polymer characterization completing the story through mass ... · polymer characterization:...

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

…we need more evidence…:Study 2015

Open Access: http://bit.ly/1FpsG73

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 !!!