STUDIES ON FLUORESCENCE ENHANCING EFFECT AND ALKALINE DEGRADATION MECHANISM OF DOXYCYCLINE AND METHACYCLINE

Degradation reaction of doxycycline or methacycline was carried out in KOH solution and intense fluorescence was obtained.A degradation mechanism of doxycycline or methacycline was suggested.

Using GC to determinate polychlorinated biphenyls in soil after pretreated with microwave-assisted alkaline degradation method

A new and simple microwave-assisted alkaline degradation （MAAD） method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls （PCBs） in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p＇ - DDT, p. p＇ - DDD and p. p＇ - DDT could be eliminated completely, and p. p＇ - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation （RSD） was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,

Analysis on degradation behaviors of sisal fibers at various pH conditions

The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.

Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and Degradation Behavior of Star-Shaped Poly(Lactic Acid)

Star-shaped poly(lactic acid)s(PLAs)with two to five arms were synthesized by ring opening polymerization using tin(II)2-ethylhexanoate as catalyst and polyols as initiators.The effects of molecular weight together with multi-arm architecture on crystallization behavior,spherulite morphology and alkaline degradation behavior of star-shaped PLAs have been investigated.The results indicate that the multi-arm architecture interfered with spherulite growth,but promoted nucleation and alkaline degradation of star-shaped PLAs.Interestingly,with the increase of molecular weight(M_(n)),the crystallization rate first increased and then decreased,while the alkaline degradation rate was the opposite.The characteristic crystallization and alkaline degradation behavior of star-shaped PLAs were discussed based on the competition between segmental mobility and central core confinement.