Daniela Held, PSS Polymer Standards Service GmbH, Mainz, Germany.
LMWHs are defined as heparin salts having an average molecular weight of less than 8000 Da and for which at least 60% of all chains have a molecular weight less than 8000 Da. GPC/SEC is the method of choice to measure the molecular weight (molar mass) and the molecular weight fractions above/below a molecular weight limit. Both, the Pharmaeuropa (EP) and the US Pharmacopeia (USP), require GPC/SEC to characterize commercially available LMWHs.
Although the calibration procedures described in the EP and USP are totally different, a dedicated GPC/SEC software can be used to analyse the heparin data in accordance with both standards precisely. Figure 1 shows the final results for the analysis of unknown low molecular weight heparin. PSS WinGPC Unity GPC/SEC software allows 2 markers to be set at 2000 and 8000 Da, to display the measured percent below 2000 Da, above 8000 Da and in between these values.
Of utmost importance is the y-axis of the result window. WinGPC Unity shows a true molar mass distribution with a w(log M) axis. Only this guarantees correct fractions above/below the molecular weight borders 2000 and 8000.3
Table 1: Comparison of experimental conditions from USP and EP for the characterization of LMWH.
1. USP Enoxaparin sodium http://www.usp.org/pdf/EN/USPNF/enoxaparinSodium.pdf
2. EP Low-Molecular-Mass (LMM) heparins Monograph 0828.
3. D. Held and P. Kilz; Quantification in LC and GC - A Practical Guide to Good Chromatographic Data [H.-J. Kuss/ S. Kromidas (eds.)], 271–302, Wiley-VCH, Weinheim (2009).
PSS Polymer Standards Service GmbH
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