Speeding up 2D chromatography (HPLCxSEC) at it s limits. ..fast, faster ups broken...

Transcription

1 30 th September 2014, Frankfurt Speeding up 2D chromatography (HPLCxSEC) at it s limits...fast, faster ups broken... Dr. Bastiaan Staal International Symposium on GPC/SEC and Related Techniques

2 How it started Why critically evaluating 2D Chromatography? Cost factor. Measurements are rather expensive and therefore oft not done, although, for complex polymers, the outcome is a very powerful kind of fingerprint. Online conventional 2D chromatography suffers from a number of weakness, like: Poor resolution in the second dimension Solvent-mixture from the 1 st dimension causes disturbance signals for e.g. DRI or Corona detector, and hence needs time to re-equilibrate, which increases significantly the total analysis time. The marginal plots of the 2D measurement, do not show a good match between the sample measured only by HPLC or SEC: Note: Marginal plot = Summed up data from 2D plot into a single dimension (either SEC, or HPLC). 2

3 So what demands do I have? Conventional 2D-LC Fast 2D-LC Time 2nd dimension (min) 6 30 sec (!) Number of tranfer injections Total analysis time (min) 360 min = 6 hrs 0.5 hrs = 30 min Flow in the first dimension should be independent from the 2 nd dimension. Setup should not include more then 2 pumps Considerations.. Which mode we choose, SECxHPLC or HPLCxSEC? SECxHPLC requires ultra fast HPLC, due to long re-equilibration time of the columns not feasible < 2 min. SEC columns should resist high pressures, and handle all kind of solvents.

4 4 Ultra fast SEC in 30 sec. possible? How to speed up SEC? Higher flow rates -> requires column that resist high pressures Increase column oven temperature (reduce viscosity) Pressure (bar) Reduce inner diameter of the SEC column Flow (ml/min) 2 x Acquity UPLC BEH C18 130A 1,7μ 4,6x150mm in THF at 130 C. 40 sec (Total analysis time = 40 min) Polystyrene standards in THF Most likely SEC in 30 sec. not feasible yet, but 40 will do. 1,35 min

5 The idea for fast 2D-LC was born The second dimension (SEC) is clear, but what about the first dimension? Injection volume into the SEC <10µL HPLC dimension should run at normal flow rates => Sample after the first dimension needs to be trapped Trap column (C18, 20 x 2.1 mm 10µL) => Linear flow 20 mm/sec (!) Mixer = 50µL 5

6 Fast 2D-LC Conditions conventional 2D-L Poor SEC resolution Solvent transfer from 1 st dimension into 2 nd dimension. The marginal plots of the 2D measurement, do not show a good match between the sample measured only by HPLC or SEC. Conditions fast 2D-LC High SEC resolution Solvent transfer from 1 st dimension into 2 nd dimension minimized (approx. 8µL). Both dimensions are run under standard conditions. The marginal plots should lead to identical chromatograms. The next challenge is, how to construct a setup that will prevent any early precipitation/contamination. 6

7 Experimental setup.. Valves, ELSD detector Pump 1 Water Pump 2 THF (GPC) Switching valves THF/Water (HPLC) ELSD SEC Pump1, pump2 Oven Injector, UV and Corona detector Corona UV Pump 1, left pump head = GPC, right pump head = used to precipitate HPLC flow. ELSD detector is used to prove break through of the HPLC side. The question is, how do we setup the switching valves 7

8 Experimental setup.. Pos A THF HPLC Pos B THF HPLC Water Water GPC GPC Waste Waste This complex setup was chosen in such a way that all capillaries are cleaned with 2 injections 8

9 Conventional 2D-LC SEC (increasing molar mass) HPLC (Water->THF gradient) 9

10 Match between the marginal distributions HPLC (created from the 2D plot) Although the same detector (corona) was used, difference in intensities are there. Conventional HPLC measurement at the same C18 column used for the 2D-LC measurements t (min) 10

11 Match between the marginal distributions SEC (created from the 2D plot) Also difference in intensities here.. SEC done at the at the same column used for the 2D-LC measurements. 11

