Use of the Garner balance in the investigation of errors in the carbon-hydrogen determination

Summary The reproducibility of weighing the mass of small-size glass Ascartte and Drierite absorption tubes with 0.25-mm capillaries on the Garner balance has been investigated. A standard error of estimate for the Ascarite tube was found to be ±1.65g and for the Drierite tube ±2.65g. Corresponding figures for light-weight aluminum absorption tubes with 0.34-mm capillaries were considerably higher. Filled glass absorption tubes standing idle in the room were found to exhibit weight increases with respect to time of the order of 0.201g/min. for Ascarite and 0.251g/min, for indicating Drierite. Tubes with larger capillaries (0.34mm) showed a more rapid weight gain.Absorption tubes filled with oxygen undergo a loss in weight, which remains the predominating phenomenon during the first 2 hours.A limiting factor is indicated by failure to obtain consistent blanks.

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Zusammenfassung Die Gewichtskonstanz kleiner C-H-Absorptionsröhrchen aus Glas mit kapillaren Verengungen von 0,25 mm innerem Durchmesser wurde mit der Garner-Mikrowaage untersucht. Die mittleren Fehler der Schätzungen wurden zu ±1,65g für das Ascariteröhrchen und zu ±2,65g für das Drieriteröhrchen berechnet. Die entsprechenden Zahlen für leichte Absorptionsröhrchen aus Aluminium mit Kapillaren von 0,34 mm innerem Durchmesser wurden merklich größer gefunden. Die Gewichtszunahme beim Liegen der gefüllten Glasabsorptionsapparate betrug 0,20g/Minute für das Ascariteröhrchen und 0,25g/Minute für das mit Indikator-Drierite gefüllte Röhrchen. Absorptionsapparate mit Kapillaren von 0,34 mm innerem Durchmesser zeigten entsprechend größere Gewichtszunahmen.Sauerstoffgefüllte Absorptionsröhrchen zeigen außerdem einen durch Austausch toit der Atmosphäre verursachten Gewichtsverlust, der während der ersten zwei Stunden überwiegt.Bisher unbekannte Faktoren verhindern es, in Leerversuchen gleichbleibende Gewichtsänderungen der Absorptionsapparate zu erhalten.

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Résumé La reproductibilité des pesées des petits tubes d'absorption en verre à ascarite et à drierite avec des capillaires de 0,25 mm sur la balance de Garner a été étudiée. On a trouvé une erreur standard de ±1, 65g pour le tube d'ascarite et de ±2,65g pour le tube de drierite et des chiffres considérablement plus élevés avec des tubes d'absorption très légers en aluminium ayant des capillaires de 0,34 mm. Des tubes d'absorption en verre remplis et suspendus inutilisés dans la pièce présentent des gains de poids par rapport au temps de l'ordre de 0,20g/min pour l'ascarite et de 0,25g/min pour la drierite. Les tubes avec capillaire plus grand (0,34 mm) ont présenté un gain de poids plus rapide. Les tubes d'absorption remplis d'oxygène subissent une perte de poids qui reste le phénomène prédominant pendant les deux premières heures. On donne un facteur limite dans l'impossibilité de fixer une valeur déterminée pour l'essai à blanc.

     

Atmospheric Pressure Photo Ionization Hydrogen/Deuterium Exchange Mass Spectrometry—a Method to Differentiate Isomers by Mass Spectrometry

In this report, a method for in-source hydrogen/deuterium (H/D) exchange at atmospheric pressure is reported. The method was named atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry (APPI HDX MS). H/D exchange was performed by mixing samples dissolved in toluene with CH₃OD solvent and analyzing the mixture using atmospheric pressure photo ionization mass spectrometry (APPI-MS). The APPI HDX spectra obtained with contact times between the analyte solution and methanol-OD (CH₃OD) of?<?0.5 s or 1 h showed the same pattern of H/D exchange. Therefore, it was concluded that APPI HDX occurred in the source but not in the solution. The proposed method does not require a specific type of mass spectrometer and can be performed at atmospheric pressure. H/D exchange can be performed in any laboratory with a mass spectrometer and a commercial APPI source. Using this method, multiple H/D exchanges of aromatic hydrogen and/or H/D exchange of active hydrogen were observed. These results demonstrated that H/D exchange can be used to distinguish between isomers containing primary, secondary, and tertiary amines, as well as pyridine and pyrrole functional groups.

Characterization of Electrochromic WO3-Layers Prepared by Sol-Gel Nanotechnology

Stable tungsten oxide coating sols suitable for electrochromic applications were prepared by a modified peroxotungstic acid route. Layers up to 250 nm thickness could be deposited on ITO-coated and/or FTO-coated glass substrates in a single dip-coating process. Optoelectrochemical measurements were employed to determine the variation of the electrochromic properties (change in optical density (OD) and switching times) of WO3-layers, investigated as a function of coating parameters, such as chamber humidity and the temperature of heat treatment. High resolution transmission electron microscopy (HR-TEM) has shown that the optimized layers possess a partially crystalline morphology with nanocrystalline regions 2–3 nm in size.     

Unique Insertion Mode of 1,7‐Octadiene in Copolymerization with Ethylene by a Constrained‐Geometry Catalyst

Summary: The copolymerization of ethylene and 1,7‐octadiene (OD) was investigated with a constrained‐geometry catalyst. The ¹³C NMR spectrum of the copolymer indicated cyclization insertion of the OD unit in the penultimate position after a single ethylene insertion step. This unique insertion mode of OD forms a 1,5‐disubstituted cyclononane unit in the main chain of polyethylene.

Copolymerization of ethylene and 1,7‐octadiene (OD) with a constrained‐geometry catalyst.     

Evaluation of a direct1H NMR method for determining logK and ΔH values for crown ether -alkylammonium cation complexation

A direct¹H NMR method for determining logK and H values for crown ether-ammonium cation complexation using milligrams of sample was tested and evaluated for accuracy and precision by comparing the results with those obtained using a titration calorimetric method. LogK values for the interactions of a non-chiral crown ether, diketopyridino-18-crown-6 (K₂P18C6), with -phenylethylammonium (PhEt⁺) perchlorate in 50%–50% and 90%–10% (v/v) mixtures of deuterated methanol (CD₃OD) and deuterated chloroform (CDCl₃) at four temperatures and, with -(1-naphthyl)ethylammonium (NapEt⁺) perchlorate in 50%CD₃OD-50%CDCl₃ (v/v) at 25°C were determined by a direct¹H NMR method. Values of H for the interactions of K₂P18C6 with PhEt⁺ in the two solvents were calculated from the temperature dependence of logK. LogK values for the interactions of a chiral crown ether, dimethyldiketopyridino-18-crown-6 (M₂K₂P18C6), with (R) and (S) enantiomers of NapEt⁺ in pure CD₃OD at 25.0°C were also determined by the NMR method. The results were compared with those determined by a calorimetric method at 25.0°C in 50%-50% and 90%–10% (v/v) mixtures of plain methanol and chloroform, in 100% plain methanol, and in a 50%-50% mixture of partially deuterated methanol (with deuterium substitution on the methanol OH group, CH₃OD) and deuterated chloroform. The log K values determined by both methods were found to be in good agreement, but the standard deviations associated with the NMR logK values were two to three times greater. The agreement of the H values determined by the two methods was poor, differing by approximately 10 kJ/mol with the NMR method giving more negative values. The standard deviations associated with the NMR H values were approximately ten times greater than those for the calorimetric values. Ion-pairing was observed for the interaction of perchlorate ion with both free and bound PhEt⁺ in 50%methanol-50%chloroform mixture. It is concluded that the NMR procedure is satisfactory for the determination of logK, but not H values.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Raman spectra from partially deuterated water and ice VI to 10.1 kbar at 28°C

High-pressure argon-ion laser-Raman spectra (4880 Å excitation) have been obtained from partially deuterated water and ice VI (20 volume % D₂O) in the OD and OH stretching regions to pressures of 10.1 kbar at 28°C. The Raman spectra from ice VI are the first to be reported at room temperature, and they are similar to the liquid spectra obtained at 9.7 kbar. Raman shifts corresponding to contour intensity maxima were observed to change with pressure rise in the OD and OH stretching regions from v =2513–2490 cm^–1 and v = 3402–3380 cm^–1, respectively, for pressures from 1 bar to 10.1 kbar (ice VI). In addition, a shoulder observed at 1 bar on the OD contour near v = cm^–1 became less distinct and was visually absent for pressures from 6.4 to 10.1 kbar, although a shoulder on the OH contour at about v = cm^–1 intensified gradually for pressures to 9.7 kbar, and abruptly upon freezing at 10.1 kbar. The small effects of pressure on the OD component percentages obtained from computer analysis indicate that hydrogen-bond breakage is not a significant effect of pressure rise, and a downward change in the position of the OD stretching component having the largest Raman shift indicates that the nonhydrogen-bonded OD units or broken O-D...O bonds that exist at 1 bar are probably transformed by close packing due to compression into weak O-D...O bonds that are angularly deformed. In addition, intensification of the OH component at v = cm^–1 upon freezing or upon pressurizing the liquid to 9.7 kbar is indicated by the computer analyses, and an increase in intermolecular coupling is thus favored, as opposed to enhancement of Fermi resonance, because the positions of components at v = cm^–1 and v = cm^–1 are nearly independent of pressure. The computer results also strengthen previous evidence indicating that the OD component which occurs at about v = cm^–1 at 1 bar arises from broken O-D...O bonds, when it is understood that the severely deformed O-D...O bonds of ice VI give rise to intensity at a Raman shift of v = cm^–1, a difference of 37 cm^–1 in the direction of stronger hydrogen-bonding.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.     

