Meeting the Requirements of U.S. EPA Method 6020B with the NexION 300X/350X

A P P L I C AT I O N N O T E
ICP - Mass Spectrometry
Authors:
Cynthia Bosnak
Paul Krampitz
Stan Smith
Ewa Pruszkowski
Ken Neubauer
PerkinElmer, Inc.
Shelton, CT
Meeting the Requirements
of U.S. EPA Method 6020B
with the NexION 300X/350X
Introduction
The Resource Conservation and
Recovery Act (RCRA) was
implemented in 1976 to protect
humans and the environment
from liquid and solid wastes. In order to help labs comply with RCRA, the United
States Environmental Protection Agency (U.S. EPA) published SW-846, titled “Test
Methods for Evaluating Solid Waste, Physical/Chemical Methods” in 1980 as a guide
for the analysis of multiple waste products. As such, SW-846 consists of numerous
methods covering a broad range of sample types and analytes. Because wastes can
impact the environment (and, ultimately, human health) through contamination of
soil and/or water, both of these matrices are covered under RCRA and SW-846.
As industry has evolved, many new chemicals have been developed that can
potentially make their way into the environment. Likewise, analytical instrumentation
has also continued to advance, both with increased capabilities and new analytical
techniques. As a result, SW-846 has required periodic updates.
The latest update (Update V) contains revisions to 23 of the
methods, including Method 6020, which is referred to as
6020B in the newly updated form. Several changes have been
made in 6020B, including the addition of new elements, new
detection-limit criteria, and multiple new quality control (QC)
parameters. Revision 2 of 6020B is anticipated to be updated
yet again in the future based on public comments.
This work demonstrates how the PerkinElmer NexION® 300X/350X
can meet the new requirements of Method 6020B in both water
and soil matrices.
Experimental
Solutions
All reagents were prepared volume/volume (v/v) with 18 MΩ
deionized (DI) water and Optima grade reagents (Fisher Scientific).
Calibration, standard, and internal standard solutions were made
from the Environmental Standard Kit for ICP-MS (PerkinElmer
Part No. N9307111), whose pertinent components are shown
in Table 1. Before making the final standards, the intermediate
stock standards listed in Table 2 were prepared. The final
calibration solutions were prepared with a diluent of 2% HNO3 +
1% HCl and are shown in Table 3. To aid with Hg washout,
200 µg/L gold was added to each solution prior to analysis.
Water standard reference materials were purchased from NIST®
(National Institute of Standards and Technology) and NRCC
(National Research Council of Canada), and soil reference
materials were purchased from High-Purity Standards™. Water
samples were run without dilution; soil samples were diluted 10x.
Table 1. Environmental Standard Kit for ICP-MS.
PerkinElmer
Part Number
Concentration
(mg/L)
N9301721
100
Ag, Al, As, Ba, Be, Ca, Cd, Co, Cr,
Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb,
Sb, Se, Sn, Sr, Tl, V, Zn
N9307805
1000
Ca, Mg, Na, K
N9307806
1000
Al, Fe
N9300253
10
N9308592
100
50
1
Elements
2
Elements
N9301721
Ag, Al, As, Ba, Be,
Ca, Cd, Co, Cr, Cu,
Fe, K, Mg, Mn, Mo,
Na, Ni, Pb, Sb, Se,
Sn, Sr, Tl, V, Zn
N9300253
Hg
N9308592
Sc
Ge
In, Rh, Tb
Standard Standard Standard Standard Standard
1
2
3
4
5
Elements
Units
Ag, Al, As, Ba,
Be, Ca, Cd, Co,
Cr, Cu, Fe, K,
Mg, Mn, Mo, Na,
Ni, Pb, Sb, Se, Sn,
Sr, Tl, V, Zn
µg/L
1
10
50
100
200
Hg
µg/L
0.1
1
2.5
5
10
Ca, Mg, Na, K,
Al, Fe
mg/L
0.1
1
5
10
20
Instrument and Hardware
All analyses were done on a PerkinElmer NexION 300X/350X
operating in Standard and Collision modes. The instrumental
and method conditions are shown in Tables 4 and 5, respectively.
The autosampler rinse consisted of 2% HNO3 + 1% HCl +
200 µg/L gold.
