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GC Instrument Validation - 2005/11/28 18:17
Friends;
I am a LC practitioner of many years and I occasionally use GC when needed. There has been a lot of interest and activity in the area of LC instrument validation. The accuracy and reproducibility of many instrument functions such flowrate, temperature, wavelength, mobile phase mixing etc have been studied. However, there is almost nothing done with GC.
I would like to hear some opinion on this matter. Why is it that almost nothing has been done to validate GCs?. Is it because of the applications?, Is it because the technology is far superior and advanced?. Please let me know what you think.
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GC Instrument Validation - 2005/11/28 18:18
It is probably because of the pharmaceutical industry's hang ups with validation. HPLC is a pharm industry tool and GC, in general, isn't.
Many of the function checks you've mentioned are equally valid for GC as for HPLC but the majority of GC applications are self calibrating, in that most will use an internal standard.
One other major difference between GC and LC is in the detector most often used. UV detectors (the most common for HPLC) are concentration detectors and factors such as flow rate and temperature cause changes in the response. FIDs (the most common GC detector) are mass detectors and will generate the same total signal no matter what speed the component of interest reaches the detector - peak height (and therefore overall sensitivity) might change but the peak area produced by a mass of sample will remain constant.
Hope that helps a bit.
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GC Instrument Validation - 2005/11/28 18:19
Benjamin,(furthering the above message..)
In my opinion,besides validating the equipment on installation, validating chromatography equipment is usually wasted effort, because method should incorporate checks to verify the correct performance of equipment.
Regulatory and Quality departments usually impose chromatography equipment validation and try to continue with periodic calibration. (Don't get too excited, I am an RA person.) Usually the departments do not understand why a chromatography method can not work like weighing or measuring length. After all you can weigh a sample at 10 labs and get the same value, can't you? When developers write methods requiring resolution, precision, and accuracy for the analyte rather than retention time, flow, column, etc. the nature of the discussion changes.
Your question relates to these thoughts. Ask the question, 'How much does the validation add to the accuracy and precision of the assay?' If you can't answer a define meaningful value, other discussions mean little.
Jim
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GC Instrument Validation - 2005/11/28 18:19
Agilent brings in calibrated test equipment to check GC temperatures, flow rates, etc. They also have brought in a calibrated integrator too. I believe they also bring in a standard column and check repeatability of a specified number of standard injections. If necessary, I could try to sift through our documentation report, which is a large binder for each instrument per year. The cost for this is about $3K per instrument, for preventative maintenance and then performance verification. The engineer comes in first day, sets up, and bakes out overnight, finishes up the next. One year they replaced an EPC module (which had been giving us a little trouble, but we hadn't ourselves identified as bad).
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GC Instrument Validation - 2005/11/28 18:21
Anonymous, As per my previous post and Jim's, if you (or your very rich company!) feel that you get good value out of the Agilent "validation" carry on spending the money. BUT please ask yourself what you actually get out of it. In your last sentence you say the EPC unit had given a little trouble so you had identified it as faulty (but not bad!!!) before the engineer arrived so what good did the validation do?
Also, what point is a "standard" column and components you are not yourself analysing. Your analysis will be using a non-standard column, a liner that you may have forgotten to change and a syringe that has been used for other samples. If you want to check reproducibility in the real world inject the same vial of your sample 10 times and check that - much more important than checking oven temperature being withing 0.01°C of that set.
Chromatography is in most cases self calibrating and anyone with a modicum of experience can see when things are going wrong. Correcting them may not be so easy - THAT is when you may need an engineer or applications specialist.
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