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High Throughput Metal Analysis using a Modern ICP and Spark Ablation Accessory A. Clavering, G. Buchbinder, N. Verblyudov, F. Bulman Rio Symposium, Sept 2008 High Purity Metals Analysis by ICP-OES with Spark Ablation We will look at: Background of these analyses

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high throughput metal analysis using a modern icp and spark ablation accessory

High Throughput Metal Analysis using a Modern ICP and Spark Ablation Accessory

A. Clavering, G. Buchbinder, N. Verblyudov, F. Bulman

Rio Symposium, Sept 2008

high purity metals analysis by icp oes with spark ablation
High Purity Metals Analysis by ICP-OES with Spark Ablation
  • We will look at:
    • Background of these analyses
    • Some common problems with metals analysis
    • Analytical considerations for high purity metals (Ag and Pb) by a variety of Atomic Spectroscopy techniques
    • High Purity Silver and Lead Analysis by ICP-OES with Spark Ablation
    • Further research for the future
background where are the results from
Background – where are the results from?
  • Pure silver analysis - Kolyma State Refinery, in the Magadan region of Russia, utilise an iCAP 6500 Duo ICP with Solid Sampling Excitation Accessory (SSEA) for the analysis of silver – the SSEA/iCAP combination replaced their DC Arc Atomcomp 2000. The silver results presented here are part of their daily routine analysis for plant control and final product evaluation.
  • Pure lead analysis - Thermo Cambridge was requested to undertake a short feasibility study to determine whether the iCAP with SSEA accessory was capable of determining low-levels of impurities (down to a MDL of 0.1ppm in solid, Ni and Te) in pure lead for a manufacturer.
problems with metal analysis by atomic spectroscopy
Problems with metal analysis by Atomic Spectroscopy
  • DC Arc analysis
    • (solid sampling) is sensitive and can determine low-level impurities in solid silver
    • Matrices containing even small quantities of Se and Te in Ag may show errors
    • Lower grade silver also shows errors.
    • Pb analysis may show similar problems to Ag – elemental volatility?
slide5

Problems with metal analysis by Atomic Spectroscopy

  • Flame AA and ICP-OES are suitable for metal analysis – precious metal bullion, lower grade metals and base metals
  • ICP is probably most suited due to multi-element capabilities, reduced matrix effects, and better sensitivity. But…
  • Problems always exist – most notably with solution chemistry
slide6

Problems: Pb and Ag analysis by Atomic Spectroscopy

  • Not all impurities will dissolve in nitric acid – possible filtration and separate treatment for insolubles – more time consuming
  • Solubility product for chlorides and silver is very low – limited solubility for AgCl when trying to dissolve with Aqua Regia – filtering may be necessary
  • Some impurities may co-precipitate – either a complexing agent is required or excess Cl- addition – impurities may still be lost
  • In Ag and Pb, elements like Sn are a problem – quite often involve procedures with hydrofluoric acid!!
the benefits of solid sampling by spark ablation
The Benefits of Solid Sampling By Spark Ablation
  • Remove most sample preparation time
    • Minimal sample preparation time is needed to prepare the “dip” sample
    • Metal sample surface only needs to be lathed – a quick and simple operation
  • The amount of sample consumed is small
    • Precious metals being expensive – minimised consumption of a sample is preferred. Spark ablation requires only small quantities of sample.
    • Metal CRMs are also expensive – may be reused many times over.
  • Spark ablation produces a much larger sampling relative to Laser ablation – thus making it ideal for bulk and solid metal sampling whereas Laser Ablation is better suited for samples which require analysis at precise locations and non-conductive samples.
icap icp coupled with ssea
iCAP ICP coupled with SSEA
  • SSEA – Separate Sampling and Excitation Accessory
  • A spark ablation system which will ablate any conductive sample to a dry metal vapour
  • The aerosol is passed directly into the ICP with an argon carrier gas
  • Normal ICP process occurs with atomisation, excitation, emission and analysis
  • The iCAP 6000 Series couples and communicates through iTEVA software
slide10

Ag Analysis: Kolyma State Refinery, Russia

Spark Ablation is an approved standard method of analysis per the Russian Standards governing body GOST

sampling quantity sample prep
Sampling Quantity / Sample Prep

At Kolyma, they ablate the silver sample and directly transfer the metal vapour into the base of the plasma torch – no other sample introduction components

ssea coupling to an icap
SSEA Coupling to an iCAP
  • ICP can directly couple to the SSEA carrier gas line or a custom-built dual nebuliser chamber can be used for rapid changeover between liquids and solids
icp oes plasma viewing
ICP-OES Plasma Viewing
  • Radial View of the Plasma – Robust, fewer chemical interferences
  • Axial View of the Plasma – best sensitivity, lowest detection limits
    • Do we improve signal to background ratios with complex spectra?
  • SSEA is commonly coupled to an iCAP Radial ICP but an iCAP Duo can also be used – radial view is useful
  • Silver and lead are not spectrally rich and signal to background is improved with the axial view
instrumental parameters ag and pb comparison
Instrumental Parameters - Ag and Pb comparison
  • Parameters of ICP - Pb
    • RF forward power – 1300 watts
    • Coolant gas flow – 12 L/min
    • Auxiliary gas flow – 1.0 L/min
    • Integration time – 30s maximum
  • Parameters of SSEA – Pb (MP 327)
    • Power level – 1
    • Frequency – 800 Hz
    • Spark Gap – 2 mm
    • Pressure in delivery line – 18 psi
  • Parameters of ICP – Ag
    • RF forward power – 1150 watts
    • Coolant gas flow – 12 L/min
    • Auxiliary gas flow – 0.5 L/min
    • Integration time – 30s maximum
  • Parameters of SSEA – Ag (MP 961)
    • Power level – 3
    • Frequency – 500 Hz
    • Spark Gap – 2 mm
    • Pressure in delivery line – 18 psi
  • Samples were lathed and ensured that the surface was smooth – the SSEA’s o-ring seal ensures no air ingress
  • Total Analysis time per sample

< 5 mins including sample change

instrumental parameters ag calibration curves
Instrumental Parameters: Ag – Calibration curves
  • Pd 340.458 nm calibration curve on the right (State Kolyma Refinery, Russia) shows a correlation coefficient of six 9s
  • Ordinarily the calibration is better than three 9s or not accepted
instrumental parameters pb calibration curves
Instrumental Parameters: Pb – Calibration curves
  • Bi 223.061nm (Thermo Cambridge, the wilds of England) shows a correlation coefficient of 0.9994.
  • Ordinarily the calibration was better than three 9s.
problems and further research
Problems and Further Research
  • Problems:
    • Lead analysis shows response or detection limits of some elements to be inconsistent with normal ICP sensitivities – Se, Cu, Na.
    • SSEA parameters are sometimes constrained by physical properties of the metals.
    • Te and Ni results comparison between OE Spark and SSEA were somewhat inconsistent on some samples.
  • Further work:
    • Categorise further materials – e.g. pure copper, “hard” alloys.
    • Research the effect of other carrier gases – helium, nitrogen – helium is already known to boost Laser sensitivity significantly
    • Alternate spray chamber conditions – using a continuous spray of a dilute acid(s) – reduces background but will it improve DLs in some applications?
high throughput metal analysis using a modern icp and spark ablation accessory23

High Throughput Metal Analysis using a Modern ICP and Spark Ablation Accessory

A. Clavering, G. Buchbinder, N. Verblyudov, F. Bulman

Rio Symposium, Sept 2008