High Sensitivity ICP-MS: Overcome the problem of complex samples

High Sensitivity ICP-MS:

Overcome the problem of complex samples

Meike Hamester, Andrew Toms and René Chemnitzer Bruker Daltonics

Berlin, Germany - Milton, Canada

Historical Product Roadmap

2003 2005

Introduced world’s most sensitive ICP-MS (Varian)

Introduced model 810 and 820 using CRI technology (Varian)

2010 Bruker acquires Varian ICP-MS

2011

Bruker launches aurora M90, world’s most sensitive ICP-MS

Bruker 810

No CRI interface Highest sensitivity No selectivity

Bruker 820

CRI interface High sensitivity High selectivity

Bruker aurora M90

CRI interface for Highest Sensitivity and Selectivity

Non CRI interface for utmost sensitivity

aurora M90:

combining highest sensitivity with selectivity

translates to results in advantage

high

sensitivity/high signal to noise ratio

low detection limits low detection limits low detection limits

short integration times short analysis times higher sample throughput

higher dilution factors less matrix effects less cone depositions less cross contamination reduced washout time

less drifts

less QC failures less re-calibration less sample volume

higher sample throughput

higher sensitivity in

interference mode low detection limits for spectrally interferenced analytes

accurate results at lowest concentration levels

high sensitivity for laser

ablation low laser energy higher spatial resolution

lower detection limits in solid samples

lower detection limits for

LC / GC coupling lower detection limits for elemental species (As, Sn, Br…)

simpler procedures, less sample volume

Benefits and side benefits of high sensitivity

5

The Bruker aurora M90 ICP-MS

Multi Patented Technology by Bruker Daltonics

Sensitivity:

Reflecting Optics concept

F

Parabolic mirror 3D control

D E

energy spread

90 degree Reflection concept for ions

9Be ~ 0.5eV

115In ~ 2eV

232Th ~ 5eV

All ions are focused into quad entrance

Sensitivity:

Ion Mirror for ICP-MS

unwanted particles

electrostatic field

MS quad

• Four electrode segments to provide 100% multidimensional control of the ion beam by

mean of parabolic field shaping

• Hollow structure allows

photons, neutrals, & particles to pass straight through to pump

Sensitivity / Signal to noise ratio:

Curved Fringing Rods to minimise noise

• Metastables can travel through the Quadrupole

• Reaching the detector area they may cause ion-electron emission

• Those pulses can not be distinguished from

analyte ions

• The background would sacrifice BECs & DLs values

• The Curved Fringes minimise continues background

Key for

low background/

high signal to noise ratio

1 2 3 4

5 6 7

Ions Neutrals Photons To detector for measurement

Removed by vacuum system

Ion Mirror

Sensitivity and Selectivity:

CRI Interface and 90 Degree ‘Reflecting’ Ion Optics

Kinetic Energy

Discrimination

gas

Exponential reduction Original

plasma jet

New, clean Plasma expansion Interference

gas

CRI cone

10

Uses He and (H₂) gasses Collisional / Reactive

Heto remove ¹⁶O³⁵Cl⁺ on ⁵¹V⁺ H₂ to remove ⁴⁰Ar⁺ on ⁴⁰Ca⁺

Selectivity:

Collision-Reaction Interface – CRI (II)

Benefits

• One-button interference management

• Auto-optimization

• Fast switching between gases

• Low maintenance

• No extra consumables

Skimmer Cone

Typical aurora M90 performance:

Normal Sensitivity and High Sensitivity modes

Normal Mode High Sensitivity

Mode (1) High Sensitivity Mode (2)

9Be (cps/ppb) 30660 102483 289763

59Co (cps/ppb) 387949 987589 1906846

115In (cps/ppb) 426560 1032937 2073298

238U (cps/ppb) 528568 936320 1723943

Background

@5amu 0.1 cps 1 cps 2 cps

CeO+/Ce+ 0.9 % 0.7 % 3.3 %

Ba++/Ba+ 0.9 % 1.9 % 1.4%

• Nebulizer: concentric glass, 400 L/min

• Spraychamber: scott-type, glas

•

Focus point lifted up

•

Ion beam diffused

•

3 mm focus

•

Sensitivity attenuated

Computer Modeling -Normal Mode

Ion beam focus Y dimension control

12

Normal

•

Ion beam focus on

entrance of Quadrupole

•

Ion beam focus: 1mm

Computer Modeling - High Sensitivity

Ion beam focus Y dimension control

13

High

Sensitivity: Uranium

(high sensitivity mode: Ion beam in focus)

