When we decided to automate the Markes Unity and Agilent GC System we took a long hard look at the choices of data systems between Chemstation and EZChrom. With many years of experience using the PerkinElmer system with Totalchrom we may have been biased but we chose EZChrom over Chemstation even though I was pretty sure that neither Agilent nor most environmental monitoring groups would embrace this choice. HP blazed the trail into environmental monitoring back in the 90's with their EnviroQuant software and the MSD in a Chemstation environment. Since then environmental labs have used Chemstation almost relentlessly with their laboratory analyses. It is understandable then why monitoring groups in agencies routinely turn to their laboratory folks when faced with the possibility of doing what is basically a laboratory-scale analytical technique in the field.
But there are some unique issues which made us chose EZChrom over Chemstation for PAMS monitoring. First, and this is a big one for me, Chemstation does not make uniquely named data files. When I brought this up with Agilent Chemstation gurus I got the "what do you mean, we have unique filenames..." but neh, neh - they have unique folder names but the files in each of these folders have the same name.... And that is only the start. For years we have deployed and operated field AutoGC systems the earliest of which were not uncommonly in a field with only a 56K modem. With the large amount of data generated by this analysis it became important to move the data automatically and after only a short time it became clear that if we did not write some software to name, zip and move data we might lose data by the sheer act of manipulating files. (We were also handicapped by having to work in Windows for Workgroups and I could tell you some real stories there...)
Then of course there is the issue of validation. No one really believed in the beginning that these systems would flawlessly detect, identify and quantify 56 VOCs whose values could just be put directly into the AQS system. So, of course, someone needed to look at the data. This meant having another version of the data system in the office. One of the more useful features of Totalchrom is that the result file carries all the information on the method used to generate it including the response factors. What this means for validators is that they do not need to worry about what happened to the method at any given time. They can generate the method used on any given day from the actual data file. This is handy when you are looking at data across a month or more where methods may have been changed. And this is the most significant reason we chose EZChrom over Chemstation. Like Totalchrom, EZChrom data files carry all the method parameters with each data file and a method can be made from a data file which can then be adjusted and used to reprocess data. With Chemstation additional files have to be archived in order to reproduce the method used at the time the sample was analyzed.
So keep in mind the downstream activities you may want to consider in your review of data for validation purposes. These systems are very robust and these lab-scale data systems have good retention time referencing and automation controls which allow these systems to be automated and run unattended. But there will always be periods where you may want to review and reprocess data and these data systems make this task much easier. A key point here is that this data is archival in nature and will be hopefully used for years to measure trends so it deserves our attention. You don't have to sacrifice laboratory quality data to take this analysis to the field.
PS for the folks who are considering a move from PE to the Agilent system - you may find EZChrom looks and feels more like Totalchrom as well.
All AutoGC systems collect, identify and quantitate the VOC targets using a data system. This category is dedicated to discussions of the methods used by data systems for this purpose. The data system may additionally control GC methods as well as thermal desorption methods, as well as relays used for the automation of introduction of routine quality control samples.
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