advances in discrimination of dyed textile fibers …...separation of dyes isolated from limited...
TRANSCRIPT
Copyright © 2007 by Stephen L. Morgan, slide 1
Stephen L. Morgan, Brandi C. Vann, Stephen L. Morgan, Brandi C. Vann, Brittany M. Baguley, and Amy R. Stefan Brittany M. Baguley, and Amy R. Stefan
Department of Chemistry & Biochemistry, The University of South Carolina, Columbia, SC 29208 Email: [email protected]
URL: http:www.chem.sc.edu/faculty/morgan
Advances in Discrimination of Dyed Textile Advances in Discrimination of Dyed Textile Fibers using Capillary Electrophoresis/Fibers using Capillary Electrophoresis/
Mass SpectrometryMass Spectrometry
Trace Evidence Symposium, Clearwater, FL16 August 2007
Copyright © 2007 by Stephen L. Morgan, slide 2
Extraction and subsequent analysis of dye components from fibers offers the possibility for enhanced discrimination of trace fiber evidence. This research addresses development of methods for high-resolution capillary electrophoresis (CE) separation of dyes isolated from limited size samples of textile fibers.
A combinatorial approach to has been employed to optimize the extraction of dyes from nylon, cotton, polyester, and acrylic fibers. The protocols have also been chosen to be compatible (volatile, absence of salts) with subsequent analysis using capillary electrophoresis (CE) or CE/mass spectrometry.
Capillary electrophoresis with both diode array and mass spectrometry (MS) detection has been demonstrated to achieve both discriminating and sensitive analysis of fiber dyes.
IntroductionIntroduction
Copyright © 2007 by Stephen L. Morgan, slide 3
“At present, much of forensic fibre dye casework is based upon comparison rather than identification. This may change, and the emphasis may shift towards comparison and identification, in which case the addition of a mass spectrometric component to the analytical scheme would be desirable. CE appears to offer reduced mechanical complexity and increased resolution of the separated dye components” [Rendle and Wiggins, 1995].
A starting pointA starting point
Copyright © 2007 by Stephen L. Morgan, slide 4
Blue acid dye discriminationBlue acid dye discrimination
C.I. acid blue 277C.I. acid blue 277
O
O
NH2
SO3Na
HN CH3
CH3
SO2NHCH2CH2OH
SO -
C.I. acid blue 239H3C
O NH
NH
O
O
H2C
NH
H2C
C
O
3
C.I. acid blue 45C.I. acid blue 45
O
O
OH
NH2
SO3-
OH
NH2
-O3S
Copyright © 2007 by Stephen L. Morgan, slide 5
Acid blue 45
Time (min)
Acid Blue 239
Acid blue 277
neutrals
Abs
orba
ce (m
AU
)
Electropherogram taken at 600 nm of three blue acid dyes extracted from nylon fibers
15 mM ammonium acetate in 40/60 ACN-H2O, pH 9.3Capillary: 75 µm i.d., 50 cm Separation at 30 kV and 25 °C
3D plot displaying migration time, wavelength and absorbance.
Although the absorbance spectra are similar there are clear structural differences based on the migration times of the dyes.
Abs
orba
ce (m
AU
)
Wavelength (nm) Time (min)
Blue dye extracts / similar UV/Vis spectraBlue dye extracts / similar UV/Vis spectra
Copyright © 2007 by Stephen L. Morgan, slide 6
Textile fiber dye extraction / CE methodsTextile fiber dye extraction / CE methods
Extracted fiber (+)
Reactive
(+)Direct
(+)Acid
(+)Cationic
(+)Disperse
(+)Vat
(-)Na2SO4
100 °C 30 minAir oxidize 1 hr
NaOH100 °C 30 min
Pyridine/H2O100 °C60 min
Pyridine/H2O/NH4OH100 °C60 min
Formic acid/H2O
100 °C60 min
Chloro-benzene100 °C30 min
Cotton Nylon Acrylic Polyester
Determine fiber type via PLM or FTIROriginal
fiber
Morgan SL, Nieuwland AA, Baguley BM, Vann BC, Stefan AR, Dockery CR, Hendrix JE, Extraction and capillary electrophoresis for forensic analysis of textile fiber dyes, Submitted to J Forensic Sci 2007.
