ICP-OES. By: Dr. Sarhan A. Salman

Transcription

1 ICP-OES By: Dr. Sarhan A. Salman

2 AGENDA -- ICP-OES Overview - Module removal Optical components and gas control overview Module replacement --Continue module replacement Manual optical alignment --Precise optical alignment Accessories overview -- Installations Diagnostics and fault finding Preventative maintenance -- PC Software

3 SITE DETAILS Fire exits Toilets No smoking Whole site Includes car park! There will be regular breaks Mobile phones off please

4 ICP-OES SPECTROSCOPY WHAT IS IT? The Periodic Table our common language H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lw Standard elements Possible but not practical due to high background levels Not measurable Unstable elements Rare gases

5 THEORY OF ATOMIC SPECTROSCOPY E n e r g y Excited states Ground state Atom 1 Atom 2 E n e r g y Each different type of atom has a unique set of energy states. Atoms usually exist in their ground state but may be raised to the excited states by applying energy. Energy is supplied as heat in a plasma.

6 ATOMIC EXCITATION AND EMISSION Heat Light

7 HEAT SOURCE Argon Plasma Radio Frequency Power 1-2 KW 27 Mhz RF frequency Electric spark starts plasma

8 PLASMA TORCH COMPONENTS Coolant Gas Auxiliary Gas Sample Carrier Gas

9 PLASMA TEMPERATURE ZONES 6000 k 6500 k 7000 k 8000 k k observation region (mm) TEMPERATURE ~ 2 x NITROUS OXIDE ACETYLENE FLAME RESIDENCE TIME ~ 2mS HIGH CURRENT DENSITY AT OUTER SURFACE GIVES DOUGHNUT-SHAPED PLASMA sample 0 DOUGHNUT SHAPE IMPROVED BY OPTIMISING SAMPLE CARRIER GAS FLOW

10 CONCENTRIC NEBULISER Used for solutions with low dissolved solids and low particulates Other options for different samples

11 RADIAL PLASMA Advantages: mimimum interferences Additional light from backlight mirror Better detection limits for complicated matrices Disadvantages: increased background continuum from the Argon plasma Relative short sample path length

12 AXIAL VIEWING Axial viewing of the central channel, encompasses all 3 (4) zones Advantages: long light path minimum Argon background Disadvantages: more interferences

13 TYPICAL ICP EMISSION SPECTRUM

14 SIMULTANEOUS OPTICS ECHELLE 46.5 degree blaze, 54.5 grooves/mm, echelle grating CID x 14.3 mm 17.5 degree quartz prism 381 mm focal length toroidal camera mirror 381 mm focal length spherical collimating mirror 53 mm entrance aperture 1:1 imaging monochromatic emission falls on 3 by 3 pixels

15 READOUT SUBARRAY CID

16 SPECTRAL VIEW 800 nm 740 nm 178 nm 177 nm Emission lines appear as spots of light

17 IRIS INTREPID SYSTEM OVERVIEW Data Station IRIS/Intrepid CPU Detection and Acquisition Electronics Plasma Control Electronics Optical System (Echelle Spectrometer) Autosampler Sample Introduction System RF Generator Pneumatic System (Gas Flows)

18 WATER CIRCUIT Water: > Camera cooling > RF coil cooling

19 PNEUMATIC CIRCUIT

20 RF BLOCK DIAGRAM RF Source Driver Amplifier Power Amplifier Bias sense DAGC Signal+ Bias Drive DAGC Signal- RF Pass RF Shunt -AGC (RF Detector) Anode Return Reflected Power (Phase) Loop RF Setpoint Caution lethal voltages DA/PA Feedback Switch Anode I Sense (Cathode Bias Board) Plasma Section Control Board

21 OPTICAL COMPONENTS the lens the slits the mirrors the prism the grating the detector

22 OPTICAL COMPONENTS: THE LENS the Intrepid II uses a single focusing lens (not an achromatic lens) focusing is done on low (UV) wavelengths only (better performance on critical elements) a focusing mirror always works better!

23 OPTICAL COMPONENTS: THE PRISM dispersion is non-linear with wavelength (resolution at high wavelengths is significantly lower than at the low end of the spectrum).

24 OPTICAL COMPONENTS: THE DIFFRACTION GRATING blaze angle d q r third order second order l1 first order l2 second order first order the diffraction angle r is a function of d, q and l d between 1200 and 3600 grooves/mm orders are overlapping; resolution increases with orders the blaze angle is selected to maximize first/second order

25 OPTICAL COMPONENTS - THE ECHELLE GRATING d grating substrate an Echelle grating is coarse (52.6 grooves/mm on the high resolution IRIS/Intrepid at 64.1 degrees blaze angle) and is used at high angles in high diffraction orders orders used are from 30 to 200, heavily overlapped

26 THE ECHELLE SPECTRUM Effect of the grating (overlapping high orders) nm order nm order nm order 50 Effect of the prism (cross-dispersion) 200 nm 400 nm 800 nm

27 THE GRATING Ca {105} Cu {103} Ba {68} Na {57} V {115} K {44} 33725

28 THE ECHELLE SPECTRUM order 44 order 57 order 68 order 103 order 105 order 115 The prism separates the orders at the same first order wavelength two different wavelengths must be of different orders!

29 THE ECHELLE SPECTRUM MULTIPLE ORDERS

30 COVERING THE ENTIRE WAVELENGTH RANGE Visible Slit Off-axis slit Slit 2 UV Slit On-axis slit Slit 1 Coverage of the desired wavelength range is achieved by using a secondary slit. A periscope assembly placed in front of slit 1 redirects the light through slit 2, 9 mm off-axis. Shifting the location of the entrance slit shifts the spectrum position in respect to the detector.

31 COVERING THE ENTIRE WAVELENGTH RANGE

32 SAMPLE INTRODUCTION INTERFACE Several configurations Consists of: Sample probe Tubing Pump Nebuliser Spray chamber Torch Most likely area for problems