Comparison of gas chromatographic and high-performance liquid chromatographic assays for the determination of debrisoquine and its 4-hydroxy metabolite in human fluids

A comparison of an established gas chromatographic assay for 4-hydroxydebrisoquine and debrisoquine and a modified high-performance liquid chromatographic assay was made. Both assays used guanoxan as the internal standard and required derivatization of all three compounds with acetylacetone at 96 degrees C for 2.5 h and subsequent ethereal extraction and cleaning steps before chromatographic analysis. For detailed pharmacokinetic studies the gas chromatographic assay was more sensitive in the measurement of low concentrations in plasma, but the liquid chromatographic assay was adequate for phenotyping the 4-hydroxylation of debrisoquine in a population. In the latter assay a mobile phase consisting of 70% methanol in water at pH 3.5 (adjusted with orthophosphoric acid containing 10 mM 1-pentanesulphonic acid was employed (flow-rate 1.5 ml/min) with a pre-column (C8) linked to a reversed-phase muBondapak C18 cartridge in a Z-module. The eluate was detected at 248 nm. With this assay it was observed that the buccal absorption of debrisoquine and 4-hydroxy-debrisoquine was affected by the pH of the buccal medium. This indicates that urinary pH may influence the excretion of both substances at high pH. The debrisoquine-to-4-hydroxydebrisoquine ratio may be dose-dependent.     

Examination of the different procedural steps in the determination of organotin compounds in water samples

Previous animal experiments suggested that the Magos cold vapor atomic absorption spectroscopic (CVAAS) method might overestimate the concentrations of inorganic mercury (I-Hg) in the presence of methylmercury (MeHg). In the present study it is shown that this error is due to a fast degradation of MeHg during the formation of the analytical signal. For brain samples, about 5% of the total amount of MeHg in the reaction vessel is degraded to I-Hg. Speciation of Hg in aqueous solution of MeHg chloride, after purification with ionexchange chromatography using the Magos method, showed that about 9% was I-Hg. Analysis by NMR of MeHg chloride and MeHg hydroxide showed that less than 1% was in the form of I-Hg. The absolute magnitude of the error in the CVAAS method is dependent on the amounts of SnCl₂ and MeHg in the reaction vessel; however, the ratio of I-Hg to total (T-Hg) is shown to be independent of the amount of MeHg (25.5–255 ng as Hg) in the reaction vessel. A procedure for corrections is proposed, based on the results from these studies and empirical data from speciation analyses of brain tissue from MeHg-exposed rats and rabbits.     

Analysis of terbutaline in human plasma by high-performance liquid chromatography with electrochemical detection using a micro-electrochemical flow cell.

A high-performance liquid chromatographic method is described for the determination of terbutaline in human plasma in the range 1-35 ng/ml. Detection was achieved using a carbon fibre micro-electrochemical detector and a column-switching system. The microelectrode cell has advantages over conventional glassy carbon electrode-based detection systems in that it is easy to prepare, flexible in its operation and suffers less trouble from problems such as air bubbles and leaks. Furthermore, it has a better detection limit for terbutaline (0.8 ng/ml) to that obtained using a conventional glassy carbon electrode flow detector (2 ng/ml). Sample clean-up was by on-line solid-phase extraction with column switching, providing a method which was sensitive and reproducible, where the mean overall coefficient of variation was 5.60% and drug recovery in excess of 86% at the concentration levels studied.     

Untersuchungen zur thermischen Zersetzung von Boraten

In spite of numerous investigations the literature data on the thermal decomposition of borax are contradictory. On the basis of thermal, X-ray, gas analytical and optical investigations this fact can be attributed to the complex decomposition mechanism. After the release of about 8 mole water the reaction product is an X-ray amorphous phase, having the thermal behaviour of glass. From this glass sodium diborate (Na₂O.2B₂O₃) crystallizes between 500–600? with further mass loss. Sodium diborate decomposes from about 700? incongruently yielding NaBO₂ vapor and B₂O₃ glass phase. After evaporation of NaBO₂ is completed the rate of evaporation of B₂O₃ increases considerably.     

Die Fehlordnung des Natriumazides und deren Einfluß auf die thermische Zersetzung, 4. Mitt.: Über die Programmierung von Zersetzungsreaktionen mit Hilfe von Korngrößenverteilungen

It is shown that in the case of thermal decomposition of sodium azide the overall kinetics can be predicted by defined particle size of the decomposed sodium azide crystals. This is always the case if the rate constant is a function of the particle size. Hence this special example can be generalized for similar decomposition reactions. It is necessary that the particles decompose independently which could be proved experimentally with sodium azide. If for this reason we state for true that the pressure/time-function of each particle size add together it is possible to set up a formula for the pressure/time-function of any particle size distribution. With the pressure/time function holding for sodium azide of uniform particle size, the total function for a Gauß distribution can be calculated exactly. Moreover, the trivial case of one single particle size and the case of two different particle sizes are discussed. Furthermore an approximation method for any arbitrary pressure/time-functions and distribution by means of “Schwerpunktdeutung” are discussed which can be carried out graphically as well as numerically. The numerical approximation is illustrated by an example. Pressure/time-functions then loose their characteristic form because of their dependence on the particle size distributions under consideration. In this case, reaction mechanism cannot be derived from pressure/time functions.     

