traffic and use for the sake of social welfare.

The investigation of coating materials for the detection of nitrobenzene with coated quartz piezoelectric crystals

Abstract Powdered activated charcoal, quadrol tetrabase and polyethylene glycol (PEG)-400 and -750 are used as coatings on 15-MHz quartz piezoelectric crystals for the detection of nitrobenzene in air. The response to nitrobenzene over the range 2–10 ppm (2–10 × 10 −6 mol mol −1 )_was almost linear for all the coatings except charcoal which exhibited marked non-linearity, as well as greater sensitivity than the other coatings. The charcoal response was linear over the range 0.7–7.6 ppm nitrobenzene. For the other coatings, sensitivity increased in the order tetrabase

Detection of toluene diisocyanate with a coated quartz piezoelectric crystal: Part 3. Practical coatings for a humidity-corrected detector

Abstract Dithizone and tri-n-octylphosphine oxide (TOPO) were tested as coatings for quartz piezoelectric crystals to be used in a detector for touene diisocyanate (TDI). Cobalt(II) chloride and polyethylene glycol (PEG) with molecular weights of 400 and 1540 were tested for suitability as coatings for detecting humidity variations so that correction for humidity could be obtained from a two-crystal system. Sensitivities for TDI of 12 and 75 Hz ppm −1 were found with dithizone and TOPO, respectively, between 0 and 1 ppm TDI. Cobalt chloride-coated crystals showed a sensitivity for water of 0.053 Hz ppm −1 at 8000 ppm water and about 40 Hz ppm −1 for TDI at the 2 ppm level. PEG-400 and PEG-1540 provided sensitivities to water of 0.038 and 0.051 Hz ppm −1 respectively, and the response was linear over the range 9000—13 000 ppm water. All coatings showed irreversible behaviour towards TDI.

Optical fibre chemical sensors

ZusammenfassungFaseroptische chemische Sensoren erlauben die Bestimmung einer großen Zahl von Anionen, Kationen, Gasen und organischen Verbindungen in Lösung oder Gasphasen. Für den direkten Einsatz in Komplexen oder aggressiven Mischungen stellen die Ansprüche hinsichtlich Selektivität, Empfindlichkeit, Langlebigkeit und Reproduzierbarkeit hohe Anforderungen an die Sensorreagentien und das schützende Membransystem. Diese Anforderungen werden dadurch gemildert, daß Probenvorbereitung und Trennverfahren vorausgeschickt werden, was die beste Ausnutzung der Sensoreigenschaften ermöglicht. Für einfachere Matrices oder solche, die im wesentlichen unveränderlich bleiben, stellen maßgeschneiderte Sensoren ein nützliches Mittel für die spezifische Bestimmung dar.Die Notwendigkeit liegt auf der Hand, daß die Reagentien über einen möglichst großen Bereich von Einsatzbedingungen hohe Empfindlichkeit und hohe Selektivität aufweisen — eine wichtige Anforderung.SummaryOptical fibre chemical sensors permit the determination of a wide range of anions, cations, gases and organic compounds in solution or gas phases. For in-line operation in complex or aggressive mixtures the requirements of selectivity, sensitivity, longevity and reproducible response impose great demands on the sensor reagents and protective membrane system. These demands will be alleviated by preceding the sensors with sample pretreatment and separation procedures and permit the best exploitation of their characteristics. For simpler analytical matrices, or those which are largely unchanging, tailored sensors provide a very useful means of specific determination. There is a clear need for high sensitivity and high selectivity of the reagent over as wide a range of conditions as possible — a demanding requirement.

Optical fibre sensor for detection of hydrogen cyanide in air. Part 2. Theory and design of an automatic detection system

Abstract An automatic spectrophotometric instrument is described which monitors the colour change due to the reaction of cyanogen chloride with 4-methylpyridine and pyrimidinetrione impregnated on XAD-7 resin beads by measuring the spectral absorption at 530–565 nm using a green light emitting diode with peak intensity at 560 nm. Background absorption was monitored using a red light emitting diode. Randomised fibre optic bundles were used to collect and guide the light to silicon planar photodiode detectors.

Optical fibre sensor for detection of hydrogen cyanide in air : Part 1. Reagent Characterization and Impregnated Bead Detector Performance

Abstract Hydrogen cyanide is detected by oxidation of the atmospheric sample with chloramine-T (sodium N -chloro-4-methylbenzenesulphonamide) impregnated on XAD-7 resin beads to yield cyanogen chloride. This reacts with 4-picoline (4-methylpyridine) and barbituric acid (pyrimidinetrione) also impregnated on XAD-7 beads, to yield a colour change with a maximum absorbance change around 530–565 nm. Using a modulated monochromated white light source and lock-in detector, the reagent system was able to detect HCN in air at 1 μl l −1 within 1 min. A flow- rate through the reagent cell of 60 ml min −1 air was chosen to give the best overall performance. Lifetime tests indicated a loss of 4-picoline due to evaporation, although reagent beads through which air was drawn at 100 ml min −1 for 66 h were still able to detect 10 μl l −1 HCN in less than 1 min. The method is not reversible and could not be used to monitor HCN concentration in air, but is nonetheless useful for the detection of HCN below its toxic level in a short time.

Analytical chemistry of synthetic routes to psychoactive tryptamines. Part I. Characterisation of the Speeter and Anthony synthetic route to 5-methoxy-N,N-diisopropyltryptamine using ESI-MS-MS and ESI-TOF-MS

5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT), a new psychoactive tryptamine derivative, has been synthesised by the Speeter and Anthony procedure. This synthetic route was characterised by ESI-MS-MS, ESI-TOF-MS and NMR. Side products have been identified as 3-(2-N,N-diisopropylamino-ethyl)-1H-indol-5-ol (5), 2-N,N-diisopropylamino-1-(5-methoxy-1H-indol-3-yl)-ethanol (6), 2-(5-methoxy-1H-indol-3-yl)-ethanol (7) and 2-N,N-diisopropylamino-1-(5-methoxy-1H-indol-3-yl)-ethanone (8).

Detection of toluene diisocyanate with a coated quartz piezoelectric crystal: Part 4. A portable automatic detector with humidity correction

Abstract Microcomputer-controlled measurement of the frequency of two differently-coated quartz piezoelectric crystals and subsequent data processing permits the immediate correction of instrumental response for fluctuations in water vapour concentration and the display of the corrected toluene diisocyanate concentration in air. Crystal pairs with coatings of polyethylene glycol 400 or 1540 or tri-n-octylphosphine oxide and cobalt(II) chloride were used to illustrate the performance of the instrument. Toluene diisocyanate can be detected over the range 0.1—15 ppm in atmospheres with relative humidities ranging from 30 to 60% without significant interference from changes in water concentration.