Analyte Loss EPA 525.2

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

75 posts Page 5 of 5
[quote="Don Shelly"][quote="LWC"]Was anyone able to come to a conclusion about the loss of PAHs?

I am having the same problem with my SUR Benzo[a]pyrene-d12 in EPA 525.3. For all of my extracted samples Benzo[a]pyrene-d12 come out to 50-65% recovery.

I have tried traditional and matrix matched calibration standards and they are almost identical.

I have tried extracting these in the dark- no improvement
I used a better quality Methanol- no improvement
The matrix match cal std use the same solvents so I don't expect those to be the culprit

All samples/std are stored in the same freezer.

I am following the EPA method as instructed for DVB disks and I cannot understand why my Benzo[a]pyrene-d12 SUR recovery is consistently low?

Any help would be appreciated, thank you!![/quote]

Unless you are using an Empore disk, or a cartridge that uses Teflon frits, you are probably losing the d12 to either glass wool in a disk or polyethylene frits in a cartridge. I have no explanation of how this can happen, but it happens.

What product are you using?[/quote]

I am using JT Baker 8068-06 speedisk. This product was sited in the method and EPA recoveries looked good. However I recently contacted Avantor (parent company Baker) and they said they've been getting complaints about leaking media. I have not heard a confirmation from their R&D yet.

According to the EPA method several extraction media can be used:
Empore SDB-XC
JT Baker speedisk DVB
Waters Oasis HLB Cart
JT Baker DVB Cart
UTC 525 cart
Horizon Atlantic DVB disk

In your experience are any of these better over another? I am prepared to switch media suppliers to alleviate this issue if the manufacturer cannot correct problem with JT BAKER disks.
Since I developed this product, I'm very biased. I recommend the UCT 525 cartridge. The disk from Horizon is also a good choice.
Don Shelly
LGC Standards
We have an aging pump that we use for our SPE extractions, do you have any advice on what to replace it with?

I'm not sure if it makes a difference or not as long as it can pull a high enough Hg reading. I cant find any reading material that specifics what to use.

Thank you!
UCT sells a good inexpensive Rocker pump that I have used in the past. Works well but not for continuous use. Draw any liquid through it and it's dead.
Don Shelly
LGC Standards
Thank you, according to the method the sample pass through rate for the UTC cartridge is only 10mL/min, do you agree with this rate or can it be sped up?
10 ml/min is recommended for optimum results. You can speed it up but some recoveries will start to drop.
Don Shelly
LGC Standards
OK thanks Don, do you have an email address I could contact you with to continue discussion about this issue?
Don Shelly
LGC Standards
LWC wrote:
Was anyone able to come to a conclusion about the loss of PAHs?

I am having the same problem with my SUR Benzo[a]pyrene-d12 in EPA 525.3. For all of my extracted samples Benzo[a]pyrene-d12 come out to 50-65% recovery.

I have tried traditional and matrix matched calibration standards and they are almost identical.

I have tried extracting these in the dark- no improvement
I used a better quality Methanol- no improvement
The matrix match cal std use the same solvents so I don't expect those to be the culprit

All samples/std are stored in the same freezer.

I am following the EPA method as instructed for DVB disks and I cannot understand why my Benzo[a]pyrene-d12 SUR recovery is consistently low?

Any help would be appreciated, thank you!!


Thank God I find this post, I am also doing 525.3.

I am having the similar issue with low Benzo[a]pyrene-d12 SURR and it is driving me crazy!

My problem is that the QCs (MB, RL and LFB) injected after ICAL and QCS are having low Benzo[a]pyrene-d12 SURR recovries (60%-70%) but most of my samples are above 80%. If I re-injected the same QCs after 20 injections of sample extracts, recovery would jump back to 80% but analytes like Tebuthiuron and Prometon would break down.

Any ideas how to solve this? Appreciate!
LWC wrote:
Was anyone able to come to a conclusion about the loss of PAHs?

I am having the same problem with my SUR Benzo[a]pyrene-d12 in EPA 525.3. For all of my extracted samples Benzo[a]pyrene-d12 come out to 50-65% recovery.

I have tried traditional and matrix matched calibration standards and they are almost identical.

I have tried extracting these in the dark- no improvement
I used a better quality Methanol- no improvement
The matrix match cal std use the same solvents so I don't expect those to be the culprit

All samples/std are stored in the same freezer.

I am following the EPA method as instructed for DVB disks and I cannot understand why my Benzo[a]pyrene-d12 SUR recovery is consistently low?

Any help would be appreciated, thank you!!


Thank God I find this post, I am also doing 525.3.

I am having the similar issue with low Benzo[a]pyrene-d12 SURR and it is driving me crazy!