Copyright © 2007 by Stephen L. Morgan, slide 7
Nylon and cotton dyes / anionic CENylon and cotton dyes / anionic CE
Electropherogram at 214 nm.Electropherogram at 214 nm. Peak identification:Peak identification: (1) neutrals; (2) Acid Blue 239; (3) Acid Yellow 156; (4) Acid Blue 324; (5) Acid Red 337; (6) DID 266; (7) Direct Red 84; (8) Direct Orange 39; (9) Direct Yellow 58, (10) Direct Blue 71-1; (11) Direct Blue 71-2; (12) Reactive Blue 250; (13) Reactive Red 198; (14) Reactive Blue 220; (15) Reactive Red 180; (16) Reactive Red 239/241.
Conditions:Conditions:Buffer: 15 mM ammonium acetate in
ACN-H2O (40:60, v/v), pH 9.3Injection: 1 psi 5 sCapillary: 50 µm i.d.,50 cmSeparation: 30 kVDetection: diode array UV/visible
Copyright © 2007 by Stephen L. Morgan, slide 8
CE / diode array detectionCE / diode array detection
Inlet Outlet
Copyright © 2007 by Stephen L. Morgan, slide 9
Silanol groups along the wall of the capillary become ionized after the capillary is filled with buffer solution.
Positive buffer ions are attracted to the negatively charged wall.
Hydrated buffer ions migrate toward the cathode and drag the bulk solution containing cations, neutrals, and anions past the detection window.
CE based on electroosmotic flow (EOF)CE based on electroosmotic flow (EOF)
EOFEOF
Fused silica capillaryFused silica capillary+ _CathodeCathodeAnodeAnode
++
---
--
___ _
+ +
++
+
+ ++
+__
++++ ++++ ++++ ++++++++++++
++++++++ ++++ ++++ ++++++++
_
Copyright © 2007 by Stephen L. Morgan, slide 10
Combinatorial optimization experimentsCombinatorial optimization experiments
3) Clamp plate, place in oven
2) Deliver solvent combinations to samples 1) Load fibers into 96-well plateExtraction conditions:Ternary solvent mixtures200 µL solvent in each well1 mm - 1.0 cm threadsHeat to 100 C, 90 C and 60 C Evaporated to drynessReconstitute in 100 µL water
96-well plate with glass inserts96-well plate with glass inserts
Liquid sampling robotLiquid sampling robot
Copyright © 2007 by Stephen L. Morgan, slide 11
Nylon / acid dyesNylon / acid dyes
Typically, nylon is dyed with acid dyes containing anionic functional groups that produce varying degrees of solubility in water
Chemical dye classes include azo (48%), metal-complex azo (31%), and anthraquinone (10%)
Dyes are bound to nylonfiber by electrostatic interactions through salt linkages.
NH
HN
O]n
O
[
]nO
NH
[
Nylon 6,6
Nylon 6
O
O
OH
NH2
SO3-
OH
NH 2
-O3S
C.I. Acid Blue 45, AnthraquinoneC.I. Acid Blue 45, Anthraquinone
N
-O3S
NOCH3
H 3CN N
OCH3
C.I. Acid orange 156, AzoC.I. Acid orange 156, Azo
O -
N
N HAc
N
SO
O
N H 2
O -Co3 +
O-
N
AcHN
N
S O
O
H2N
O-
C.I. Acid Blue 171, Metal-AzoC.I. Acid Blue 171, Metal-Azo
Copyright © 2007 by Stephen L. Morgan, slide 12
Combinatorial experimental design was applied to the extraction of acid dyes from nylon using water, aqueous ammonia (12 M), and pyridine.
661616933333310
16661681616667050506500505505004
100003010002001001
% pyridine% NH3% H2ODesign point
Mixture designs for three solventsMixture designs for three solvents
Copyright © 2007 by Stephen L. Morgan, slide 13
Anthraquinone Blue BAnthraquinone Blue B
ABB 60 DEG 60 min
The design was replicated twice for a total of 20 experiments The amount of dye recovered was measured using a UV/visible microplate reader Pooled relative standard deviations of replicate experiments are 4.0-7.0%.
96-well plate with glass inserts96-well plate with glass inserts
Nylon / anthraquinone blueNylon / anthraquinone blue BB
Copyright © 2007 by Stephen L. Morgan, slide 14
Acid Blue 171: metal complexAcid Blue 171: metal complexAcid orange 156: AzoAcid orange 156: Azo R2=.9197R2=.9235
A diagonal ridge ranging from equal mixtures of pyridine:water, to pyridine: ammonia is present in the extraction of all acid dye classes
Nylon / azo and metal complex azoNylon / azo and metal complex azo
Stefan AR, Dockery CR, Nieuwland AA.; Roberson SN, Hendrix JE, Morgan SL. Combinatorial optimization for the extraction of anthraquinone, azo, and metal complex acid dyes from nylon fibers for forensic trace analysis. Submitted to J Forensic Sci 2007.
