Applications of ICP-MS for

Trace Elemental Analysis in the

Hydrocarbon Processing Industry

Fundamentals and Applications to the Petrochemical Industry

Outline

• Some background and fundamentals of ICPMS

• Proposed ICPMS method for ASTM • Preliminary Results for D7111-11 • Preliminary Results for D5185-09

• Advantages of ICP-MS

• Summary

Inductively Coupled Plasma Mass Spectrometry • Key applications are:

– Environmental – Foods – Semiconductor – Clinical – Chemical/Petrochemical – Pharmaceutical – Consumer Goods – Forensic – Geological – Nuclear – Academic/Research

• ICP-MS market growing fast as technology improves and encroaches upon traditional GFAA and ICP-OES markets

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Comparison of Elemental Analysis Techniques for Liquid Samples

Firstly, What is ICP-MS?

ICP - Inductively Coupled Plasma

• high temperature ion source • decomposes, atomizes and ionizes

the sample

MS - Mass Spectrometer

• Uses quadrupole mass analyzer • Mass range from 7 to 250 amu (Li to U...)

– separates all elements in rapid sequential scan

– isotopic information available

• Measures ions, using dual mode detector – Sub ppt to ppm levels

An elemental analysis technique

ICP-MS combines the detection limits of Graphite Furnace AA (or better) and the sample throughput of ICP-OES

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Simplified Schematic – the functional components

Converts liquid sample to aerosol

Decomposes sample matrix

and forms ions

Focuses ions and removes photons and

neutrals

Removes spectral

interferences (polyatomic

ions)

Separates ions by m/z – unit

mass resolution

Detects ions and transfers counts to data

system

Sample Introduction

Plasma Ion Source

Ion lenses Collision/ Reaction Cell

Quadrupole MS

Detector

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Nearly all modern ICP-MS instruments employ some form of Collision/Reaction Cell to remove polyatomic (molecular) interferences

General ICP-MS Components/Technology

1. The liquid sample is mixed with argon gas by the nebulizer to form an aerosol..

2. The smallest droplets pass through the spray chamber and into the ion source - the plasma

3. The sample is desolvated and ionized in the plasma

4. Ions are extracted from the plasma by extraction lenses in the interface region

5. Ion lenses focus and collimate the ions. The Omega lens bends the ion beam off-axis to prevent photons from striking the detector

7. The quadrupole mass spectrometer separates ions based on their mass to charge ratio. The selected ions continue on to the detector

8. Ions are measured using a discrete dynode detector providing 9 orders of linear dynamic range 6. Interference Ions

are removed from the ion path by reaction/collision/KED effects in the cell

Processes in ICP-MS Plasma

Mostly the same as ICP-OES

The ICP-MS Torch Torch and plasma nearly identical to ICP-OES

ICP-MS Plasma/Vacuum Interface

• Plasma gases and sample ions pass through sample cone into the interface, or expansion stage − First stage of 3 stage vacuum system − Gases expand into a vacuum

• The ions are “sampled” by the skimmer cone and pass into the intermediate stage − Cone geometry is critical for efficient transport of ions

• Extraction lenses create a voltage field behind skimmer. − Voltage field begins the process of focusing the ion beam.

Ext. 2

Ext 1

Energy Energy

Cell Entrance

Cell Exit

Energy loss from each collision with a He atom is the same for analyte and polyatomic ion, but polyatomics are bigger and so collide more often

At cell entrance, analyte and polyatomic ion energies overlap. Energy spread of both groups of ions is narrow, due to ShieldTorch System

Polyatomic ions

Analyte ions

Polyatomic ions

Analyte ions

Energy distribution of analyte and interfering polyatomic ions with the same mass

Bias voltage rejects low energy (polyatomic) ions

By cell exit, ion energies no longer overlap; polyatomics are rejected using a bias voltage “step”. Analyte ions have enough residual energy to get over step; polyatomics don’t (energy discrimination)

Principle of for removing polyatomic interferences He Mode and KED (Kinetic Energy Discrimination)

