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FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL PROFILING AND EVALUATION OF HOMOGENEITY IN SODA- LIME CONTAINER GLASS Karen J. Harrington.

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Presentation on theme: "FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL PROFILING AND EVALUATION OF HOMOGENEITY IN SODA- LIME CONTAINER GLASS Karen J. Harrington."— Presentation transcript:

1 FORENSIC APPLICATIONS OF LA-ICP-MS: ELEMENTAL PROFILING AND EVALUATION OF HOMOGENEITY IN SODA- LIME CONTAINER GLASS Karen J. Harrington

2 Inductively Coupled Plasma 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

3 Laser 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

4 Homogeneity 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?

5 Previous Research on Homogeneity – 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

6 Homogeneity 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

7 Project 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?

8 Background – 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

9 Background – Stage II Determine normal/natural manufacturer variability – Hourly runs – Daily runs – Simultaneous/daily for multiple furnaces

10 Method – 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

11 Method – 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.

12 Method – 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

13 Method – Instrumentation Perkin-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. 4 th Quarter – 20.

14 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 I

15 Comparison AreasDistinguishable Elemental Profiles Indistinguishable 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

16 Results – Stage I Comparison AreasDistinguishable Elemental Profiles Indistinguishable 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

17 Results – Stage I Comparison AreasDistinguishable Elemental Profiles Indistinguishable 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

18 Results – Stage I Comparison AreasDistinguishable Elemental Profiles Indistinguishable 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

19 Results – Stage 2 (hourly) Comparison AreasDistinguishable 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.

20 Results – Stage 2 (hourly) Comparison AreasDistinguishable Elemental Profiles Indistinguishable elemental profiles 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 Ratios Sr/Zr Na/Al Ca/Mn Zn/Rb Fe/Cr Ba/Pb Ni/V Ti/Li Ca/Nd Sn/La Mg/Cu As/Y Hf/Th Sb/Pr U/Ta Group 1 0 (0) 8 (4) 0 (0) Group 2 6 (0) 0 (0) 1 (0) 0 (0) 5 (2) 0 (0) Group 1 vs. Group 2 0 (0) 1 (1) 0 (0) 1 (0) 0 (0)

21 Results – Stage 2 (daily) Comparison AreasDistinguishable Elemental Profiles Indistinguishable elemental profiles 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

22 Results – Stage 2 (daily) Comparison Areas Distingui shable Elementa l Profiles Indistingui shable 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. Table 4 – 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 Ratios Sr/Zr Na/Al Ca/Mn Zn/Rb Fe/Cr Ba/Pb Ni/V Ti/Li Ca/Nd Sn/La Mg/Cu As/Y Hf/Th Sb/Pr U/Ta Group 3 30 (21) 5 (1) 3 (0) 15 (1) 0 (0) 22 (14) 0 (0) Group 4 1 (0) 0 (0) 1 (0) 33 (21) 0 (0) 17 (10) 0 (0) 8 (0) 1 (0) 0 (0) Group 5 2 (1) 0 (0) 14 (5) 50 (40) 1 (0) 34 (23) 0 (0) 19 (5) 0 (0) 16 (6) 0 (0)

23 Results – Stage 2 (simultaneous daily) Comparison AreasDistinguishable Elemental Profiles Indistinguishable elemental profiles 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

24 Results – Stage 2 (simultaneous daily) Table 5 – 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: 6 (15 comparisons) No. of distinguishable pairs Elemental Ratios Sr/Zr Na/Al Ca/Mn Zn/Rb Fe/Cr Ba/Pb Ni/V Ti/Li Ca/Nd Sn/La Mg/Cu As/Y Hf/Th Sb/Pr U/Ta Group 6 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)

25 Conclusion - 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

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

27 Conclusion – simultaneous daily 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.

28 Conclusion – significant information 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, (2001).

29 Final 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 days 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).

30 Future Research Multiple manufacturer studies Bottle distribution (cases, vendors) More effective statistical studies

31 Acknowledgments Sacramento County District Attorney Laboratory of Forensic Services and Staff Gallo Glass Company University of California, Davis: Forensic Science Masters program California Criminalistics Institute

32 Contact Information Karen Harrington


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