comparative review of analytical methods for determination ...comparative review of analytical...
Post on 16-Jan-2020
11 Views
Preview:
TRANSCRIPT
Ask The Expert Webinar Series
Comparative Review of Analytical Methods for
Determination of 1,4-Dioxane: Which One Is
Best For My Project?
Eric Redman
Director of Technical Services
TestAmerica
Michael Wilken
Technology Team
The Dow Chemical Company
As a solvent stabilizer for
1,1,1-Trichloroethane
(TCA) and other
chlorinated solvents
As a solvent in lacquers,
paints, resins, pharma,
etc.
As a contaminant in
ethoxylation chemistry
and products (surfactants,
detergents, PEG)
Potential Sources/Uses
Synthetic industrial
chemical
Completely miscible in
water – Very low Henry’s
law constant
Low vapor pressure for
VOCs
Boiling point near water
Density near water
Migrates rapidly in
groundwater – weak
adsorption to particulates
Physical and Chemical
Properties
High water solubility +
low VOC vapor pressure
= poor “inert gas”
extraction efficiency
Poor purge efficiency
Elevated reporting
limits
Calibration anomalies
Carryover problems
Analytical Challenges –
Method 8260 – Full Scan
Very common method
supported at 17 TestAmerica
labs
RLs range from 40 – 1000 ug/L.
Median at 100 ug/L
MDLs range from 10 – 150 ug/L.
Median ~ 40 ug/L
LCS recovery of 40 – 160% is
typical. Average near 100% at
many labs but significant variability
High frequency of positives > MDL
in MBs (3%)
Method 8260B Full Scan –
QC Criteria
3 8260 MBs after 10,000 ppb
Calibration Standard Injection
MB #1
1300 ppb
MB #3
< 10 ppb
MB #2
65 ppb
High water solubility +
high SVOC vapor
pressure = poor
“liquid/liquid” extraction
efficiency
LLE methods 3510 and
3520
LCS recoveries are
lower than average for
SVOCs
Inherent low bias
Analytical Challenges –
Method 8270 Full Scan
Relatively common method
supported at 9 TestAmerica Labs
RLs range from 1 – 20 ug/L.
Median at 10 ug/L
MDLs range from 0.5 – 10 ug/L.
Median ~ 3 ug/L
LCS recovery of 30 – 70% is
typical. Average near 50% at
many labs, but less variability
than 8260
Low frequency of positives > MDL
in MBs (< 0.5%)
Method 8270 Full Scan
QC Criteria
8260- both samples
and standards are
extracted
8270- only samples
are extracted
8260 vs 8270 Full Scan –
Sample Results
Pros
Widely available
Low cost in conjunction with
other analytes
Can accommodate high
concentration samples
Cons
Low bias for 8270
High RLs for 8260
Carryover potential for 8260
8260 and 8270 Full Scan –
Pros and Cons
UCMR 3 – Method Reference Limit = 0.07 ppb
Presence in Drinking Water
4915 PWS tested using Method 522 with 1,4-
Dioxane detected in 1077 systems (21%)
EPA calculated 10E-6 cancer risk at 0.35 ug/L and
established non-enforceable screening level for residential
water use at 0.67 ug/L. Still no MCL.
Snapshot of Regulatory Levels
Enforceable State Limits
MA Regulatory Limit = 0.30 ug/L
NJ Regulatory Limit = 0.40 ug/L
CO Cleanup Standard = 0.35
ug/L
NH Reporting Limit = 0.25 ug/L
CA Notification Level = 1.00 ug/L
C.Hiegel with TriHydro, as presented at NEMC in August,
2016
Provides low RLs (at or below
0.2 ug/L)
Uses “solid phase” extraction
(SPE) without extract
concentration
Optimized for 1,4-Dioxane
Uses Selected Ion Monitoring
Improved accuracy and
precision
LCS limits 70-130%
Average recovery 93%
Uses low sample volume
Applicable to surface water and
groundwater as well as DW
Strengths of Method 522
Method 522 – Best Available
Good sensitivity at the RL (0.2
ug/L)
Rugged, reliable, accurate, and
precise.
BUT………..
Not widely available
Standalone method for 1,4-
Dioxane
Higher cost
No isotope dilution/recovery
correction if matrix impacts
Not routinely applied to
wastewater or industrial discharge
Use Selected Ion Monitoring
(SIM)
Results in improved sensitivity
Apply isotope dilution
technique
Corrects for poor extraction
efficiency
Reduces calibration anomalies
Improves ruggedness and
reproducibility
Optimize ‘inert gas’ extraction
for 8260
Can We Improve Methods 8260
and 8270?
