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921.
922.
Silyl enol ethers derived from 1-indanone, 2-indanone, α-tetralone and 4-chromanone react with thionyl chloride to give α-oxo sulfines (3) which can be either isolated or trapped by a cycloaddition reaction with a diene. 相似文献
923.
924.
Summary A study has been made of possible interferences upon the determination of selenium by hydride generation atomic absorption spectrometry (HGAAS), due to the presence of other hydride forming elements such as As, Ge, Bi, Te, Sn and Sb, and to a volatile element such as Hg. The interfering effects of these cations were determined at several concentration levels using sodium borohydride as the reductant and a commercially available semi-automatic system for the generation and the flameless combustion of the hydrides. It has been demonstrated that the determination of selenium by HGAAS is relatively free from interferences with regard to other elements that form volatile hydrides, except for tin and bismuth that strongly interfere.
Einfluß von flüchtige Hydride bildenden Elementen auf die Selenbestimmung als Hydrid durch AAS
Zusammenfassung Bei der AAS-Bestimmung von Selen als Hydrid wurde der Einfluß der hydridbildenden Elemente As, Ge, Bi, Te, Sn, Sb sowie auch des flüchtigen Elements Hg untersucht. Die Untersuchungen wurden bei verschiedenen Konzentrationen mit Natriumborhydrid als Reduktionsmittel durchgeführt. Dabei wurde ein handelsübliches halbautomatisches System zur Erzeugung und flammenlosen Verbrennung der Hydride benutzt. Es zeigte sich, daß die Selenbestimmung bis auf die stark störenden Elemente Sn und Bi relativ frei von Beeinflussungen ist.相似文献
925.
A highly sensitive gas chromatographic-mass spectrometric (GC-MS) analytical method for the determination of the opioid narcotics fentanyl, alfentanil, and sufentanil in industrial hygiene personal air samples and surface contamination wipes was developed and comprehensively validated. Sample preparation involved a single step extraction of the samples with methanol, fortified with a fixed amount of the penta-deuterated analogues of the opioid narcotics as internal standard. The GC-MS analytical procedure using selected ion monitoring (SIM) was shown to be highly selective. Linearity was shown for levels of extracted wipe and air samples corresponding to at least 0.1-2 times their surface contamination limit (SCL) and accordingly to 0.1-2 times their time weighted average occupational exposure limit (OEL-TWA) based on a full shift 9601 air sample. Extraction recoveries were determined for spiked air samples and surface wipes and were found to be quantitative for both sampling media in the entire range studied. The air sampling method's limit of detection (LOD) was determined to be 0.4 ng per sample for fentanyl and sufentanil and 1.6 ng per sample for alfentanil, corresponding to less than 1% of their individual OEL for a full shift air sample (9601). The limit of quantification (LOQ) was found to be 1.4, 1.2, and 5.0 ng per filter for fentanyl, sufentanil, and alfentanil, respectively. The wipe sampling method had LODs of 4 ng per wipe for fentanyl and sufentanil and 16 ng per wipe for alfentanil and LOQs of respectively, 14, 12, and 50 ng per wipe. The analytical intra-assay precision of the air sampling and wipe sampling method, defined as the coefficient of variation on the analytical result of six replicate spiked media was below 10 and 5%, respectively, for all opioids at all spike levels. Accuracy expressed as relative error was determined to be below 10%, except for alfentanil at the lowest spike level (-13.1%). The stability of the opioids during simulated air sampling was investigated. For fentanyl and sufentanil a quantitative recovery was observed at all spike levels, while for alfentanil recoveries ranged from 60.3 to 85.4%. When spiked air samples were stored at ambient temperature and at -15 degrees C quantitative recovery was found for fentanyl and sufentanil after 7 and 14 days. For alfentanil a slight loss seemed to occur upon storage during 7 days, being more explicit after 14 days. Ambient storage of spiked wipes seemed to lead to significant losses of all opioids studied, yielding recoveries of 37.7-88.3%. Upon storage of similar wipes at -15 degrees C a significantly higher recovery was found ranging from 77.3 to 88.3%. The developed analytical and sampling procedures have been recently applied in an explorative field study of which the results of surface contamination wipe sampling are presented in this paper. To our knowledge, this is the first study addressing the development and validation of analytical procedures for the assessment of external occupational exposure to potent opioid narcotics. 相似文献
926.
927.
Systems with a gauge degeneracy are characterized either by supplementary conditions, or by a set of generators of gauge transformations, or by a set of constraints deriving from Dirac's canonical constraint method. These constraints can be expressed either as conditions on the field algebra , or on the states on . In aC*-algebra framework, we show that the state conditions give rise to a factor algebra of a subalgebra of the field algebra . This factor algebra, , is free of state conditions. In this formulation we show also that the algebraic conditions can be treated in the same way as the state conditions. The connection between states on and states on is investigated further within this framework, as is also the set of transformations which are compatible with the set of constraints. It is also shown that not every set of constraints can give rise to a nontrivial system. Finally as an example, the abstract theory is applied to the electromagnetic field, and this treatment can be generalized to all systems of bosons with linear constraints. The question of dynamics is not discussed. 相似文献
928.
Wilhelm Bögershausen und Hendrik Roelof Van der Walt 《Fresenius' Journal of Analytical Chemistry》1965,213(3):161-173
Summary The paper presents a method for the analysis of gases, solutions and powdered samples by using a high-current arc discharge (80 amperes) in argon atmosphere. The determination of Ca, Al, Si and Cu in samples containing Na shows no interelemental effect.Temperatures from 16,000°K up to 26,700°K have been measured. By adding small quantities of N2, H2 and He to the argon plasma, changes in its geometrical shape, as well as the temperature distribution could be observed.
Auszug aus der Dissertation von Hendrik Roelof van der Walt, Phys.-Chem. Institut der Technischen Hochschule, München 1965. Tag der Promotion 14. Mai 1965.
Für anregende Hinweise und Diskussionen möchten wir Herrn Doz. Dr. H. Krempl und Herrn Dr. O. Vierle herzlich danken. Auch dem Bayerischen Staatsministerium für Wirtschaft und Verkehr und der South African Iron and Steel Ind. Corp., Ltd., Pretoria/Südafrika, sind wir für die bereitgestellten Mittel zu Dank verpflichtet. 相似文献
Auszug aus der Dissertation von Hendrik Roelof van der Walt, Phys.-Chem. Institut der Technischen Hochschule, München 1965. Tag der Promotion 14. Mai 1965.
Für anregende Hinweise und Diskussionen möchten wir Herrn Doz. Dr. H. Krempl und Herrn Dr. O. Vierle herzlich danken. Auch dem Bayerischen Staatsministerium für Wirtschaft und Verkehr und der South African Iron and Steel Ind. Corp., Ltd., Pretoria/Südafrika, sind wir für die bereitgestellten Mittel zu Dank verpflichtet. 相似文献
929.
Hendrik Kokelenberg C. S. Marvel 《Journal of polymer science. Part A, Polymer chemistry》1970,8(11):3235-3249
In an attempt to prepare polymers which might be oxidized to compounds soluble in alkali diphenyl 1,5-anthracenedicarboxylate was reacted with diaminobenzidine, dimercaptobenzidine, and diaminobiphenol in the melt and with dimercaptobenzidine dihydrochloride in polyphosphoric acid. Compounds of high molecular weight were obtained and their thermal and oxidative stability evaluated. Model compounds were prepared and their ultraviolet spectra compared with those of the polymers. Oxidation with nitric acid or chromium trioxide yielded some anthraquinone derivatives, but side reactions prevented the formation of useful products. 相似文献
930.