Use of biosensors for rapid drug residue analysis without sample deconjugation or clean-up: a possible way forward.

The drug salbutamol (SBL) is a beta-agonist that may be used illegally as an animal growth promoter. SBL is also a good example of a drug which is excreted in the form of glucuronides and sulfates. Such metabolites cause complexities in analysing for the presence of drug residues. In the majority of cases a process of deconjugation and sample clean-up is required prior to analysis. This is both time consuming and causes some loss of accuracy. In this study, the urine of calves treated with SBL orally for 3 d was collected during and after medication. Samples were assayed before and after hydrolysis by two different methods, radioimmunoassay (RIA) and a newly developed biosensor immunoassay (BIA). Some samples were also analysed by GC-MS. The results clearly showed that both screening assays (RIA and BIA) found high concentrations of SBL residues throughout the study. This was especially true in the BIA method. It was also demonstrated that urine sample analysis without the need for deconjugation or clean-up could be achieved. Results obtained by GC-MS tended to be an order of magnitude lower than the corresponding screening test results. This work showed that biosensor based veterinary drug residue testing procedures can be developed which can generate results in real time without the need for time consuming sample preparation.     

Dilute solution parameters of polymethylphenylsiloxamers

Dilute solution parameters were determined for polymethylphenylsiloxamer fractions (5 × 10⁴ < M < 1.5 × 10⁶) in toluene, cyclohexane, and diisobutylamine (θ ≈ 30.4°C). The data are interpreted by the procedure suggested by Flory and Fox. Minor deviations from theory are noted. Polymers from both cis- and trans-cyclotrisiloxanes were investigated. The major portion of the work, however, was concentrated on fractions derived from the trans form. From the data obtained, a characteristic ratio of dimensions (r /r )^½ of 1.56 was determined. The hydrodynamic parameter Φ was determined to be (2.0 ± 0.3) × 10²¹. The appropriate model for the polymer is indicated to be the impermeable random coil with slight hindrance to rotation about backbone skeletal bonds.     

Polymerization of hexamethylcyclotrisiloxane with a biscatecholsiliconate. II. Kinetics of polymerization

The kinetics of polymerization were investigated for the polymerization of hexamethylcyclotrisiloxane (D₃) in toluene with methanol or water as an initiator, benzyltrimethylammonium bis(o-phenylenedioxy)phenylsiliconate as a catalyst, and dimethyl sulfoxide (DMSO) as a promoter. The rate of initiation was found to be comparable with both water and methanol. Addition of catechol drastically reduces the rate of initiation. The rate of propagation was found to be dependent upon the catalyst, DMSO, catechol and the aging of the catalyst solution. Two types of functional groups were postulated to be present during the propagation reaction, i.e., ?SiOH (dormant form) and ?SiONR₄ (living form). The former can be converted to the latter by R₄NOH derived from hydrolysis of catalyst. A postulated mechanism of polymerization with biscatecholsiliconate is presented.     

Ueber den forensisch-chemischen Nachweis mehrerer Pflanzenstoffe

Ohne Zusammenfassung     

Light scattering and intrinsic viscosity investigation of polymethyl-3, 3, 3-trifluoropropylsiloxamer

Solution parameters for the polymer poly-γ-trifluoro-propylmethylsiloxamer has been determined in cyclohexyl acetate, methyl hexanoate, and ethyl acetate. Interpretation of data follows the theory of Fox and Flory. In contrast to poly-dimethylsiloxane, an increased steric hindrance to rotation about the siloxane bond occurs as evidenced by the characteristic ratio of root-mean-square end to end dimensions, (r₀² /r_0f² )^1/2, found to be 1.90 and 1.96 at 25.0 and 72.8°C, respectively. This increase is considered to be primarily due to nearest-neighbor interaction of the polar substituent on the silicon atom. The relation, [η]θ ∝ M^1/2, was observed to hold for this polymer system. The hydrodynamic model appropriate for the polymer is a random coil considerably more permeable to solvent flow than is generally reported for linear polymers. The universal parameter ? was determined to be 1.5 × 10²¹. The effect of temperature on polymer configuration is indicated to be negligible.     

Linearer Stark-Effekt desR-Zentrums in LiF

The K-ionization cross section of Aluminium by electron impact was measured detecting quantitatively the Al-K X-rays emitted by thin targets of known mass thickness. The apparatus and the measurements are briefly described. The experimental results are considerably higher than the values of the theories using the Born approximation. The discrepancy increases with increasing energy of the incoming electron. At twenty-fold threshold energy for example, the measurements are higher thanBurhop's calculations by a factor of 1.7. It is shown that considering the process ofK-ionization the influence of the nuclear field on the impact electron increases with decreasing atomic number. Thus, the calculations ofRudge andSchwartz using coulomb wave functions for the impact electron, are closest to the measurements (maximum deviation 16%). The formula ofGryzinski based on classical calculations is a good approximation to the experimental results if multiplied by a factor 1.23.