Michael Maiwald

Sample purification for spectroscopic high-pressure investigations by dynamic supercritical fluid extraction

Abstract A method for the high resolution purification of 1,4-bis-( n -alkylamino)-9,10-anthraquinone dyestuff samples based on a modified supercritical fluid chromatography (SFC) equipment was developed to minimize errors in high-pressure solubility measurements. Impurities and by-products were eluted in a continuous CO 2 flow, the purification process could be observed by a diode array spectrophotometer. The fact that both static and dynamic solubility experiments of a selected dyestuff gave consistent results turned out to be a credit point for this new method, which can be universally used for other purifications, too. Besides, the necessity of calibrating directly in the solvent gas is demonstrated, since some organic solvents lead to characteristic spectral effects which can strongly disagree with those in CO 2 . Our experiments showed a weakening of these effects towards longer alkyl chains of this substance class. In a separate section, some remarks are given concerning the use of wavenumbers instead of wavelengths in such experiments.

Final report on EURAMET.QM-S8: Analysis of impurities in pure and balance gases used to prepare primary standard gas mixtures by the gravimetric method

This supplementary comparison (EURAMET.QM-S8) concerns the purity analysis of nitrogen as used in reference gas mixture preparation. This project was carried out without adding impurities to the gas used for this comparison, and is therefore more representative to evaluate the analysis of carbon monoxide, carbon dioxide, methane, oxygen, argon and water impurities in high-purity nitrogen. The analysis of the amount-of-substance fraction water was optional. Two 50 litre high purity nitrogen cylinders were purchased from a well-qualified supplier of specialty gases. The listed components were expected to be present in the pure nitrogen at the target levels as a result of the purification of the nitrogen. From the start of this comparison it was clear that the comparison may not lead to reference values for the constituents analysed. The results indicate that analyses of high purity gases are often limited by the limits of detection of analytical equipment used. The reports of the participating laboratories also indicate that there is no agreed method of determination of the uncertainty on a detection limit value. The results provide useful information on the performance of participants. For all analysed components there is reasonable agreement in results for LNE, VSL, METAS and NPL. For BAM only the argon result is in agreement. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).