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Polymer characterization: completing the story through mass spectrometry
…or how we let the materials talk...
Franky Puype Laboratory of Analytical Chemistry Institute for Testing and Certification, Zlin-CZ
Define problem/(EU)directive
Selecting method
Analytical support
Evaluate data
Working out cases scientifically
Working out cases technically
Prevention / Cost saving/ Market screening
Analytical chemistry for clients:
Mass spectrometry at ITC…
2 ICP-MS 2 TD-GC-MS 4 XX-GC-MS 1 DI-MS 1 LC-MS
Thermal desorption GC-MS
50-650ºC / 1-120 min. Inert atmosphere
Small sample
Thermal desorption Gas chromatography Mass spectrometry
40-320ºC
40-1200 Da 70eV ionization Electron impact
M/z separation
Thermal desorption GC-MS
Evaluation of the quantitative analysis of PBDEs in plastics by thermal desorption GC-MS for soluble polymers
Puype F., Samsonek J. (2008) Organohalogen Compounds, 70;1522-1525
deca
BDE-
209
octa
BDEs
nona
BDEs
hept
aBDE
-183
hexa
BDE-
154
hexa
BDE-
153
pent
aBDE
-99
pent
aBDE
-100
tetr
aBDE
-47
Quantification and identification of residual target and non-target analytes from polymer surfaces by using a Fast Automated Scan/SIM Type (FASST)
simultaneous mass spectrometry detector…
SIM
SCAN
Puype, F.; Samsonek, ISBN 978-80-7454-335-7, p 296-299
Assessment of Fick`s second migration law and Arrhenius diffusion equation on the accelerated diffusion by thermal desorption GC-MS…
100 % recovery @ 250°C 60 minutes (PS matrix)
Modification of Arrhenius diffusion equation towards analytical recovery data
Increasing volatility 100°C 60 minutes
F. Puype and J. Samsonek; 2014, ISBN 978-80-7454-335-7, p 300-305
Blooming of brominated flame retardant by overdosing in the mixture
HB
CD
Polyurethanes by TD-GC-MS: FREE isocyanate characterization (250-400°C programmable injection, 3 minutes)
Rentention time (min.)
Identified compounds
Area percent report
15,0 15,5 17,0
2,2`-MDI 2,4`-MDI 4,4`-MDI
2,3 17,4 51,1
20,5 21,0 21,5
Trimeric MDI
28,8
27-30 Tetrameric MDI 0,4
O
O
N
N
O
O
NN
O
N
O
O
N
N
O
O
N
N
MDI dimers
MDI trimers
MDI tretramers
Rubber additives by TD-GC-MS (250°C, 2 minutes)
10,5 Flectol TMQ 10,6 o-Cyanobenzoic acid 11,5 Fatty acid 11,8 Methylmercaptobenzothiazole 13,0 Fatty acid 14,3 Fatty acid 15,2 Fatty acid
15,65 Fatty acid 16,4 Fatty alcid 16,8 6PPD
others Mixture of aliphatic hydrocarbons and fatty acids + esters
2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0 32.5
0.00
0.25
0.50
0.75
1.00
1.25
1.50
(x10,000,000)
Flectol TMQ 6PPD
Methylmercapto benzothiazole
Provenance by comparative method: foreign particle??
Particle
Foreign particle?? Hydrocarbon profile
Particle
Foreign particle?? Irgafos 168?
Foreign particle: yes
Particle
Thermal desorption GC-MS: Anti-rodent present?
