This monograph method employed a two-step gradient elution profile covering a concentration range of hydroxide from 15 to 85 mM. The Xenoic® XAMS-HC high-capacity suppressor used in this application could successfully minimize the background and noise over the entire gradient range, thus allowing determination of low levels of contaminants.
Analysis of Clodronate and related substances according to European Pharmacopoeia 9.0 method (monograph 2017:2119) using sodium hydroxide gradient 15-45 mM (0-10 min), 45-55 mM (10-22 min), 55-85 mM (22-23 min), 85 mM (23-25 min), followed by an equilibration at 15 mM during 10 min, on an IonPac AS11-HC column (250×4 mm). Eluents were stored in EQAX-B1 eluent bottles equipped with EQAX-TC1 trap cartridges for carbon dioxide removal. Background reduced by XAMS-HC high-capacity suppressor with ASUREX-A200 automatic regenerator keeping the background increase <1.7 µS/cm during the gradient. Eluent pumping by two Metrohm 818 IC Pumps controlled by 762 IC Interface, and conductivity detection by Shodex CD-200 detector at range 51.2 mS/m. An IonPac ATC-HC trap column was used to trap anionic contaminants from the eluent, wherefore gradient start and sample injection was delayed compensating for this additional 2 min dwell time. Injection of 20 µL of clodronate 1.25 g/L in water, giving signals around 300 µS/cm.
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