Native vs photoinduced chemiluminescence in dimethoate determination

The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05ngmL -1 without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%. © 2011 Elsevier B.V.This work was supported by the Ministry of Education and Science of Spain (Project CTM2006-11991) and FEDER funds.Catalá Icardo, M.; López Paz, JL.; Choves Barón, C.; Pena Badena, A. (2012). Native vs photoinduced chemiluminescence in dimethoate determination. ANALYTICA CHIMICA ACTA. 710:81-87. https://doi.org/10.1016/j.aca.2011.10.043S818771

H2Electra – a platform for comparative analysis of integration concepts for hydrogen-based electric propulsion in regional aircraft

Over the past decade numerous novel concepts for electric flight have been elaborated. Each unique in its own way and based on various assumptions and technological advances projected for the future. Within each concept design decisions have to be made on component level, propulsion system level and aircraft level. In order to be able to evaluate and analyse both, advanced components technologies and innovative propulsion system architectures, as well as to understand the effect of each design decision, a common baseline platform has been developed to allow for comparative analyses. This work presents such a platform with the hydrogen-based electrified regional aircraft concept called H2Electra. The iterative design process developed for this purpose is presented. It allows for a holistic approach to the development of an aircraft, its electrified propulsion system as well as the sizing of the components therein. Two propulsion system integration concepts are being considered in the evaluation: one partially fuselage-integrated and one nacelle-integrated. Challenges and trade-offs between the two concepts were analysed and evaluated, with safety and reliability being key design and decision-making metrics, alongside block-fuel efficiency and power density. In particular, the design decision on a suitable bus voltage and its effect on the powertrain sizing and integration were investigated

Chromatographic hair analysis for natural kavalactones and their metabolites. A preliminary study

Purpose: Kava is a traditional Pacific beverage made from the root of Piper methysticum. It is mainly used for its sedative properties due to lipophilic lactones called kavalactones. Kava action mechanisms include cell membrane stabilisation, inhibition of intracellular Ca2+ increase and enzyme inactivation. Chronic or heavy consumption of kava is responsible for the skin taking on a scaly aspect. Biologically, an isolated increase in serum gamma-glutamyltransferase is noted. “Kava bars” or “nakamals” are numerous in the Pacific. In northern Australia, the use of kava is regulated in order to fight against the abuse of this drink. In metropolitan France, we note the presence of some kava bars in several cities. In New Caledonia, in ten years (December 2002–May 2013), we identified twenty-six cases where kavalactones were found in the blood of perpetrators or victims of fatal accidents (resulting in nineteen deaths and twenty-one people seriously injured), suicides and attacks. In addition, in nine cases of sudden unexplained deaths, significant concentrations of kavalactones were found in the blood of the victims. These figures, however, are understated as toxicological screening was not done systematically. As all toxicological laboratories are not identically equipped, we developed three simple and sensitive methods for the determination of kavalactones in human hair using HPLC-DAD, LC-MS/MS and GC/TOF-MS. Methods: Hair samples were collected from nine people of different origins (Caucasian, Melanesian, Indonesian and African). Kava consumption varied among these people (from a single oral dose of a medication sold on the internet, to a daily intake of several units of the kava beverage). Results: Using HPLC-DAD, the concentrations of kavalactones in human hair samples ranged between 0.2 and 25 ng/mg for kavain, 0.5 and 34 ng/mg for 7,8-dihydrokavain, 0.7 and 8 ng/mg for yangonin, 1 and 14 ng/mg for 5,6-dehydrokavain (=desmethyoxyyangonin) and 0.9 and 6 ng/mg for the metabolite 12-hydroxy-5,6-dehydrokavain. Methysticin, 7,8-dihydromethysticin and the metabolite 11-hydroxy-5,6-dehydrokavain were detected but not quantified. Additionally, 12-hydroxykavain and 12-hydroxy-7,8-dihydrokavain were detected by LC-MS/MS in one case. General screening for other drugs as well as confirmation of the HPLC-DAD results was performed by GC/TOF-MS. Conclusions: The results of this pilot study indicate that kavalactones (kavain, 7,8-dihydrokavain, methysticin, 7,8-dihydromethysticin, 5,6-dehydrokavain (=desmethyoxyyangonin) and yangonin) accumulate in the keratin matrix of hair and can provide an easily applicable system for assessing chronic consumption of kava. This preliminary study must continue on a larger number of subjects using GC/TOF-MS and LC-MS/MS in order to conduct a comparative analysis among the three methods

Kava ichthyosis: a nitric oxide synthase inhibition?

Purpose: Kava is a traditional Pacific beverage made from the root of Piper methysticum. It is mainly used for its sedative properties due to lipophilic lactones called kavalactones. Various preparations or medications made from this plant can be purchased via the internet. Kava action mechanisms include cell membrane stabilisation, inhibition of intracellular Ca2+ increase and enzyme inactivation. Chronic or heavy kava consumption results in the skin taking on a scaly aspect. Biologically, an isolated increase in serum gamma-glutamyltransferase is apparent. Cases of sudden death after heavy kava sessions have occurred in Australia, and nine cases in New Caledonia were reported by our forensic laboratory during the 2000−mid-2013 period. No clear explanation has been given. We describe the possible action mechanism. Methods: We monitored 116 heavy kava drinkers. A multiple-probe drug cocktail was used on six other volunteers, all heavy and chronic kava drinkers, before and after kava abstinence to carry out CYP450 phenotyping. Results: The heavy chronic drinkers showed an isolated increase in GGT without any biological or clinical abnormality other than scaly skin. With the multiple-probe drug cocktail an inhibition of the CYP1A2 isoenzyme was demonstrated. In kava dermopathy a lack of epithelial nitric oxide production leading to an increased S-nitroso-glutathione degradation by the epithelial gamma-glutamyltransferase should be considered. Conclusions: As there are close structural and functional similarities between nitric oxide synthase (NOS) and CYP1A2, and as we have formerly demonstrated that kava inhibits CYP1A2, an inhibition of NOS in chronic kava drinkers must be studied to see if ichthyosis can be explained, and if high blood GGT level is a reflection of epithelial cell GGT activity. Furthermore, a decrease in NO bioavailability can cause myocardial and vascular dysfunctions and hypercoagulability, leading to acute coronary syndrome or ischemic stroke. This mechanism should be explored in cases of “post-kava session sudden death”