Bitrex + Permethrin
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0 23.0 24.0 25.0 26.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
(x10,000,000)
Batch to batch differences… Sample from early 20xx Rubber sample Sample from late 20xx Rubber sample
Tris (2-ethylhexyl)trimellitate TOTM plasticizer
Not intentionally added substances NIAS – ABS carplast
STY
RE
NE
Dim
ers
STY
RE
NE
DIE
LS A
LDE
R T
RIM
ER
S
Dim
ers
Non intentionally added substances NIAS – Oligomers ABS/SAN
CH2
N
CH2
1a
N
δ+
δ−
CH21b
CH2
ABS/SAN: Non intentionally added substances Diels-Alder chemistry between SAN monomers
- One step reaction - Thermally induced - Several combinations
possible - Main emissions - Unavoidable reaction
R
R
CH2
R
R
RCH3
R
+(R or S chirality)
N
N
N
N
N
THAN
THNP
THNE
These compounds have been found in a sample after blooming and can appear as a white cloud during physical stress on the car part
ABS/SAN: Diels-Alder chemistry Final formation of trimers
ABS/SAN: Emission testing: VDA 278 for car indoor material
VOC – toluene 90ºC 30 minutes Limit = 100 ug/g FOG – hexadecane 120ºC 60 minutes Limit = 250 ug/g
- free styrene always presented - acrylonitrile is minor - no butadiene is observed (ABS).
0
20
40
60
80
100
0 5 10 15 20 25FOG value (ug/g n-hexadecane equivalent)
area
per
cent
age
SAN
trim
ers
Puype, F.; Samsonek, J. (2013) ``Identification and screening of Diels-Alder cycloaddition reaction products from acrylonitrile-(butadiene)-styrene based copolymers by mass spectrometry and their impact on the car-indoor environment``, Slovak University of Technology, Chemické listy, Vol. 107, p 169-172, ISSN 0009-2770
Direct Inlet – Electron Impact – Mass Spectrometry
Yellowing of PP based polymers after storage in darkness !!
Reference
batch
Defect
batch
Direct Inlet – Electron Impact – Mass Spectrometry
Direct Inlet – Electron Impact – Mass Spectrometry
Irganox 3114 is a big molecule cannot be separated by classical GC
(MW 784 Da)
What we know…
Irgafos 168 Irganox 3114 Magnesium-aluminium hydrotalcite
O-O-
O
OH
OH
Mg
OHOH
OH
Al
OH
OH
Mg
OHOH
OH
Al
OH
Mg+
OH
Mg+
HOH
HOH
HOH
HOH
OH
OH
O
O
O
N
NN
OH
Sample Al content (mg.kg-1)
Mg content (mg.kg-1)
MgO/ Al2O3 ratio
Yellow PP
79,6 ± 8,0 100,0 ±,10,0 3,18
Non-yellow 54,1 ± 6,0 66,6 ± 7,0 3,11
Looking for a link…
Irganox 3114
BHT
Additive and yellowing precursor
BHT – QM
Yellow substance
OH
OH
O
O
O
N
NN
OH
OH
O
TD-GC-MS data
Direct Inlet – Electron Impact – Mass Spectrometry
DI-EI-Mass spectrum = Σ Molecular ions (M+i) + Σ Post Ion Source Decay fragmentation ions (PSDi)
B → B+*→ B+ (M+i)
Int.
B+ (M+i)
M/e
Only B presented
DI - Mass spectrum = Σ Molecular ions + Σ Post Ion Source
Decay fragmentation ions (PSD)
Direct Inlet – Electron Impact – Mass Spectrometry
DI-EI-Mass spectrum = Σ Molecular ions (M+i) + Σ Post Ion Source Decay fragmentation ions (PSDi)
B → B+*→ B+ (M+i)
AB → AB+* → A* + B+ (PSDi)
Int.
AB+
B+ (PSDi)
Int.
B+ (M+i)
M/e M/e
Only B presented AB breaks down by EI
Direct Inlet – Electron Impact – Mass Spectrometry
DI-EI-Mass spectrum = Σ Molecular ions (M+i) + Σ Post Ion Source Decay fragmentation ions (PSDi)
B → B+*→ B+ (M+i)
AB → AB+* → A* + B+ (PSDi)
Int.
M/e
AB+
B+ (PSDi)
B+ (M+i)
Int.
AB+
B+ (PSDi)
Int.
