1. Eliminating Molecular Interferences in ICP-MS for the Simplest Method Development
Dr. Torsten Lindemann

2. What are Molecular Interferences ?
Isotope
Interference
31P
15N16O 14N16OH
30Si1H
12C19F
47Ti
32S15N 33S14N 1H32S14N
52Cr
40Ar12C 36Ar16O
36S16O
1H234S16O
56Fe
40Ar16O
40Ca16O
28Si2
60Ni
44Ca16O
23Na37Cl
23Na214N
28Si32S
75As
40Ar35Cl
40Ca35Cl
Molecular species which occur at the same nominal mass as the analyte:
Formed in the plasma and/or interface
Originate from the matrix and the Ar plasma gas
Matrix dependent
Plasma condition dependent

3. Quadrupole and Sector Field Mass Spectrometers
Quadrupole: Sector Field:
+ve DC
+ve RF
-ve DC
-ve RF
Unit Resolution High Resolution
Collision / Reaction Cell necessary R=m/Δm

4. iCAP Q Quadrupole ICP-MS: QCell with Flatapole for Interference Removal
SEM with > 9 orders of linear dynamic range and long lifetime
Thermo Scientific™ iCAP™ Q Quadrupole ICP-MS
Quadrupole mass analyzer
QCell with Flatapole for improved ion transmission and reliable interference reduction with He KED and
reaction cell chemistry (non-consumable)
Cones & Lenses:
easily accessible
RAPID lens for efficient
removal of neutral
species (maintenance-free)

5. iCAP Q Quadrupole ICP-MS: QCell with Flatapole for Interference Removal
SEM with > 9 orders of linear dynamic range and long lifetime
Thermo Scientific™ iCAP™ Q Quadrupole ICP-MS
Quadrupole mass analyzer
QCell with Flatapole for improved ion transmission and reliable interference reduction with He KED and
reaction cell chemistry (non-consumable)
Cones & Lenses:
easily accessible
RAPID lens for efficient
removal of neutral
species (maintenance-free)

6. High Resolution ICP-MS ELEMENT 2
Electrostatic Analyzer
Ion Detection
Magnet
Interface (sampler & ground potential
8 kV Ion Acceleration
& Focusing
Ion Production

7. 40Ar35Cl Interference on 75As
m/z
40Ar35Cl 75
75As
m/z 75

8. Small Mass Difference Between 75As and 40Ar35Cl
m/z
40Ar35Cl
74.931
75As
m/z

9. Resolution to Resolve InterferencesLR HR
5 µm MR
16 µm
Resolution R = m/Δ m
LR: Low Resolution: R ≥ 300
MR: Medium Resolution: R ≥ 4 000
HR: High Resolution: R ≥
It takes < 1 s to change resolution
The slit width defines the ion beam entering the magnetic field
Narrower slits are used for higher resolution

10. As in Low Resolution
75As?
Low Resolution

11. As in Low Resolution
75As?
Low Resolution

12. As in Medium Resolution

13. As is Resolved from ArCl in High Resolution
m/z
75As
m/z

14. As Quantification: We Measure only As
High Resolution
75As
m/z

15. P in 1000 mg/L Si / 3% HF / 2% HNO3

16. P in 1000 mg/L Si / 3% HF / 2% HNO3 (MR)
12C19F
Medium Resolution
30Si1H
1H14N16O
31P

17. Interferences in 1000 ppm Si / 3% HF / 2% HNO3 (MR)
28Si16O
29Si18O
28Si19F
12C16O2
44Ca
47Ti ?
35Cl16O
40Ar12C
36S16O
36Ar16O
1H230Si19F
52Cr ?
51V

18. Interferences in 1000 ppm Si / 3% HF / 2% HNO3 (MR)?
28Si2
40Ar16O
28Si30Si ? ?
56Fe
58Ni
29Si16O18O
28Si19F2
28Si35Cl
28Si38Ar
66Zn
63Cu ? ?

19. P Calibration in 1000 ppm Si: 1, 5, 10, 50, 100, 500 ppt
4400 cps / ppb P
6 ppt LoD
70 ppt BEC

20. 1:10 Diluted Seawater: Removal of Interferences in Medium Resolution

21. 1:10 Diluted Seawater: Removal of Interferences in Medium Resolution
31P16O
15N16O2
35Cl16O
34S16O1H
47Ti
51V
52Cr
40Ar12C
40Ca12C
36S16O
35Cl17O
40Ar15N
55Mn ?

22. 1:10 Diluted Seawater: Removal of Interferences in Medium Resolution
42Ca16O1H
43Ca16O
23Na36Ar
40Ar18O1H
40Ar16O
40Ca16O
44Ca12C ?
56Fe
59Co
60Ni
44Ca16O
23Na40Ar ? ?
63Cu

23. Ti in 10 % H2SO4

24. 33S14N 47Ti ? Ti in 10 % H2SO4 (MR) Medium Resolution
4000 cps / ppb Ti
0.2 ppt LoD
0.77 ppt BEC ?

25. 52Cr 36S16O ? Cr in 10 % H2SO4 (MR) Medium Resolution
53000 cps / ppb Cr
0.15 ppt LoD
0.5 ppt BEC ?

26. Figures of Merit P Ti Cr Matrix 1000 ppm Si / 3 % HF / 2 % HNO3
10 % H2SO4
Sensitivity
4400 cps/ppb
4000 cps/ppb
53000 cps/ppb
Background Equivalent Concentration
70 ppt
0.77 ppt
0.5 ppt
Limit of Detection
6 ppt
0.2 ppt
0.15 ppt

27. Conclusions
With Sector Field ICP-MS it is not necessary for the analyst to have any information about the sample or the expected interferences before analysis. Just dilute and shoot.
All interferences are simply separated and observed by conducting a survey scan with an increased mass window.
Methods can be defined with isotopes to be analyzed in different resolution settings with switching times between resolutions ≤ 1 s.
This allows fast sample throughput without sacrificing the multielemental capabilities of ICP-MS.
High mass resolution provides visual, simple and unequivocal data confidence.
This confidence in the accuracy of the results makes Sector Field ICP-MS the ideal tool for applications where indisputable results are required. This is the reason why Sector Field ICP-MS is used in many regulatory and metrology institutions.