Microsecond spICP-MS for dual-element detection ... · Microsecond spICP-MS for dual-element...

Manuel David MontañoColorado School of MinesJuly 10th, 2014

Microsecond spICP-MS for dual-element detection: Environmental and Analytical Applications

Manuel David Montaño

ERC Teleconference SeminarColorado School of Mines

July 10th, 2014

1


2

spICP-MS dual-element detection

Benn, T.; Westerhoff, P. Environmental Science and Technology, 2008

• Entry of ENMs into the environment

• Principles and operation of spICP-MS

• Particle-by-particle dual-element analysis Isotopic ratio determination (Ag NPs) Core-shell nanomaterials

o Sed-FFF fraction collection

o Particle size and number

determination

Natural vs. engineered NPs

o Bulk elemental ratios

o Cerium dioxide ENPs in

stream water


3

ENM Environmental Release

Nowack, B. et al. Environment International, 2013.

• Increasing production of ENPs will lead to inevitable environmental release and exposure

• Release of nanomaterials can come at any point during fabrication and use

• Little information regarding quantity, fate, and behavior of ENPs in environment


4

ENM Environmental Release

Aqueous environment will contain varied assortment of nanomaterials

Important properties to characterizeo Particle sizeo Aggregation stateo Particle number concentrationo Surface groups / chemistry

Challenges for environmental analysiso Low expected release

concentrations (ng L-1)o Changes to surface chemistry /

dispersity by environmental molecules (i.e. humic acid)

o High background of naturally occurring nanomaterials

Montaño, M. et al. Environmental Chemistry, Accepted


5

Environmental Transformation of ENMs

Alvarez, ACS Nano, 2009


6

Need for Advanced Nanometrology

National Nanotechnology Initiative Workshop, Arlington VA, 2009


7

Need for Advanced Nanometrology

National Nanotechnology Initiative Workshop, Arlington VA, 2009


8

Single Particle ICP-MS

Montaño, M. et al. Environmental Chemistry, 2014

• Utilizes short dwell times (ms) to detect discrete particle events

• Environmentally relevant detection limit (ng/L)

• Need particles of sufficient mass to be detected

• Can distinguish particle and dissolved


9

Principles of spICP-MS Operation

Montaño, M. Unpublished Data

0 50 100 150 200

0

100

200

300

400

500

600

700

800

Co

unts

Time (sec)

2% HCl

500ppt Au

1000ppt Au

1500ppt Au

2000ppt Au

0 1 2

0

100

200

300

400

500

600 Au signal

Au

sig

na

l (S

ign

al In

tensity)

Conc. (ppb)

Equation y = a + b*x

Weight No Weighting

Residual Sum

of Squares

465.89825

Pearson's r 0.99893

Adj. R-Square 0.99714

Value Standard Error

Au signal Intercept -4.39476 9.65296

Au signal Slope 294.23719 7.88161

0.00 1.00x10-8

2.00x10-8

0

100

200

300

400

500

600

Avg. counts

/dw

ell tim

e

mass/dwell time


Weight No Weighting

Residual Sum

of Squares

465.89825

Pearson's r 0.99893



Avg.

counts/dwell

time

Intercept -4.39476 9.65296

Slope 3.12509E10 8.37104E8

Dissolved standards Calibration curve Mass flux curve


10

Principles of spICP-MS Operation

Montaño, M. Unpublished Data

0 50 100 150 200

0

100

200

300

400

500

600

700

800

Co

unts

Time (sec)

2% HCl

500ppt Au

1000ppt Au

1500ppt Au

2000ppt Au

0 1 2

0

100

200

300

400

500

600 Au signal

Au

sig

na

l (S

ign

al In

tensity)

Conc. (ppb)


Weight No Weighting

Residual Sum

of Squares

465.89825

Pearson's r 0.99893



Au signal Intercept -4.39476 9.65296

Au signal Slope 294.23719 7.88161

0.00 1.00x10-8

2.00x10-8

0

100

200

300

400

500

600

Avg. counts

/dw

ell tim

e

mass/dwell time


Weight No Weighting

Residual Sum

of Squares

465.89825

Pearson's r 0.99893



Avg.

counts/dwell

time

Intercept -4.39476 9.65296

Slope 3.12509E10 8.37104E8

Dissolved standards Calibration curve Mass flux curve

0 100 200

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Au N

P #

3 (

cts

)

Time (sec)

Au NP #3

0 250 500 750 1000 1250 1500 1750 20000

20

Co

unt

Au NP #3 (cts)

Au NP #3

75 80 85 90 95 100 105 110 115 120 125

0

10

20

30

40

50

60

Count

Size (D.nm)

Au NP #1

Raw particle counts Frequency of particle counts Particle size / number


11

Analytical Challenges – High particle no. conc.

