This document discusses issues with solid phase extraction (SPE) as a sample preconcentration method. SPE provides lower detection limits than large sample volumes but can show artifacts from incomplete recovery. The Regional Monitoring Program uses SPE to process 100L water samples through glass fiber filters and XAD2 resin columns. Comparisons of 100L SPE samples to 4L solvent extraction samples show the SPE method may underestimate for high organic samples due to short contact times, while overestimating for low organic samples where solvent extraction recovers more. Alternatives like switching to solvent extraction are not preferable due to increased sampling and shipping volumes required. The status quo 100L SPE method is preferred if its tendencies toward over or under-estimation are taken into account.

1. Solid Phase Extraction Issues
TRC September 2007

2. Solid Phase Extraction (SPE)
 Provides a means for preconcentrating water
phase organics to allow lower detection limits
without logistically intimidating sample sizes
(~20L equivalent per analyte type- PCBs,
PAHs, etc)
 May show some artifacts of incomplete
recovery, depending on a number of factors,
e.g. DOC, sample size, collection speed

3. RMP Collection Methodology
 100L sample, pumped at 1.5L/min by Infiltrex
300 through wound glass filter (nominal 1um
pore) and columns (2x70g) of XAD2 resin.
 Most recent cruise increased volume pumped
through filter to increase PBDE signal relative
to blanks (no change in pumping speed)

4. Infiltrex vs Whole Water
 4L whole water
sample vs 100L
Infiltrex
particulate (filter)
+ dissolved
(XAD2)
2003 PCB 100L vs 4L
y = 1.5875x + 0.046
R2
= 0.9916
0
2
4
6
8
10
12
0 2 4 6 8 10 12
100 L results (pg/L)
4
L
results
(pg/L)
BG30

5. 2004
2004 PCB 100L vs 4L
y = 1.1164x - 0.615
R2
= 0.9309
y = 0.5856x + 0.432
R2
= 0.9754
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
100L results (pg/L)
4L
results
(pg/L)
SB026W
SPB010W

6. 2005
2005 PCB 100L vs 4L
y = 1.2096x + 0.0227
R
2
= 0.9891
y = 0.7442x + 0.1428
R2
= 0.9925
0
5
10
15
20
25
30
35
40
45
50
0 10 20 30 40 50
100 L results (pg/L)
4
L
results
(pg/L)
SB036W
CB015W

7. Bias Trend?
site year
max
PCB
(100L) slope SS DOC
BG30 2003 6 1.59 23.5 1606
CB015 2005 10 1.21 3.8 1014
SPB010 2004 22 1.12 34.5 1650
SB036 2005 40 0.74 9.0 2463
SB026 2004 65 0.59 18.0 1870

8. Bias Trend?
 Does not track TSS (SSC)
 4L (liquid-liquid) solvent extraction recovery
high for low organics (=totPCBs)
– 100L short contact time = lower recovery?
 100L solid phase extraction high(er) for high
organics samples
– 4L solvent volume = limited equilibrium?

9. Alternatives
 Switch to liquid-liquid extraction
– Likely accurate for low organics
– Underestimate for high concentrations
– PCB/PBDE, PAH, OCP, OPP, backup = 4L x 5
bottles/site x 22 sites = 110 bottles, 440L to ship
 Status quo 100L SPE- (preferred?)
– Maintain awareness of tendencies
– Considered minimum concentrations
– More accurate for high concentration samples