My problem is that the QCs (MB, RL and LFB) injected after ICAL and QCS are having low Benzo[a]pyrene-d12 SURR recovries (60%-70%) but most of my samples are above 80%. If I re-injected the same QCs after 20 injections of sample extracts, recovery would jump back to 80% but analytes like Tebuthiuron and Prometon would break down.

Any ideas how to solve this? Appreciate!
liyanghenry wrote:
LWC wrote:
Was anyone able to come to a conclusion about the loss of PAHs?

I am having the same problem with my SUR Benzo[a]pyrene-d12 in EPA 525.3. For all of my extracted samples Benzo[a]pyrene-d12 come out to 50-65% recovery.

I have tried traditional and matrix matched calibration standards and they are almost identical.

I have tried extracting these in the dark- no improvement
I used a better quality Methanol- no improvement
The matrix match cal std use the same solvents so I don't expect those to be the culprit

All samples/std are stored in the same freezer.

I am following the EPA method as instructed for DVB disks and I cannot understand why my Benzo[a]pyrene-d12 SUR recovery is consistently low?

Any help would be appreciated, thank you!!


Thank God I find this post, I am also doing 525.3.

I am having the similar issue with low Benzo[a]pyrene-d12 SURR and it is driving me crazy!

My problem is that the QCs (MB, RL and LFB) injected after ICAL and QCS are having low Benzo[a]pyrene-d12 SURR recovries (60%-70%) but most of my samples are above 80%. If I re-injected the same QCs after 20 injections of sample extracts, recovery would jump back to 80% but analytes like Tebuthiuron and Prometon would break down.

Any ideas how to solve this? Appreciate!


We are running this analysis also and had similar problems with the Benzo[a]pyrene-d12. We had to extend the drying step to remove more water from the extraction cartridges ( using the Waters XLB) and that helped a lot with the recovery. I was having half of my batch fail low, and when the Blank or LFB would fail, that would take out the whole batch QC wise.

When we had trouble this summer with the HVAC, and I did some extraction batches with the building humidity near 80%, almost every one would fail, once that was under control and I could pull dry air through the cartridges for 20-30 minutes my recoveries improved and I had several batches pass without a single failure. Experiment with dry times. The method says to dry 10 minutes at 20 inches vacuum, but it can be difficult to reach 20 inches when you are pulling air through so many cartridges. If recovery increases as dry times increase that could be the problem. Just keep an eye on the first surrogate the elutes, as once you get to a certain point it can begin to decrease recovery with longer dry times. At one hour we had unacceptable recovery of that early surrogate but good recovery of the Benzo[a]pyrene-d12.

We had a conference call with EPA about method 530 problems and I asked about dry times for 525.3 and they said it could be extended within reason. We also had to use matrix matched standards to achieve good recoveries near the MRL since for some analytes there is a lot of background from the preservatives, it can affect the surrogates slightly also.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
liyanghenry wrote:
LWC wrote:
Was anyone able to come to a conclusion about the loss of PAHs?

I am having the same problem with my SUR Benzo[a]pyrene-d12 in EPA 525.3. For all of my extracted samples Benzo[a]pyrene-d12 come out to 50-65% recovery.

I have tried traditional and matrix matched calibration standards and they are almost identical.

I have tried extracting these in the dark- no improvement
I used a better quality Methanol- no improvement
The matrix match cal std use the same solvents so I don't expect those to be the culprit

All samples/std are stored in the same freezer.

I am following the EPA method as instructed for DVB disks and I cannot understand why my Benzo[a]pyrene-d12 SUR recovery is consistently low?

Any help would be appreciated, thank you!!


Thank God I find this post, I am also doing 525.3.

I am having the similar issue with low Benzo[a]pyrene-d12 SURR and it is driving me crazy!

My problem is that the QCs (MB, RL and LFB) injected after ICAL and QCS are having low Benzo[a]pyrene-d12 SURR recovries (60%-70%) but most of my samples are above 80%. If I re-injected the same QCs after 20 injections of sample extracts, recovery would jump back to 80% but analytes like Tebuthiuron and Prometon would break down.

Any ideas how to solve this? Appreciate!


We are running this analysis also and had similar problems with the Benzo[a]pyrene-d12. We had to extend the drying step to remove more water from the extraction cartridges ( using the Waters XLB) and that helped a lot with the recovery. I was having half of my batch fail low, and when the Blank or LFB would fail, that would take out the whole batch QC wise.

