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 Page 3 October 21, 2013
Comparison of Elemental Analysis Techniques for Liquid Samples
Firstly, What is ICP-MS? An elemental analysis technique ICP - Inductively Coupled Plasma MS - Mass Spectrometer high temperature ion source decomposes, atomizes and ionizes the sample 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 ICP-MS combines the detection limits of Graphite Furnace AA (or better) and the sample throughput of ICP-OES Page 5 October 21, 2013
Simplified Schematic the functional components Sample Introduction Plasma Ion Source Ion lenses Collision/ Reaction Cell Quadrupole MS Detector 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 Nearly all modern ICP-MS instruments employ some form of Collision/Reaction Cell to remove polyatomic (molecular) interferences Page 6 October 21, 2013
General ICP-MS Components/Technology 1. The liquid sample is mixed with argon gas by the nebulizer to form an aerosol.. 3. The sample is desolvated and ionized in the plasma 5. Ion lenses focus and collimate the ions. The Omega lens bends the ion beam offaxis 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 2. The smallest droplets pass through the spray chamber and into the ion source - the plasma 4. Ions are extracted from the plasma by extraction lenses in the interface region 6. Interference Ions are removed from the ion path by reaction/collision/ked effects in the cell 8. Ions are measured using a discrete dynode detector providing 9 orders of linear dynamic range
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 1 Ext. 2
Principle of for removing polyatomic interferences He Mode and KED (Kinetic Energy Discrimination) Polyatomic ions Analyte ions Energy distribution of analyte and interfering polyatomic ions with the same mass Polyatomic ions Bias voltage rejects low energy (polyatomic) ions Analyte ions Energy Energy At cell entrance, analyte and polyatomic ion energies overlap. Energy spread of both groups of ions is narrow, due to ShieldTorch System Cell Entrance 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 Cell Exit 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) Page 11 October 21, 2013
Energy Discrimination Ionic Radii m / z 75 m / z 51 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 Approx Ionic Radii (pm) 300 250 200 150 100 50 0 As+ ArCl+ Simple Species V+ ClO+
Energy Discrimination Ionic Radii 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 Approx Ionic Radii (pm) 400 350 300 250 200 150 100 50 0 Anything larger than 150pm will be filtered out Cu S 2 m / z 65 SO 2 NOCl Complex Species ArMg CaOH
ORS 3 Reaction Mode Another tool for removing interferences 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 Reaction gas Reaction product ion On-mass interference Analyte Analyte Analyte and interfering ions enter reaction cell Interference M + MR + Interference reacts to form product ion Quad set to original analyte mass rejects interference product ion(s) Reactive interferences are converted to product ions at a new mass can be rejected by analyzer quad, which is set to original analyte mass
ORS 3 Reaction Mode Another tool for removing interferences 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 Reaction gas Original interfering ion On-mass interference Analyte Analyte and interfering ions enter reaction cell Analyte M + MR + Analyte reacts to form product ion Analyte product ion Quad set to analyte product ion mass rejects original interfering ions Reactive analyte is converted to product ions at a new mass interferences remain at original mass and are rejected by analyzer quad
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 O 2 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 ORS 3 Octopole Reaction System 3 rd 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 Acquisition mode(s) Sample introduction devices Sample uptake Interface Autosampler Agilent 7700x ICP-MS Hydrogen and High Energy Helium (HEHe) cell modes Glass nebulizer and 700 mm length capillary tube Quartz torch with 1.5 mm bore injector Natural aspiration Platinum sampling cone and skimmer cone 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 23 Na [ H2 ] 1.9% 1.2 24 Mg [ H2 ] 1.8% Normalized Concentration 1 0.8 0.6 0.4 0.2 0 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 ] 0 50 100 150 200 250 300 350 400 450 Elapsed time, min 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 10 B H 2 n. d. 920 16 25 1.5 5 n. d. 23 Na H 2 n. d. 19 n. d. 25 4.1 n. d. n. d. 24 Mg H 2 n. d. 5.2 3.6 37 6.6 2.6 n. d. 27 Al HEHe 0.4 8 n. d. 31 8.3 1.4 n. d. 40 Ca H 2 0.3 6.4 3 42 10 11 0.3 48 Ti HEHe 0.1 0.9 0.2 33 8.1 1.8 0.2 51 V HEHe 0.5 0.5 0.4 31 7.7 1.4 0.9 52 Cr HEHe 0.1 1.8 1.3 37 8 1.9 0.3 55 Mn H 2 0.3 2.6 1.3 36 8 2.2 0.4 56 Fe H 2 1.2 41 0.6 39 8.9 10 0.6 59 Co HEHe 0.2 1.1 0.1 0.9 0.3 0.2 0.4 60 Ni HEHe 0.4 2 0.9 30 6.4 1.9 0.1 63 Cu HEHe 2.1 14 4.8 41 7.4 2.8 0.5 66 Zn HEHe 58 78 8.2 35 52 250 3.6 95 Mo HEHe 0.1 0.6 0.2 31 6.9 1.5 0.3 107 Ag HEHe 0.1 4.7 0.1 27 6.8 1.5 0.2 114 Cd HEHe 0.1 12 0.5 30 6.4 1.5 0.3 118 Sn HEHe n. d. 610 3.8 36 7.4 2 0.2 138 Ba H 2 0.9 0.2 0.1 30 8.4 17 0.4 208 Pb 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 H 2 0.85 2.1 Na 23 H 2 0.79 1.9 Mg 24 H 2 0.18 2.5 Al 27 He 0.03 0.11 P 31 He 28 33 Ca 40 H 2 0.14 0.13 Ca 44 H 2 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 H 2 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 H 2 0.01 0.01 Pb 208 He 0.005 0.01 Concentration Measured (ppb) Recovery Spiked 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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