Inclusion Complexes Formed by Sodium Dodecyl Sulfate and Cyclodextrin-Based Nanotubes

The complexation of sodium dodecyl sulfate with molecular tubes based on - and -cyclodextrins synthesized by the suspension method was studied. The binding was studied by the isothermal titration calorimetry in aqueous solutions. For tubes based on -cyclodextrins, the enthalpy of complexation, the dissociation constant of the resultant complex, and the molar fraction of binding sites in a tube were calculated. The experimental and published data on the determination of the ligand binding parameters were compared for tubes synthesized by different methods. In the case of tubes based on -cyclodextrins, they were shown to form associates under the conditions of experiment. As a result, the proportion of binding sites significantly decreases. The presence of associates was also confirmed by osmometric measurements. In this connection, the complexation between sodium dodecyl sulfate and tubes can be discussed only at the qualitative level.     

Open-tubular liquid chromatography under turbulent and secondary flow conditions

Summary Liquid chromatography in open tubes at flow rates around 0.1 cm · s^–1 and less can generate an enormous number of theoretical plates but suffers from long analysis times. The Golay and van Deemter equations are also obeyed with high accuracy.If straight tubes of circular cross section and very smooth inner surface are used, secondary flow effects can be neglected. Thus the plate height should depend only on the flow velocity and the number of theoretical plates should decrease with increase in linear flow, whereas the number of plates per unit time should be constant.Under turbulent conditions, however, the plate height seems to be more or less independent of linear flow over a wide range. Increasing the flow to several hundred cm · s^–1 causes, for example, 0.2 mm ID capillaries to show the reverse effect and a slight decrease in plate height is found. Alkali treated and silanized capillaries below 100 m i. d. deviate from the Golay prediction before turbulence occurs and a relative decrease in the plate height and thus higher efficiency is found possibly caused be secondary flow effects in the coiled tube or the roughness of the inner walls. These effects allow an increase in the efficiency of given open-tubular systems simply by increasing the solvent velocity drastically. Although plate heights are in the range mm to cm, efficiencies, in theoretical plates per second, similar to classic HPLC, are found. Therefore the quite interesting possibility of overcoming the well-known restrictions of classical HPLC to achieve high efficiency liquid chromatograms exists.Presented at the 17th International Symposium on Chromatography, September 25–30, 1988, Vienna, Austria.     

Surface modification by calcium ions—Effect on chromatographic properties of silica

Summary A liquid chromatographic method incorporating column-switching and fluorimetric detection for the determination of triamterene in untreated urine, is described. The urine samples (5 L) were directly introduced onto an Hypersil ODS-C18, 30 m (20 mm×2.1 mm I.D.) pre-column. Polar urinary compounds were removed by flushing the pre-column with water for 1 min, and the analyte was then switched onto an HP-LiChrospher RP C18,5 m (125 mm×4mm ID) analytical column using an acetonitrile/phosphate buffer gradient elution. Fluorescence detection was performed at 230 nm excitation and 430 nm emission wavelengths. The recovery of drug was 102±2% in the 0.10–20.0 g/mL concentration range, the limit of detection being 5 ng/mL. A validation of the usefulness of this procedure was accomplished by analysing urine extracts obtained from real samples.Hypersil ODS is not a product of Merck, Germany. Please give supplier (p. 5).     

