FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL PROFILING AND EVALUATION OF HOMOGENEITY IN SODA- LIME...

FORENSIC APPLICATIONS FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL OF LA-ICP-MS: ELEMENTAL

PROFILING AND PROFILING AND EVALUATION OF EVALUATION OF

HOMOGENEITY IN SODA-HOMOGENEITY IN SODA-LIME CONTAINER GLASSLIME CONTAINER GLASS

Karen J. Harrington

Inductively Coupled Plasma Inductively Coupled Plasma Mass Spectrometry (ICP-MS)Mass Spectrometry (ICP-MS)

Previous method of RI predominantly used Elemental analysis research began three decades

ago Allows classification of product type and use Shown to be a discriminating technique for forensic analysis

Drawbacks Dangerous digestions Sample size requirements Destructive nature

Laser ablation (LA)-ICP-MSLaser ablation (LA)-ICP-MS

A viable method for forensic glass comparisons

Creates aerosol of super-fine glass fragments– Advantages

Decreased sample prep. time Minimal sample consumption Maintains good sensitivity for most elements Less risk of contamination

HomogeneityHomogeneity

Are elements consistent within a glass item (micro-homogeneity)?– Natural heterogeneity (result of manufacturing)

Contamination, natural variation in raw material

How do elements vary between glass items?– Variation beyond natural fluctuation?

Previous Research on Previous Research on HomogeneityHomogeneity

– LA-ICP-MS does reveal small natural variations in glass

– Understanding homogeneity within a unit of glass is a factor when:

Comparing samples from same categorical sources Comparing samples from different manufacturers

HomogeneityHomogeneity

Glass items typically maintain some homogeneity overall

Glass of the same type can often be distinguished on an item-item basis

Glass bottles tend to be more variable and may not be distinguishable from each other within one manufacturer

Project GoalsProject Goals

How consistent are elemental profiles in glass bottles?

What are appropriate match-criteria to balance false positives and false negatives?

How variable are glass bottles within a manufacturer?

Background – Stage IBackground – Stage I

Verify valid set of match-criteria– Examine homogeneity of a single bottle– Determine what criteria allow for treatment of

bottle as a whole unit

Background – Stage IIBackground – Stage II

Determine normal/natural manufacturer variability– Hourly runs– Daily runs– Simultaneous/daily for multiple furnaces

Method – Sample SelectionMethod – Sample Selection

Gallo Glass Company, Modesto, CA Typical soda-lime, with cullet (25% recycled) Stage 1

– 10 bottles from two furnaces, variable time intervals, colors, types (3 fragments each from neck, sidewall, base regions of each bottle)

Stage 2– Hourly, daily, daily simultaneous furnace

Method – Analyte SelectionMethod – Analyte Selection

Analytes were selected from an acid digestion of selected bottles from the population.

Ratios were determined based on %RSD and mass-to-charge values.

Method – Comparison CriteriaMethod – Comparison Criteria

T-tests and ANOVA were found to be unacceptable for the purposes of this project.

Typical case-work match-criteria of ±2 SD was used

Method – InstrumentationMethod – InstrumentationPerkin-Elmer ELAN DRC II ICP-MS (a)New Wave Research Nd: YAG LA (1 =

213nm) unit (b)

a, b Dodds, A.J., Land, D.P., Pollock, E.M. Determination of Elemental Homogeneity in Automotive Windshields by LA-ICP-MS. The CACNews. 4th Quarter 2005. 17 – 20.

10 comparisons of multiple regions showed indistinguishable elemental profiles for 13 ratios with ± 2SD.

When ± 3SD was applied to Sr/Zr and Fe/Cr (the two consistently problematic ratios), all 10 bottles showed indistinguishable elemental profiles for 15 ratios.

Results – Stage IResults – Stage I

Results – Stage IResults – Stage IComparison Areas Distinguishable

Elemental ProfilesIndistinguishable elemental profiles

Inside Neck vs. Sidewall Inside Sidewall vs. Base Inside Base vs. Neck Outside Neck vs. Sidewall Outside Sidewall vs. Base Outside Base vs. Neck Neck vs. Sidewall, all Sidewall vs. Base, all Base vs. Neck, all Inside vs. Outside




Inside Neck vs. Sidewall, Ca/Mn

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

#1 #11

#23

#29

#34

#47

#58

#59

#70

#148

Sample #

Co

nc

en

tra

tio

n

Mean (iN)

Mean (iS)




Neck vs. Sidewall, Ca/Mn

0.01000.0

2000.03000.0

4000.05000.0

6000.0

Sample #

Co

nc

en

tra

tio

n

Mean (N)

Mean (S)




Inside vs. Outside, Ca/Mn

0.0

1000.0

2000.0

3000.0

4000.0

5000.0

Sample #

Co

nce

ntr

atio

n

Mean (i)

Mean (o)

Results – Stage 2 Results – Stage 2 (hourly)(hourly)

Comparison Areas Distinguishable Elemental Profiles

Indistinguishable elemental profiles

Group 1 – furnace 3 *Group 2 – furnace 2 *Group 1 vs. Group 2

* Group 1 (one bottle distinguishable for 1 ratio) and Group 2 (two bottles distinguishable for 3 ratios) show some distinguishable elemental profiles from other bottles.