8270 SIM With Isotope Dilution
Good sensitivity at RL (0.4 ug/L)
RLs equivalent to 522 if needed
LCS recovery 90 – 110%
Average recovery 101%
Can be coupled with other SIM
analytes (PAHs, PCP, etc)
Uses ‘standard’ 8270 liquid/liquid
extractions and sample volumes
Applicable to wastewater,
industrial discharge, and other
complex matrices, IF low RLs
required
8260 SIM With Isotope Dilution
and Heated Purge
Sufficient sensitivity at 1 ug/L
RLs < 1 ug/L difficult to achieve
Reliable detection at 0.4 ug/L only
with significant laboratory effort
LCS recovery 80 – 120%
Average recovery 105%
Can be coupled with other VOC
SIM analytes (VC, EDB, TCP, etc)
Widely available
Relatively low cost
Vulnerable to carryover
Lab B at 0.4 ug/L
Annual Dow PT Samples
Annual PT samples 11 preferred laboratories
Plus 10 other laboratories
Blended real samples For VOC, SVOC, metals,
anions analysis
1,4-Dioxane from all
available methods in lab
No 1,4-dioxane spiked
0
200
400
600
800
1000
1200
1400
1 2 3 4 5 6 7 8 9 10 11 21 1 2 3 4 5 6 7 8 9 10 11
µg
/l
Comparison 8260 and 8270 PT Study NEAT sample
8260
8260 SIM
8260 Isotope
HRGC/HRMS
8270
8270 SIM
8270 Isotope
8270
*
‡
0
100
200
300
400
1 2 3 4 5 6 7 8 9 10 11 21 1 2 3 4 5 6 7 8 9 10 11
µg
/l
Comparison 8260 and 8270 PT Study DILUTED samples 8260
8260
8260 SIM
8260 SIM
8260 Isotope
8260 Isotope
HRGC/HRMS
HRGC/HRMS
8270
8270
8270 SIM
8270 SIM
8270 Isotope
8270 Isotope
8260 8270
* ‡
8260
* corrected for recovery rate
‡ continuous extraction
Annual Dow PT samples
Direct Comparison With Different Samples
• 4 preferred
laboratories
• Blended real samples
• 1,4-Dioxane from all
available methods in
lab
• No 1,4-dioxane
spiked
0
5000
10000
15000
20000
25000
30000
µg
/l
Sample 1 (neat)
0
1000
2000
3000
4000
5000
6000
µg
/l
Sample 2 (diluted) ‡ continuous extraction
Direct Comparison - Different Samples
Direct Comparison Over Wider Concentration Range
3 preferred
laboratories
Blended real samples
Diluted 1:10 and 1:100
No 1,4-dioxane spiked
1900
2290 2310
2070 2020
2360
1460
735
1170
209 231
250 180 186
232 129 98.4
78.6 0 18.8 0
19.1 18.5
21.8 15.9
9.7 5.79
0
500
1000
1500
2000
2500
82
60
C
82
60
C
82
60
C
82
60
C SIM
82
60
C SIM
82
60
B SIM
82
70
D
82
70
D
82
70
D
82
60
C
82
60
C
82
60
C
82
60
C SIM
82
60
C SIM
82
60
B SIM
82
70
D
82
70
D
82
70
D
82
60
C
82
60
C
82
60
C
82
60
C SIM
82
60
C SIM
82
60
B SIM
82
70
D
82
70
D
82
70
Dµ
g/l
1,4-Dioxane comparison 8260 vs 8270
neat sample
1:10 dilution 1:100 dilution
Direct Comparison Over Wider Concentration Range
0
20
40
60
80
100
120
140
% R
eco
very
rate
Recovery Rate 8260
0
20
40
60
80
100
120
140
% R
eco
very
rat
e
Recovery Rate 8270
Recovery Rate Comparison
Summary
VOC methods (8260) deliver
substantially higher data than
unmodified 8270 in all studies
with REAL WORLD samples
The differences can be up to a
factor of 3
This may be due to:
poor extraction and no surrogate
recovery correction
VOC methods are not capable
of analyzing in sub ppb-range
without further optimization
Method 522 does not require
surrogate recovery correction
Moving Forward
We are in urgent need of a reliable
method!
One step is the implementation of the
isotope dilution method
Why? The differences between VOC
and SVOC methods may be the result
of NOT correcting for recovery rate of
surrogate standard(s) which are
typically only 30% - 70% for SVOC
(8270) methods
Isotope dilution corrects for low
recoveries and extraction variability
8270-SIM with isotope dilution
provides data quality equivalent to
Method 522, and better than 8260-
SIM for RLs < 1 ppb
Ask The Expert Webinar Series
Thank you for attending
To submit a question, type it into the Questions panel in the GoToWebinar toolbar and click Send.
If you have any additional questions for today’s presenter you may submit them directly to:
Please be sure to visit the Ask the Expert Webinar Series web page for other scheduled webinars at:
http://www.testamericainc.com/services-we-offer/webinars
To view a recording of this webinar session, please contact:
MarketingDepartment@testamericainc.com
Comparative Review of Analytical Methods for Determination of
1,4-Dioxane: Which One Is Best For My Project?
top related