Functionality-type and chemical-composition separation of poly(lactide-co-glycolide) using gradient elution normal-phase liquid chromatography with basic and acidic additives

End groups of poly(Lactide-co-glycolide) (PLGA) play an important role in determining the properties of polymers for use in drug delivery systems. For instance, it has been reported that the encapsulation efficiency in PLGA microspheres varies significantly between ester-terminated and acid-terminated PLGA. More importantly, the in-vivo degradation time of such polymer excipients is influenced by the functional end-group of the copolymer used.The end group distribution in PLGA polymers has been studied using electrospray and matrix-assisted laser-desorption/ionization – high-resolution mass spectrometry. In both cases, the application of these methods is typically limited to PLGA having a molecular weight of up to 4 kDa. 13Carbon-nuclear-magnetic-resonance has also been reported as a method to differentiate and quantify PLGA end groups with a molecular weight up to 136 kDa. However, reported NMR methods take over 12 h per sample, limiting throughput.Cryoprobe NMR can reduce the time required for the process, however such NMR equipment is costly, which makes it unsuitable for the quality control of PLGA.Here, we present a normal-phase liquid chromatography method capable of resolving functionality type distribution (FTD) and, partially, chemical composition distribution (CCD) in commercial PLGA polymers obtained from ring opening polymerization. This method can separate PLGA polymers with a molecular weight of up to 183.0 kDa while also enabling the simultaneous separation of the difference of Lactic acid (LA)/Glycolic acid (GA) ratios.To achieve this, a cross-linked diol column was used with a ternary gradient from HEX to 0.1 % v/v TEA in EA to 0.1 % v/v FA in THF to allow first for the elution of mono-ester terminated PLGA, followed by the di-acid terminated. In addition, a separation of ester-terminated PLGA in the difference of the LA/GA ratio was achieved.This method is expected to aid in understanding the correlation between PLGA's FTD, CCD, and physical properties, facilitating product development and quality control

Residuen in honing [Thema Kwaliteit]

Verslag van het symposium op 27 en 28 april 2004 in Celle (Duitsland), dat het vervolg vormde op het symposium van oktober 2002 over residuen in honing. Het hoofdthema was het stopzetten van het gebruik van medicamenten die tot residuen leiden, met name antibiotica. Aan de orde kwamen o.a. geïntegreerde (duurzame) varroamijtbestrijding (Varroa destructor) en de hierbij toegepaste middelen in de amateur- en beroepsimkerij, de wenselijkheid van wettelijke normen voor medicamenten en residuen of juist een totaal verbod op residuen, en de (onvermijdelijke) komst van de Kleine bijenkastkever (Aethina tumida) in Europa en de bestrijding van dit diertj