1.700.000 cps/ppb

²³⁸

U

9

Be in Urine

• Dilution 1:10

• MDL: 0.3 ppt

Sensitivity: Beryllium in Urine

Gadolinium

They are used for:

• conventional diagnostic radiology

• angiography

• computed tomography (CT)

• magnetic-resonance-tomography (MRT)

Gadolinium compounds are used as contrast agents in medical checkups as they intensify differences in density between different types of tissues

Water soluble unspecific complexes of Gadoliniumkomplexe with 0,5 Mol/l Gd

linear complexes Gd-DTPA; -BMA

Magnevist, Omniscan

makrocyclic complexes Gd-DOTA; Gd-HP-DO3A Dotarem, Prohance

Gadolinium in densely populated areas of Berlin

17

Sensitivity: Detection of Gadolinium (

¹⁵⁸

Gd)

508.000 cps/ppb Gd (¹⁵⁸Gd)

Selectivity:

Typical Interference: ⁴⁰Ar³⁵Cl interference on ⁷⁵As

19

Reducing CaO (and ArO) interference on Fe

Normal Sensitivity CRI no gas

Normal Sensitivity CRI He

High Sensitivity CRI no gas

High Sensitivity CRI He

cps/ppb 89219 22354 731393 124151

0 100000 200000 300000 400000 500000 600000 700000 800000

Sensitivity [cps/ppb]

Sensitivity: Different CRI Modes

59

Co

Sensitivity and Selectivity:

BEC: Different modes of operation (all CRI Interface)

59

Co

NS NS & Ca NS & Ca &

He HS HS & Ca HS & Ca & He

BEC [ppt] 6.00 60.9 5.10 5.8 82 6.2

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

BEC [ppt]

100 ppm Ca

Normal Sensitivity Mode

• Ion beam ‘de-focused’

• Sensitivities > 200.000 cps / ppb

• CRI II interface utilizing He and H₂ for interference reduction

High Sensitivity Mode

• Ion beam in focus

• Sensitivities > 1.000.000 cps / ppb

• CRI II interface for interference reduction

• Sensitivities > 100.000 cps / ppb in He mode

Bruker aurora M90 ICP-MS:

combining highest sensitivity with selectivity

Many other features…

Plasma generation, all digital detector, automated aerosol dilution…….

Bruker aurora M90 ICP-MS

…unique features and fascinating applications

•

Ground-breaking Plasma exitation – the ‚Turner interlaced coils‘

•

Intelligent detector design – full digital DDEM detector

•

Full range of applications

Bruker RF Plasma System -”Twin Coil” design

• Two interlaced RF coils

 Driven in opposing directions

• Results in balanced RF field for plasma generation

• Very robust plasma

 Efficient energy transfer to plasma

• No secondary discharge

 Low kinetic energy distribution of ions

• No mechanical shielding required

 For cool plasma operation

 High sensitivity

 Low oxide ratios

• Ideal for laser ablation

 Decomposition of laser aerosol

Detector Technology in the Bruker M90

•

Detectors in mass spectrometers convert ions into electrical pulses

•

The pulses are measured or counted by the electronics, resulting in the signal observed by the operator

26

Quadrupole

Signal Output e^-

e^- e^-

+ ^e-

How a Detector Works

Discrete Dynode Electron Multiplier (DDEM)

•

Impact of ion results in multiple ejections of electrons from dynode surface (conversion)

•

Multiple electron ejections continue at each dynode (amplification)

•

Result - ion impact leads to the formation of a large pulse of electrons (detection)

Quadrupole

Signal Output e^-

e^- e^-

+ ^e-

Conventional ICP-MS Detectors – the Problem

• Traditional ICP-MS detectors will saturate once they reached a few million counts/sec

Quadrupole

Signal Output e^-

e^- e^-

+ ^e-

• As ICP-MS instruments became more and more sensitive over time and were able to see lower concentrations of analytes, this meant the highest concentration the

instrument could read without over-ranging also dropped.

Higher concentration samples had to be diluted

Conventional ICP-MS Detectors -the “Solution”?