Effect of the interface on separation in multicapillary gas chromatography-based hyphenated techniques for speciation analysis of organometallic compounds

This paper reports the effect of transfer line (TL) internal diameter (i.d.) on gas chromatographic separation characteristics such as efficiency and speed, when a multicapillary (MC) column is used for speciation analysis of mercury. Five different TL consisting of fused-silica capillaries with 0.15, 0.20, 0.25, 0.32, and 0.53 mm i.d. are compared. The separation efficiency and total chromatographic run time are critically affected by the i.d. of the TL. Narrow capillaries (i.d.0.20 mm) produce minimum peak dispersion whereas wide capillaries result in narrow peaks and shorter chromatographic analysis times. A thermodynamic approach is proposed to describe the motion of the analytes through the separation column and TL. The model provides good agreement with the experimental data for high pressures (35 psig) and wide TL (0.25 mm i.d.).Dedicated to the memory of Wilhelm Fresenius     

High-speed analysis for acid-rain anions by Single-Column Ion Chromatography (SCIC)

Summary Single Column Ion Chromatography (SCIC) combines ion exchange separation with direct electrical conductivity detection. Because no supressor column is used in SCIC the post-column dead volume is minimized. This means that HPLC technology can be applied to reduce analysis times. The analysis of chloride, nitrate, and sulphate can be accomplished in 6 min using a standard 250×4.6 mm LC column packed with a low-capacity ion-exchange chemically bonded silica leading to a sensitivity of 100 ppb. A 1 min analysis for chloride, nitrate, and sulphate at the ppm level is possible using a 30×4.6 mm column eluted with 4mM phthalate buffer at pH 4.5.Presented at the 14th International Symposium on Chromatography London, September, 1982     

The separation of amino acid enatiomers on optically active dipeptide carborane stationary phases

Summary N-Trifluoroacetyl (TFA) dipeptide-o-carboranyl propyl esters of L-valyl-L-valine and L--amino-n-butyryl-L--amino-n-butyric acid have been prepared and the properties of these two new stationary phases for the gas-liquid chromatographic sepaation of amino acid enantiomers have been examined. It was found that the amino acid derivatives have shorter retention times, while maintaining good separation factors, on these carborane phases as compared to other dipeptide stationary phases. Both high and low boiling derivatives have been resolved on a 165 m×0.5 mm capillary column. The new phases have greater thermal stability and can be utilized over a wide temperature range.     

Analysis of the fusariotoxins zearalenone and vomitoxin (deoxynivalenol) in human foods and animal feeds by high-performance liquid chromatography (HPLC)

Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C ₁₈ ¹ column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses.     

An improved method for the determination of S-Carboxymethyl-L-cysteine in biological fluids with precolumn derivatization and on-line clean-up

Summary In order to follow levels of S-Carboxymethyl-L-cysteine in biological fluids for a period as long as three half-lives after drug administration during pharmacokinetic studies, an improved method for its determination had to be developed. Like the previous one, this method uses a protein precipitation step followed by an O-Phthalaldehyde derivatization step and then an HPLC on-line clean-up. This latter was obtained by means of a switching valve system, including a Nucleosil CN 5 m (3 cm × 4.6 mm i.d.) precolumn and a Spherisorb ODS 5 m (15 cm×4.6 mm i.d.) analytical column. The sensitivity limit was improved to 0.1 g/ml in plasma samples and 0.2 g/ml in urine samples.This method was applied in studies comparing single (0.75 g) and repeated (0.75 g tid) oral administration of the drug to 30 elderly patients and 20 healthy volunteers. Results showed that the half-life was 40% longer in elderly patients than in healthy volunteers, and that area under the plasma concentration versus time curve (AUC) values in elderly patients were twice those obtained with young subjects.     

Asymmetric calix[4]-thiacalix[4]arene tubes: Synthesis and ionophore properties

Asymmetric p-tert-butylcalix[4]-p-R-thiacalix[4]arene tubes (R = tert-Bu, H, 1-adamantyl) were prepared for the first time by reaction of tosyloxyethoxy derivative of p-tert-butylcalix-[4]arene and the corresponding p-R-thiacalix[4]arenas in acetonitrile in the presence of K₂CO₃. Complex formation of compounds obtained with sodium, potassium, and rubidium iodides in CDCl₃-CD₃OD, 4:1, was studied by means of ¹H NMR. The ionophore properties of the molecule were governed by the character of substituents on the upper rim of the thiacalixarene fragment, and only the molecular tube containing a fragment of the p-(1-adamantyl)-thiacalix[4]arene quantitatively bound potassium ions (quickly) and rubidium ions (slowly).     

