Industry: chromatography

Liquid chromatography (LC) is a cornerstone of modern quality
control and status monitoring thanks to its ability to separate
substances based on their molecular properties across a wide
range of samples. However, the diversity of chromatographic
modes and how specific circumstances affect the outcome in
each case also make LC a complex method that requires skilled
personnel to ensure reliable results.

In this section Diduco has gathered examples from liquid chromatography experiments that are not industry specific but rather highlights concepts or effects that together help build the knowledge of how changes in conditions affect analytical outcomes and thereby the validity of the results. As with other information on this website, the focus is on LC modes which can accomplish separation of polar and charged structures, i.e., ion chromatography (IC), ion exclusion chromatography (IEC / ICE), hydrophilic interaction chromatography (HILIC), or reversed phase (RP). The latter mode is what dominates in instruments for high performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography (UHPLC) separations.

Applications

ion chromatography

Preserving eluent quality with dedicated storage protected from ambient carbon dioxide

To ensure that liquid chromatography analysis methods meet regulatory demands of retention repeatability as dictated by pharmacopoeia and the ICH guidelines, it is important to protect weakly buffered eluents from ambient carbon dioxide. The formation of carbonate species will otherwise change the pH and strength of the eluent, thus shifting retention.

ion chromatography

Comparing suppressed and non-suppressed ion chromatography

Suppressed ion chromatography with conductivity detection is a powerful and sensitive technique to analyse charged ionic species, especially anions of strong acids. The chemically regenerated membrane suppressor Xenoic® XAMS can enable analysis of such anions down to levels of a few microgram per litre (part per billion, ppb).

HILIC

Separation of nucleosides and nucleobases

Being one of the basic components of all cells as building blocks of DNA and RNA, there is a high and growing need for bioanalytical methods to determine nucleosides, nucleobases and related compounds in a variety of samples. Hydrophilic interaction chromatography is one of the most suitable approaches for this, due to the hydrophilicity of these compounds as demonstrated by their negative logP and logD values.

ion chromatography

Column screening using hydroxide gradients for ion chromatography method development

Hydroxide gradient elution is an effective approach in ion chromatography analysis due to its ability to separate organic acids and anions with a wide range of characteristics. During method development of such protocols, scouting gradients is a quick way to rapidly screen different columns and assess their potential for a certain analysis situation and sample composition.

ion chromatography

Isocratic separation of four small monovalent organic acids using a weak hydroxide eluent

Singly charged anions of small organic acids can be challenging to separate due to their low retention on many ion chromatography columns. During method development for their analysis several different columns often need to be compared to find a separation selectivity that is suitable for the set of compounds in question.

ion chromatography

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 approach in ion chromatography since they can be converted into pure water with nearly zero conductivity.

ion chromatography

Partial separation of structurally similar organic acids at isocratic conditions

Small organic acids are an important group of chemical compounds that needs to be analysed and quantified in many different industries. This application shows ion chromatography of a variety of organic acids using a non-optimized isocratic carbonate-based eluent.

ion chromatography