Copyright © 2007 by Stephen L. Morgan, slide 15
Hydrogen bonding provides substantivity of direct dyes to cotton
Reactive dyes are covalently attached to hydroxyl groups
C.I. Reactive Red 1 covalently bonded to cellulose
Rendle, D.F.; Crabtree, S.R.; Wiggins, K.G.; Salter, M.T. "Cellulase Digestion of Cotton Dyed with ReactiveDyes and Analysis of the Products by Thin-Layer Chromatography," J. Soc. Dye. Colour 1994, 110, 338-341.
Using a combinatorial approach, best extraction of direct dyes from cottonwas achieved at 50:50 water:pyridine
Reactive dyes are extracted from cotton using 1.5% NaOH
Dye extracts from mixture combinatorial design
Cotton / direct and reactive dyesCotton / direct and reactive dyes
Copyright © 2007 by Stephen L. Morgan, slide 16
15 mM ammonium acetate in 40/60 ACN-H2O, pH 9.3Capillary: 50 µm i.d., 50 cm (82 cm for CE-MS)Separation at 30 kV and 25 °C using 214 nm
anionicanionic dyes dyes
Peak identification: (1) neutrals; (2) Reactive Blue 21; (3) Reactive Yellow 160; (4) Reactive Orange 72; (5) Reactive Blue 19; (6) Reactive Yellow 176; (7) Reactive Violet 5; (8,9) Reactive Black 5 and Reactive Blue 250; (10) Reactive Red 198; (11) Reactive Blue 220; (12) Reactive Red 180; (13) Reactive Red 239/241.
O
O
NH2
NH
SO3-
SO2CH2CH2OSO3-
Reactive blue 19Reactive blue 19
Cotton / direct and reactive dyes / CECotton / direct and reactive dyes / CE
Copyright © 2007 by Stephen L. Morgan, slide 17
Cotton fiber /reactive dye extracts / CECotton fiber /reactive dye extracts / CE
Electropherogram at 214 nm of a reactive dye (C.I. reactive violet 5, marked by an arrow)
extract after SPE clean up.
Electropherogram at 214 nm of a reactive dye (C.I. reactive violet 5, marked by an arrow)
extracted from cotton using NaOH
C.I. reactive violet 5
C.I. reactive
violet 5
Dockery CR, Stefan AR, Nieuwland AA, Roberson SN, Baguley BM, Hendrix JE, Morgan SL. Automated extraction of direct, reactive, and vat dyes from cellulosic fibers for forensic trace analysis by capillary electrophoresis. Submitted to J Forensic Sci 2007.
Copyright © 2007 by Stephen L. Morgan, slide 18
Cotton / vat dye extracts / CECotton / vat dye extracts / CE
Buffer: 15 mM ammonium acetate in acetonitrile-water (40:60, v/v), pH 9.3 + reducing agent (sodium dithionite)
NaS2O4
OH
HO
C.I. vat orange 9
DAD electropherograms at 280 nmDAD electropherograms at 280 nm
Copyright © 2007 by Stephen L. Morgan, slide 19
Wavelength (nm)
Abs
orba
nce
(mA
U)
UV/Vis spectrum of vat dye standard
UV/Vis spectrum of vat dye extract
Wavelength (nm)A
bsor
banc
e (m
AU
)
Spectra of vat dye standard and extract are the same No change in dye constitution due to extraction conditions
Vat dye / UV/visible confirmationVat dye / UV/visible confirmation
Dockery CR, Stefan AR, Nieuwland AA, Roberson SN, Baguley BM, Hendrix JE, Morgan SL. Automated extraction of direct, reactive, and vat dyes from cellulosic fibers for forensic trace analysis by capillary
electrophoresis. Submitted to J Forensic Sci 2007.
Copyright © 2007 by Stephen L. Morgan, slide 20
Acrylic / basic (cationic) dyesAcrylic / basic (cationic) dyes
Acrylic is composed of 85% repeating acrylonitrile units and 15% monomers and is typically dyed with basic (cationic) dyes
Dyes are bound to acrylic fiber through salt linkages provided by initiator and terminator fragments (sulfonate or sulfate acid groups)
Optimum extraction conditions were found at 50:50 formic acid:water
x y
n
*H2C
HC
H2C C *
CN
R
R'
NNCH3
CH3N
N
N N
CH3
H2C
C.I. Basic Red 46
Acrylic
Copyright © 2007 by Stephen L. Morgan, slide 21
Electropherogram at 214 nm.Electropherogram at 214 nm. Peak identification: (1) Basic Red 22, (2) Basic Yellow 21, (3) Basic Blue 159, (4) Basic Red 14, (5) Basic Blue 41, (6) Basic Blue 45, (7) Basic Red 18.
