Question

1) List the desired characteristic of an HPLC detector {4} 11) Briefly, but informatively, describe the following columns in liquid chromatography, a Guard column b Scavenger column {4} One of the recent developments in liquid chromatography is in column chemistry. Le hydrophilic interaction liquid chromatography (HILIC) Briefly, but informatively, discuss the importance of this development

Answer 1

1) The desired characteristics of an HPLC detector are many, and most of them are characteristics commonly desired in detectors. Among the most important ones:

• High sensitivity with a fast, reproducible and predictable response.
• Good response to all solutes, or at least predictable specificity.
• Wide linear dynamic range.
• Response unaffected by changes in temperature and mobile phase flow.
• Respond independent of the mobile phase.
• It shouldn't contribute to extra-column band broadening.
• Reliable and convenient to use.
• Provide qualitative and quantitative information on the detected peak.

2) Their functions are similar:

a) Guard columns are place between the injector and the analytical column to capture any particulate material present in the sample, pump debris. They are usually built with the same material as the analytical column, albeit shorter and with larger size particles.

b) A scavenger column is placed between the pump and the injector. They are also useful for the elimination of particulate material from solvents prior reaching the pump, thus avoiding damage to this part of the equipment. They can be easily removed and cleaned when necessary.

III) Hydrophilic interaction liquid chromatography (HILIC) is an alternative high-performance liquid chromatography (HPLC) mode for separating polar compounds.Like normal phase-liquid chromatography, HILIC employs traditional polar stationary phases such as silica, amino or cyano, but the mobile phase used is similar to those employed in the reverse phase-LC mode. HILIC also allows the analysis of charged substances, as in ion chromatography. HILIC has many specific advantages over conventional normal phase-LC and reverse phase-LC. For example, it is suitable for analyzing compounds in complex systems that always elute near the void in reverse phase chromatography. Polar samples always show good solubility in the aqueous mobile phase used in HILIC, which overcomes the drawbacks of the poor solubility often encountered in normal phase-LC. Expensive ion pair reagents are not required in HILIC, and it can be conveniently coupled to mass spectrometry (MS), especially in the electrospray ionization (ESI) mode. In contrast to reverse phase-LC, gradient elution HILIC begins with a low-polarity organic solvent and elutes polar analytes by increasing the polar aqueous content.