Montaño, M. et al. Environmental Chemistry, In Press

500μs

• Nanoparticle events occur over a few hundred microseconds

• Millisecond dwell times may be too large, resulting in coincidence

• This can lead to:o Underestimation of particle

numbero Inaccurate sizing of particles


12



10ms dwell time






13



500μs10ms dwell time10ms dwell time






14

Analytical Challenges – High dissolved background


NP event• Nanoparticles entering the

plasma are ionized and detected

• The occurrence of background ions is shown as an elevated background

• If the concentration is high enough, it can mask the presence of a nanoparticle event


15



Dwell time

• Nanoparticles entering the plasma are ionized and detected




16



NP eventDwell time

Dwell time• Nanoparticles entering the

plasma are ionized and detected




17

Microsecond-single particle ICP-MS


Conventional single particle ICP-MS analyzes dilute concentration of nanoparticles at short dwell times (~10ms)

Nanoparticles events occur over span of hundreds of microseconds (10ms too long)

Microsecond dwell times parse nanoparticle events into a distribution of intensity

Improves ability to analyze high particle number concentrations and high dissolved backgrounds

Opens the door for multi-element analysis on a particle-by-particle basis

30.2 30.3 30.4 30.5 30.6

0

100

200

300

400

500

600

700

800

900

1000

ICP

-MS

Res

pons

e (c

ount

s)

Time (sec)

31.10

0

50

100

150

200

250

ICP

-MS

Res

pons

e (c

ount

s)

Time (sec)

Co

nve

nti

on

al (

10

ms)

10

0μ

s d

well

tim

es


18

Improving Particle Resolution: Overcoming coincidence

Montaño, M. et al. Environmental Science: Nano, 2014

11.110 11.115 11.120 11.125 11.130

0

20

40

60

80

100

120

140C

ounts

Time (sec)

392 counts

287 counts

352 counts

2ppb 100nm Au NPs (0.1ms)


19



11.110 11.115 11.120 11.125 11.130

0

20

40

60

80

100

120

140C

ounts

Time (sec)

392 counts

287 counts

352 counts10ms10ms



20



11.110 11.115 11.120 11.125 11.130

0

20

40

60

80

100

120

140C

ounts

Time (sec)

392 counts

287 counts

352 counts

3ms 3ms 3ms 3ms 3ms 3ms 3ms



21



• Microsecond spICP-MS vastly improves particle resolution

• Particle number concentrations and sizing can be better determined


22

Reducing Background Interference


20 22 24 26 28 30 32 34 36 38 400

200

400

600

800

1000

1200

1400

ICP

-MS

response (

counts

)

Time (sec)

0.1ms dwell time

3ms dwell time

10ms dwell time30.845 30.846 30.847 30.848 30.849 30.8500

20

40

60

80

ICP

-MS

re

sp

on

se

(co

un

ts)

Time (sec)

• Reducing dwell time results in a reduction of counts from dissolved analyte

• Lower dwell times allow for better resolution between background and analyte signals

500ppt Ag+ + 50ppt Ag NPs


23

Reducing Background Interference


Increasing Dissolved Ag+ Concentration

Decreasin

g dw

ell time


24

Dual-element Detection in spICP-MS


• New microsecond dwell times allow for the analysis of two elements within a single particle

• Applied to the analysis of complex (core-shell) nanomaterials

• Possible method for differentiating between naturally occurring and engineered nanomaterials


25

Principles of Dual-element Analysis


Time required for the quadrupole to switch between the two masses

Dwell time of a given mass analyte


26

Limitations of dual-element ICP-MS

NP events (500μs)

• The length of the settling time results in “lost” analyte signal

• Analysis is not simultaneous, and will result in variable signal of the two analytes

• Currently qualitative on a particle by particle basis, but can be quantitative with the overall average of signal intensity


27


Settling Time





28


Settling Time Ag detection





29


Settling Time Ag detection Au detection





30

Proof of Concept – Isotopic Ratios


• 60nm silver nanoparticles were analyzed for isotopes 107Ag and 109Ag

• These two isotopes occur in early equal ratios naturally

(107Ag: 51.35% and 109Ag: 48.65%)

• Some individual peaks show ratios similar to natural isotopic abundance

• Average of overall intensities match closely with natural abundance:

(107Ag: 50.7% and 109Ag: 49.2%)(n= 125000)


31

Core-shell Nanomaterials

30 nm 15 nm15 nm

• Some nanomaterials have complex morphologies such as a core-shell structure

• Examples of core-shell nanomaterials includeo Carbon-coated metal oxides for catalysis o Metal sulfide capped semiconducting

quantum dots

• Both the core and shell must contain an detectable amount of mass to be analyzed by dual-element spICP-MS


