How to Clean a ELSD for Polysorbate analysis - WKB345982

OBJECTIVE or GOAL

Remove any buildup of most organic films using methanol as a final displacement rinse.

ENVIRONMENT

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

PROCEDURE

Milford Demo Lab ELSD Cleaning Procedure for Polysorbate:

Objective: To remove any buildup of organic films using methanol as a final displacement rinse.
General approach: Using warm solvent and a heated tube, we are going to clean the ELSD surfaces by sequential rinses of water and methanol. Methanol acts as a displacement solvent which can remove any non-volatile organics.

Note 1: There is some flexibility, as this procedure was not fully optimized!  Flushing your detectors at least 3 times with the solvent cycle of ~20 mins of 50/50 water/methanol followed by ~20 mins of water and finally ~20 mins of methanol. Do this 3 times for a new detector (See Figure 1), additional rinses may be needed if you do not get a good baseline. For best results use Milli-Q Water and LCMS grade Methanol.

Note 2: This also acts a shutdown method, extend the run time to 123 mins which adds 1 hour of dry time at the end. Include it into your sample set then attached a shutdown method that shuts off the lamp, column heater, etc. (See Figure 2)

Note 3: If you’re involving a external switch, make sure the system is flowing into the ELSD for these flushes. remember to replace the column with a union.

Figure 1. Plan a run time of 62 mins, this will only cycle through the solvent rinses. Use Inject Immediate Standards to collect data; use a Condition Column if you do not want to collect data.

Figure 2. Utilize this same cycle + dry time as a shutdown flush/shutdown extend this to 123 mins. Additionally, include a shutdown method to shut off your column and lamp, and lower the gas flow to fully shutdown the system.

Figure 3. Typical pressure profile and ELSD signal (of a clean detector).

Basic Parameters:
Mobile Phase Line C = Methanol

Mobile Phase Line D = Water

Column: 50C

Gradient Table:
50/50 Water/Methanol, followed by 100% water, then 100% methanol.1 min switch over for a total of 62 mins.
For shutdown, continue this gradient another 60mins for 1hr of drying the drift tube (bakeout period) and optics.
[You can of course switch Line C/D with the corresponding gradient table switch, I just had line D in water].

ELSD Parameters:
Gain: 80
Data Rate: 20 pps
Time Constant: Normal, 0.1000 sec
Gas Pressure: 50 psi
Nebulizer: Heating at 90%
Drift Tube: 80C ± 5C

Appendix:
Screenshots of Flush Method:

Note 4: With an optional Diverter Valve the ELSD can control it with the external switches (if available).  This can be used to automate the switch between the ELSD during the wash and then again away during the bakeout period.

For Full Shutdown: (it is reccomended switching to waste to not inadvertently flood the ELSD for start up).

Example Chromatography:

Before cleaning, A representative blank injection with solvent spiking:

After Cleaning, A representative blank post cleaning with no or little observed solvent spiking:

ADDITIONAL INFORMATION