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

Transcription

1 High Sensitivity ICP-MS: Overcome the problem of complex samples Meike Hamester, Andrew Toms and René Chemnitzer Bruker Daltonics Berlin, Germany - Milton, Canada

2 Historical Product Roadmap Introduced world s most sensitive ICP-MS (Varian) Introduced model 810 and 820 using CRI technology (Varian) Bruker acquires Varian ICP-MS Bruker launches aurora M90, world s most sensitive ICP-MS

3 aurora M90: combining highest sensitivity with selectivity 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

4 Benefits and side benefits of high sensitivity 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 high sensitivity for laser ablation lower detection limits for LC / GC coupling low detection limits for spectrally interferenced analytes low laser energy lower detection limits for elemental species (As, Sn, Br ) accurate results at lowest concentration levels higher spatial resolution lower detection limits in solid samples simpler procedures, less sample volume

5 The Bruker aurora M90 ICP-MS Multi Patented Technology by Bruker Daltonics 5

6 Sensitivity: Reflecting Optics concept DE energy spread Parabolic mirror 3D control 90 degree Reflection concept for ions F 9 Be ~ 0.5eV 115 In ~ 2eV 232 Th ~ 5eV All ions are focused into quad entrance

7 Sensitivity: Ion Mirror for ICP-MS Four electrode segments to provide 100% multidimensional control of the ion beam by mean of parabolic field shaping unwanted particles Hollow structure allows photons, neutrals, & particles to pass straight through to pump electrostatic field MS quad

8 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

9 Sensitivity and Selectivity: CRI Interface and 90 Degree Reflecting Ion Optics To detector for measurement Ions Neutrals 7 Photons 6 4 Removed by vacuum system Ion Mirror Kinetic Energy Discrimination

10 Selectivity: Collision-Reaction Interface CRI (II) Benefits One-button interference management Auto-optimization Fast switching between gases Low maintenance No extra consumables Uses He and (H 2 ) gasses Collisional / Reactive He to remove 16 O 35 Cl + on 51 V + H 2 to remove 40 Ar + on 40 Ca + CRI cone gas Skimmer Cone Original plasma jet Interference Exponential reduction New, clean Plasma expansion gas 10

11 Typical aurora M90 performance: Normal Sensitivity and High Sensitivity modes Nebulizer: concentric glass, 400 L/min Spraychamber: scott-type, glas Normal Mode High Sensitivity Mode (1) High Sensitivity Mode (2) 9 Be (cps/ppb) Co (cps/ppb) In (cps/ppb) U (cps/ppb) cps 1 cps 2 cps CeO+/Ce+ 0.9 % 0.7 % 3.3 % Ba++/Ba+ 0.9 % 1.9 % 1.4%

12 Computer Modeling -Normal Mode Ion beam focus Y dimension control Normal Focus point lifted up Ion beam diffused 3 mm focus Sensitivity attenuated 12

13 Computer Modeling - High Sensitivity Ion beam focus Y dimension control High Ion beam focus on entrance of Quadrupole Ion beam focus: 1mm 13

14 Sensitivity: Uranium (high sensitivity mode: Ion beam in focus) cps/ppb 238 U

15 Sensitivity: Beryllium in Urine 9 Be in Urine Dilution 1:10 MDL: 0.3 ppt

16 Gadolinium Gadolinium compounds are used as contrast agents in medical checkups as they intensify differences in density between different types of tissues They are used for: conventional diagnostic radiology angiography computed tomography (CT) magnetic-resonance-tomography (MRT) 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

17 Gadolinium in densely populated areas of Berlin 17

18 Sensitivity: Detection of Gadolinium ( 158 Gd) cps/ppb Gd ( 158 Gd)

19 Selectivity: Typical Interference: 40 Ar 35 Cl interference on 75 As 19

20 Reducing CaO (and ArO) interference on Fe

21 Sensitivity [cps/ppb] Sensitivity: Different CRI Modes Co Normal Sensitivity CRI no gas Normal Sensitivity CRI He High Sensitivity CRI no gas High Sensitivity CRI He cps/ppb