• To overcome this limitation, the dual-mode or “pulse- analog” detector was developed

Quadrupole

Signal Output e^-

e^- e^-

+ ^e-

• Instead of counting individual pulses, it ‘averages’

high rates of pulses into a steady current

• This current is proportional to the incoming ion flux from the quadrupole

Conventional ICP-MS Detectors -the problems with the “Solution”

•

The slope of the response in analog mode is often different than in pulse-counting mode

•

Difficult to make a single calibration curve over wide range

•

The ‘cross-calibration’ can drift, and requires frequent verification or re-calibration – weekly or even daily

•

Detector lifetime can be

greatly shortened in analog mode

Schematic of Detector Operation

•

The detector converts ions into electrical pulses.

Adjustment of voltage applied to control dynode provides attenuation of final output signal

•

Three operating modes; None (Off), Medium and High

31

‘V’ Control 4^th Dynode

Signal Output

Quadrupole

Gain Controlled

Ion to e^-

Conversion

Amplification e^-

e^- e^-

+ ^e-

32

•

Unique to Bruker

•

Long lifetime due to gain control protection

•

^{> 109} dynamic range

•

Fast operation

•

Simple attenuation correction set up in software

•

Attenuation of electrons not ions, avoids mass bias

effects

•

Excellent long term stability and precision

Bruker All Digital Detector

Easy – Fast - Stable

Bruker ICP-MS Detector

– Short and Long Term Stability

• Detector attenuation factors were re-measured/re- calibrated 33X over 21 months

• Even though detector operating voltage changes over time, attenuation factors remain stable

• Typically, detector needs recalibration every 2-3 months

Isotope Norm-Med Atten Med-High Atten

Pb208 1.94% 2.34%

Th232 1.87% 2.56%

U238 1.76% 2.4%

Bruker ICP-MS Detector -Accuracy

•

Measurements made in all 3 modes

•

^{Margin of}

experimental error

encompasses

‘true’ value in all cases

Shaulis, B., T. J. Lapen, and A. Toms (2010),

Signal linearity of an extended range pulse counting detector: Applications to accurate and precise U‐Pb dating of zircon by laser ablation quadrupole ICP‐MS,

Geochem. Geophys. Geosyst., 11, Q0AA11,doi:10.1029/2010GC003198.

35

NIST 1515 Apple Leaves Standard Reference Material

ICPMS wt.% stdev. Reference wt.% stdev.

Ca 1.494 0.016 1.526 0.015

Mg 0.269 0.002 0.271 0.008

K 1.62 0.01 1.61 0.02

ICPMS µg/g stdev. Reference µg/g stdev.

Al 285 2 286 9

AS 0.039 0.0007 0.038 0.0077

Ba 48 0.4 49 2

B 27.6 2.6 27 2

Cu 5.54 0.02 5.64 0.24

Pb 0.48 0.023 0.47 0.024

Mn 55 0.2 54 3

Hg 0.041 0.002 0.044 0.004

Mo 0.104 0.007 0.094 0.013

Ni 0.93 0.07 0.91 0.12

Se 0.05 0.011 0.05 0.009

Na 27.8 7.9 24.4 1.2

Sr 23 2 25 2

V 0.28 0.02 0.26 0.03

Zn 13.0 0.8 12.5 0.3

NIST 8436 Durum Wheat Flour

A Joint Material of Agriculture Canada and NIST

ICPMS wt.% stdev. Reference wt.% stdev.

K 0.311 0.023 0.318 0.014

Mg 0.097 0.0003 0.107 0.008

P 0.247 0.01 0.290 0.022

ICPMS mg/kg stdev. Reference mg/kg stdev.

Ca 261 35 278 26

Fe 39.1 1.2 41.5 4

Zn 22.4 1.8 22.2 1.7

Mn 16.3 1.0 16 1

Na 16.8 0.4 16.0 6.1

Al <15 BW 11.7 4.7

Cu 4.6 0.2 4.3 0.6

Ba 1.94 0.06 2.11 0.47

Rb 1.8 0.04 2 0.4

Se 1.17 0.02 1.23 0.09

Sr 1.16 0.07 1.19 0.09

Mo 0.6 0.03 0.7 0.12

Ni 0.17 0.02 0.17 0.08

Cd 0.09 0.01 0.11 0.05

Pb 0.020 0.009 0.023 0.006

Cr <0.05 0.023 0.009

V 0.024 - 0.021 0.006

Co 0.010 0.002 0.008 0.004

Hg <0.002 0.0004 0.0002

Applications – Food/Agriculture

(CRI-He)³⁵Cl¹⁶O,

34S¹⁶O¹H

• Matrix and trace elements measured in one run using the automatic detector attenuation

• Elements interferred by molecular ions are measured with CRI in collision mode using He

36

Applications – Analysis of Nanoparticles

Analysis of Silver (Ag) Nanoparticles

•

^The ‘number of signals’ is very dependent on the concentration.

