524.2?

[Bigbear]

Just survived(?) an audit where desorb times came up again.
I begged to be able to go back to the 2 min. I had been using. I whined like a little kid saying that little Jimmy's mom lets him desorb @ 2 min.

So the question is, would you folks be willing to share your region and if you are desorbing for 2 min using 524.2?

My point If EPA methods are national and if anyone has been granted the ability to desorb for 2 min, then we all should have the option.

I don't like what I see in 524.3 starting with the $6000 it will cost to add an autosampler chiller.


Thanks
Bear

[LindseyPyron]

Dear Bear,

We see differences all over the country on this issue. I can tell you that most of the country is NOT absorbing at 4 min. The while issues come down to interpreting:

11.2.1 Non-cryogenic interface -- After the 11-minute purge, place the purge and
trap system in the desorb mode and preheat the trap to 180°C without a
flow of desorption gas. Then simultaneously start the flow of desorption
gas at a flow rate suitable for the column being used (optimum desorb
flow rate is 15 mL/min) [u]for about four minutes[/u], begin the GC temperature
program, and start data acquisition.

As a whole, "about 4 minutes" is very grey by EPA standards. If they want to mandate a parameter, words like MUST are used more regularly. Of course, many auditors ignore this. There are other parts of the methods that can be an issue as well, but auditors pay no attention to these such as "Be sure that the trap is cooler than 25°C, then open the sample syringe valve and inject the sample into the purging chamber." No one that I know of has thier trap ready temp at 25 degrees.

When we first made our Evolution P&T, we incorporated a function called "Desorb Flow Control" because of this 4 minute fiasco. This allows the purge and trap system to be in desorb for 4 minutes, but at a programmed time (say 30 seconds into desorb) the purge and trap adds additional flow to dramatically increase the split rate for the rest of desorb. This flushes any additional water that would come over during this long desorb time.

I know this probably does not help you, but I would look into 524.3. There are some parts of this methods, like the ability to shorten purge times, that can help a production laboratory run more samples in a 12hr tune that can make the switch justifiable. Be aware however, that this is not a fully promulgated methods. This went through a new procedure the EPA has developed to expedite methods being released. This means it is not open to public comment so in essence, is OPTIONAL to states as to whether or not they want to adopt this or not....just another lovely discussion to have with your auditor.

[Yama001]

I am in Rhode Island - I think that is Region 1? The EPA is pretty much a hydra when it comes to regulation, with each region an empire all its own, with thier specific sticking points.

We are mostly regulated under the Contract Lab Program where the EPA is concerned; the desorb time issue never comes up there, or from the various auditers from states and other federal programs. It is possible we are just lucky and the issue has not come up - we pretty much use anywhere from 30 seconds to 1 minute. One of our sister labs comes from a drinking water (500 series) orientation; I'll see if this ever comes up for them.

(Lindsey's company, btw, is an excellent resource on volatiles issues - truly a joy to deal with).

I guess you can always waste Helium (not a popular approach with the supply restrictions) and blast your split flow up after your preffered desorb time using the gas saver feature on Agilent GCs. This is close to what Lindsey describes with the Evolution; the drawback here is the Agilent feature will keep that high split flow for the rest of the run.

These dodges are frustrating; the auditors do not necessarily have the background to judge effectively, so they will default to the ancient parameters set down by Bellar et al back at the creation. I can't blame them; if you told me to audit a metals labs I would be stuck in the same position.


You have sympathy, anyhow
Tim

[Bigbear]

Thanks
Lindsey I desorb for 3 min ( auditor says this is about 4 min) and using my Agilent GC's gas saver function up the inlet flow to 150 cc/min wich I would be the same .
Oh did I add that 524.3 would cut our batch time to 5 hours vs 12 using 524.2? We do a sample in about 30 min. once the first purge cycle has completed.
Tim bingo . I am in region 1 as well. Someone I know I know about who used to be in the industry in RI was allowed to desorb for 2 min. I am aware and use the gas "waster" to the extent I hold my column @ end of ramp temp for 10 additional min to help dry the system. It still cools in time so that the gc waits for the P&T.

[Yama001]

I am checking with coworkers in Massachusetts and Florida - they may have left fot the holiday, but I see what they have to say next week.

[koba]

Here is the official (?) response from EPA

Steve Wendelken forwarded your question concerning Method 524.2 desorb
time on to me. The statement in the method of "about 4 minutes" was to
avoid issues with people demanding that desorb time be exactly 4.00000
minutes. It should be interpreted as times that could be rounded to 4,
such as 3.5 to 4.4. It was not meant to permit people to have
drastically shorter times.

If you have any further questions, please feel free to contact me.


David J. Munch
U.S. EPA
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
Phone: (513) 569-7843
Fax: (513) 569-7191

[Yama001]

Our Massachusetts location is stuck with the 4 minute desorb, though that is driven by thier state regulator (MADEP). They have heard some labs get away with a shorter desorb, but that may well be getting more focus in the future. I imagine my lab will be moving to the dreaded 4 muntes as well

Have a good weekend folks.

[LindseyPyron]

Thanks for the kind words Tim! We do try to a a good resource, but it is nice to be appreciated from time to time!

[Bigbear]

On a sort of tangent for folks doing 524 with Agilent GC/MS.
How many not using the "water kit" are using a 3mm draw out plate? When I became aware of the problem water causes with 5973's I had lost certification. Working with an Agilent support engineer , we shot gunned my problem to get me back in service. I used a 6mm plate which cut the water as well as my lo end response. Some of my cpd's in my 0.5 standard didn't have a distinct peak. I'm now using a 3mm plate and am lovin my low end peaks, but my calibrations don't last very long. I calibrated last week and today my IS and surrogate areas are roughly 70% of initial calibration.
Wish there was a jet sep for the newer systems!!!!

[LindseyPyron]

We have a new source which may help your stability problems. It seems to work in most cases, but not all, just depends upon your system. We have one lab that was calibrating once every 1-2 weeks for 624 and now calibrates once every 6-8 weeks. http://www.estanalytical.com/presentati ... %20Kit.pdf

[twranger]

Pennsylvania requires the 4 min desorb as well, we have to use an Agilent performance turbo to suck out the extra water. By the way, does anyone use the OIAnalytical system? We tried one a few years ago, but I'm told it transferred too much water for us to use.

[James_Ball]

It has been many years since I used an OI system, back then we used a jet separator instead of the split interface and that would take care of the extra water. If you can use a trap like the VOCarb 3000 that will allow a dry purge you can eliminate a lot of the extra water doing that even if you do not have a moisture control setup on the physical plumbing of the purge and trap.

The EPA really doesn't care if what is written causes us problems, they just don't want to worry to update an older method to fit newer/better instruments. If what is written were to cost us $1,000,000 a year in maintenance to run $1,000 worth of samples they would be ok with that. If you really look at 524.2 there is a section within it they had to add to comply with the mandate that all methods be moved to performance based. They stated that you can make changes in all setting including oven temperature program, column stationary phase, column diameter and length, and trap packing material and desorb temperatures, and those are considered to be non major modifications, but changing trap desorb time is not allowed due to that being considered a major modification to the method