The acoustic spectrophonometer: a novel bioanalytical technique based on multifrequency acoustic devices

A measurement technique similar to optical absorption spectroscopy but based on evanescent acoustic waves is described in this paper. This format employs a planar spiral coil to vibrate a single crystal of quartz from 6 to 400 MHz, in order to measure multifrequency acoustic spectra. Consistency with the defined Sauerbrey and Kanazawa terms K1 and K2 when applied to multiple frequencies was found for these specific operating conditions in terms of a significant fit between the measured and calculated values: For an IgG surface density of 13.5 ng mm(-2) the measured value of K1 is 22.5 x 10(-6) and the calculated value is 20.4 x 10(-6), whilst for glycerol viscous loadings of 5.131 cP the measured value of K2 is 0.47 and the calculated value is 0.54. Thus for these specific surface loadings the multifrequency data fits to the predictions of the Sauerbrey model to within 10% and to Kanazawa model within 13%. However collective frequency shifts for 5.131 cP solutions of sucrose, dextran and glucose were found to exhibit an unanticipated additional variability (R2 < 0.4) with frequency, but retained a square root of frequency dependency within a factor 2 of the interpolated K2 values. The response to the 5.131 cP dextran solution was found to be significantly below the other isoviscous solutions, with a substantially reduced frequency shift and K2 value than would be expected from its bulk viscosity. In comparison with these viscous solutions, IgG protein films consistently produced linear frequency shifts with little scatter (R2 > 0.96) that were proportional to the operating frequency, and fully consistent with the Sauerbrey model under these specific conditions. A t-test value of 14.52 was calculated from the variance and mean of the two groups, and demonstrates that the acoustic spectrophonometer can be used to distinguish between the acoustic impedance characteristics of two chemical systems that are not clearly differentiable at a single operating frequency.     

Hypersonic evanescent waves generated with a planar spiral coil

A planar spiral coil has been used to induce hypersonic evanescent waves in a quartz substrate with the unique ability to focus the acoustic wave down onto the chemical recognition layer. These special sensing conditions were achieved by investigating the application of a radio frequency current to a coaxial waveguide and spiral coil, so that wideband repeating electrical resonance conditions could be established over the MHz to GHz frequency range. At a selected operating frequency of 1.09 GHz, the evanescent wave depth of a quartz crystal hypersonic resonance is reduced to 17 nm, minimising unwanted coupling to the bulk fluid. Verification of the validity of the hypersonic resonance was carried out by characterising the system electrically and acoustically: Impedance calculations of the combined coil and coaxial waveguide demonstrated an excellent fit to the measured data, although above 400 MHz a transition zone was identified where unwanted impedance is parasitic of the coil influence efficiency, so the signal-to-noise ratio is reduced from 3000 to 300. Acoustic quartz crystal resonances at intervals of precisely 13.2138 MHz spacing, from the 6.6 MHz ultrasonic range and onto the desired hypersonic range above 1 GHz, were incrementally detected. Q factor measurements demonstrated that reductions in energy lost from the resonator to the fluid interface were consistent with the anticipated shrinkage of the evanescent wave with increasing operating frequency. Amplitude and frequency reduction in contact with a glucose solution was demonstrated at 1.09 GHz. The complex physical conditions arising at the solid-liquid interface under hypersonic entrainment are discussed with respect to acceleration induced slippage, rupture, longitudinal and shear radiation and multiphase relaxation affects.     

A novel transformation of O-methyldalbergin

O-methyldalbergin and related 4-phenylcoumarins are markedly different from ordinary coumarins in their behaviour towards alkali. They are stable in boiling alkali and on addition of mercuric oxide yield coumarilic acids. Phenyl-coumarilic acids undergo decarboxylation readily when boiled with aqueous alcoholic mercuric chloride to yield phenyl substituted coumarones.     

Grafting onto wool. VIII. Graft copolymerization of methyl methacrylate (MMA) by use of Ce4+ -amine system as redox initiator

In an attempt to determine the role of a variety of amines in ceric-ion-initiated grafting, poly-(methyl methacrylate) was graft copolymerized onto Himachali wool in the presence of a variety of amines that included ammonia, diethylamine (DEA), dipropylamine (DPA), triethylamine (TEA), triethanol amine, and pyridine. All amines (with the exception of DEA) reduced the percent grafting. The reactivity of various amines toward graft copolymerization followed the order: DEA > DPA > NH₃ > TEA > triethanol amine > Py. An explanation based on the basicity, nucleophilicity, and steric requirement of amines is given to explain the observed reactivity order shown by the various amines toward graft copolymerization.     

Behavior of rifampicin in association with<Emphasis Type="Italic"> β</Emphasis>-cyclodextrin in aqueous media: a spectroscopic and conductometric study

The behavior of rifampicin (D) with -cyclodextrin (-CyD) in aqueous media (W) has been examined by means of UV-vis spectroscopy and conductivity measurements over the temperature range 15–30 °C. The UV-vis study has been used to characterize the systems. The estimated molar absorption coefficient for D/CyD/W system was 10757±280 M^–1 cm^–1 in comparison to the value of 6133±99 M^–1 cm^–1 for D/W system. The conductivity was measured (i) as a function of [D] for binary D/W systems, (ii) as a function of [CyD], keeping the concentration of drug constant, for D/CyD/W system, and (iii) as a function of [D] in the presence of a constant cyclodextrin concentration. Two transition points were observed for D/CyD/W system at constant [CyD], which were assigned as cac-1 and cac-2. The stoichiometry of the association was estimated from the conductivity data. This was obtained from [drug] value at which the change in slope of occurs. The standard free energy change, of aggregation was also calculated from the critical concentration data. An attempt has also been made to estimate the stoichiometry of -cyclodextrin:rifampicin association.     

Normal coordinate treatment of actinide(IV)-hexabromides

Molecular force field studies of hexabromo-thorates(IV) and-uranates(IV) have been carried out using four different force field models. Weighted least square adjustment has been used to fit the observed frequencies. Mean amplitudes of vibration have also been calculated at 0°K and 298°K. The trends of force constants and mean amplitudes have also been discussed.

---

Normal-Koordinaten Berechnungen an Actiniden(IV)-hexabromiden

Zusammenfassung Es wurden für die Rechnungen an Hexabromo-thoraten(IV) und-uranaten(IV) vier verschiedene Modelle herangezogen. Die beobachteten Frequenzen wurden mittels gewichteter Kleinster-Fehlerquadrat-Methode angepaßt. Die Trends bei den Kraftkonstanten und den mittleren Amplituden der einzelnen Verbindungen werden diskutiert.