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A combination of viscometry, Raman scattering and 'H NMR measurements has been used to study the effect of temperature changes on the properties of solutions of poly(ethy1ene oxide) in H 2 0 or D20. The viscosity data show that the overall dimensions of the polymer chains decrease with increasing temperature, while the Raman spectra indicate a simultaneous decrease in chain helicity. Polymer 'H NMR spin-lattice relaxation times, in D 2 0 are consistent with a mechanism in which small segments of the chain reorient at a rate controlled by the solvent viscosity up to a temperature of ca. 80°C.

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Sulfonamide antibiotics are widely used to prevent bacterial infections in livestock, and residues are commonly found in milk and meat. Packed column supercritical fluid chromatography (pSFC) with detection using ultra violet (UV) and atmospheric pressure chemical ionisation (APCI) mass spectrometry (MS) provides a versatile method for the detection and quantification of six major sulfonamides. The APCI mass spectra for all the sulfonamides consisted of protonated molecules at low cone voltages. Increasing the cone voltage led to informative fragmentation patterns, which provided structural information for identification purposes. The pSFC-APCI-MS technique was shown to be linear (r2 > or = 0.999) over the concentration range 0.1-50 micrograms ml-1 using total ion current. The precision and the accuracy of the system and validation of sample preparation are acceptable, with RSD < 2% and relative error 8%. Selected ion monitoring gave detection limits as follows: sulfadiazine 41, sulfamethoxazole 45, sulfamerazine 47, sulfamethizole 59, sulfamethazine 181 and sulfadimethoxine 96 micrograms l-1, which are lower than the amounts permitted in milk products. The APCI pSFC-MS system was shown to have a high degree of reproducibility. The technique was then applied to determine the above sulfonamides in milk. The results obtained show that there are no matrix effects from the milk and that the detection limits remained as stated for the standard solutions.

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