SCP Science - Plasma Test

7/27/2019 SCP Science - Plasma Test

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Maintaining and Assuringthe Performance of an ICP

Spectrometer: A QCApproach

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Presented by: Art Ross, Director of Research and Development

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Authors: David Smith, Quality Assurance Manager, and

Art Ross, Director of Research and Development

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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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Frequency: Quarterly

Possible causes for poor or varyingresults:

Sample introduction sytem;

Environmental conditions;

Recirulating cooling system Possible electronic instablity


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Results

60 very poor


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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



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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

6

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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.



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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

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1/24

/200

6

1/31

/200

6

2/7/20

06

2/14/200

6

2/21

/200

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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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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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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

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1/22

/06

2/22

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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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