Table 4. Instrumental Conditions.
Parameter
Value
Sample uptake rate
Nebulizer
Spray chamber
Injector
Nebulizer flow
Plasma flow
Auxiliary flow
RF power
Torch depth
Cones
250 µL/min
Glass concentric (Meinhard C 0.5)
Glass cyclonic (baffled)
Quartz, 2.5 mm i.d.
Optimized for < 2% oxides
16 L/min
1.2 L/min
1600 W
+2 mm
Ni
Table 5. Method Parameters.
Element
Mass
Mode
Be
9
Standard
Na
23
Collision
Mg
24
Collision
Al
27
Collision
Hg
K
39
Collision
Sc
Ge
In, Rh, Tb
Ca
44
Collision
V
51
Collision
Cr
52
Collision
Mn
55
Standard
Table 2. Intermediate Solutions.
PerkinElmer
Part Number
Table 3. Calibration Standards.
Concentration
(mg/L)
10
Diluent
2% HNO3
1
2% HNO3 + 1% HCl
10
5
0.1
2% HNO3 + 1% HCl
+ 10% MeOH
Fe
56
Collision
Co
59
Collision
Ni
60
Collision
Cu
63
Collision
Zn
66
Collision
As
75
Collision
Se
78
Collision
Mo
95
Standard
Ag
107
Standard
Cd
111
Collision
Standard
Sb
121
Ba
137
Standard
Hg
200
Standard
Tl
205
Standard
Pb
208
Standard
Results and Discussion
Quality Control Terminology
When using Method 6020B, the user must be familiar with and understand the Quality Control (QC) definitions and criteria, which are
summarized in Table 6.
Figure 1 shows a flow chart of the daily operation scheme, including QC. First, instrument performance optimizations are performed
automatically using SmartTune Express in Syngistix™ for ICP-MS software. Next, the calibration standards are analyzed, followed by the
initial QC checks and samples, which consist of a mixture of soil and water certified reference materials, along with periodic QC
checks (CCB, CCV, MB, LCS, MS, MSD). After all the samples have been analyzed, final QC checks are analyzed.
Table 6. Quality Control Parameters Used in Method.
Name
Definition
Limits
Reference*
ICB
Initial Calibration Blank
< 0.5 times the LLOQ
10.5.4
ICV
Initial Calibration Verification
± 10% of true value
7.24, 10.5.1
LLOQ
Lower Limit of Quantification
(Low Level Verification)
± 20% of true value
10.5.2
SIC
Spectral Interference Check
< 2 times LLOQ
9.9
CCB
Continuing Calibration Blank
< LLOQ
10.5.5
CCV
Continuing Calibration
Verification
± 10% of true value
10.5.3
Notes
Daily Optimizations
Secondary source near (but not
equal to) the mid calibration
Calibration Standards
Initial QC Checks
ICB, ICV, LLOQ, SIC
MS
Matrix Spike
± 25% of spike level
MSD
Matrix Spike Duplicate
< 20 relative
percent difference
9.7.2
Run every batch of 20 samples
MB
Method Blank
< LLOQ
9.7.1
Alternates: - 50% of regulatory
limit- 10% of lowest sample
Laboratory Control Sample
± 20% of
true value
9.7.3
Internal Standard
> 70% recovery
9.10
CAL
Calibration
R > 0.995
10.4
Lowest calibration standard
must be at or below LLOQ
IDL
Instrument Detection Limit
Mean + 3SD
9.3
10 replicate analyses
LCS
IS
9.7.2
Mid-level calibration read back
Run every batch of 20 samples
Run every batch of 20 samples
Samples
Soils and waters
Periodic QC Checks
Every 10 Samples: CCB, CCV
Every 20 Samples: MB, LCS, MS, MSD
Final QC Checks
CCB, CCV
Figure 1. Daily workflow for running Method 6020B.
* Refers to section of the Method 6020B where these are discussed
3
Analysis
Before analyzing samples, the LLOQs and IDLs of the method
were established. The LLOQ (or low-level verification) was
established using the low-level calibration standards. The lowlevel standard must recover within + 20% of the true value. A
new way of establishing IDLs is defined in Method 6020B: the
mean of the blank is added to three times the standard deviation
of ten replicate analyses of the reagent blank. The LLOQs and
IDLs are shown in Table 7.