Results – Stage 2 Results – Stage 2 (hourly)(hourly)



Group 1 – furnace 3 *Group 2 – furnace 2 *Group 1 vs. Group 2

* Group 1 (bottle # 38 for 1 element) and Group 2 (bottles #48 and #50 for 3 elements) show some distinguishable elemental profiles from other bottles.

Table 3 – Relative Discrimination Capabilities ±2 SD (±3 SD for Sr/Zr and Fe/Cr)Numbers in parenthesis = ±3SD (±4SD for Sr/Zr and Fe/Cr)

Number of Samples: 12/group (66 comparisons) No. of distinguishable pairs

Elemental RatiosSr/ZrNa/AlCa/MnZn/RbFe/CrBa/PbNi/VTi/LiCa/NdSn/LaMg/CuAs/YHf/ThSb/PrU/Ta

Group 10 (0)8 (4)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)

Group 26 (0)0 (0)1 (0)1 (0)0 (0)5 (2)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)

Group 1 vs. Group 20 (0)0 (0)1 (1)1 (1)1 (1)1 (1)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)1 (0)0 (0)

Results – Stage 2 Results – Stage 2 (daily)(daily)



Group 3 – 7/19/05 – 7/30/05 (after 5 days) *

Group 4 – 7/31/05 – 8/15/05 (after 8 days)

Group 5 – 8/9/05 – 8/21/05 (after 4 days)

* 1 bottle was indistinguishable from another that was manufactured 11 days later

Results – Stage 2 Results – Stage 2 (daily)(daily)

Comparison Areas

Distinguishable Elemental Profiles


Group 3 – 7/19/05 –

7/30/05

(5 days*)

Group 4 – 7/31/05 – 8/15/05

(8 days)

Group 5 – 8/9/05 – 8/21/05

(4 days)

* 1 bottle was only distinguishable from others that were 11 days or more apart.


Number of Samples: 12/group (66 comparisons) No. of distinguishable pairs


Group 330 (21)

5 (1)3 (0)

15 (1)0 (0)

22 (14)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)0 (0)

Group 41 (0)0 (0)1 (0)

33 (21)0 (0)

17 (10)0 (0)0 (0)0 (0)0 (0)0 (0)8 (0)1 (0)0 (0)0 (0)

Group 52 (1)0 (0)

14 (5)50 (40)

1 (0)34 (23)

0 (0)0 (0)0 (0)0 (0)0 (0)

19 (5)0 (0)

16 (6)0 (0)

Results – Stage 2 Results – Stage 2 (simultaneous daily)(simultaneous daily)



Furnace 1 vs. Furnace 2 Furnace 2 vs. Furnace 3 Furnace 3 vs. Furnace 1 Furnace 1 vs. Furnace 1 Furnace 2 vs. Furnace 2 Furnace 3 vs. Furnace 3

Results – Stage 2 Results – Stage 2 (simultaneous daily)(simultaneous daily)


Number of Samples: 6 (15 comparisons) No. of distinguishable pairs


Group 60 (0)0 (0)

13 (12)15 (12)12 (12)13 (12)

0 (0)8 (4)0 (0)8 (6)8 (8)2 (0)0 (0)

11 (8)0 (0)

Conclusion - hourlyConclusion - hourly

Bottles manufactured from the same furnace are typically not distinguishable when compared hourly

80 – 90% of bottles manufactured within a daily production lot from the same furnace share indistinguishable elemental profiles

Conclusion - dailyConclusion - daily

Bottles manufactured from the same furnace between 4 and 8 days apart (11 maximum) are typically distinguishable.

Conclusion – simultaneous Conclusion – simultaneous dailydaily

Bottles manufactured at the same time from different furnaces are distinguishable.

Additionally, some bottles manufactured at

the same time on two consecutive days from the same furnace may be distinguishable.

Conclusion – significant Conclusion – significant informationinformation

Supports previous research– Same case/six-pack are indistinguishable 1

– Indistinguishable profiles are typically from same manufacturer 2

Gallo Glass Company – Produces 800 cases/hour– 1 billion bottles per year

1 Trejos, T and Almirall, J.R. Sampling strategies for the analysis of glass fragments by LA-ICP-MS Part I. Micro-homogeneity study of glass and its application to the interpretation of forensic evidence. Talanta. 67(2) 388 – 395 (August 2005).

2 J.R. Almirall. Glass as evidence of association. In Mute Witness; When Trace Evidence Makes the Case, M. Houck (Ed.), Academic Press, San Diego, CA, USE, 139-155 (2001).

Final ConclusionsFinal Conclusions

Still important to collect/examine multiple fragments from question sample 1

Provides evidentiary value to forensic examinations– Can distinguish between furnaces of same

manufacturer– Can distinguish between bottles from the same

furnace after approximately 8-11 days1 Trejos, T and Almirall, J.R. Sampling strategies for the analysis of glass fragments by LA-ICP-MS Part I. Micro-homogeneity study of glass and its application to the interpretation of forensic evidence. Talanta. 67(2) 388 – 395 (August 2005).

Future ResearchFuture Research

Multiple manufacturer studies

Bottle distribution (cases, vendors)

More effective statistical studies

AcknowledgmentsAcknowledgments

Sacramento County District Attorney Laboratory of Forensic Services and Staff

Gallo Glass CompanyUniversity of California, Davis: Forensic

Science Masters programCalifornia Criminalistics Institute

Contact InformationContact Information

Karen Harrington

[email protected]

FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL PROFILING AND EVALUATION OF HOMOGENEITY IN SODA- LIME...

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