Conditions:Conditions: Buffer: 45 mM ammonium acetate in
acetonitrile-water (60:40, v/v), pH 4.7 Capillary: 50 µm i.d., 50 cm Injection: 1 psi, 5 s Separation: 20 kV, 25 C Detection: diode array UV/vis 214 nm
Acrylic / basic cationic dyes / CEAcrylic / basic cationic dyes / CE
NCH3
N
N
N
S
CH3
Peak 1: C.I. basic red 22Peak 1: C.I. basic red 22
Copyright © 2007 by Stephen L. Morgan, slide 22
Polyester does not contain ionic or covalentdye sites and is typically dyed with water insoluble disperse dyes.
The literature (e.g., Laing, et al.) suggests that disperse dyes can be extracted from polyester with chlorobenzene and heat for 30 min. We agree.
Disperse dye extracts
O
O
O
O
[]n
Electron microscope photo of polyester fibers
O2N N N
OCH3
N
N
HO
C.I. Disperse Orange 29
Polyester / disperse dyesPolyester / disperse dyes
Copyright © 2007 by Stephen L. Morgan, slide 23
Abs
orba
nce
(mA
U) 70
605040
30
2010 0
1
2 3 4
C.I. Disperse Yellow 114
NACE conditions for disperse dyes:Buffer: 80 mM ammonium acetate in
acetonitrile-methanol (75:25, v/v), pH 9Separation: 20 kVPeak identification: (1) Disperse Red 343,
(2) Disperse Blue 73, (3) Disperse Yellow 114, (4) Disperse Orange 29
Polyester / disperse dyes / CEPolyester / disperse dyes / CE
Electropherogram at 214 nm of Disperse Orange 29 extracted from polyester
Copyright © 2007 by Stephen L. Morgan, slide 24
Electropherogram at 400 nm of C.I. Acid orange 156 standard
Abs
orba
nce
(mA
U)
Time (min)
Wavelength (nm)
Acid dye (standard) / CEAcid dye (standard) / CE
Copyright © 2007 by Stephen L. Morgan, slide 25
Time (min)
Electropherogram at 400 nm of C.I. Acid orange 156 extracted from 10 cm nylon fiber
Acid dye nylon extract (10 cm) / CEAcid dye nylon extract (10 cm) / CE
Wavelength (nm)
Abs
orba
nce
(mA
U)
Copyright © 2007 by Stephen L. Morgan, slide 26
Acid dye nylon extract (5 cm) / CEAcid dye nylon extract (5 cm) / CE
Electropherogram at 400 nm of C.I. Acid orange 156 extracted from 5 cm nylon fiber
Time (min)
Wavelength (nm)
Abs
orba
nce
(mA
U)
Copyright © 2007 by Stephen L. Morgan, slide 27
Acid dye nylon extract (2.5 cm) / CEAcid dye nylon extract (2.5 cm) / CE
Electropherogram at 400 nm of C.I. Acid orange 156 extracted from 2.5 cm nylon fiber
Time (min)
Wavelength (nm)
Abs
orba
nce
(mA
U)
Copyright © 2007 by Stephen L. Morgan, slide 28
Acid dye nylon extract (1 cm) / CEAcid dye nylon extract (1 cm) / CE
Electropherogram at 400 nm of C.I. Acid orange 156 extracted from 1 cm nylon fiber
Time (min)
Wavelength (nm)
Abs
orba
nce
(mA
U)
Copyright © 2007 by Stephen L. Morgan, slide 29
Petrick, et al. analyzed dyes extracted from acrylic and polyester fibers followed by HPLC/DAD/MS
1:1 formic acid: water extraction of basic dyesCompared extraction efficiency of 4:3 mixtures of pyridine and water to 4:3
mixtures of acetonitrile and water for disperse dyesAnalyzed dyes from 5 cm single acrylic fiber and polyester fibers
Huang, et al. analyzed acid, basic, and disperse dye pairs by LC/MSExtracted unknown dyes from 10 different red cotton fibers Unknown fiber length Fibers distinguished based on extraction protocol (SWGMAT), ionization in the
mass spectrometer, chromatographic behavior, and mass spectra
Huang, M.; Russo, R.; Fookes, B.; Sigman, M. “Analysis of Fiber Dyes by Liquid Chromatography Mass Spectrometry (LC-MS) with Electrospray Ionization: Discrimination Between Dyes with Indistinguishable UV-Visible Absorption Spectra” J. For. Sci. 2005 (50) 3.
