scp science - plasma test
TRANSCRIPT
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Maintaining and Assuringthe Performance of an ICP
Spectrometer: A QCApproach
SCP SCIENCE
Presented by: Art Ross, Director of Research and Development
SCP SCIENCE
Authors: David Smith, Quality Assurance Manager, and
Art Ross, Director of Research and Development
SCP SCIENCE
Member of CRMMA
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Abstract
Todays need for continuous accuracy and
demonstration of analytical competence has
created the need for the periodic checking of
ICP spectrometer performance.Monitoring selected critical instrument
parameters and taking appropriate corrective
action can prevent operational and
mechanical problems that will lead toanalytical errors and instrument downtime.
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References
Jean-Michel Mermet and Emanuelle Poussel
ICP Emission Spectrometers: 1995
Analytical Figures of Merit.Goal was to establish performance criteria to
select the best ICP instrument for the
analytical requirements.
We adapted the criteria to provide a Quality
Control tool for ICP spectrometers.
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Quality Control Tests
Monitoring critical instrument parameters like;
Warm up time
Long term stability Resolution
Repeatability
Plasma robustness
Signal to noise ratio Raw count verification
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General
ICP Spectrometer used:
Model: Spectro Ciros Vision EOP (2004)
Software: Smart Analyzer ver. 1.50.0534
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General
Operating Conditions: Power of Plasma: 1400w
Argon flow rates:
Coolant: 14 l/minAuxiliary: 1 l/min
Nebulizer flow: 0.99 l/min
Nebulizer type: Spectro Cross flow
Spray chamber: Scott
Sample introduction: Peristaltic pump
Note: It is important to maintain the same instrument operating conditionsfrom one test to the other to permit comparison between results. Ifchanges occur, they are to be noted.
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Warm-up time (Short-term stability)
Purpose: Time required for ICP to becomesufficiently stable for quantitative analysis.
Method: Relative Standard Deviation (RSD)of 5 integrations on 4 sets of data
Ar (I) 404.442
10 ppm Ba (II) 455.403
10 ppm Zn(II) 206.200 difference in intensity between subsequent sets is
within +/-1% for all three lines.
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Warm-up time (Short-term stability)
Frequency: Quarterly
Possible causes for poor or varyingresults:
Sample introduction sytem;
Environmental conditions;
Recirulating cooling system Possible electronic instablity
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Warm-up time (Short-term stability)
Results
60 very poor
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Warm-up time (Short-term stability)
Corrective Action:
Verify sample introduction system
Cleanilness of sample introduction system
Pump tubing,
Draining of spray chamber,
Pulsation of nebulizer,
Monitor room temperature for fluctuations;
Verify chiller is working correctly
Clogged fliters on cooling system
Cooling filters on instrument
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Warm-Up Time (minutes)
0
2
4
6
8
10
12
14
16
Nov-05
Dec-05
Jan-06
Feb-06
Mar-06
Date
TIme(Minutes
)Action taken: Cleaned
torch, changed tubing andcleaned nebulizer.
Warm-up time (
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Long-term stabilityPurpose: To monitor analytical drift overtime to minimize required recalibration or
restandardization.Method: Comparison of RSD on 5 sets of 10integrations at 0, 30, 60, 180, 300 and 480minutes.
Ar (I) 404.442
10 ppm Ba (II) 455.403 10 ppm Zn(II) 206.200
Frequency: Quarterly
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Long-term stability
Results
5% very poor
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Long-term stability
Corrective Action: Verify sample introduction system - specifically
the nebulizer: Worn out pump tubing
Salting on the tip of injector; Devitrefication of torch
Temperature fluctuations in room temperaturefor non heated optics
If argon RSD values are unstable, verify Argonsupply Pressure variations; Purity; Faulty regulator;
Freezing of liquid cylinder.
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Long-term stability
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Dec-05 Jan-06 Feb-06 Mar-06
Month
%RSD
Ar (I)
Ba (II)
Zn (II)
Long-term stability (2 to 3 %)
Leak detected in valve on argon supplyline which caused inconsistent pressure.
Valve replaced.
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Resolution
Purpose: To determine wavelength resolution.Better resolution means less spectral interference andbetter Signal to Background Ratio (SBR).
Frequency: YearlyMethod: Profile analysis of Ba(II) 230.424 nm.Width of the peak at 1/2 its height in nanometers.