12 Injections in pure THF in the first dimension. HPLC (Water->THF gradient) Totally irreproducible. Difference To much water in from mixer at the SEC column, does not affect the column, but causes retention very poor time chromatography. between A delay time both between the 2 switching vales was introduced to minimize the 50µL. prep. columns? SEC (decreasing molar mass) Conditions: Flow 1 st dimension (HPLC) 1 ml/min isocratic THF. Water to precipitate sample 1 ml/min. Flow 2 nd dimension (SEC) at 80 C in THF at 1 ml/min. 12

13 Injections in pure THF in the first dimension. HPLC (Water->THF gradient) Difference in retention time between both prep. columns? SEC (decreasing molar mass) Conditions: Flow 1 st dimension (HPLC) 1 ml/min isocratic THF. Water to precipitate sample 1 ml/min. Flow 2 nd dimension (SEC) at 80 C in THF at 1 ml/min. 13

14 Injections in pure THF in the first dimension. HPLC (Water->THF gradient) Significant improvement after minimizing pressure difference between HPLC and SEC SEC (decreasing molar mass) Conditions: Flow 1 st dimension (HPLC) 1 ml/min isocratic THF. Water to precipitate sample 1 ml/min. Flow 2 nd dimension (SEC) at 80 C in THF at 1 ml/min. 14

15 No results yet HPLC (Water->THF gradient)? SEC (decreasing molar mass) Conditions: Flow 1 st dimension (HPLC) 1 ml/min isocratic THF. Water to precipitate sample 1 ml/min. Flow 2 nd dimension (SEC) at 80 C in THF at 1 ml/min. 15

16 No results yet It is not understood why the system does not stay stable. To avoid the 50µL mixer volume into the SEC column, a delay between the valves was set at 3000 milliseconds. Only if both dimensions have similar pressures the system seems to function. The valves used, are only stable till 350 bar. Most likely that cross flows might disturb the separation, which is hard to detect. 16

17 Conclusions and outlook Conclusions: SEC within 40 seconds should be feasible. Without mixer, no sufficient precipitation occurs. Redissolution of the precipitated sample is not an issue for this sample. Pre-UPLC columns are very sensible to particles Not everything is fully understood at this point Outlook This setup will also allow more orthogonal chromatography like HPLC (polar) x HPLC(apolar) Convert this concept at systems that run at 1000 bar. 17

18 Acknowledgments Yvonne Matheis Roland Stritesky Till Gründling 18

19 What all went wrong.. Different firmware causes a cutoff of the UV signal Valves only pressure resistant till 350 bars. Injector didn t inject reproducible. NanoLC C18 columns didn t have enough capacity. ELSD Detector broke down. Switching valves requires a delay time, not trivial Pre-UPLC columns got blocked Column ovens broke down HPLC column started to leak Besides the regular things, pumps starts to leak, implementation in to the software, leaking fittings. The only thing that survived so far, where the GPC columns. 19

20 Running the APC in HFIP PMMA Standards in HFIP w% KTFA 1 x 125µ Flow 1.0 ml/min 630 Bar 1 x 450µ Flow 1.0 ml/min 550 Bar 1 x 45µ Flow 1.0 ml/min 830 Bar 20

21 Running the APC in HFIP PMMA Standards in HFIP w% KTFA 2 x 45µ Flow 0.5 ml/min 610 Bar 3 x 45µ Flow 0.5mL/min 900 Bar 1 x 45µ Flow 1.0 ml/min 830 Bar 21

22 The PEG problem.. Mixed B columns (2x) PEG standards in THF at a flow rate of 1.0 ml/min

23 The PEG problem.. Mixed E columns (2x) PEG standards in THF at a flow rate of 1.0 ml/min

24 The PEG problem.. SDV columns 3 (10 3 Å, 10 5 Å, 10 6 Å) PEG standards in THF at a flow rate of 1.0 ml/min

25 The PEG problem..

26 The PEG problem..