Dear all,
I've got a question (and a doubt) regarding how to define raw data for chromatographic outputs, and I'd like to know your opinion. We are supposed to keep raw data available for inspections, etc.
We know that before being integrated, a chromatogram is basically a table of time and the voltage output, which gives the magnitude of the response to the substance amount. These data are the result of the measurement process but we need some mathematical manipulation called integration, to transform them in analytically useful information.
This integration process is performed by an algorithm which depends on several integration parameters. This algorithm usually changes between different providers. Also, it is difficult to keep the same integration parameters for a given lot of bio-sample chromatograms, mostly because of presence of interfering peaks that occasionally can appear, clouding the chromatogram interpretation.
Finally, the peak area (or height) is the number used as the response, to obtain the drug concentration in the sample. This number is a consequence of having not only a chromatogram but also a given integration algorithm and a given set of integration parameters
Therefore, questions are:
What is raw data? is it the instrumental file containing the time versus peak response? If so, how can I assure that from these data I’ll get the same number to be used in concentration calculations? Should I keep a copy of the integration parameters for every chromatogram?
From a different point of view, could I define the integrated chromatogram (the printed report) as the raw data? Once the chromatogram is integrated and printed, I see this as an equivalent to the absorbance displayed by a spectrophotometer or the pH, which is also a voltage mathematically transformed by the pH-meter. In this case I would be focusing on the peak area (height) number rather than the chromatogram itself.

Thanks in advance

Although FDA's perspecitive is under review ( look at Draft Guidances on FDA web site) most raw data include the raw data and meta data. Raw data is the signal vs. time and the metadata is any parameter used to calculate the result. If you are using electronic records I believe that you need to maintain both meta-data and raw data to be compliant.

There is much more to a raw data file than just the time vs. abs. which you state. Most, if not all, also contain info on the method used for the acquisition of the data, time, date, user, version of sfw, etc, etc. This data should be kept for as long as your SOP's state, as well as the result data.