Table 7. LLOQs and IDLs.
Table 8. Results for NIST 1643e Trace Elements in Water.
Element
Certified (µg/L)
Measured (µg/L)
Be
13.98
13.05
93
Na
20740
20021
97
Mg
8037
7769
97
Al
141.8
154.7
109
103
K
2034
2090
Ca
32300
31508
98
V
37.86
37.21
98
103
Cr
20.4
21.0
Mn
38.97
35.94
92
98.1
97.6
100
Element
LLOQ (µg/L)
IDL (µg/L)
Fe
Be
0.2
0.004
Co
27.06
26.71
100
62.41
62.18
100
102
Na
20
0.665
Ni
Mg
20
0.134
Cu
22.76
23.16
Al
20
0.689
Zn
78.5
75.3
96
K
50
5.57
As
60.45
59.12
98
Ca
100
9.04
V
0.5
0.074
Cr
0.2
0.040
Mn
0.2
0.025
Fe
20
0.486
Co
0.2
0.002
Ni
0.2
0.015
Cu
0.5
0.015
Zn
0.2
0.135
As
0.2
0.020
Se
11.97
11.89
99
Mo
121.4
118.9
98
Ag
1.062
1.012
95
Cd
6.658
6.175
93
Sb
58.3
54.7
94
Ba
544.2
564.2
104
n/c
Hg
n/c
n/c
Tl
7.445
7.400
99
Pb
19.63
20.04
102
n/c = not certified
Se
0.2
0.083
Mo
0.2
0.007
Ag
0.2
0.003
Element
Certified (µg/L)
Measured (µg/L)
% Recovery
Cd
0.2
0.005
Be
3.026
2.879
95
Sb
0.2
0.001
Na
3137
2859
91
Ba
0.2
0.003
Mg
1058.6
1038.0
98
Table 9. Results for NIST 1640a Trace Elements in Natural Water.
Hg
0.2
0.007
Al
53
56
105
Tl
0.5
0.048
K
579.9
605.7
104
Pb
0.2
0.005
Ca
5615
5763
103
V
15.05
14.66
97
Cr
40.54
39.79
98
Mn
40.39
35.53
88
Fe
36.8
36.6
100
The accuracy of the method was demonstrated with the analysis
of multiple certified reference materials (CRM), as shown in Tables
8 and 9 for waters and Tables 10 and 11 for soils. All recoveries
are within 10% of the certified values, except for those which
result from common contaminants.
Co
20.24
20.01
99
Ni
25.32
24.80
98
Cu
85.75
88.24
103
Zn
55.64
55.94
101
As
8.075
7.979
99
Se
20.13
20.20
100
Mo
45.6
44.3
97
Ag
8.081
7.978
99
100
Cd
3.992
3.999
Sb
5.105
4.853
95
Ba
151.8
149.7
99
Hg
n/c
n/c
n/c
Tl
1.619
1.663
103
Pb
12.101
12.652
105
n/c = not certified
4
% Recovery
Table 10. Results for Soil Solution A (certified material from High Purity Standards).
Table 11. Results for Soil Solution B (certified material from High Purity Standards).
Element
Certified (µg/L)
Measured (µg/L)
% Recovery
Element
Certified (µg/L)
Measured (µg/L)
% Recovery
Be
n/c
0.14
n/c
Be
n/c
0.13
n/c
Na
70000
65053
93
Na
100000
90469
91
Mg
70000
67778
97
Mg
80000
76842
96
Al
500000
492818
99
Al
700000
697175
100
K
200000
203823
102
K
210000
213085
102
Ca
350000
332435
95
Ca
125000
120772
97
V
100
97
97
V
800
780
98
101
Cr
n/c
2.83
n/c
Cr
400
404
Mn
100
97
97
Mn
100000
95582
96
Fe
200000
202367
101
Fe
350000
360264
103
Co
n/c
3.83
n/c
Co
100
103
103
Ni
300
289
96
Ni
200
200
100
Cu
300
320
107
Cu
3000
2934
98
Zn
1000
963
96
Zn
70000
67177
96
As
200
193
97
As
6000
5779
96
Se
10
10
101
Se
n/c
0.08
n/c
Mo
n/c
1.62
n/c
Mo
n/c
4.88
n/c
Ag
n/c
0.88
n/c
Ag
n/c
0.86
n/c
Cd
n/c
4
n/c
Cd
200
199
100
Sb
30
30
100
Sb
400
387
97
Ba
5000
5022
100
Ba
7000
6896
99
Hg
n/c
0.09
n/c
Hg
n/c
0.17
n/c
Tl
n/c
1.41
n/c
Tl
n/c
1.64
n/c
Pb
400
412
103
Pb
60000
66682
111
n/c = not certified
n/c = not certified
Table 12 shows recoveries from a river water CRM, as well as the
results from one of the matrix spikes and matrix spike duplicates.
