Fast, inexpensive, and reliable HPLC method to determine monomer fractions in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The determination of the monomer fractions in polyhydroxyalkanoates is of great importance for research on microbial-produced plastic material. The development of new process designs, the validation of mathematical models, and intelligent control strategies for production depend enormously on the correctness of the analyzed monomer fractions. Most of the available detection methods focus on the determination of the monomer fractions of the homopolymer poly(3-hydroxybutyrate). Only a few can analyze the monomer content in copolymers such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which usually require expensive measuring devices, a high preparation time or the use of environmentally harmful halogenated solvents such as chloroform or dichloromethane. This work presents a fast, simple, and inexpensive method for the analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high-performance liquid chromatography. Samples from a bioreactor experiment for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Cupriavidus necator H16 were examined regarding their monomer content using the new method and gas chromatography analysis, one of the most frequently used methods in literature. The results from our new method were validated using gas chromatography measurements and show excellent agreement. Key points ∙ The presented HPLC method is an inexpensive, fast and environmentally friendly alternative to existing methods for quantification of monomeric composition of PHBV. ∙ Validation with state of the art GC measurement exhibits excellent agreement over a broad range of PHBV monomer fractions

Zuechtung von defektarmen dotierten und undotierten GaAs-Einkristallen mit dem vertikalen Gradient-Freezing-Verfahren Kurze Darstellung der Ergebnisse und Abschlussbericht

Multi zone furnaces, automation concepts and laboratory technologies have been developed using the Vertical Gradient Freeze technique for single crystal growth of GaAs with the aim to produce a low dislocation density. The crystallization prozess is performed by an electronically controlled temperature field without moving the furnace or the sample. A command variables generator free programable yields the temperature time programs for the fully automatized growth process. On the basis of a complex process simulation the crystal growth rate, the As partial pressure as well as the temporal and local temperature gradients could be adjusted with high precision and optimized by systematic growth experiments. The crystals grown are characterized by dislocation densities up 1 to 3 x 10"3 cm"-"2, a large area cellular structure and a low density of microdefects. Si-doped and semi-insulating crystals with reproducible physical properties were grown both in (100) and (111) orientation, respectively. The possibility of affecting the crystal properties by post-growth annealing was shown experimentally. (orig.)SIGLEAvailable from TIB Hannover: F95B346+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman