laser ablation icp-ms in forensic glass analysis: a decade ... laicpms pps.pdfla-icp-ms in forensic...

Session: New Developments and State of the Art in Trace Evidence Examinations

Laser Ablation ICP-MS in Forensic Glass Analysis: A Decade of Experience

BundeskriminalamtForensic Science Institute

Germany

KT13@bka.bund.de

LA-ICP-MS in Forensic Glass Analysis

1996 Trace Symposium San AntonioWilfried StoeckleinThe Forensic Analysis of Float GlassCharacterization of Glasses fromInternational Sources

LA-ICP-MS in Forensic Glass Analysis

The Forensic Analysis of Float Glass -Characterization of Glasses from International SourcesW. Stoecklein, 1996

Elemental analysis of 61 glasses of global origin(28 Europe, 19 U.S.A., 14 Japan)(38 colorless, 21 green, 2 brown)(13 producers, 7 countries)

Elemental analysis (ICP-MS, WDXRF)Determination of RI

LA-ICP-MS in Forensic Glass Analysis

The Forensic Analysis of Float Glass -Characterization of Glasses from International SourcesW. Stoecklein, 1996

Liquid digestion:0,5-2 mg of cleaned glass fragments (from bulk) +

hydrofluoric acid, nitric acid, perfluoric acid

Hot plate fuming to dryness

Resolvation with 5 % nitric acid containing Rh int. std

ICP-MS

LA-ICP-MS in Forensic Glass Analysis

The Forensic Analysis of Float Glass -Characterization of Glasses from International Sources

Results

10 % of the examined glasses were indistinguishable by RI.

Full differentiation of all glasses was possible by ICP-MS.

Selection of elements which proved highest discrimination.

Characterization of glass origin (Japan, U.S.A., Europe).

LA-ICP-MS in Forensic Glass Analysis

The forensic Analysis of Float Glass -Characterization of Glasses from International Sources

ConclusionQuantitative analysis of 30 elements by ICP-MS improves evidential value of glass examination.

LA-ICP-MS in Forensic Glass Analysis:

Laser Ablation

Lase

r

Glass

Lase

rLa

ser

Glass

Lase

r

carrier gas (He)

Plasma~7000 °C

carrier gas and sample MS

Total destruction & ionisation of the sample

LA-ICP-MS in Forensic Glass Analysis:

• Measurements possible on small samples

(~0,5 mm; ~ 0,02 in)

• No sample preparation (time saving)

• “Quasi non-destructive” analysis due to small sample

uptake

• No problems measuring on rough surfaces (as in µ-XRF)

• Quantitative analysis of 20 major, minor and

trace elements in one analytical run

Why LA-ICP-MS ?

History of instrumentation

1992 Installation of ICP-MS Fisions PQ2+

1996 Addition of UV-laser ablation system (1064 nm)

1997 Exchange of UV by Infrared laser ablation (266 nm)

2003 Replacement of old system with new LA-ICP-MS system (213 nm)

LA-ICP-MS in Forensic Glass Analysis

LA-ICP-MS in Forensic Glass Analysis:

ICP-MS Fisions PQ2+ IR-laser ablation VG Microprobe

LA-ICP-MS in Forensic Glass Analysis:

LA

MSICP -

• Until now SRM NIST 612 (50 ppm) is used for quantitative

analysis of float glasses

• Better results by using a standard:

• with the same matrix (composition of main elements)

• with concentration of trace elements in the same range

as typical float glass

Why matrix matched standards ?

both are not given by NIST 612

FGS 1 standard(low concentration)

d = 9 cmh = 8 cm

R&D Project BKA - SCHOTT AG:Development of new calibration standards

BKA-FGS 1:diameter: 10 mm thickness: 3 mm

R&D Project BKA - SCHOTT AG:Development of new calibration standards

NITECRIME activities on glass

• EU network project 2001-2005

• Main focus on float glass (highest forensic interest)

• Development of a protocol for glass analysis with LA-ICP-MS

• Evaluation of new calibration standards

Workpackage 3.1 Instrumental validation ETH Zürich

Two interlaboratory tests (3.1.1. & 3.1.2)

Workpackage 3.2 Glass BKA

Two interlaboratory tests (3.2.1 & 3.2.2)Introduction of new matrix matchted standards (FGS 1 & 2)

In total: Four interlaboratory tests dealing with glassThree interlaboratory tests with similar set-up

NITECRIME activities on glass

Instrument combinations:

193 nm

213 nm

266 nm

266 nm high power

Sector field ICP-MS

Quadrupole ICP-MS

Laser Ablation Mass spectrometer

Participants of collaborative exercises

Curtin University of Technology, Perth, AustraliaFBI, QuanticoFlorida International University, MiamiETH Zürich, Swiss Federal Institute of Technology NFI, Rijswijk, The NetherlandsUS Customs, SpringfieldBKA, Wiesbaden, Germany

NITE CRIME Summary 1/2

• Similar quantitative results by labs with completely different LA-ICP-MS combinations (most RSD << 10 % intra-laboratory).