October 9, 2013 Page 11

Energy Discrimination – Ionic Radii

0

50

100

150

200

250

300

Simple Species

As+

ArCl+

V+

ClO+ A

ppro

x Io

nic

Rad

ii (p

m) Any polyatomic

species will have a larger-cross section than single ions

The larger polyatomics will collide with the cell gas a greater number of times than the smaller analyte ions and loose energy

Low energy ions cannot enter the QP

m/z 75 m/z 51

0

50

100

150

200

250

300

350

400

Complex Species

Energy Discrimination – Ionic Radii

Cu

S2

SO2

NOCl

ArMg

CaOH

App

rox

Ioni

c R

adii

(pm

)

Energy Discrimination is NOT a reaction process – does NOT rely on reaction pathways that are species dependant

Simply acts as a physical filter for the larger polyatomic ions

Is applicable for ANY polyatomic

m/z 65

Anything larger than 150pm will be filtered out

1. On-Mass Measurement: Unreactive analyte does not react with chosen cell gas, remains at original m/z and so can be separated from reactive interferences

Reactive interferences are converted to product ions at a new mass – can be rejected by analyzer quad, which is set to original analyte mass

ORS3 Reaction Mode Another tool for removing interferences

Reaction product ion

On-mass interference

Analyte

Reaction gas

Interference M+ MR+

Analyte and interfering ions enter reaction cell

Quad set to original analyte mass – rejects interference product ion(s)

Analyte

Interference reacts to form product ion

2. Mass-Shift Measurement: Reactive analyte reacts with chosen cell gas, is moved to a new product ion mass and can be separated from unreactive interferences

Reactive analyte is converted to product ions at a new mass – interferences remain at original mass and are rejected by analyzer quad

ORS3 Reaction Mode Another tool for removing interferences

Original interfering ion

On-mass interference

Analyte

Reaction gas

Analyte M+ MR+

Analyte and interfering ions enter reaction cell

Quad set to analyte product ion mass – rejects original interfering ions

Analyte product ion

Analyte reacts to form product ion

Quadrupole Mass Analyzer

• Also referred to as the “quad”, or “QP” • 4 hyperbolic rods are electronically paired. • RF and DC voltages are applied and ramped

- x and y rods are out of phase with each other. • QP behaves as a filter -- all masses may enter, however only one mass exits

the QP at any point in time - All ions except the target ion are unstable – they exit the QP out to the

side, and are pumped away by the vacuum system. - QP continuously scans the mass range during acquisition. - Can acquire each mass between 0-260 amu in approx. 0.1s.

Single mass at QP exit

Electron Multiplier Detector

•Ions exiting the QP strike the first dynode of the detector. •Creating a cascade of electrons which is amplified and counted •One ion results in one pulse of electrons.

Key Hardware and Software Requirements For Organic Analysis

O2 Option Gas MFC • Added to Aux gas at torch

• Allows Organics to be analyzed directly by ICPMS

• Auto setup of conditions New MassHunter Software and Torch Design • Modified firmware and software startup settings ensure

reliable ignition with organic solvents

• New torch design provides improved tolerance to volatile organic solvents

ORS3 Octopole Reaction System • 3rd Generation Octopole

• Allows analyses of difficult elements - Si, P, S & Se

Preliminary Results D7111-11

Determination of Trace Elements in Middle Distillate Fuels (Modified for ICP-MS)

Preliminary Results D7111-11 Modified for ICP-MS

Instrument Agilent 7700x ICP-MS

Acquisition mode(s) Hydrogen and High Energy Helium (HEHe) cell modes

Sample introduction devices

Glass nebulizer and 700 mm length capillary tube Quartz torch with 1.5 mm bore injector

Sample uptake Natural aspiration Interface Platinum sampling cone and skimmer cone Autosampler I-AS

Reagents Standard solutions of organic metals were CONOSTAN oil standards. Kerosene, as the diluent solvent, was purchased from Kanto Chemicals. No further purification was applied to kerosene.

