Chromatography Forum

I'm transferring a method developed on an Agilent 6890.

Uses a 30m x 0.32 x 0.5um Wax column, split injection (2.5 to 1), 0.5 uL inj vol., injection solvent is 100% ethanol (cannot change it due to extraction issues), column constant flow 3.0 mL/min of N2.

Analyte of interest elutes at 10.5 minutes, and validation performance was excelent. (RSD < 0.5%, Tailing 0.95)

Tried to transfer method to another lab that only has PE Clarus 500 GCs. With above parameters, peak elutes at 7.0 minutes and fronts badly (column overload). Eventually changed flow to 1.5 mL/min and achieved 10.3 min retention. Split ratio increased to 20 to 1 to minimize fronting (tailing 0.85).

Still having repeatability problems (RSD>5%).

Has anyone seen 6890 to Clarus 500 method transfer problems?

Any ideas as to the cause the drastic flow and split changes necesary to achieve similar chromatography?

(We've ruled out the typical hardware and column installation issues.)

The injector geometry is slightly different between these 2 instruments, so perhaps that explains the split difference, but for the life of me I have no idea why the flow needed to be cut in half!

Thanks,
Jon

How much injection volume do you have in each injector liner?

Are they of the same type of liner?

Are the actual temperatures of the injector the same? (not what the GC says is the temperature, the ACTUAL temperature! )

Are the injection speeds the same? PLUNGER movement rate?

Are the residence time of the needle the same for both instruments? Are the needle tips of the same design?

You have found a test which indicates a difference in environment between the two GCs. Now you have to find a way to figure out what that difference is.

best wishes,

Rod

The PE liner volume is slightly larger than the Agilent, though both should be ok per vapor volume calculator that Agilent provides.

We used a standard straight sided inlet liner with fused silica wool for both instruments.

As for injector temps... didn't actually measure the temps. I do know that the GC I was using had just (successfully) been useed for a different method transfer (PE GC to PE GC), so I assume the programmed temp is correctly applied. Further evidence that temp is not an issue is that the chromatogram peak profile is identical to the Agilent profile when 1.5 mL/min flow is implemented.

Injection speeds: Agilent had SLOW set to OFF... on the PE we tried slow, normal, and fast and fast seemed to improve things, though obviously didn't solve the whole problem.

Plunger movement rates would be whatever the defaults are for the instruments... Do Agilent and PE plunger rates differ significantly?

As for residence time, we set a preinjection dwell of 0.5 and a postinection dwell of 0.2 on the Agilent. We could find no way of implementing such settings on the Clarus 500... Does anyone know a way of setting dwell times on the Clarus?

Needle tips appeared to be the same.

As for your last statement Rod... that is my fear! I am hoping someone out there in the GC world (an Agilent or PErkin-Elmer technical rep????) has seen something similar before and can point me in the right direction. Eveything I have seen so far points to the injection process.

Thanks Rod and thank you to anyone else that can help out here.

Jon

Jon,

I would first concentrate on the large difference in retention time between the two systems. You say that you have the Agilent calculator. Input the numbers and see if you have the correct flows and head pressures on each system. All of these systems follow a law of physics for the flow in a capillary column, and it is the same law for Agilent and PE. Either the pressure is wrong in one of the systems, or the column is not the same. Please also ensure that you have the correct carrier gas set in each instrument, as this is also part of the equation.

Gasman

Yes indeed the pressures do differ.

For the Agilent, we used 3.0 mL/min. constnat flow and achieved a 10.5 min rention time. The pressuere at injection was around 12 psi if I remember correctly.

For the Clarus, we are currently using 1.5 mL/min and getting a 10.3 min. retention time. The pressure at injection is about 7 psi.

We are using exactly the same column in each instrument. (I removed it from the 6890 and shipped it from our lab to theirs.)

That is what has me so perplexed... same column, same carrier gas (N2), same temperature parameters, yet different retention!

The pressure seems to be correct for a 30m x 320 column using nitrogen carrier gas. Take the numbers from the calculator as being correct. Any system using this column should give 3ml/min. MEASURE the flow coming out of the column with the same headpressure set on each instrument, do not at the moment rely on any figures shown in a display. You should do this on both instruments, as either could have an error.

Gasman