Note: Results for float glass, not for std material!Note: Results for embedded glass, not for fragments!

• A protocol for optimised laser ablation conditions (as given in the fourth interlaboratory test) improved both the precision and the accuracy of quantitative results.

• The new matrix matched float glass standards FGS 1 and FGS 2 can be used as calibration or tuning standards for the quantitative analysis of float glass.

NITE CRIME Summary 2/2

Latkoczy, Becker et al. J. For. Sci. 2005; 50(6):1327-1341

LA-ICP-MS in Forensic Glass Analysis:

Reanalysis of the 63 float glasses of global origin by LA-ICP-MS

Six replicate measurements App. 80 µm crater diameter

Single shot Time resolved analysis

10 Hz, 10J/cm2

Crater dimension: 5 - 100 µm

Nd:YAG-laser 213 nm

Smaller than a hair

LA-ICP-MS in Forensic Glass Analysis:

Variation of main & minor element concentration of 63 float glasses of global origin

B o x - W h i s k e r P l o t s f o r 6 3 f l o a t g l a s s e s ; c o n c e n t r a t i o n s m a i n & m i n o r e l e m e n t s i n µ g / g

N a M g A l S i K C a5 0

5 0 0

5 0 0 0

5 0 0 0 0

5 0 0 0 0 0

M e d i a n 2 5 % - 7 5 % 1 0 % - 9 0 % O u t l i e r E x t r e m e v a l u e

Variation of trace element concentration of 63 float glasses of global origin

B o x - W h i s k e r P l o t s f o r 6 3 f l o a t g l a s s e s ; c o n c e n t r a t i o n s f o r t r a c e e l e m e n t s i n µ g / g

T i M n S r Z r L a P b0 , 5

5 , 0

5 0 , 0

5 0 0 , 0

5 0 0 0 , 0

M e d i a n 2 5 % - 7 5 % 1 0 % - 9 0 % O u t l i e r E x t r e m e v a l u e s

Differentiation of origin by potassium and aluminum content

A l u m i n u m ( µ g / g )

Pota

ssiu

m (µg

/g)

0 2 0 0 0 4 0 0 0 6 0 0 0 8 0 0 0 1 0 0 0 0 1 2 0 0 00

2 0 0 0

4 0 0 0

6 0 0 0

8 0 0 0

1 0 0 0 0

E u r o p eU . S . A .J a p a n

Differentiation of container glass from float glass

Data set of 63 float glasses of global origin

Data set of 20 container glasses of German origin

Differentiation of container glass from float glass

f l o a t c o n t a i n e r

g l a s s e s

0

2 0 0 0

4 0 0 0

6 0 0 0

8 0 0 0

1 0 0 0 0

1 2 0 0 0

39K

f l o a t c o n t a i n e r

g l a s s e s

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

49Ti

f l o a t c o n t a i n e r

g l a s s e s

0

5 0

1 0 0

1 5 0

2 0 0

2 5 0

3 0 0

3 5 0

4 0 0

55Mn

f l o a t c o n t a i n e r

g l a s s e s

0

1 0 0 0 0

2 0 0 0 0

3 0 0 0 0

4 0 0 0 0

5 0 0 0 0

6 0 0 0 0

7 0 0 0 0

8 0 0 0 0

9 0 0 0 0

42Ca

C a / M g

Pb [µ

g/g]

0 2 4 6 8 1 0 1 2 1 4 1 60

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

2 0 0

2 2 0

2 4 0

f l o a t g l a s s e sc o n t a i n e r g l a s s e s

Differentiation of container glass from float glass

0

20000

40000

60000

80000

100000

120000

0 20 40 60 80 100

Time [sec]

Cou

nts

perS

econ

d

30 secIntegrationTime

Fragment 6271 µg

Time resolved analysis signal of Cerium from fragment 6

Analysis of small fragments

0

20000

40000

60000

80000

100000

120000

0 20 40 60 80 100

Time [sec]

Cou

nts

perS

econ

d

12 secIntegrationTime

Fragment 4193 µg

Time resolved analysis signal of Cerium from fragment 4

Analysis of small fragments

0

20000

40000

60000

80000

100000

120000

0 20 40 60 80 100

Time [sec]

Coun

tspe

rSec

ond

5 secIntegrationTime

Fragment 3

Time resolved analysis signal of Cerium from fragment 6

Analysis of small fragments

Findings

0,1-1,5 % lower RSD are achieved when excluding the results of the two measurements of fragment 3.

