Log in
Register|
najatmughrabi ☆ 2008-11-19 08:32 (5243 d 08:40 ago) Posting: # 2728 Views: 4,982 |
|
|
Dear Forum Subscribers Good morning
Thanking you in advance for your valuable feedback Have a nice day  Najat |
|
Helmut ★★★   Vienna, Austria, 2008-11-19 13:51 (5243 d 03:20 ago) @ najatmughrabi Posting: # 2736 Views: 4,193 |
|
|
Dear Najat! ❝ 1. […] integration mode changes automatically within the same run […] ❝ in a haphazard way for both the analyte and the internal standard without any external modification. That’s quite common. ❝ Would appreciate why this is happening... Numerical integration depends not only on the parameters you are able to set in the chromatographic data system (e.g., retention time window, RT shift, threshold, peak width, preferred integration method,…), but also on internal parameters of the algorithm itself (how many data points are used in upslope/downslope of the peak, whether polynoms or splines are used, slice bundling, etc. – ask the manufacturer; but don’ be disapointed if they don’t come up with anything usable). In an actual chromatogram (depending on both external parameters and internal algorithms) the data system may ‘come to the conclusion’ (haha!), that it may be better to change from one integration method to another one. That’s the reason one should always inspect all chromatograms and go with a manual integration if the automatic one obviously failed. ❝ … and would it affect the integrity of the generated data from regulatory point of view (both European and US-FDA)? For the FDA you must report the reintegrated chromatograms; EMEA’s BE-draft is a little bit strange (see here). ❝ 2. Part of the LC-MS/MS analysis involves performing system suitability at the beginning; the analyst modified the chromatograms to get a better base-line for the internal standard. Calculations of the CV before modification fails the acceptance criteria while those after modification pass the acceptance criteria. Fine. ❝ Kindly advice how is this looked into from regulatory point of view? Does this invalidate the whole run even if the standard curve and QCs pass? Oops! The idea of a system suitability test is to check whether the entire equipment is able to perform as intended before actual matrix samples are injected. No calibration and QCs at this time… I’m not a regulator, but I would be very reluctant to accept such a procedure – personally I would either reject the run, or have a deep look in the system suitability SOP and the training of analytical staff… — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
|
najatmughrabi ☆ 2008-11-19 15:30 (5243 d 01:42 ago) @ Helmut Posting: # 2740 Views: 4,029 |
|
|
Dear Helmut Thank you for your feedback You have stated that ❝ That’ the reason one should always inspect all chromatograms and go with a manual integration if the automatic one obviously failed. Does this mean that all the chromatograms within a run should have the same integration mode (e.g. base to base) and if any chromatograms were integrated with a different mode (e.g. valley) within the same run they should be manually re-integrated to the (base to base) mode? Thank you and best regards Najat -- Edit: Standard quotes restored. [Helmut] |
|
Helmut ★★★ Vienna, Austria, 2008-11-19 16:35 (5243 d 00:37 ago) @ najatmughrabi Posting: # 2741 Views: 4,272 |
|
|
Dear Najat! ❝ ❝ That’s the reason one should always inspect all chromatograms and go with a manual integration if the automatic one obviously failed. ❝ ❝ Does this mean that all the chromatograms within a run should have the same integration mode (e.g. base to base) and if any chromatograms were integrated with a different mode (e.g. valley) within the same run they should be manually re-integrated to the (base to base) mode? No. The analyst should visually inspect all chromatograms. For a particular chromatogram the automatically changed integration mode may be ‘correct’; in such a case leave it as it is. Only if the automatic integration obviously failed (this may happen quite often in the lower signal range where a lot of noise is present) the analyst should set the baseline manually. Most analysts I know would simply draw the new baseline with the mouse, rather than change integration parameters a couple of times until the system comes up with a better integration (this would result in a lot of trial-and-error…). If you change the integration parameters for the entire batch, you would again have to inspect all chromatograms, and repeat this cycle maybe forever…  — Dif-tor heh smusma 🖖🏼 Довге життя Україна! Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
|
Ohlbe ★★★ France, 2008-11-20 01:18 (5242 d 15:54 ago) @ najatmughrabi Posting: # 2742 Views: 4,045 |
|
|
Dear Najat, ❝ 2. Part of the LC-MS/MS analysis involves performing system suitability at the beginning; the analyst modified the chromatograms to get a better base-line for the internal standard. No problem if the re-integration (either manual, or by modifying integration parameters for some samples) was indeed performed to get a better integration, and all samples in the run were integrated in a similar way (when I write "similar" I don't mean the same parameters for all samples, or base-to-base for all samples, but the same "look" for samples with similar concentrations). Discussions should only arise if the integration was obviously biased. According to the report of the 2006 Crystal City conference: As part of qualifying instruments, performance of system suitability ensures that the system is operating properly at the time of analysis. System suitability checks are more appropriately used for chromatographic methods to ensure that the system is sufficiently sensitive, specific, and reproducible for the current analytical run. However, the system suitability tests do not replace the required run acceptance criteria with calibration standards and QC samples. System suitability tests, when appropriate, are recommended to ensure success, but are not required, nor do they replace the usual run acceptance criteria. If the chromatogram integrations of the suitability test were indeed manipulated, that's quite bad; but if the calibration curve and QCs are OK you may still be able to save the run. If you re-analyse the samples, some authorities may even question your decision, stating that the first run was valid... Whatever you decide, should be properly documented. Regards Ohlbe |
Ing. Helmut Schütz