Calibration 5ppm (w/w in kerosene) of mixed standard was prepared from CONOSTAN standards. 0, 2, 10 and 50ppb (w/w) solutions were obtained by serial dilution of this stock standard solution. Yttrium internal standard was added into each working standard solution.

Long term stability – 7 hours continuous analysis 10ppb spiked diesel oil

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300 350 400 450

Nor

mal

ized

Con

cent

ratio

n

Elapsed time, min

23 Na [ H2 ] 24 Mg [ H2 ]31 P [ HEHe ] 40 Ca [ H2 ]48 Ti [ HEHe ] 51 V [ HEHe ]52 Cr [ HEHe ] 55 Mn [ H2 ]56 Fe [ H2 ] 59 Co [ HEHe ]60 Ni [ HEHe ] 63 Cu [ HEHe ]66 Zn [ HEHe ] 75 As [ HEHe ]78 Se [ H2 ] 95 Mo [ HEHe ]107 Ag [ HEHe ] 114 Cd [ HEHe ]118 Sn [ HEHe ] 138 Ba [ H2 ]208 Pb [ HEHe ]

23 Na [ H2 ] 1.9% 24 Mg [ H2 ] 1.8%

31 P [ HEHe ] 0.5% 40 Ca [ H2 ] 1.5%

48 Ti [ HEHe ] 1.8% 51 V [ HEHe ] 1.3% 52 Cr [ HEHe ] 1.1% 55 Mn [ H2 ] 0.9% 56 Fe [ H2 ] 1.0%

59 Co [ HEHe ] 1.1% 60 Ni [ HEHe ] 1.3% 63 Cu [ HEHe ] 0.9% 66 Zn [ HEHe ] 2.0% 75 As [ HEHe ] 2.7%

78 Se [ H2 ] 1.5% 95 Mo [ HEHe ] 1.4% 107 Ag [ HEHe ] 0.9% 114 Cd [ HEHe ] 1.3% 118 Sn [ HEHe ] 1.4%

138 Ba [ H2 ] 1.1% 208 Pb [ HEHe ] 1.4%

Preliminary Results D7111-11 Metallic impurities in fuel oils (ug/kg), ppb kerosene alcohol white gas

A white gas

B diesel oil regular

gas high-octane

gas

10B H2 n. d. 920 16 25 1.5 5 n. d. 23Na H2 n. d. 19 n. d. 25 4.1 n. d. n. d. 24Mg H2 n. d. 5.2 3.6 37 6.6 2.6 n. d. 27Al HEHe 0.4 8 n. d. 31 8.3 1.4 n. d. 40Ca H2 0.3 6.4 3 42 10 11 0.3 48Ti HEHe 0.1 0.9 0.2 33 8.1 1.8 0.2 51V HEHe 0.5 0.5 0.4 31 7.7 1.4 0.9 52Cr HEHe 0.1 1.8 1.3 37 8 1.9 0.3

55Mn H2 0.3 2.6 1.3 36 8 2.2 0.4 56Fe H2 1.2 41 0.6 39 8.9 10 0.6 59Co HEHe 0.2 1.1 0.1 0.9 0.3 0.2 0.4 60Ni HEHe 0.4 2 0.9 30 6.4 1.9 0.1 63Cu HEHe 2.1 14 4.8 41 7.4 2.8 0.5 66Zn HEHe 58 78 8.2 35 52 250 3.6 95Mo HEHe 0.1 0.6 0.2 31 6.9 1.5 0.3 107Ag HEHe 0.1 4.7 0.1 27 6.8 1.5 0.2 114Cd HEHe 0.1 12 0.5 30 6.4 1.5 0.3 118Sn HEHe n. d. 610 3.8 36 7.4 2 0.2 138Ba H2 0.9 0.2 0.1 30 8.4 17 0.4 208Pb HEHe 0.3 0.9 0.4 27 6.6 1.6 0.4