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Resolution
Result
Compare to manufacture specification
Possible causes for poor or varying results:
Problems with system optics; Ambient temperature variations in lab.
Corrective Action:
Verify optical viewing position.
Monitor room temperature
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Repeatability
Purpose: To monitor instrumentprecision.
Method: RSD of 15 consecutivereadings of Mg(I) 285.213 nm.
Frequency: Monthly
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RepeatabilityResults Simultanously
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Repeatability
Corrective Action:
Verify sample introduction
blockages in nebulizer;
Worn-out pump tubing.
Voltage line stabilizer.
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Repeatability
0.000
0.100
0.2000.300
0.400
0.500
0.600
0.700
0.800
12/5/200
5
12/12/20
05
12/19/20
05
12/26/20
05
1/2/20
06
1/9/20
06
1/16/200
6
1/23
/200
6
1/30
/200
6
2/6/20
06
2/13/200
6
2/20
/200
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/200
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Date
%
RSD
Repeatability (0.5 to 0.8%)
Verification and replacement of pumptubing.
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Plasma Robustness
Purpose: To monitor sensitivity tomatrix effects.
Method: Net line intensity ratio ofMg(II) 280.270 nm and Mg(I) 285.213nm.
Frequency: Quarterly
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Plasma Robustness
Results
> 10 Excellent (low sensitivity to matrix
effects) 10 to 8 Very Good
8 to 6 Good
6-4 poor
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Plasma RobustnessPossible causes for poor or varyingresults:
Plasma power; Optical viewing position.
Corrective Action: Optimize plasma power;
Position of torch in load coil;
Check for load coil deformation.
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Plasma Robustness
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
Nov-05 Dec-05 Jan-06 Feb-06 Mar-06
Date
Rat
io
Plasma Robustness (6.0 to 8.0)
Results very stable. No
action required.
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Signal to Background Ratio
Purpose: To verify total instrumentoptimization and ensure detection limits
are optimal.Method: Ratio of 15 readings taken ofblank at 231.604 nm and Ni(II) at
231.604 nmFrequency: Monthly
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Signal-Background Ratio
Results
>30 Excellent
30 to 20 very good
20 to 10 good
10 to 2 poor
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Signal-Background RatioPossible causes for poor or varyingresults:
Improper torch alignment with optical interface; Nebulizer flow.
Corrective Action:
Optimization of torch with the optical interface;
Optimize nebulizer flow.
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Signal to Background Ratio
8.0
10.0
12.0
14.0
16.0
18.0
20.0
22.0
11/29/20
05
12/6/200
5
12/13/20
05
12/20/20
05
12/27/20
05
1/3/20
06
1/10/200
6
1/17/200
6
1/24
/200
6
1/31
/200
6
2/7/20
06
2/14/200
6
2/21
/200
6
2/28
/200
6
Date
Rati
o
Signal to Background Ratio (10 to 20)
Adjust torch position.
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Raw Count Verification
Purpose: To monitor intensitystability.
Method: 10 intensity readings taken of26 elements at specified wavelengths.10 ppm for all except K (100 ppm) and
Si (5 ppm).Frequency: Monthly
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Raw Count Verification
Possible causes for poor or varyingresults:
Degradation of torch and/or injector;
Clouding over of optical interface;
Torch position;
Nebulizer flow rate
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Raw Count Verification
Corrective Action: Clean or replace torch and/or injector; Clean optical interface; Optimize torch position;
Optimize nebulizer flow.
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Mg
8.0E+07
9.0E+07
1.0E+08
1.1E+08
1.2E+08
1.3E+08
1.4E+08
6/22
/05
7/22
/05
8/22
/05
9/22
/05
10/22/05
11/22/05
12/22/05
1/22
/06
2/22
/06
Raw Count Verification (results)
Clean torch and injector.
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ConclusionEasily self-managed by any lab technician
Allows lab manager to predict when routine maintenance isrequired.Tests take between 5 and 30 minutes Long term stability requires 90 minutes over 8 hours
Good ROI for preventing down timePredicts when system is ready to use i.e. Warm up time
Can be use to suggest frequency of Preventative MaintenanceNon specific to manufacture of instrument
Also available for ICP-MS
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Conclusion
SCP SCIENCE offers necessary documentation andsolutions with PlasmaTEST. PlasmaTEST is
available for both ICP-AES and ICP-MS.
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Questions?
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