Soil Samples for VOC: Tradition versus 5035A

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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Our state relies on 8260 and 5030/5035 for purge and trap VOC's. What is your lab doing if you get soils in and need to hold them for more than 48 hours. Here is a quote from Appendex A of 5035A....

A.5.0 HISTORY OF PRACTICES IN THE SAMPLING AND PREPARATION OF SOLID MATERIALS FOR VOC ANALYSIS

A.5.1 Traditional Practices

Over the past 20 years, solid samples obtained for VOC analysis were collected using a spatula -type device to completely fill a container for transfer off-site before the introduction of certain preparation steps and analysis within a 14-day holding time. VOC sampling procedures recommended the use of clean stainless steel utensils to completely fill either 40-mL to 250-mL glass containers. The containers were then closed with polytetrafluoroethylene (PTFE)-lined caps. Sample containers were stored in coolers at 4 ± 2E C and shipped to field or off-site support laboratories for subsampling (usually with 1 to 5 g aliquots) and subsequent analysis. The common holding time for these bulk soil samples, held at 4 ± 2EC, was 14 days.


A close reading of 5035 is nearly as restrictive as 5035A. Basically stating there is no way to have a 14-day hold time without either freezing or MeOH preservation.

Now we have vendors from out of state that insist that all samples be taken with TerraCore samplers into pre-weighed VOA's with 5-10mL of MeOH. Apparently, the only way to have a 14-day hold time, other than freezing all samples to <-7C and no less than -20C. See for example method 5035A Table A.1.

What has been the tradition in your states if you are doing 8260 VOC's on soils?
Also, I believe that in method 5035 these two sections are used to justify using the "Traditional" collection methods....

2.2 High concentration soil method - generally applicable to soils and other solid samples with VOC concentrations greater than 200 µg/kg.

The sample introduction technique in Sec. 2.1 is not applicable to all samples, particularly those containing high concentrations (generally greater than 200 µg/kg) of VOCs which may overload either the volatile trapping material or exceed the working range of the determinative instrument system (e.g., GC/MS, GC/FID, GC/EC, etc.). In such instances, this method describes two sample collection options and the corresponding sample purging procedures.

2.2.1 The first option is to collect a bulk sample in a vial or other suitable container without the use of the preservative solution described in Sec. 2.1. A portion of that sample is removed from the container in the laboratory and is dispersed in a water-miscible solvent to dissolve the volatile organic constituents. An aliquot of the solution is added to 5 mL of reagent water in a purge tube. Surrogates and internal standards (if applicable) are added to the solution, then purged using Method 5030, and analyzed by an appropriate determinative method. Because the procedure involves opening the vial and removing a portion of the soil, some volatile constituents may be lost during handling.

6.2.3 High concentration soil sample not preserved in the field

The collection of high concentration soil samples that are not preserved in the field generally follows similar procedures as for the other types of samples described in Secs. 6.2.1 and 6.2.2, with the obvious exception that the sample vials contain neither the aqueous preservative solution nor methanol. However, when field preservation is not employed, it is better to collect a larger volume sample, filling the sample container as full as practical in order to minimize the headspace. Such collection procedures generally do not require the collection of a separate aliquot for dry weight determination, but it may be advisable to collect a second sample aliquot for screening purposes, in order to minimize the loss of volatiles in either aliquot.


Then if a sample was really really hot (if you smell anything when you open the jar; you must) one subsampled 10g from the jar into a vial containing 10mL of P&T MeOH, put on gentle rotator, then sonicated and then centrifuges. A 50uL aliquot of that MeOH in the typical 5mL of DIWater gave an effective 100X dilution of the soil. Which is also mentioned as appropriate in 5030c for running 'MeOH soil extracts'.
In our state the traditional "soil packing" method is used, since they have not updated the regs for over 20 years. (we are still required to reference 8260B).

We also receive samples in preserved 40ml vials, usually a pack with two that are preserved with sodium bisulfite/water 5ml and one with methanol and one unpreserved jar for total solids or further dilution. These have 14 day holding times.

If received in the Encore sampler they have 48 hour hold time, to put them into the 40ml sample vial, which then extends to 14 day.

If you are purging in the 40ml vial, and the sample is taken in a 40ml vial, then you should not lose any of the analytes as they will be trapped in the headspace which is drawn off during the purge process.

So far I have not had an auditor question any of the above practices.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
In our state the traditional "soil packing" method is used, since they have not updated the regs for over 20 years. (we are still required to reference 8260B).

We also receive samples in preserved 40ml vials, usually a pack with two that are preserved with sodium bisulfite/water 5ml and one with methanol and one unpreserved jar for total solids or further dilution. These have 14 day holding times.

If received in the Encore sampler they have 48 hour hold time, to put them into the 40ml sample vial, which then extends to 14 day.

If you are purging in the 40ml vial, and the sample is taken in a 40ml vial, then you should not lose any of the analytes as they will be trapped in the headspace which is drawn off during the purge process.

So far I have not had an auditor question any of the above practices.

Your second paragraph is essentially the method 5035A sample set.

I think the traditional method used 5030A for how soils should be handled for purge and trap and this is how I learned it for our lab. Subsequent versions of 5030 left out the instructions for handling low concentration samples and refer one to method 5035. I did not realize there was a controversy until a vendor insisted their soil handling criteria for VOC's would only be guided by method 5035A.

