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Hydroxide gradient elution of organic acids and inorganic anions

Gradient elution is a powerful tool when aiming to separate many compounds having a wide range of different chemical characteristics. Hydroxide gradients are the most common in ion chromatography since they can be converted into pure water with nearly zero conductivity.

Using hydroxide eluents results in low increase of baseline level and noise which thus facilitate peak integration and increase calibration reliability. However, to accomplish this, the suppressor and its regeneration system must be efficient and have a high capacity to successfully suppress strong eluents. The Xenoic® XAMS membrane suppressor can, when combined with the Xenoic® ASUREX-A200 automatic regenerator, be used to suppress eluents up to 50 mM, or even higher if an extra concentrated regeneration solution is used (see the operation manual for ASUREX-A200). For even stronger eluents, the Xenoic® XAMS-HC high-capacity suppressor with the Xenoic® ASUREX-A200 automatic regenerator is recommended.

Hydroxide gradient separation of organic acids and inorganic anions

Hydroxide gradient separation of organic acids and inorganic anions on an IonPac AS11-HC column (250×4 mm) using an eluent containing 1-50 mM NaOH in water pumped at 1.0 mL/min at 30 °C from an EQAX-B1 eluent bottle equipped with an EQAX-TC1 trap cartridge for carbon dioxide removal. Background reduced by XAMS suppressor with ASUREX-A200 automatic regenerator keeping the background increase <1.5 µS/cm from start to finish. An inert Shimadzu Prominence system with modules CMB-20A, 2x LC-20Ai, DGU-203R, SIL-20AC, CTO-20A, and CDD-10Avp was used. Injection of 50 µL of fluoride (1), lactate (2), glycolate (3), formate (4), pyruvate (5), chloride (6), nitrite (7), malate (8), tartrate (9), bromide (10), nitrate (11), sulfate (12), oxalate (13), phosphate (14), citrate (15), at concentrations ranging from 4 to 40 mg/L in water, giving signals up to 50 µS/cm.

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