32

Experimental Set-up

Suwanpetch, R.; Montaño, M.; Tadjiki, S.; Ranville, J. In preparation, 2014

• Gold core (30nm) – Silver shell (15nm) nanoparticles were analyzed by single particle ICP-MS

• Fractions were collected from both Flow field flow fractionation (AF4) and Centrifugal-FFF (Sed-FFF)

• AF4 is a separation technique based off of hydrodynamic diameter

• Centrifugal-FFF separates according to a particles buoyant mass

Asymmetrical Flow Field Flow Fractionation (AF4)

Centrifugal Field Flow Fractionation (Sed-FFF)


33

Flow Field Flow Fractionation Chromatograms


0 10 20 30 40 50 60

0

10000

20000

30000

40000

50000

Inte

nsity (

cp

s)

Retention time (min)

Ag-107

Au-197

0 500 1000 1500 2000

0

10000

20000

30000

40000

50000

60000

ICP

-MS

Response (

counts

)

Time (sec)

107

Ag Response

197

Au Response

AF4 coupled to ICP-MS Sed-FFF coupled to ICP-MS

• Both fractograms show co-eluting of gold and silver peaks

• Evidence for one single particles, instead of individual gold and silver particles in solution


34

Flow Field Flow Fractionation Chromatograms - Mixtures


• Separation of a mixture by AF4 would show just one particle type at 60nm

• Separation of particles by Sed-FFF would show particle of similar mass

• Analysis by spICP-MS can differentiate between core-shell (bi-metallic) and single metal nanomaterials


35

Particle size of Core-shell NMs by spICP-MS

15 20 25 30 35 40 45 50 55 60

15

20

25

30

35

40

45

50

55

Dia

mete

r (n

m)

Time (min)

Au-ST

Au-JR

15 20 25 30 35 40 45

30

35

40

45

50

55

60

65

70

75

Dia

mete

r (n

m)

Time (min)

Ag-ST

Ag-JR

Gold Core Diameter ComparisonTotal Diameter Comparison

(Based on silver mass)

• Particle sizes are consistent with distribution of intensity by FFF-ICP-MS

• Gold core at peak maxima (30min) is 30nm

• Total diameter at peak maxima (assuming 30nm core) is ~45nm



36

Particle Number Concentration Comparison

15 20 25 30 35 40 45 50

0

1x108

2x108

3x108

4x108

5x108

6x108

7x108

8x108

9x108

Part

icle

num

ber

conc. (P

art

icle

s/L

)

Time (min)

107Ag nanoparticles

197Au nanoparticles

20 30 40 50

0.0

5.0x107

1.0x108

1.5x108

2.0x108

2.5x108

Pa

rtic

le n

um

be

r co

nc.

(Pa

rtic

les/L

)

Time (min)

107Ag Nanoparticles

197Au Nanoparticles

Replicate 1 Replicate 2

• Discrepancy in particle number concentration (# of events detected)

• Possible loss of gold analyte signal to background due to small size



37

Particle Number Concentration Comparison

15 20 25 30 35 40 45 50

0

1x108

2x108

3x108

4x108

5x108

6x108

7x108

8x108

9x108

Part

icle

num

ber

conc. (P

art

icle

s/L

)

Time (min)

107Ag nanoparticles

197Au nanoparticles

20 30 40 50

0.0

5.0x107

1.0x108

1.5x108

2.0x108

2.5x108

Pa

rtic

le n

um

be

r co

nc.

(Pa

rtic

les/L

)

Time (min)

107Ag Nanoparticles

197Au Nanoparticles

Replicate 1 Replicate 2

• Discrepancy in particle number concentration (# of events detected)

• Possible loss of gold analyte signal to background due to small size



38

Dual-element Analysis of Core-shell NPs

• Dual-element analysis of NPs show presence of both gold and silver

• Some gold signal may be lost to the background

• Dual element analysis and individual particle analysis shows consistent elemental intensity ratios:Dual element analysis

107Ag: 77.7% /197Au: 22.3%Individual particle analysis 107Ag: 71.2%/ 197Au: 28.8%



39

Environmental Analytical Challenges – Natural Nanomaterials

Kiser, M. et al. Environmental Science and Technology, 2008

Ti-containing mineral in biosolid (Kiser)

TiO2 nanoparticles in toothpaste

• ENPs will be released into an environment containing several naturally occurring nanomaterials

• Natural nanomaterials are present in concentrations much higher than expected release concentrations

• Many of these nanomaterials will be of similar chemical composition to their engineered analogues


40

Environmental Analytical Challenges – Natural Nanomaterials

Kiser, M. et al. Environmental Science and Technology, 2008

Ag nanoparticles prepared by silver ammonia reduction (Panacek)