When we had trouble this summer with the HVAC, and I did some extraction batches with the building humidity near 80%, almost every one would fail, once that was under control and I could pull dry air through the cartridges for 20-30 minutes my recoveries improved and I had several batches pass without a single failure. Experiment with dry times. The method says to dry 10 minutes at 20 inches vacuum, but it can be difficult to reach 20 inches when you are pulling air through so many cartridges. If recovery increases as dry times increase that could be the problem. Just keep an eye on the first surrogate the elutes, as once you get to a certain point it can begin to decrease recovery with longer dry times. At one hour we had unacceptable recovery of that early surrogate but good recovery of the Benzo[a]pyrene-d12.

We had a conference call with EPA about method 530 problems and I asked about dry times for 525.3 and they said it could be extended within reason. We also had to use matrix matched standards to achieve good recoveries near the MRL since for some analytes there is a lot of background from the preservatives, it can affect the surrogates slightly also.


Thank you for your reply.

I think my problem was mainly due to the instrument. The Benzo[a]pyrene-d12 SURR that failed low around 50-70% for my QCs will always increase by 10-20% if I reinjected them after the whole run(20 injections between). That means any extracted samples that injected after my non-extracted ICAL and QCS would fail the Benzo[a]pyrene-d12 SURR. I also noticed the target ion 264 would break down to 263 when SURR recovery is low.

I suspected the matrix affects the system resulting in the degradation of ion 264, as more extracted samples (at least 10 injections) runing through the GC/MS, the system is kinda conditioned well enough for that SURR. But the sensitivity near the MRL for some early eluting compounds would go bad. What a Dilemma!

As for drying time, we've been doing ten minutes with nitrogen flowing through the system. Room humidity seems to be an issue but that can't explain why SURR recovery would come back for my reinjected QC and never fail for my samples.

I had no problem using non-extraced ICAL and QCS for the past two years, so matrix matched ICAL would be my next move if Benzo[a]pyrene-d12 SURR issue not resolved.

Where would the active site be if the instrument cannot reproduce the abdunce of 264 for the Benzo[a]pyrene-d12 SURR?
I have only seen loss of deuterium if the sample has a very low pH near 1, with the buffer in the samples that should not happen. I have found though that I can not get a good calibration on a perfectly clean instrument. By the time I can hold a good calibration they inlet has been contaminated by the matrix of the samples until I have nearly 50% breakdown of the DDT and Endrin in the tune test mixture. After that point it will run stable until it is cleaned again. I really can't see how this method would work well for those analytes even though they are listed in the method. The biggest problem is finding a clean potassium citrate for the preservative. When I was first working on the method and did some extractions with only DI water, unpreserved, I had great results, afterwards I had a lot of trouble once the preservative was added. Something in that matrix causes a high background at the end of the run and I believe that is what causes the Benzo[a]pyrene to quantify lower.
The past is there to guide us into the future, not to dwell in.
Hello,
I'm running EPA 525.3 method and i have same problems with Benzo[a]Pyrene-D12 but also with others PAH (Benzo[a]Pyrene, Benzo(b)Fluoranthene, Benzo(k)Fluoranthene, Indeno(1,2,3-cd)Pyrene).
I'm using Speedisk® Column H2O-Phobic DVB cartridge and after fortified sample extraction i obtain recoveries around 50% only for these compounds and their surrogate.
Have you solved this problem then?

My Conditions:

-No Chlorine in tap water
-Extraction speed:8 ml/min in a dark room
-Amber glassware
-Dry time 10 minutes using full vacuum (20 inches)
-Removal of residual water method: sodium sulfate.

Thanks in advance.

WK.
Wolff_Kishner wrote:
Hello,
I'm running EPA 525.3 method and i have same problems with Benzo[a]Pyrene-D12 but also with others PAH (Benzo[a]Pyrene, Benzo(b)Fluoranthene, Benzo(k)Fluoranthene, Indeno(1,2,3-cd)Pyrene).
I'm using Speedisk® Column H2O-Phobic DVB cartridge and after fortified sample extraction i obtain recoveries around 50% only for these compounds and their surrogate.
Have you solved this problem then?

My Conditions:

-No Chlorine in tap water
-Extraction speed:8 ml/min in a dark room
-Amber glassware
-Dry time 10 minutes using full vacuum (20 inches)
-Removal of residual water method: sodium sulfate.

Thanks in advance.

WK.


I haven't used the disk extraction but as above found that the more water present in the extraction media the lower the PAH recovery. Also need to mention we had to do the Matrix Matched calibration standards where we extracted 10 blank water extracts without surrogate and brought them to 1ml each, then combined into a solution to use to make standards. It makes noisy standards, but compensates for the background that comes from the preservatives in the samples and will also make the recoveries match better.
The past is there to guide us into the future, not to dwell in.
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