B+ (M+i)
M/e M/e
Only B presented AB breaks down by EI AB breaks down by EI and B was already presented
OH
OH
O
O
O
N
NN
OH
+*
PSD
OH
O
O
O
N
NH
N
OH
+*
Irganox 3114, M+* M/z 783 (PSD but also M
+*), M/e 565
550 600 650 700 750 8000.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0(x1,000)
565.40
783.65
550.40
535.40521.40703.40596.40 769.40
500 550 600 650 700 750 8000.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00(x100,000)
783.70
565.40
550.40
768.70509.35 727.65711.45577.40
464.40614.40520.30 750.60
820.80
Yellowing issue with irganox 3114 (PP parts)
M/e 783 = M+ M/e 565 = M-BHT!! The irganox 3114 is releasing BHT…
140 150 160 170 1800.00
0.25
0.50
0.75
1.00
1.25
(x100,000)
161.10
163.15175.15
147.15
145.15
169.05 187.15
141.15 173.15157.15 185.10179.20
Releasing BHT influenced by the pH change in the system and create yellow substances (due to the presence of acid scavengers after Ziegler-Natta)
O OH
Yellowing issue with irganox 3114 (PP parts)
yellow samples
100 200 300 400 500 600 7000.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25(x10,000)
57.20
203.20
161.15
91.15
147.15
260.30 332.20436.45 647.55565.40346.30
303.15783.80
384.75 592.40493.40 631.40 708.60
M-H+ M-BHTQM+H
M-BHTQM2+2H
163.2 BHT-tert.butyl
161.1 BHTQM-tert.butyl
At M+-1 (irganox 3114QM) no peaks seen
782.6
203.2 BHTQM-tert.butyl O
OH
M+i @ 565 M/e 74,3 % (RSD 10 %, n=3)
M+i @ 161 M/e and 163 M/e 78,8 % (RSD 1,2%, n=3)
OH
OH
O
O
O
N
NN
OH
OH
O
O
O
N
NH
N
OH
OH
O
OH
O
O
O
NH
NH
N
M+i @ 347 M/e is 6,1 % (RSD > 20 %, n=3)
Irganox 3114
So….
Puype, F.; Samsonek, J. (2012) ``Evaluating the yellowing reaction mechanism of irganox 3114 in non-woven PP fabrics in the presence of magnesium-hydrotalcite acid scavenger by direct inlet-electron impact-mass spectrometry``, Plastko 2012, Tomas Bata University, ISBN 978-80-7454-137-7
Not only yellowing…
O
N+O- O-
OH
N+O- O
BASE
ACID
Benzoic form Quinone formcolorless
50.0 75.0 100.0 125.0 150.0 175.0 200.0 225.0 250.0 275.0 300.00.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
3.25
3.50
3.75
(x1,000)236.20
57.10
162.15
220.20
131.20 251.25188.2069.10173.20 207.2097.20 145.2073.10
111.20283.20 305.20257.30
TD-GC-MS MS
Contaminants in black polymeric food contact articles
2 neighbouring companies producing polymer based food-contact articles made similar products…. ..similar products had different prices and different quality… …one of them wanted to know the chemical difference between similar products.
XRF measurement: Sb and Br
BFR Identification • TD-GC/MS
– 24-h static migration in toluene – GCMS-QP2010 Series, Shimadzu equipped with PY-
2020iD, Frontier Laboratories
decaBDE-209 REACH: PBT + vPvB
TBBPA REACH: suspected reprotoxic, potential endocrine disruptor, suspected PBT/vPvB [1]
decaBDPE-209 !!! Since 2009 on the market!!!
[1] European Chemicals Agency (ECHA): Community rolling action plan (CoRAP) update covering years 2015, 2016 and 2017 (PDF), 17. March 2015, https://echa.europa.eu/documents/10162/13628/corap_list_2015-2017_en.pdf
…brominated flame retardants…
TBBPA PBDES HBCD
? ?
? ? ? ? ? ? ?
? ?
? ? ?
?
? ? ?
?
Regulations for FCAs - EC – Migration Test [1]: Regulation on plastic materials
and articles intended to come into contact with food.