22 BEC [ppt] Sensitivity and Selectivity: BEC: Different modes of operation (all CRI Interface) ppm Ca 59 Co NS NS & Ca NS & Ca & He HS HS & Ca HS & Ca & He BEC [ppt]

23 Bruker aurora M90 ICP-MS: combining highest sensitivity with selectivity Normal Sensitivity Mode Ion beam de-focused Sensitivities > cps / ppb CRI II interface utilizing He and H 2 for interference reduction High Sensitivity Mode Ion beam in focus Sensitivities > cps / ppb CRI II interface for interference reduction Sensitivities > cps / ppb in He mode Many other features Plasma generation, all digital detector, automated aerosol dilution.

24 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

25 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

26 26 Detector Technology in the Bruker M90 Quadrupole e + - e - e - e - Signal Output 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

27 How a Detector Works Discrete Dynode Electron Multiplier (DDEM) Quadrupole e + - e - e - e - Signal Output 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)

28 Conventional ICP-MS Detectors the Problem Quadrupole e + - e - e - e - Signal Output Traditional ICP-MS detectors will saturate once they reached a few million counts/sec 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

29 Conventional ICP-MS Detectors -the Solution? Quadrupole e + - e - e - e - Signal Output To overcome this limitation, the dual-mode or pulseanalog detector was developed 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

30 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

31 31 Schematic of Detector Operation Quadrupole Gain Controlled e + - e - e - e - Signal Output Ion to e - Conversion Amplification V Control 4 th Dynode 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

32 Bruker All Digital Detector Easy Fast - Stable Unique to Bruker Long lifetime due to gain control protection > 10 9 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 32

33 Bruker ICP-MS Detector Short and Long Term Stability Detector attenuation factors were re-measured/recalibrated 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 Pb % 2.34% Th % 2.56% U % 2.4%

34 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: /2010GC

35 Applications Food/Agriculture 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 NIST 8436 Durum Wheat Flour A Joint Material of Agriculture Canada and NIST NIST 1515 Apple Leaves Standard Reference Material ICPMS wt.% stdev. Reference wt.% stdev. Ca Mg K ICPMS µg/g stdev. Reference µg/g stdev. Al AS Ba B Cu Pb Mn Hg Mo Ni Se Na Sr V Zn (CRI-He) 35 Cl 16 O, 34 S 16 O 1 H ICPMS wt.% stdev. Reference wt.% stdev. K Mg P ICPMS mg/kg stdev. Reference mg/kg stdev. Ca Fe Zn Mn Na Al <15 BW Cu Ba Rb Se Sr Mo Ni Cd Pb Cr < V Co Hg <

36 Applications Analysis of Nanoparticles Analysis of Silver (Ag) Nanoparticles Silver NP (PLANO GmbH, Wetzlar) where measured with an aurora M90 ICP-MS using a sample introduction with microconcentric nebulizer and Twister Cyclonic Spray Chamber (GE, Australia). Important Parameters The Size of the particle determines the intensity of the signal 36 The Concentration defines the frequency of signals observed as number of peaks per minute 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

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 37

38 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 (Dd 3 ). Therefore from 20-80nm (4 3 ) 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

39 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 40

41 Aerosol Dilution- One-Click Optimization - automatically

42 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 More efficient nebulization L/min Aerosol Dilution Settings L/min Low L/min gas dilution L/min High gas dilution Less efficient nebulization 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 44

45 Seawater Analysis using Aerosol Dilution 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 100% 0% 56Fe 75As 78Se 52Cr 59Co 68Zn 114Cd Pb % Recovery 105% 109% 99% 109% 92% 95% 110% 101%

46 Summary Unmatched Sensitivity High efficiency ion mirror Excellent detection limits Attractive to laser ablation All-digital Detection System Only detector to offer 10 9 working range in pulsecounting (digital) mode No cross-calibration of digital-analog modes required 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

47 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

48 Q&A