Introduction to System Suitability Tests Michael Wright Bioanalytical Services LGC Fordham, UK

Transcription

1 Introduction to System Suitability Tests Michael Wright Bioanalytical Services LGC Fordham, UK Science for a safer world

2 13/10/

3 What is a System Suitability Test (SST)? Also referred to as a System Suitability Sample (SSS) A standard or extracted sample (*in extraction solvent) Usually contains internal standard Stored in a stable manner if possible Sample ID Rack Code Vial Position Reagent Blank DWP96 1 Reagent Blank DWP96 2 SST DWP96 3 Reagent Blank DWP96 4 Injected onto your LC-MS before you submit your sample batch 13/10/2016 3

4 What does it tell us? 1) Retention Time 2) Instrument Response (or Signal:Noise) 3) Peak Shape When combined with a back pressure reading it provides us with a wealth of knowledge.

5 What type? Generic OR Specific 13/10/2016 5

6 What do the SST and Back Pressure tell us? 1) The HPLC is OK Mobile Phases Column Flow rate Column Oven Auto-sampler Injection Seals Valves (Carry-over)

7 What do the SST and Back Pressure tell us? 2) The Mass Spec is OK Ionisation Gas Flow Source Ion transmission Detection

8 What doesn t the SST and Back Pressure tell us? Sample extraction issues Contaminants from the extraction solvents (Reagent Blank/Control Blank)

9 Setting Up the Acceptance Criteria 1) Determine SST concentration (LLOQ or match to LLOQ?) 2) Run before every validation batch to obtain a feel for normal Instrument API3200 Back Pressure at t0 Retention Time Intensity S:N P A/S Maintenance Notes DATE Pump A/B Pump C/D 25OHD3 25OHD2 25OHD3 25OHD3 27/03/ /03/ LLOQ looks poor, QC Low out 28/03/ Fresh Mobile Phases 01/04/ Weekly & Monthly 02/04/ /04/ Weekly 11/04/ Leak in column oven 11/04/ /04/ ) From these experiments set the SST acceptance limits 4) You will need to do this for each type of LC-MS instrument 13/10/2016 9

10 Retention Time: Minimum Intensity 1200cps Minimum Signal:Noise 20:1 Peak Asymmetry (A S ) h A C Time A s = CB/AC B } 10 % of peak height (h) Plate Count (N) t N 5.54 W R 0.5 2

11 Different machines 25OH Vitamin D SST XIC of +MRM (4 pairs): / Da ID: 25OHD3 1 from Sample 137 (2014_08-04 post weekly) of SST.wiff (Heated Nebulizer) Max cps OHD3 RT: 4.64min Older instrument In te n s ity, c p s Lower Limit 2400cps 3-epi- 25OHD Time, min XIC of +MRM (4 pairs): / Da ID: 25OHD3 quant from Sample 28 (2014_08_04) of SST.wiff (Heated Nebulizer) Max. 7.3e4 cps. Newer instrument In te n s ity, c p s 7.3e4 7.0e4 6.5e4 6.0e4 5.5e4 5.0e4 4.5e4 4.0e4 3.5e4 3.0e4 2.5e4 2.0e4 1.5e4 1.0e Lower Limit 2.0e4 cps 25OHD3 RT: 4.75min Time, min epi- 25OHD

12 How much RT shift/ BP change/ Peak symmetry change is still OK? No hard and fast rule batch failures during establishment/validation as a guide If the method is already live or there weren t (m)any failures during method development then. Guess! Try not to make a rod for your own back (not too tight unless you have cause & don t set unnecessarily low LLOQs) Initial criteria are opinions that you then review over time Look at every batch failure as an opportunity to review these criteria to make it a better tool 13/10/

13 Retention Time Ensure that the criteria are set so that the peak doesn t shift into a drastic gradient change Monitor IS in batches with altered RT to look for ionsuppression issues Back Pressure Limits for fittings Check traces to see the % change over the gradient (extrapolate for changes at t0*) Peak Shape (A S and N) Known interferences? Integration Assists in judging column lifetimes 13/10/

14 Example: adding in known interferences XIC of +MRM (4 pairs): / Da ID: 25OHD3 1 from Sample 221 ( TN) of SST.wiff (Heated Nebulizer), Smoothe... Max cps OH OH OHD 3 HO In te n s ity, c p s HO 3epi -25OHD Time, min

15 Example something a little different: Unknown interferences 1 Normetanephrine 2 3 Metanephrine

16 Something has gone wrong.

17 I can t see anything Step 1 start simple Correct method being run? Is there anything in the vial? Is the vial in the correct position? Did the auto-sampler pick up the sample? Needle depth? Wash solvents full? Is the LC connected to the MS? Is the back pressure OK? YES Spray in the source? Correct probe? (ESI vs APCI) corona needle? Divert valve correct? Check ion path Signal Minimum Intensity Retention Time Time NO Correct mobile phases? Lines not purged properly Too High Blockage in lines somewhere? Column too old? Too Low Leak somewhere? Fluctuating Leak on single pumphead Pump seals

18 Signal Signal What is it doing over there? Retention Time Time Retention Time Time No point looking at the Mass Spec Is the back pressure OK? Yes Mobile phase made correctly? Gradual change? (column degradation) Correct wash solvents loaded (peak shape OK?) Injection mode correct? No Mobile phase made correctly? All lines purged correctly? Leak somewhere (early and late peaks) Faulty pump (swap A&B lines and see if RT changes Gradual change? (column degradation) 13/10/

19 Right time - but it is a bit small Signal Minimum Intensity Can t rule out the HPLC or MS Back pressure will often be OK but check anyway Time SST sample mixed properly? Mobile phase made correctly? Auto-sampler working properly?.. blockage/ leak/ wash solvent/ injection mode (*can check with manual injector) Leak somewhere after the column? Correct ion probe? Capillary extended in probe? APCI Corona needle positioned correctly? Mass Spec within calibration? Gradual change across all methods? (MS needs cleaning) Sudden drop MS source/ion guide/q1 may need cleaning Vacuum OK? Gas pressures OK? 13/10/

20 Where did all that come from? Signal Minimum Intensity Time SST sample mixed properly? Mobile phase made correctly? Right amount injected? Mass Spec set to correct resolution? Correct ion probe? Was MS incorrectly calibrated before? Recent maintenance performed? (Source/Gas/Vacuum) Is it really a problem? Can you just inject less? 13/10/

21 It looks ugly SST sample solvent correct? Auto-sampler wash solvents OK? Mobile Phases OK? Pumps OK and delivering gradient? Leak somewhere? Peak tubing cut squarely and fitted correctly? Column degradation? 13/10/

22 It s EVERYWHERE! Signal Minimum Intensity Reagent Blank Sample ID Rack Code Vial Position Reagent Blank DWP96 1 Reagent Blank DWP96 2 Signal Reagent Blank SST DWP96 3 Reagent Blank DWP96 4 Signal SST Ghost Peaks are often a sign that your mobile phase or auto-sampler wash contains a contaminant Signal Reagent Blank Time 13/10/

23 It wont go away Carry-over peaks point the finger at: Auto-sampler wash not working Internal damage to injection port Signal Signal Minimum Intensity Reagent Blank Reagent Blank Issue with peak not being fully eluted from SST Peak tubing not being cut squarely and fitted correctly Signal SST Signal Reagent Blank Time 13/10/

24 Questions? Science for a safer world