Schnelle Methoden zur Bestimmung der Hauptelemente in den Konzentraten und Mutterlaugen der Seesalzgewinnung

Zusammenfassung Es werden Methoden zur Bestimmung der Hauptelemente in den Mutterlaugen bei der Seesalzgewinnung beschrieben. Die Kationen und Anionen werden durch Ionenaustausch in einer Kolonne mit Wofatit KPS-200 in H-Form getrennt. Im Durchlauf werden Chlorid und Sulfat als Summe und Chlorid allein bestimmt. Sulfat wird als Differenz berechnet. Calcium, Magnesium und Eisen bestimmt man komplexometrisch. Die Summe Kalium und Natrium bestimmt man komplexometrisch als Magnesium nach lonenaustausch in einer Wofatit KPS-200-Säule in Mg²⁺-Form. Natrium wird als Natriumzinkuranylacetat bestimmt, und Kalium ergibt sich aus der Differenz.     

Quantum chemical study of the tautomerism, geometry, and electronic structure of 1,2,3- and 1,2,4-triazoles

A systematic study was carried out on the tautomerism and geometry of 1,2,3- and 1,2,4-triazoles using the semiempirical AM1, PM3, MNDO, and MINDO/3 methods and nonempirical quantum chemical methods taking account of electronic correlation (MP2). The semiempirical methods were found to give incorrect results for the tautomerism of these triazoles, while the nonempirical methods correctly give the energy relationships and show enhanced stability for 2H-1,2,3- and 1H-1,2,4-triazoles attributed to the interaction of the unpaired electron pairs of the adjacent nitrogen atoms. Optimization of the geometry of 2H-1,2,3-triazole by the nonempirical methods showed that bases such as 6-21G and more expanded bases must be used and that electronic correlation should be taken into account. The use of updated calculation methods in the case of 1H-1,2,4-triazole did not give improved results.Prof. Asen Zlatarov University, 8010 Burgas, Bulgaria. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 645–651, May, 1998.     

Benzthiazolderivate, 5. Mitt.: Dequartärisierung und nucleophile Substitution von Benzthiazoliumsalzen

Zusammenfassung Benzthiazoliumsalze (I) reagieren, wie an 20 Beispielen gezeigt wird, mit nucleophilen Partnern unter gleichzeitiger Labilisierung des Oniumsystems zu 2-substituierten 2,3-Dihydro-benzthiazolen (dequartärisierende nucleophile Substitution). Der Reaktionsverlauf wird von der Art der nucleophilen Komponente bestimmt: Freie Amino-(Hydrazino)-Verbindungen und I lassen sich im Molverhältnis 21, die Alkalisalze von Aminocarbonsäuren und-sulfosäuren im Molverhältnis 11 umsetzen. Verbindungen mit reaktiver Methylengruppierung reagieren glatt mit der äquivalenten Menge I, wenn in Gegenwart einer Base gearbeitet wird. Die verwendeten I-Verbindungen sind: 2-Äthoxy-3-methyl-benzthiazolium-tetrafluoroborat (VII) und 2-Methylmercapto-3-methylbenzthiazolium-methylsulfat (VIII).     

Multidimensional On-Line SPE for Undisturbed LC-MS-MS Analysis of Basic Drugs in Biofluids

In bioanalytical LC-MS-MS matrix effects influencing the ionization process are a major concern with respect to the quality of the results obtained. In general such matrix effects are directly related to an insufficient sample clean-up of the biofluids. In order to establish a MS-adequate clean-up procedure for basic analytes present in biofluids (e.g. urine, plasma) which is based on solid-phase extraction (SPE) principles a combination of tailor-made SPE column packings and automated column-switching was developed. This novel, multidimensional (MD) SPE platform relies on the combination of a SPE column packed with a restricted access material (RAM) allowing size-exclusion and reversed phase chromatography (SEC-RPC) and a second SPE column packed with a mixed-mode phase (MMP) allowing ion exchange and reversed phase chromatography (IEX-RPC). For the evaluation of this MD-SPE platform 8 tricyclic antidepressants and two metabolites were chosen as model analytes. In order to monitor matrix effects, i.e. ion suppression, postcolumn infusion experiments were performed and compared with a two-dimensional SPE column mode (SEC-RPC). The MD-SPE platform is highly efficient for removal of low and high molecular weight sample components which suppress ionization to varying extend. In addition electrospray ionization of the model analytes is not affected by inter- or intra-individual variations in the composition of the matrix investigated. It is also independent of the species the biofluids originate from. It was demonstrated that the MD-SPE platform has a generic potential with respect to on-line SPE of basic drugs having a pKa > 6.5 and a moderate to low polarity and being present in different biofluids.     

A semiempirical and ab initio MO study of the tautomers ofN-unsubstituted pyrazolones [hydroxy pyrazoles]

Semiempirical (MNDOC, MINDO/3, AM1, and MNDO) and ab initio (STO-3G and 4-31G basis sets) calculations on the relative stabilities, structures, and dipole moments of the 8 theoretically possible tautomeric forms of pyrazolone are reported. It is shown that MNDO + CI and MINDO/3 predict that 5-hydroxy pyrazole, 3-hydroxy pyrazole, and 2-pyrazolin-5-on are the most stable. These results correspond to the known experimental data. Of all used quantum chemical methods, the MINDO/3 results for the dipole moments of the investigated tautomers are in best agreement with the known experimental data. The electronic excitation energies were calculated using the CNDO/S-CI method. The results are in good agreement with the experimental UV spectra.     

Strong electric field eigenvalue asymptotics for the Schrödinger operator with electromagnetic potential

We consider the Schrödinger operator with electric potential V, which decays at infinity, and magnetic potential A. We study the asymptotic behaviour for large values of the electric field coupling constant of the eigenvalues situated under the essential-spectrum lower bound. We concentrate on the cases of rapidly decaying V (e.g. V L ^m/2( ^m ) for m 3) and arbitrary A, or slowly decaying V (i.e. V(x |x|^– , (0,2), as |x| ) and magnetic potentials A corresponding to constant magnetic fields B = curl A.Partially supported by the Ministry of Culture, Science and Education under Grant No. 52.     

Sharp bounds on the number of scattering poles for perturbations of the Laplacian

Sharp bounds on the numberN(r) of the scattering poles in the disc |z|r for a large class of compactly supported perturbations (not necessarily selfadjoint) of the Laplacian in ⁿ ,n3, odd, are obtained. In particular, in the elliptic case the estimateN(r)Cr ⁿ+C is proved.Partially supported by Bulgarian Scientific Fondation under grant no. MM8/91     

Raman spectroscopic study of the hydration of short-chain poly(oxyethylene)s C <Subscript>1</Subscript>E<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>C <Subscript>1</Subscript> (<Emphasis Type="Italic">n</Emphasis>=1−4)

The hypothesis that the degree of hydration of poly(oxyethylene) (POE) in aqueous solution depends on the mole ratio of water molecules to ether oxygen atoms in the molecule has been verified by studying the isotropic Raman spectra in the O−H stretching region for four short-chain POEs (C ₁E _n C ₁ withn=1−4). Excellent coincidence of the O−H stretching Raman band for all four POEs studied in the range of mole ratio H₂O/O _ether from 25 to 0.6 was observed, thus confirming the assumption stated above. A conclusion that all ether oxygen atoms in the POE molecule participate in hydrogen bonding with water molecules has been made.