I understand 5035 allows that septum caps on packed soil jars and freezing <48 hrs from lab receipt will give a 14 day hold time.
In 8.1.3 it is talking about the methanol vial used as the High Level sample for dilution.

The next to last entry in table A.1 says if the vial contains the sodium bisulfate and water it can be stored for 14 days at 4C just like the methanol preserved one.

If the lowest detection limits are needed then it is better to use the aqueous sodium bisulfate since the methanol method normally involves a 1:50 dilution of the methanol into water for analysis. Purging from the headspace of the methanol preserved vial could cause problems with the early eluting analytes that ride on the methanol hump as it passes through the column.
The past is there to guide us into the future, not to dwell in.
Here is the traditional method from 5030A....

7.3.3.1 Low-concentration method: This is designed for
samples containing individual purgeable compounds of <1 mg/kg. It
is limited to sediment/soil samples and waste that is of a similar
consistency (granular and porous). The low-concentration method is
based on purging a heated sediment/soil sample mixed with
organic-free reagent water containing the surrogate and, if
applicable, internal and matrix spiking standards. Analyze all
reagent blanks and standards under the same conditions as the
samples.
7.3.3.1.1 Use a 5 g sample if the expected
concentration is <0.1 mg/kg or a 1 g sample for expected
concentrations between 0.1 and 1 mg/kg.
7.3.3.1.2 The GC system should be set up as in
Section 7.0 of the specific determinative method. This should
be done prior to the preparation of the sample to avoid loss
of volatiles from standards and samples. A heated purge
calibration curve must be prepared and used for the
quantitation of all samples analyzed with the low-
concentration method. Follow the initial and daily
calibration instructions, except for the addition of a 40 Co
purge temperature for Methods 8010, 8020, and 8021.
7.3.3.1.3 Remove the plunger from a 5 mL Luerlock type
syringe equipped with a syringe valve and fill until
overflowing with organic-free reagent water. Replace the
plunger and compress the reagent water to vent trapped air.
Adjust the volume to 5.0 mL. Add 10 μL each of surrogate
spiking solution and internal standard solution to the syringe
through the valve. (Surrogate spiking solution and internal
standard solution may be mixed together.) Matrix spiking
solutions, if indicated, should be added (10 μL) to the sample
at this time.
7.3.3.1.4 The sample (for volatile organics) consists
of the entire contents of the sample container. Do not
discard any supernatant liquids. Mix the contents of the
sample container with a narrow metal spatula. Weigh the
amount determined in Section 7.3.3.1.1 into a tared purge
device. Note and record the actual weight to the nearest 0.1
g.

This was cut out of later versions of 5030 (B & C) and method 5035 was supposed to take over. But most states continued using 5030A for 20 years.
James_Ball wrote:
In 8.1.3 it i talking about the methanol vial used as the High Level sample for dilution.

The next to last entry in table A.1 says if the vial contains the sodium bisulfate and water it can be stored for 14 days at 4C just like the methanol preserved one.

If the lowest detection limits are needed then it is better to use the aqueous sodium bisulfate since the methanol method normally involves a 1:50 dilution of the methanol into water for analysis. Purging from the headspace of the methanol preserved vial could cause problems with the early eluting analytes that ride on the methanol hump as it passes through the column.
I routinely do the methanol extraction on soils that come in and are very high in BTEXGRO. Sometimes I get samples that are low level but full of organic matter that absorbs the surrogates. I try purging the minimum amount (1g) first. Then I do 20g into 10mL of MeOH, sonicate and I have found that ISS and spike recoveries are all good if I inject 100uL of the methanol extract into the 5 mL of water in the syringe for purge and trap. So, that's a 25X dilution. Normally for samples that have very high GRO or BTEX, I use 10g and 10mL and inject 50uL into the 5mL of water in the syringe for a 100X dilution. Of course, I have to note that in the sample narrative.
LALman wrote:
James_Ball wrote:
In 8.1.3 it i talking about the methanol vial used as the High Level sample for dilution.

The next to last entry in table A.1 says if the vial contains the sodium bisulfate and water it can be stored for 14 days at 4C just like the methanol preserved one.

If the lowest detection limits are needed then it is better to use the aqueous sodium bisulfate since the methanol method normally involves a 1:50 dilution of the methanol into water for analysis. Purging from the headspace of the methanol preserved vial could cause problems with the early eluting analytes that ride on the methanol hump as it passes through the column.
I routinely do the methanol extraction on soils that come in and are very high in BTEXGRO. Sometimes I get samples that are low level but full of organic matter that absorbs the surrogates. I try purging the minimum amount (1g) first. Then I do 20g into 10mL of MeOH, sonicate and I have found that ISS and spike recoveries are all good if I inject 100uL of the methanol extract into the 5 mL of water in the syringe for purge and trap. So, that's a 25X dilution. Normally for samples that have very high GRO or BTEX, I use 10g and 10mL and inject 50uL into the 5mL of water in the syringe for a 100X dilution. Of course, I have to note that in the sample narrative.


The old way of doing these was 50ul into 5ml after extracting 5g with 10ml methanol which gave a 200X dilution, this was directly from the CLP back in the day when we were doing those almost 30 years ago. The calibration then was from 5ppb to 200ppb, the 1g sample extended that up to 1000ppb then the medium level cut any 1000ppb to 5ppb, but you could go more dilute if needed.

The methods suggest making a separate calibration for medium levels because of the extra methanol, but I never found it to be a problem.
The past is there to guide us into the future, not to dwell in.
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