Care should be taken when investigating very small and flat fragments, where only one or two shots are possible due to quantification problems with short TRA signals resulting in poorer reproducibilities.

Glass case

Physical examinations/ GRIM case report

Chemical examinations

(ICP-MS, SEM, XRF)case report

samples distinguishable

Step by step approach in forensic glass analysis

Side view

mean RI (pre-ablation) = 1,51927 ± 3x10-5

Investigation of change of RI by LA interaction

FBI/BKA homogeneity study2006

• FBI laboratory bought commercial window pane

FBI: GRIM, ICP-OES BKA: LA-ICP-MS

• measurements on 44 fragments from the same source

Flat Sheet DiagramSheet – 48”x48” Squares – 4”x4”

144143142141140139138137136135134133

132131130129128127126125124123122121

120119118117116115114113112111110109

108107106105104103102101100999897

969594939291908988878685

848382818079787776757473

727170696867666564636261

605958575655545352515049

484746454443424140393837

363534333231302928272625

242322212019181716151413

121110987654321

- 4 inch samples- 1 inch samples

• RI analysis – glass displays homogeneity– The sheet does not show any trend in variation but

varies as a whole within the expected range.

• ICP-OES analysis – glass displays homogeneity– There are no noticeable trends in the sheet.– The error associated with the method is larger than

the variation in the sheet.

Results of the homogeneity study

Analysis of variance

significant influence of sample inhomogeneities on LA-ICP-MS results for several elements (Al, Zr, Hf, Pb)

- due to the high spatial resolution of the method (sampling of 2 µg instead of mg) micro heterogeneity of the glass

Results of the homogeneity study

LA-ICP-MS: RSD for the mean values of 44 samples

0%

2%

4%

6%

8%

Li Na

Mg Al K C

a Ti Mn Fe Rb Sr Zr Sn Ba La Ce

Nd Hf

Pb

Match criterion

Glass fragments originating from different sources

Glass fragments originating from the SAME source

=Error Type II

=Error Type I

• Hotellings T²-Test:– requires more measurements than elements (i.e.20)– impractical

• T-Test:– often two fragments of the same glass can be

discriminated– too many Type I errors

• N-sigma criteria:– best choice for our application

Possible match criteria

Amount of errors type I and type II in dependence on n and m

1

10

100

1000

2--02--

12--

22--

33--

03--

13--

23--

34--

04--

14--

24--

36--

06--

16--

26--

310

--010

--110

--210

--310

--520

--6

Match criteria (n-Sigma & m "allowed" elements)

Num

ber o

f err

ors

Fehler 1. Art

Fehler 2. Art

Optimization of the match criterion

Error type IError type II

Optimised Match Criterion

• 4-sigma criterion

• 0 element may be distinguishable

• FBI-Glass: 44 data sets, 946 pairwise comparisons

Type I errors: 10 (1,06 %)

• 05_Stat: 63 data sets, 1953 pairwise comparisons

Type II errors: 3 (0,15 %) =

Summary

• Introduction of matrix matched std FGS 1 & 2

• NITE CRIME activity: LA-ICP-MS produces accurate data for the comparison of float glasses (protocol)

• FBI/BKA glass project (micro homogeneity & type I error)

• Reanalyses of 63 float glasses of global origin (type II errors)

• Optimized match criterion: 4-sigma criterion

• Further validation led to ISO 17025 accreditation of LA-ICP-MS method in May 2007

• Routine application in casework

Thanks to Maureen Bottrell, Jodi Webb & Robert Koons (FBI).Special thanks to Dr. Peter Weis, Marc Dücking, Peter Watzke/BKA.

Thanks to all NITECRIME members for their support, especially:J. Almirall, FIU, U.S.A.J. Buscaglia, R. Koons, FBI Academy, U.S.A.D. Günther, C. Latkoczy, ETH Zürich, SwitzerlandS. Montero, G. van der Peijl, NFI, NetherlandsJ. Watling, Curtin University, Perth Australia,V. Zdanowicz, U.S. Customs, U.S.A.

A. Walther, SCHOTT AG, for the good co-operation.

Thanks