NMR Studies on Solution Structures of Methanol and Ethanol Saturated with CO2

²H and ¹⁷O NMR relaxation times, T ₁(²H) and T ₁(¹⁷O), and ²H NMR chemical shifts, δ(²H), in CO₂-saturated CD₃OD and C₂D₅OD solutions were measured at 313.2 K over the pressure range up to ~6 MPa. The rotational correlation times, τ _r, of the CD and OD axes within CD₃OD and C₂D₅OD molecules and the CO axis within the CO₂ molecule were determined from T ₁(²H) and T ₁(¹⁷O), and the magnetic susceptibility-corrected chemical shifts, δ _corr, were derived from δ(²H). The differences in τ _r and δ _corr observed between the two alcohol systems: τ _r and δ _corr of OD in C₂D₅OD, decreased rapidly with increasing CO₂ concentration, while those of OD in CD₃OD remained almost unchanged at mole fractions of CO₂, \( x_{\text CO_{2}} \) , lower than ~0.25 and then slightly decreased at higher \( x_{\text CO_{2}} \) . The hydrogen bonding structure in C₂D₅OD was found to be gradually broken down by CO₂ dissolution. On the other hand, in CD₃OD, it has been revealed that the hydrogen bonding structure can persist at \( x_{\text CO_{2}} \)  < ~0.25 but then collapses at higher \( x_{\text CO_{2}} \) .     

Durchflu?analytische Phosphatbestimmung unter Verwendung geometrisch verformter offener R?hren

Zusammenfassung Am Beispiel der Phosphatanalyse wird demonstriert, daß mittels geometrisch verformter offener Röhren (gestrickte Capillaren) die Nachweisempfindlichkeit und der Analysendurchsatz bei der Durchflußinjektionsanalyse verbessert werden können. Mit einer 250 cm langen Capillare (0,25 mm i.D.) bei einer Reaktionstemperatur von 70° C und einer Reaktionszeit von 4 s kann man nach der Methode von Eibl und Lands bis zu 0,2 ppm Phosphat nachweisen. Mit dieser Anordnung können bis zu 300 Analysen pro Stunde durchgeführt werden. Als vorteilhaft erwies sich die Verwendung einer Cyclonmischkammer zur intensiven Durchmischung von Probe und Reagens.

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Determination of phosphate by flow injection analysis with geometrically deformed open tubes

Summary The use of geometrically deformed open tubes (knitted capillaries) for the sensitive and fast determination of phosphates by flow injection analysis is described. A 250 cm long capillary (0.25 mm i.d.) at 70° C is sufficient to determine with a reaction time of 4 s as low as 0.2 ppm phosphate by using the method of Eibl and Lands. With this set-up about 300 determinations per hour can be carried out. The use of a cyclon mixing chamber proved to be advantageous for thorough mixing of sample and reagent.

     

Highly sensitive method for the determination of a new anthracycline: Pirarubicin

Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 m, with a mobile phase of acetonitrile/methanol/formate-buffer.     

Measurements of Room-Temperature Phosphorescence Spectra of Polycyclic Aromatic Compounds Using Pullulan Films Containing β-Cyclodextrin and 2-Bromoethanol

A clear film was easily prepared by air-drying anaqueous solution of pullulan (6%w/w) containing -cyclodextrin(CD, 1%w/w) and 2-bromoethanol (1%v/w). The resultingpullulan film was used as a substrate for simple measurements ofroom-temperature phosphorescence (RTP) spectra of polycyclicaromatic compounds (PACs). Only a drop (ca. 10 L) of a 100 gmL^-1 sample solution in 95% ethanol was spotted onto the surfaceof the disk film (7–8 mm diameter) and the solvent wasallowed to evaporate at room temperature. The sample-spottedfilm was pasted on a glass plate (75 × 20 × 1 mm) with smallamounts of a starch glue. The plate was mounted into a solidsample holder, or alternatively inserted diagonally into a 1-cm cell holder.Without a dry gas flush during the measurements, RTPspectra based on the CD inclusion complexes of PACs wereobtained from six typical two- and three-ring compounds,including naphthalene, acenaphthene, fluorene, phenanthrene,carbazole, and dibenzofuran. Only anthracene did notproduce a discernable phosphorescence signal by the presenttechnique. This technique was directly applied to the spectralidentification of acenaphthene in commercially available kerosene.     

High-Performance Liquid Chromatographic Determination of Cinnarizine in Workplace Air

Summary Cinnarizine is a pharmaceutical drug used in the treatment of cerebral and peripheral vascular diseases. A reversed-phase liquid chromatographic method with fluorescence detection has been developed for determination of the drug in workplace air. Air sampling in the workplace is performed on perchlorovinyl filters (FPP), the filters are extracted with methanol for 40 min, and the extract (50 L) is injected and separated on a 250 mm × 4.6 mm i.d., 5 m particle, C₈ reversed-phase column with 1% ammonium acetate (pH 4.5)–acetonitrile, 1:4 (v/v), as mobile phase at a flow rate of 1 mL min^–1.