A New Web-Based Application for Modeling Gas Chromatographic Separations

Transcription

1 A New Web-Based Application for Modeling Gas Chromatographic Separations Jaap de Zeeuw**, Rebecca Stevens*, Amanda Rigdon, Linx Waclaski*and Dan Li* *Restek Corporation, Bellefonte, PA, USA **Restek Corporation, Middelburg, The Netherlands

2 Developing a new method Choose the best column: stationary phase Consult colleague Wish to see a chromatogram how well the stationary phase separates my components Consult databases Literature Retention indices Chromatogram libraries Modeling

3 Using databases: Chromatograms Hydrogen sulfide Enter name here, for instance hydrogen sulfide

4 Sulfur components on Rxi-1ms Information includes Column dimensions GC-Conditions Peak identification and ret. time Download as PDF file Search options include: Component name Cass nrs Synonyms Matrix Component groups Method nrs (EPA, ASTM..)

5 Modeling GC is very interesting for modeling because there are only a limiting number of parameters Selectivity Stationary phase type Impact of temperature Retention Film thickness Column diameter and length Temperature Carrier gas velocity (ID, length, type of gas, temperature, outlet pressure)

6 2 situations Changing an EXISTING method Faster, other gas, other column dimension, vacuum detector No change of stationary phase Developing a NEW method Select the MOST SELECTIVE stationary phase OPTIMIZE chromatographic conditions

7 Predicting separations There are mathematical relations between the parameters which makes it possible to predict peak position Most known are the Retention indices

8 Biggest challenge in GC modeling Calculating the retention time in temperature programmed mode When a component travels through a column at a different temperature, the interactions will be different. Changing temperature program or flow: Some separations improve Some separations go worse or disappear Peak swapping

9 Peak swapping Some examples

10 Rt-TCEP: Elution of benzene at different temperatures

11 Rtx-CL-Pesticides: peak swapping of pesticides

12 Rtx-5ms: the more complex the sample, the more risk separations will change 10ºC/min 13ºC/min 16ºC/min

13 Rtx-5ms: the more complex the sample, the more risk separations will change 10ºC/min 13ºC/min 16ºC/min

14 How to prevent this? Translate methods correctly, so the elution temperatures match up with the original method The method translator will help you to achieve this

15 EZGC Method translator and Flow-Calculator

16 Which Situations can benefit? When methods are changed, also the oven temperature program must be changed Optimizing the separation When a faster analysis is required (change of flow) When there is change of column dimensions Moving from a FID to a MS method (vacuum) Work with another carrier gas (N2 or H2) A combination from the above 16

17 2 situations Changing an EXISTING method Faster, other gas, other column dimension, vacuum detector No change of stationary phase Developing a NEW method Select the MOST SELECTIVE stationary phase OPTIMIZE chromatographic conditions

18 Select the most selective stationary phase This is not easy as interaction of component with stationary phase depends on: π - π interactions Van der Waals forces (Dipole, Londen) And these interactions are temperature dependent For a given component and given stationary phase the impact of temperature can be calculated EZGC

19 EZGC basics The EZGC chromatogram modeler was introduced in 2014 It s a free to use web application Input : a list of target compounds Output : a model chromatogram and suitable GC method conditions Column : Rtx -VMS, 30 m x 0.25 mm x 1.4 µm Carrier Gas : Helium, constant 1.68 ml/min Linear Vel. : 40.0 cm/sec Oven Temp : 35 C (hold 3.0 min) to C/min to C/min

20 Compound structure information

21 Enter Pro EZGC The Pro EZGC chromatogram modeller, introduced in 2016 Is also a free to use web application Input : a list of target compounds Output : a model chromatogram and suitable GC method conditions....but also.. Column : Rtx -VMS, 30 m x 0.25 mm x 1.4 µm Carrier Gas : Helium, constant 1.68 ml/min Linear Vel. : 40.0 cm/sec Oven Temp : 35 C (hold 3.0 min) to C/min to C/min

22 Pro EZGC Adding new functionalities to the chromatogram modeler Full control over modeling GC conditions: you can immediately see what the impact is on the separation of YOUR components Separation shown on multiple stationary phases: select optimal phase Change the type of carrier gas (He, H2, N2, Ar/CH4) Change the flow (linear gas velocity) Change the oven conditions: temperatures and time Change the column dimension: select length, ID and film thickness Change from pressurized to vacuum detection

23 Pro EZGC Adding new functionalities to the chromatogram modeler Full control over modelling GC conditions Critical pair targeting Interactive optimization Save and revisit your models

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25 Pro EZGC : compound selection The first step is to select the compounds of interest Option 1: search by compound name or CAS# Option 2: search by stationary phase Enter a compound list here

26 The Initial Solution Select a solution A modeled chromatogram is obtained along with predicted separation metrics The solution can be used as is or alter it to specific needs

27 Rtx-VMS Rtx-1 Rxi-624Sil MS

28 Pro EZGC compound selection The first step is to select the compounds of interest Option 1: search by compound name or CAS# Option 2: search by stationary phase Select a phase Select a library

29 Choose Phase and Library

30 Pro EZGC compound selection The first step is to select the compounds of interest Option 1: search by compound name or CAS# Option 2: search by stationary phase Select a phase Select a library Select compounds / criticals

31 Option 2: Search by stationary phase: setting compound criticals Select all components that need to be modelled: Here are 6 components selected From the 6, there are 3 targeted that MUST resolve

32 Optimizing GC Conditions Helium, hydrogen, or nitrogen carrier Any dimension column can be modeled Flow control is set by the Results heading EOF, SOF or full custom Oven program can be up to 5 ramps Refine oven program searches ramp rates

33 Pro EZGC Best Chromatogram and on multiple stationary phases Select column dimensions. (Length, ID, df) Select impact of all temperature settings Select impact of gas control settings and type of gas No GC required No columns to be purchased No FTE required Fastest way to check out applications at minimal costs Its a100% free service, available in many languages

34 Choosing a different column dimension

35 Separation on 20m x 0.18mm Rxi-5Sil MS

36 Expanded view

37 Refine oven program Changing oven program

38 Original 15.5 min. First refinement 13 min. Second refinement 11 min. FIFTH refinement 7 min.

39 Changing oven temperature yourself 3.6 min.

40 Operate at a higher Flow 13 min. 6 min.

41 Fast GC Shorten retention times.. Short, narrow bore, thinner film columns Hydrogen carrier (or even faster) Fast temperature ramp rates High utilization of peak capacity What happens to predictive accuracy?

42 Example: Fast GC for Volatiles 6.2 min.

43 How well does the fast model align with real result? Modeled Real

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45 Pro EZGC Different languages

46 Pro EZGC Features Best Chromatogram and on multiple stationary phases Select column dimensions. (Length, ID, df) Select impact of all temperature settings Select impact of gas control settings and type of gas Works with pressurized and vacuum detection systems No GC required No columns to be purchased No FTE required Fastest way to check out applications at minimal costs Its a100% free service, available in many languages

47 Pro EZGC Constraigns Only components that are in the database can be modelled using specific phases Start temperature needs to be set in relation with solvent BP Limited to liquid stationary phases Peaks are 100% Gaussian: overload / tailing is not modeled There maybe more selective phases available that are not in this database Visit:

48 Thank you for your attention Visit us at booth 4520 or visit