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Ahem,
it could be a ton of things. Matrix effect, variation stemming from different sources of plasma ("But is passed the selectivity experiments blah blah"). Even solar flares can under the right circumstances be detected by LC-MS/MS.
Different stocks, different storages, different equipment, pipetting errors, robot programming, different this, different that. And you get some info by also looking at the slope of the cal. curve in those cases.
But still, let us discuss how to establish the presence of the phenomenon before addressing causes? Let us say the average IS of cals+QCs in one run is 8x the average IS of cals+QC's in another run and all passing the usual criteria.
Would you be concerned?
Yes? Why?
No? Why not?
Not enough info? Which questions would you ask? (I would e.g. consider matrix sources used for QC's+cals, pipetting, volumes, station, method settings, columns, possibly grid anomalies if I can get such info, but all that will usually leave a blank)
❝ ❝ ❝ […] "perhaps it is the ion source blah"
❝ ❝
❝ ❝ If a stable isotope labeled internal standard is used, that’s the only reasonable explanation for me.
❝
❝ Well, it could also be a wrong dilution during the preparation of a new working solution, a variable recovery...
it could be a ton of things. Matrix effect, variation stemming from different sources of plasma ("But is passed the selectivity experiments blah blah"). Even solar flares can under the right circumstances be detected by LC-MS/MS.
Different stocks, different storages, different equipment, pipetting errors, robot programming, different this, different that. And you get some info by also looking at the slope of the cal. curve in those cases.
But still, let us discuss how to establish the presence of the phenomenon before addressing causes? Let us say the average IS of cals+QCs in one run is 8x the average IS of cals+QC's in another run and all passing the usual criteria.
Would you be concerned?
Yes? Why?
No? Why not?
Not enough info? Which questions would you ask? (I would e.g. consider matrix sources used for QC's+cals, pipetting, volumes, station, method settings, columns, possibly grid anomalies if I can get such info, but all that will usually leave a blank)
—
Pass or fail!
ElMaestro
Pass or fail!
ElMaestro
Complete thread:
- IS response variations Ohlbe 2019-09-04 19:03 [Regulatives / Guidelines]
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- IS response variations nobody 2019-09-06 16:21
- More on IS response variations Ohlbe 2019-11-12 11:32
- More on IS response variations ElMaestro 2019-11-12 12:27
- More on IS response variations Helmut 2019-11-12 13:24
- More on IS response variations ElMaestro 2019-11-12 13:38
- More on IS response variations Helmut 2019-11-12 13:41
- More on IS response variations Ohlbe 2019-11-12 13:56
- More on IS response variationsElMaestro 2019-11-12 16:25
- More on IS response variations Ohlbe 2019-11-12 18:14
- More on IS response variations ElMaestro 2019-11-12 18:39
- Not more on IS response variations Ohlbe 2019-11-13 00:06
- Not more on IS response variations nobody 2019-11-13 10:06
- the run passes = there is no problem? ElMaestro 2019-11-13 17:35
- the run passes = there is no problem? nobody 2019-11-13 19:17
- the run passes = there is no problem? ElMaestro 2019-11-13 17:35
- Not more on IS response variations nobody 2019-11-13 10:06
- Not more on IS response variations Ohlbe 2019-11-13 00:06
- More on IS response variations ElMaestro 2019-11-12 18:39
- More on IS response variations Ohlbe 2019-11-12 18:14
- More on IS response variationsElMaestro 2019-11-12 16:25
- More on IS response variations ElMaestro 2019-11-12 13:38
- More on IS response variations Helmut 2019-11-12 13:24
- More on IS response variations ElMaestro 2019-11-12 12:27
Ing. Helmut Schütz