– Positive List [2,3]: All chemicals listed here were individually evaluated for their toxicity and migration behaviour by EFSA which defined a specific migration limit for controlled migration and evaluation of the FCA
– BFRs are not listed in this positive list …not allowed to be used as initial substances for the manufacture of FCAs sold on the European market.
[1] Regulation (EC) No. 10/2011 of 14 January 2011 [2] Directive (EC) No. 1183/2012/EU of 30 November 2012 amending and correcting Regulation (EU) No 10/2011 [3] Regulation (EC) No. 202/2014 of 3 March 2014 amending European Commission Regulation (EU) No. 10/2011
• Mlada Fronta Dnes (CZ Newspaper)
Enlarged Study 2013
• 5 European countries • 30 samples, mainly black 49 test points
Thermo cup lid body – typically bromine negative
Thermo cup sliding stopper – typically bromine positive
Results 2013 • TD-GC-MS
– Black thermo-cup (sliding stopper) sampled in Frankfurt – 740 mg kg-1 bromine, technical decaBDE
Results 2013 • From 49 test points 15 test points contained bromine
with in 14 cases BFRs detected.
• Mainly technical decaBDE was detected.
• In many cases more than 1 type of BFR (with TBBPA) was detected which might indicate a mixture of polymers. Also newer BFRs were detected.
• The overall bromine concentrations were too low to effectively achieve flame retardancy (< 0,2 weight %)!
44
Results 2013 • Additional applied technique: ATR-FTIR
– IRTracer-100+ GladiATR 10, Shimadzu – Non-destructive polymer identification
Recycled polymers – study 2015
Sample Sample Colour Main polymer a
Detected monomers (Pyrolysis GC-MS)
Macromolecular contamination a
Br content b
(mg kg-1)
Detected BFRs c
1 Egg cutter Black PP/PE 4-ethenyl-cyclohexene; styrene; α-methylstyrene;
Benzoic acid
HIPS/ PBT or PET
57 TBBPA, decaBDE
2 Electric frying pan Black PBT 1,4-butadiene; 4-ethenyl-cyclohexene;
styrene; α-methylstyrene
HIPS or ABS or SAN 5975 TBBPA, DBDPE
5 Movable lid (thermocup cover)
Black ABS Methylmethacrylate; Benzoic acid
PMMA/ PBT or PET
504 TBBPA, decaBDE
10 Screwable closure (thermocup cover)
Black PP/PE Methylmethacrylate; styrene;
α-methylstyrene
PMMA PS
PBT or PET
n.d. n.d.
Notes: a The main polymer and possible polymeric contaminants were interpreted from FTIR spectra combined with pyrolysis GC-MS data b Measured by XRF; n.d.means not detected and implements a limit of detection of 40 mg kg-1 c Measured by thermal desorption GC-MS.
E-waste cities
…and now the evidence…
Recycled polymers – study 2015 Element Sample 1 Sample 2 Sample 5 Sample 10
As 4.0 7.2 4.0 -
Cd 2.0 - a 5.5 -
Ce 8.9 7.3 - -
Cr 19 2.4 6.5 -
Cu 37 - 20 -
Dy 0.42 - - -
Fe 1200 59 75 4.8
Hg 0.14 0.019 0.81 -
La 2.4 - - -
Nd 2.5 - - -
Ni 3.0 1.9 2.4 0.54
Pb 99 - 26 -
Pr 4.5 - - -
Sb - 500 110 -
Y 2.0 - - -
Zn 100 30 38. 25
Elemental composition of the samples. All data in mg/kg. a “-” means not detected with a value below the LOD for the selected element
Conventional Pyrolysis GC-MS (ISO 7270-1 and ISO 17257)
PE >500 °C
TGA
PYROLYSIS-GC-MS
2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5 (x10,000,000)
Triplet order of elution Diene – Alkene - Alkane C10 C11 C12
>C40
Quantitative pyrolysis PVP in PA6
sample % PVP a 3,8 b 4,2 c 3,7 d 4,0
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
(x10,000,000)
The signal area % signal of vinylpyrolidinone in (vinylpyrolidinone +caprolactam) was used as quantifier.
