VOC Lab improvements

[vocguy]

The lab that I work at is looking to improve on the current systems that we have in place. We currently are looking to replace a few 5970's with newer models i.e. 5975, 5972, or 5973. There is also a heavy use of water mode with Archon autosamplers, which has caused a problem. On a couple of occasions, the concentrator failed to drain and overfilled the lines creating active sites through the lines. This led to interest in the Encon concentrator or any other newer model that may have a foam/moisture sensor that would prevent said problem. The overall question is, for volatile compounds pertaining to 8260 and such, which of the newer instrumentation would be more reliable for speed and accuracy of results. The other important question is if the literature is accurate for the Encon concentrator or Tekmar Velocity XPT. Any help is greatly appreciated.

[LabRoach]

Hi!

5972 work great for 8260 but are no longer supported by Agilent. 5973's and 5975's tend to be more sensitive and slightly less stable. But all of these systems should perform fine. The 5970 does work well, but the amount of MS parts is crazy.

For the A/S / P&T, I do not like the EST/PTS/Varian Archons or 8100s. My experience has been filled with errors and stopped sequences. I follow everything the techs and their supervisors suggest and they continue to stop. Also my experience with foam sensors is that most of the time they trigger for reasons other than foaming. I prefer Tekmar though I found their units to be hit or miss. They continue to refine and produce technology, while EST/PTS continues to use the Encon. My biggest problem with my Encon is the poor design of the Mort(moisture retention) Heater. Way too easy to develop active sites. Flushing hardly helps and it usually means replace a $600 part every few months. The Velocity and Stratum have higher flowrates which does help with carryover and speed. But I have had active sites in the Velocity's focusing loop. The Aquatek70 autosampler (only for running water samples) is solid and a far better XYZ arm design than the Archon or 8100. In my experience, I've had about 6 Aquatek70 errors. About 200 on the Archons and about 600 on the 8100's when running waters.

But to prevent foaming, you should screen samples prior to loading. If you screen via GC/FID headspace, you'd be able to tell if a sample will foam when preparing the screen. This is crucial when dealing with unknown environmental samples.

I feel the literature is fair, but these are their best systems without any unusual matrices introduced. Run a few nasty samples then all bets are off.

[vocguy]

Hi,

The instrumentation issue is that the primary instrument of use is 5970's which are slowly starting to not work as well, and the desire is to get the newer technology while it is available. The one thing that was looked at was the simultaneous SIM/Scan capability of the 5975. We do heavily use 5973 although several service techs will tell you that the 73 is not good for voc analysis.
The concentrator problem is that the overfilling cannot be predicted, and if the sensor can prevent it then it is worth the hassle. We can accomodate the active site problem by the use of electroformed nickel tubing which will get rid of the problems up to about six months. If you can expand on this, it would be greatly appreciated.