However, if the concentration is too high you will get signal overlap of multiple nanoparticles

•

Silver NP (PLANO GmbH, Wetzlar) where measured with an aurora M90 ICP-MS using a sample introduction with micro- concentric nebulizer and Twister Cyclonic Spray Chamber (GE, Australia).

Important Parameters

•

The ‘Size’ of the particle determines the intensity of the signal

•

^The ‘Concentration’ defines the frequency of signals observed as number of peaks per minute

37

Applications – Analysis of Nanoparticles

Analysis of 5nm Ag NPs using different dwell times

•

A criticle parameter in ICP-MS analysis of NP is the Dwell Time. Although a dwell time of <500 µs would be preferable, the sensitivity for the 5 nm particles is not sufficient to get a required signal to noise ratio

Applications – Analysis of Nanoparticles

•

Single particle signals measured within 180 s were averaged.

•

If the NP are assumed to be spherical in shape, the volume increases by third power with the diameter (Dd³).

•

Therefore from 20 - 80nm (4³) is a 64 fold increase in volume of the particle..!

ICP-MS Signals of Silver NP with different diameter and concentration.

•

For Silver - good correlation between ‘Intensity and Particle Size’ can be demonstrated on the aurora M90 ICP-MS

Cd in Seawater (1/10 diluted)

40

Automated Aerosol Dilution

Minimizes sample preparation by extending matrix tolerance of ICP-MS

•

For samples containing 0.2 to 4% Total Dissolved Solids

• Eg. seawater contains ~3.5% TDS

•

In line dilution via detuning of nebulizer efficiency

& sheath gas dilution effect

•

Achieve 10-fold dilution without additional sample prep

•

Suitable for seawater, metals and mining, high TDS effluents

Aerosol Dilution-

One-Click Optimization - automatically

Auto-optimization progress

•

Automatic tuning routines optimize plasma and ion optic parameters for best sensitivity and low oxide and double charged formation

43

Typical Analysis Settings

0.1-0.3 L/min 0.8-1.1 L/min

More efficient nebulization

Low gas dilution

Aerosol Dilution Settings

0.8-1.1 L/min 0.1-0.3 L/min

Less efficient nebulization

High gas dilution

Followed by automatic

optimization of ion optic settings…….

44

Auto-Optimization of Aerosol Dilution

Pre-Programmed Dilution Settings

Low Dilution

5-fold dilution

Samples with ~1-2% TDS Metals and mining, effluents

High Dilution

10-fold dilution

Samples with ~2-4% TDS

• Seawater

5-fold reduction in oxide interferences

• Rare Earths

Ability to measure As and Se directly at masses 75 and 78

Other instruments need to add oxygen to measure masses 91 and 94

% Recovery of 10ug/L multi-element spiked into undiluted seawater

0%

100%

% Recovery 105% 109% 99% 109% 92% 95% 110% 101%

56Fe 75As 78Se 52Cr 59Co 68Zn 114Cd Pb

Seawater Analysis using Aerosol Dilution

Summary

All-digital Detection System

• Only detector to offer 10⁹ working range in pulse- counting (digital) mode

• No cross-calibration of digital-analog modes required

Unmatched Sensitivity

• High efficiency ion mirror

• Excellent detection limits

• Attractive to laser ablation

Simplified Interference Management

• Innovative Collision-Reaction Interface (CRI II)

• Removes interferences at plasma interface, not the ion beam

• Simplified setup and maintenance

Low Maintenance Design

• Hollow ion mirror design requires no cleaning

• No need for additional cleaning / replace of interference management technology

27.06.2012 46

Future article:

Atomic Perspectives Column:

Efficient Removal of Polyatomic

Spectral Interferences for the Multielement Analysis of Complex

Human Biological Samples by ICP-MS

Spectroscopy 27 (7), pp 20-27, July 2012

Q&A