Petrick, L.; Wilson, T.; Fawcett, R. “High-Performance Liquid Chromatography-Ultraviolet-Visible Spectroscopy-Electrospray Ionization Mass Spectrometry Method for Acrylic and Polyester Forensic Fiber Dye Analysis,” J. For. Sci. 2006 (51), 771-779.
Recent literature (2005-2006)Recent literature (2005-2006)
Copyright © 2007 by Stephen L. Morgan, slide 30
CE with UV/visible / MS detectionCE with UV/visible / MS detection
High sensitivity Reliability Ease of use minimized daily
maintenance
EOF
Copyright © 2007 by Stephen L. Morgan, slide 31
Co-axial Sheath flow interface. (1) capillary adjustment; (2) capillary from CE; (3) extension capillary; (4) microvolume tee; (5) stainless steel capillary, end of extension capillary, and nebulizing tip; (6) nebulizer gas (N2); (7) make-up flow. [Waters/Micromass]
CE-DAD/MS sheath flow interfaceCE-DAD/MS sheath flow interface
External xenon lamp seen in background.(1) inlet buffer block; (2) deuterium lamp aperture (now redundant); (3) DAD; (4) coolant T-piece; (5) fiber optic from xenon lamp; (6) fiber optic to DAD; (7) standard Beckman aperture with rubber donut ring; (8) capillary; (9) CE-MS interface. The xenon lamp and power supply can be seen in the background
Copyright © 2007 by Stephen L. Morgan, slide 32
Basic dyes / CE/MS with positive ESI/MSBasic dyes / CE/MS with positive ESI/MS
m/z 273
m/z 317
m/z 434
m/z 347
m/z 344
m/z 371
m/z 428 Conditions: Sheath flow rate: 1.7 µL/min Nebulization gas: 8 psi ESI voltage: 3718 V Cone voltage: 17 V
Estimated LOD’s for basic dyes vary from 0.2 to 0.4 µg/mL. For a 5 µL injection volume, this represents ~2 pg.
Copyright © 2007 by Stephen L. Morgan, slide 33
2 mm acrylic / basic dye extract / CE/MS2 mm acrylic / basic dye extract / CE/MS3
2
1
Peak identification: (1), (2), (3).
Extraction conditions:2 mm tri-dyed acrylic fiber10 µL water:formic acid
(1:1, v/v) addedHeated at 100 C for 1 hEvaporated to drynessReconstituted in 5 µL water
CE conditions:45 mM ammonium acetate in
acetonitrile-water (60:40, v/v), pH 4.7Injection: 20 kv 10 sec
MS Conditions:Sheath flow rate: 1.7 µL/min Nebulization gas: 8 psi ESI voltage: 3718 V Cone voltage: 17 V
Basic Violet 16
Basic Blue 159
Basic Yellow 28
Copyright © 2007 by Stephen L. Morgan, slide 34
1
2
3m/z 427
m/z 659
m/z 424
Acid dye (anionic) / CE-DAD-MS with ESI (-)Acid dye (anionic) / CE-DAD-MS with ESI (-)
Dye 1
Dye 2
Dye 3
Sample: 0.1 mg/mL acid dye mixture CE conditions: 30 kV with 3 psi (separation), 2psi – 10 sec injection, 50 µm i.d.Buffer conditions: 15 mM Ammonium Acetate with 40 % Acetonitrile pH 9.3 MS conditions: -3300 V (cap), 50 V (cone), 10 psi (gas), 4 µL/min 50:50 IPA/ H2O, 1 % TEA
N
12
3
CE/DAD at 319 nm
CE/MS
UV/visible spectra
Copyright © 2007 by Stephen L. Morgan, slide 35
CE-DAD/MS of extracted nylon fiberCE-DAD/MS of extracted nylon fiber
Dye 1
Dye 2
Dye 3
Sample: Extract from nylon 6,6 fiber with 3 acid dyes CE conditions: 30 kV with 3 psi (separation), 2psi – 20 sec injection, 50 µm i.d.Buffer conditions: 15 mM Ammonium Acetate with 40 % Acetonitrile pH 9.3 MS conditions: -3300 V (cap), 50 V (cone), 10 psi (gas), 4 µL/min 50:50 IPA/ H2O, 1 % TEA
1
2
m/z 427
m/z 659
m/z 424
m/z 676
3
nylon
N1 2
3
CE/DAD at 319 nm
CE/MS
UV/visible spectra
Copyright © 2007 by Stephen L. Morgan, slide 36
Dye identification/characterizationDye identification/characterization
Interpretation of fragmentation pattern. All fragments are singly charged species.