Investigations in the fie ld of substituted furanurona ldehydes steric directivity of the nitromethane condensation

Summary 1. The condensation of the anomeric methyl 2,3-di-O-benzyl-D-xylofuranosiduronaldehydes with nitromethane has been studied.2. It has been shown that the position of the substituent at the glycosidic center has an influence on the steric directivity of this reaction.3. The structure of the 6-nitro-6-deoxyhexofuranosides synthesized has been confirmed by their conversion into known derivatives of methyl D-glucofuranosides.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 8–12, January–February, 1972.     

Die Kristallstrukturen der Diquecksilber(I)-Salze von Aminobenzolsulfonsäuren

Crystal Structures of Dimercuri (I) Salts of p- and m-Sulfanilic Acids The crystal structures of the compounds Hg₂(p-H₂N–C₆H₄–SO₃)₂ ( 1 ), Hg₂(m-H₂N–C₆H₄–SO₃)₂ ( 2 ), and Hg₂(m-H₂N–C₆H₄–SO₃)₂ · 2H₂O ( 3 ) contain leaf-structures ( 1 and 3 ) or chain-structures ( 2 ), with nearly linear groups N–Hg–Hg–N, Hg–O-contacts and hydrogen-bridging bonds. The smaller density of 3 compared with 1 –caused by the steric hindrance through the ligand – declared the incorporation of water for raising the stabilising interaction in the crystals. The compound 3 is the kinetic controlled, the compound 2 the thermodynamic controlled product.     

Thiophosphinatokomplexe der Lanthanoiden. II. Dicyclohexylthiophosphinatokomplexe des NdIII und ErIII

Thiophosphinate Complexes of Lanthanides. II. Molecular Structures of [Nd((cyclo-C₆H₁₁)₂POS)₃(H₂O)]₂ and NH₄[Er((cyclo-C₆H₁₁)₂POS)₄(H₂O)₂] The title compounds are formed by the reaction of NH₄((C₆H₁₁)₂POS) and Ln(ClO₄)₃ (Ln ? Nd³⁺, Er³⁺). Their structures have been determined by single crystal X-ray diffraction. In the dimeric compound, the (C₆H₁₁)₂POS^? ions act partly as bidentate chelates and partly as monodentate O-donors. The dimers are formed by doubly coordinating oxygen atoms of two ligands. In the ionic compound, Er is only sixfold (octahedrally) coordinated by the oxygen atoms of 4 ligands and two water molecules. The structures of so far known thiophosphinate complexes of lanthanides are discussed with respect to stereochemistry and ligand bonding.     

Kalorimetrische messungen zur ermittlung der spezifischen grenzflächenenergie einer zweiphasigen Cu-7,5 At.-% In-legierung

With the help of a commercial heat-flux calorimeter the enthalpy change was measured as a function of the interlamellar spacing for lamellar precipitated Cu-In samples. This is related to the replacement of the two-phase structure (α + δ) by the homogeneous solid solution (α₀. From this, the specific interfacial enthalpy of the α-δ interface was determined to be ΔH^δ = 1100 ± 550 mJ m^?2. A value of ΔH^c = 1320 ± 60 J mol^?1 results for the chemical part of the total measured transformation enthalpy. A value of ΔS^δ = 0.66 mJ m^?2 K^?1 was estimated for the specific interfacial entropy and using the Gibbs-Helmholtz equation the specific interfacial free energy was calculated as ΔG^δ = 700 ± 400 mJ m^?2 at 600 K.     

Dynamic and structural models of pyrimidine in the lowest excited singlet state

Problems on the normal vibrations of pyrimidine in the ground and excited states are solved. The matrices of rotation and shift of normal coordinates due to electronic excitation and Franck-Condon integrals are calculated. The vibronic spectra of pyrimidine are interpreted. Based on this interpretation, bond lengths and bond angles in the electronically excited first singlet state of the molecule are calculated: C₁C₂ 1.388 å, C₂N₃ 1.366 å, N₃C₄ 1.352 å, C-H 1.099 å; C₆C₁C₂ 105.5?, N₃C₄N₅ 127.8?, H₂C₂N₃ 110.1?.