Recovery of Certified Elements in NIST-1634C Residual fuel oil

Element Reference mg/kg Result mg/kg Recovery

Na 37 37.7 102%

V 28.19 +- 0.40 28.0 99%

Co 0.1510 +- 0.0051 0.147 97%

Ni 17.54 +- 0.21 17.2 98%

As 0.1426 +- 0.0064 0.148 104%

Se 0.1020 +- 0.0038 0.102 100%

Ba 1.8 1.87 104%

Preliminary Results – D5185-09

Determination of Additive Elements, Wear Metals, and Contaminants in

Used Lubricating Oils and Determination of Selected Elements

in Base Oils (Modified for ICP-MS)

Preliminary results – D5185-09 Modified for ICP-MS

• Essentially same methodology, instrument conditions, calibration, and sample prep were used as for D7111-11

• Samples were diluted into either Kerosene or O-Xylene

• Lubricating oils were purchased from various sources on common market

Calibrations prepared from Conostan 21 Dilution in kerosene

Unit CALBLK CALSTD1 CALSTD2 CALSTD3 CALSTD4 Na ppm 0 0.005 0.02 0.1 0.5 Mg ppm 0 0.5 2 10 50 P ppm 0 0.5 2 10 50

Ca ppm 0 0.5 2 10 50 Zn ppm 0 0.5 2 10 50 Mo ppm 0 0.1 0.4 2 10 Al ppb 0 0.2 0.8 4 20 Fe ppb 0 0.2 0.8 4 20 Cd ppb 0 0.2 0.8 4 20 Ti ppb 0 0.2 0.8 4 20 V ppb 0 0.2 0.8 4 20 Cr ppb 0 0.2 0.8 4 20 Mn ppb 0 0.2 0.8 4 20 Ni ppb 0 0.2 0.8 4 20 Cu ppb 0 0.2 0.8 4 20 Ag ppb 0 0.2 0.8 4 20 Sn ppb 0 0.2 0.8 4 20 Ba ppb 0 0.2 0.8 4 20 Pb ppb 0 0.2 0.8 4 20

Method Performance – Detection limits Analyte m/z mode DL (ppb) BEC(ppb)

B 10 H2 0.85 2.1

Na 23 H2 0.79 1.9

Mg 24 H2 0.18 2.5

Al 27 He 0.03 0.11

P 31 He 28 33

Ca 40 H2 0.14 0.13

Ca 44 H2 2.2 1.2

Ti 49 He 0.14 0.01

V 51 He 0.005 0.01

Cr 52 He 0.05 0.26

Fe 54 H2 0.06 0.02

Mn 55 He 0.01 0.005

Ni 60 He 0.02 0.02

Cu 63 He 0.05 0.26

Zn 66 He 0.21 0.33

Zn 67 He 0.33 0.29

Mo 95 He 0.005 0.005

Ag 107 He 0.01 0.01

Cd 114 He 0.005 0.01

Sn 118 He 0.005 0.01

Ba 137 H2 0.01 0.01

Pb 208 He 0.005 0.01

Concentration Spiked

Measured (ppb) Recovery (%) unspiked spiked

B 50 4.3 47 85 Na 50 4.3 69 119 Mg 50 2.9 57 108 Al 10 19 28 90 Ca 50 145 198 106 Ti 50 2.3 59 113 V 50 0.15 56 112 Cr 10 1.3 13 117 Mn 50 0.77 59 116 Fe 50 5.8 34 62 Ni 10 2.8 12 112 Cu 10 5.1 17 119 Zn 50 2 62 120 Mo 50 0.83 55 108 Ag 10 0.37 11 106 Cd 10 1.1 12 109 Sn 10 0.45 12 116 Ba 50 5.7 60 109 Pb 50 8.2 54 86

Kerosene Certified Value % (uncertainty) Calcium 0.36 0.359 (0.011) Magnesium 0.78 0.821 (0.038) Phosphorus 0.78 0.788 (0.028) Zinc 0.87 0.873 (0.022)

Recoveries - NIST 1848 Lubricating Oil Additive Package

Summary

• ICP-MS methods can be easily adapted from existing ICP-OES methods with only minor changes.

• ICP-MS offers 2 or more orders increased sensitivity

• ICP-MS suffers fewer interferences – easily managed using CRC technology

• ICP-MS can provide isotopic information useful for confirmation

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