The CRM recoveries are generally within 10% of the certified
values, consistent with the other CRMs analyzed. In addition,
both the matrix spike and matrix spike duplicate pass the
method-defined acceptance criteria, as shown in Table 6.
Table 12. SLRS-4 River Water: Analyte, Matrix Spike and Matrix Spike Duplicate Recoveries.
Element
Be
Na
Mg
Al
K
Ca
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
As
Se
Mo
Ag
Cd
Sb
Ba
Hg
Tl
Pb
n/c = not certified
Certified (µg/L)
Measured (µg/L)
0.007
2400
1600
54
680
6200
0.32
0.33
3.37
103
0.033
0.67
1.81
0.93
0.68
n/c
0.21
n/c
0.012
0.23
12.2
n/c
n/c
0.086
< LLOQ
2090
1590
55
710
5840
< LLOQ
0.36
2.97
104
0.037
0.72
1.87
1.08
0.68
< LLOQ
0.18
< LLOQ
0.011
0.25
12.7
n/c
< LLOQ
0.091
Recovery (%)
*
87.1
99.5
102
105
94.2
*
109
88.1
101
112
108
104
116
100
*
85.7
*
91.7
109
104
n/c
*
106
* = < LLOQ
Spike Concentration
(µg/L)
Matrix Spike
(% Recovery)
Matrix Spike Duplicate
(Relative % Difference)
50
5000
5000
5000
5000
5000
50
50
50
5000
50
50
50
50
50
50
50
50
50
50
50
0.5
50
50
94.3
85.0
92.2
95.3
99.5
93.5
91.2
93.3
97.3
99.0
92.5
92.5
95.1
106
95.5
97.6
92.9
98.0
99.4
95.2
97.3
107
102
103
6.34
0.05
0.05
0.06
0.05
0.03
6.37
6.89
5.77
0.06
6.33
6.21
5.91
5.52
6.07
6.22
6.45
6.22
5.90
6.29
4.85
0.00
5.90
5.84
5
The robustness of the method was determined by running
samples for ten hours using the workflow scheme in Figure 1 and
monitoring the internal standard recoveries over time. The results
are shown in Figure 2 and indicate that internal standard
recoveries are well within the 30% required by Method 6020B.
Conclusion
This work has demonstrated the ability of the NexION 300X/350X,
running in both Standard and Collision modes, to easily meet
the requirements of U.S. EPA Method 6020B for both water and
soil samples. Unique instrument design characteristics minimize
instrument maintenance, daily tuning/optimization, and increase
stability, thereby allowing the analysis of more samples.
Figure 2. Internal standard recoveries over 10 hours.
Consumables Used
Peristaltic Pump
MP2
Standard
Component
Description
0.64 mm id (orange/white), flared, 2-stop
N8145201
Internal standard addition tubing
0.19 mm (orange/red), flared, 2-stop
N8145194
Drain tubing
1.30 mm id (gray/gray), Santoprene, 2-stop
N8145173
Internal standard addition tee
Tee for adding internal standard on-line
N0777294
Sample uptake tubing
0.38 mm id (green/orange), flared, 2- stop
N0777042
Internal standard addition tubing
Drain tubing
Internal standard addition tee
0.19 mm (orange/red), flared, 2-stop
1.30 mm id (gray/gray), Santoprene, 2-stop
Tee for adding internal standard on-line
N0773111
N0777444
N0777294
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011973_01PKI
Part Number
Sample uptake tubing