Ion
abun
danc
e
MS/MS spectrum of C.I. Basic Blue 3 obtained using positive ion electrospray ionization (ESI+)
Ion mass (m/z)
O
N
NN
O
N
N HN
m /z 296
O
N
NN
m /z 280
O
N
NNH
O
N
NN
m /z 252
m /z 236
m /z 3 24324
280
236
Copyright © 2007 by Stephen L. Morgan, slide 37
CE/DAD/MS analysis: nylon fiber extract with CE/DAD/MS analysis: nylon fiber extract with 3 acid dyes after laundering with Tide3 acid dyes after laundering with Tide®®
UN
U
U
FB
U
2
unknown
unknown
Dye 3
Dye 2
Dye 1
m/z 438
m/z 394
m/z 427.7
m/z 659
m/z 424
Washing adds 4 unknown CE/DAD/MS peaks
Dyes 1 and 3 not visible in CE-DAD at 319 nm due to loss after laundering
Dyes 1 and 3 visible in MS signal, but signal significantly noisier and peaks broader
FB peak from sample
Tide Standard
Wavelength, nm
UV/visible spectra
RIC
Minutes
CE/MS
CE/DADat 319 nm
Copyright © 2007 by Stephen L. Morgan, slide 38
CE/DAD/MS analysis: nylon fiber extract with CE/DAD/MS analysis: nylon fiber extract with 3 acid dyes after 12 mo. accelerated weathering3 acid dyes after 12 mo. accelerated weathering
N1 2
3
Dye 1
Dye 2 Dye 3
Weathering is affecting all three dyes in a similar manner
Few degradation products seen Nylon polymer present in MS signal
due to extraction process or what?
Dye 3
Dye 2
Dye 1
Nylon
m/z 427
m/z 659
m/z 424
m/z 676
CE/DAD at 319 nm
RIC
Minutes
UV/visible spectra
Wavelength, nm
CE/MS
Copyright © 2007 by Stephen L. Morgan, slide 39
Nylon polymer components in extractsNylon polymer components in extracts
* N N
O
O
H
H
N N
O
O
H
H
N N *O
O
H
H
m/z 1014 (4.5-Nylon 6,6 units)
m/z 901 (4-Nylon 6,6 units)
m/z 788 (3.5-Nylon 6,6 units)
m/z 676 (3-Nylon 6,6 units)
m/z 563 (2.5-Nylon 6,6 units)
NN
O
O
H
H
**
C12H22N2O2••
Exact Mass: 226.17N
N*
O
O
H
H
**
*
Adipic acidC6H14N2
••
Exact Mass: 114.12
Hexamethylene DiamineC6H8O2
••
Exact Mass: 112.05
The 0.5 unit on these masses is due to adipic acid on the end of the polymer chain
RIC
Minutes
CE/MS
Copyright © 2007 by Stephen L. Morgan, slide 40
Although microextraction/CE/MS is destructive to the sample, only an extremely small sample is required (~1-2 mm of a single 15 μ diameter fiber). Automated micro-extractions and CE offer the forensic analyst reproducible analyses (% RSDs ranging from 5-25%) with limits of detection in the picogram range.
CE methods compatible with MS have been developed. The sheath-flow CE/MS interface is suited to routine dye analysis, exhibits stability and ease of use, and requires little maintenance.
CE/DAD-MS methods for cationic textile dyes have been optimized. CE/DAD-MS methods for anionic dyes have been developed and applied to extracted samples.
CE/DAD and CE/MS provide qualitative and semi-quantitative “fingerprint” for dyes extracted from evidence fibers. Discrimination may be enhanced through matching CE migration times, molecular weight, and structural fragmentation.
ConclusionsConclusions
Copyright © 2007 by Stephen L. Morgan, slide 41
AcknowledgementsAcknowledgements
This research was supported under a contract award from the Counterterrorism and Forensic Science Research Unit of the Federal Bureau of Investigation’s Laboratory Division. Points of view in this document are those of the authors and do not necessarily represent the official position of the Federal Bureau of Investigation.