Quantitative pyrolysis: PVoH in PA6
y = 0,0104x - 0,0934 R² = 0,9961
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
10 15 20 25 30 35 40 45
Rat
io 2
-but
enal
/cap
rola
ctam
weight % PVOH/PA6
4 mixtures of PVoH and PA6 were mixed and measured (n=3)
Typical results are: 19,0 ± 0,8 weight % PVoH in PA6 (n=2)
Puype, F.; Samsonek, J. (2014) `` Internal standardization for analytical pyrolysis, thermal desorption and quantitative in-source desorption by electron impact ionization: strategies for polymer science``, ISBN 978-80-7454-335-7, p 138-141
Quantitative pyrolysis: quantification of the bromination degree of brominated polystyrene
Thermal stability Better performance than classical BFR additives No migration/blooming >79 types of BFR on the market Some are restricted/limited – speciation required (PBDEs, PBBs, HBCD)
Unzipping - depolymerization
PYROLYSIS GC-MS
Puype, F. (2008) ``Pyrolysis coupled with GC-MS for the rapid characterization of synthetic polymers`` ISBN 978-80-968433-5-0
Quantitative pyrolysis: quantification of the bromination degree of brominated polystyrene
Monobromostyrene
Isomers
Dibromostyrene
isomers
Tribromostyrene
isomers Tetrabromostyrene
isomers Br
CH2
Quantitative pyrolysis: quantification of the bromination degree of brominated polystyrene
Name # Br Area Area*# Br
bromostyrene 1 4352225 4352225
dibromostyrene 2 149947047 299894094
tribromostyrene 3 217125137 651375411
tetrabromostyrene 4 17544206 70176824
SUM 388968615 1025798554
Bromination degree: Σ(Area*#)/Σ (Area) = 2,64
Condition:
- all monomers are obtained by the same fragmentation mechanism
- By combining the bromination degree (weight factor) and area…
Pyrolysis GC-MS @ 650 °C (polymer identification/CR)
Chloroprene + dechlorination products
Pyrolysis of PMMA at 650°C
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
(x1,000,000)
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
(x100,000)MMA
Benzene MMA
Toluene
Styrene
Benzoic acid methylester at tR 4 minutes (SIM !!)
O
O
O
O
Benzoylperoxide initiator
TMAH thermochemolysis • TMAH/methanol • TMAH is liquid and easy to apply (mixing with polymers is possible and recommended) • TMAH reacts quick (versus silylation) • During reactive pyrolysis TMAH decomposes • TMAH is organic (not like KOH, no salts!)
TMAH TMAH in action
Reactive pyrolysis
• Reactive pyrolsis requires TMAH/MeOH for selective thermolysis of condensed polymers.
• Conditions: 440°C • 2 minutes • Cleaner pyrograms • Selective cleavage
TMAH
Reactive pyrolysis GC-MS: PC
CH3
O
CH3
CH3
OOME-tert.Butylphenol
ME-Bisphenol A
New trends in thermoplastics: composites in aerospace, defense and automotive
- Improved crosslinking
- Good-to-excellent heat resistance properties - Relatively cheap (polyetherimide, addition cure resins)
conventional pyrolysis (600°C)
OH
CH3
OH
CH3CH3
OH
CH2CH3
OH
OO
NNMDI/MDA isomers Phenol and alkylphenols
Phenol formaldehyde resin with typical PU monomers ? Strange: isopropylphenol!
reactive pyrolysis (440°C, TMAH)
TMAH derivates
BPA-dimethylether Unsaturated alkyl derivates from bisphenol A / MDA
Phenol formaldehyde resin with typical PU monomers ? Strange: isopropylphenol! + BPA + alkylated BPA derivates….
solution….addition cure resins
PY-GC-MS: MDI/MDA + phenolic compounds
Reactive pyrolysis: Alkylphenolic and phenolic compounds (BPA derivates)
Cross linked Alder-ene of 4,4`-bismaleoimido diphenyl methane (BMM) with 2,2`-diallyl bisphenol A (DABA). This 2-component bismaleimide formulation cures by the copolymerization of maleimide and alkyl groups as the major reaction.
