Are there special considerations when using normal phase with an ELS detector? - WKB121166

ENVIRONMENT

• 2420 Evaporative Light Scattering Detector
• 2424 Evaporative Light Scattering Detector
• ACQUITY UPLC ELS Detector

ANSWER

There are generally no reports of tubes or instrument damage from using normal phase with an ELS detector. There is no THF/hexane kit to replace for an ELS detector, but there are some things that the customer may want to take note of:

1. Nebulizer heater

For typical reverse-phase separations, the nebulizer heater is not recommended. Reverse-phase separations typically use the cooling function, or the nebulizer heater is turned off. This is to avoid introducing excess material into the drift tube that cannot be nebulized.

The only time a nebulizer heater is a benefit to the separation is when running normal-phase solvents such as hexane. This is to maximize the amount of material getting into the drift tube.

The method for peak response can be optimized with the nebulizer heater off. Then turn it on to no more than 5 degrees less than the drift tube temperature, and re-inject to see if the response increases. If there is no increase in response, you can leave the nebulizer heater off. If nebulizer temperature is used, make sure that it is never higher than the drift tube temperature because it will cause the material to condense when it gets further into the drift tube.

2. Siphon drain tube

The normal-phase solvents tend to dry out in the siphon drain tube rather quickly. When they dry out, the component of interest entering the drift tube can get drained right out of the detector if the siphon tube is dry. The user may want to fill it with non-volatile solvents (water or IPA) at the beginning of each run and pay attention to the tube throughout the run to be sure it does not dry out. 

Typically, you'll see an inch or two of the solvent build up in the drain tube before it cascades down to the waste container. If you don't see the accumulation of waste, the siphon drain tube is dry.

ADDITIONAL INFORMATION