O
O
N
O
O
N
CH2
OHOH
CH3
CH3
CH2
BMM
DABA
polyetherimide
Pyrolysis GC-MS
RO
O
CH3
CH3
O
O
R
N
O
O
NOH
CH3CH3
OH
OH
CH3
CH3
OH
OH
CH3
CH3
NH2
O
O
N
Reactive Pyrolysis GC-MS
CH3
CH3
CH3
CH3
N
N
Polyetherimide
Polyurethanes: TBBPA presented?
TMAH derivates Polyether distribution (as dimethylethers)
TBBPA (functionality=2) Presented or not?
Brominated flame retardants…
Polyurethanes: TBBPA presented?
TMAH derivates Polyether distribution (as dimethylethers)
TBBPA dimethylether detected
525.0 550.0 575.00.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
3.25(x10,000)
556.8
554.8
571.9
569.9560.9
575.9541.9524.9
TMAH
SIMdata Mass spectrum
Brominated flame retardants…
MDI (MDA) ratio by reactive pyrolysis…possible!
PMDI
MDI isomers
4,4`-MDI 2,4`-MDI
2,2`-MDI
Methyl-MDI
Inorganic mass spectrometry ICP-MS for elemental quantification
Inorganic mass spectrometry combined with DI
50 100 150 200 250 300 350 400 450 500 550 600 6500.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
(x10,000)
575.15
287.7063.00
191.00
609.1098.15207.05
304.65117.15 154.10 339.85 645.10261.85 500.95 533.20445.00 479.00401.10
Figure 2: DI-MS mass spectrum of a dichlorinated phtalocyanine-type
coordination complex of copper (II) after clean-up from the PVB matrix.
63Cu+
65Cu+
[M-Cl2]3+
[M-Cl]3+
[M-Cl2]2+
[M-Cl]2+
[M-Cl2]+
[M-Cl]+
[M]+
ClCl
CuN- N
-
N
N
N
N
N
N
chemical structure of the identified dichlorinated phtalocyanine-type
coordination complex of copper (II).
Puype, F. (2014) ``Combined method of GPC-ICP-MS; ICP-MS and DI-MS for speciation of unknown organometallic compounds``, ICP information newsletter, volume 39, special edition.
Inorganic mass spectrometry: Pt in silicone
0
50
100
150
200
250
sample 1 sample 2 sample 3 sample 4 sample 5 sample 6 sample 7 sample 8 sample 9 sample10
sample11
obtained concentrations of Pt (mg kg-1)
Full Time Range TIC : NIST 8013 A NOT dilluted.d
RT(min)
0.3 0.6 0.9
Co
un
t
3x10
0
1
2
3
Nanoparticle sizing measurement
NIST 8013: 60 nm GOLD
Nanoparticle sizing measurement
Anatase TiO2 NIST 8013, 60 nm Au
Nanosilver from textile Double distribution of anatase TiO2
1// ELUTE project as associated partner (U-Birmingham) - To evaluate the ability of screening-level tools for the measurement of Br to provide surrogate measures of
BFR concentrations. - To elucidate past temporal trends in environmental levels of BFRs and PBDD/Fs and use these data to test the
hypothesis that increased BFR use has increased contamination with PBDD/Fs. - To improve scientific understanding of the environmental degradation and metabolism of BFRs.
2// Subcontracted co-author for CEN on guidance document: ``Detection and identification of nano-objects in complex matrices`` in cooperation with the Technische Universität, Dresden, Germany.
3// Subcontracted co-author Chapter: ``RoHS and spectroscopy`` Encyclopedia of Spectroscopy and Spectrometry, Elsevier. 4// other papers are coming….
Activities:
Thanks for your attention !!!