Ag nanoparticles found in sock fabric (Benn)

Ag nanoparticles synthesized by Aspergillus flavus (Vigneshwaran)


41

ENM vs. NNP Properties

Most engineered nanomaterials have naturally occurring analogues

Some key differences can be used to differentiate natural and engineering NMs

Environmental processes may drastically affect some of these properties (i.e. surface coatings, aggregation state, size distribution)

Elemental composition may remain the most unchanged property in the environment



42

Elemental Ratio Analysis

1) Montaño, M. et al. Environmental Chemistry, In Press2) O’Loughling, E. et al. Environ Sci. and Tech. 20033) Burgos, W. et al. Geochimica et Cosmochimica Acta. 2008

• Elemental ratios may be used to differentiate engineered and naturally occurring nanomaterials

• Natural nanomaterials may have broader size distribution than more tightly controlled ENMs

• Particle-by-particle analysis of elemental ratios (μsec-spICP-MS) can be used to differentiate between naturally occurring and engineered nanomaterials

Uraninite nanoparticles precipitated on mixed Fe(II)/Fe(III) hydroxides

Uraninite nanoparticles precipitated from soluble U(VI) by Shewanella oneidensisMR-1 strain


43

Elemental Ratio Analysis


Natural elemental ratios show a trend with a natural variation

Statistically significant deviations outside confidence interval of trend may be presence of engineered nanomaterials

May require significant amounts of engineered nanomaterial

Limited information about physical/chemical state of nanomaterials (i.e. aggregation)

Ce 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛𝜇𝑔𝐿

La 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛𝜇𝑔𝐿

=

1.7𝜇𝑔𝐿 𝐶𝑒

1𝜇𝑔𝐿

𝐿𝑎= 1.7

1.7𝜇𝑔𝐿 Ce +

170𝑛𝑔𝐿 𝐶𝑒𝑂2 𝑁𝑃𝑠

1𝜇𝑔𝐿 𝐿𝑎

= 1.87


Analysis of a natural nanoparticle will show presence of many elements

Summation of elemental signal can be used to give elemental ratio on a particle basis

Engineered nanomaterial will show the presence of only one element, or have a different elemental ratio

Requires sufficient mass to produce an appreciable, detectable signal

44

Particle-by-particle Elemental Analysis







45








46




47

Analysis of an Impacted Natural System

• Analysis of a nearby natural stream (Clear Creek, Golden, CO, USA) showed presence of particles containing Ce and La (fig. A and C)

• Ratio was consistent with literature values

• 80-100nm engineered cerium dioxide was spiked into natural water

• Elemental ratio shifted toward cerium. Presence of cerium-only particles persisted (fig. B and D)



48

Conclusions and Future Outlook

Conclusions

Future Research

Conventional single particle ICP-MS uses dwell times too large for accurate particle sizing and counting

The presence of natural nanomaterials will impede the detection and characterization of engineered nanomaterials

Microsecond dwell times off the ability to improve particle resolution, reduce background signal and introduce particle-by-particle elemental ratios

More work is required to improve sensitivity of single particle ICP-MS to detect smaller particle sizes

New TOF-ICP-MS may be used to detect several elements within a single particle*

Develop methods to identify aggregation state of nanomaterials in the environment

Borovinskaya, O. et al. JAAS, 2013.


49

Acknowledgements

Ranville Research Group

Collaborators:o Hamid Badiei, Samad

Bazargan, Pritesh Patel, Dylan McNair, Kenneth Neubauer(Perkin Elmer)

o Christopher Higgins (CSM)o Soheyl Tadjiki (PostNova

Analytics)o Rabiab Suwanpetch

Fundingo Semiconductor Research

Corporationo EPA Contract No. EP-C-11-039

Pictured from left to right: Jacob Williamson, Rabiab Suwanpetch, Jingjing Wang,Dr. James Ranville, Angela Barber, Evan Gray, Manuel Montaño, Elizabeth Traudt


50

References

1. Nowack, B.; David, R.; Fissan, H.; Morris, H.; Shatkin, J.; Stintz, M.; Zepp, R.; Brouwer, D. Potential release sceanrios for carbon nanotubes used in composites. Environment International, 2013, 59, pp. 1-11.

2. Montano, M.; Ranville, J.; Lowry, G.; von der Kammer, F.; Blue, J. Current status and future direction for examining engineered nanomaterials in natural systems. Environmental Chemistry. Accepted April 2014.

3. Kiser, M.; Westerhoff, P.; Benn, T.; Wang, Y.; Pêrez-Rivera, J.; Hristovski, K. Titanium Nanomaterial Removal and Release from Wastewater Treatment . Environmental Science and Technology. 2008, 43, pp. 6757-6763.

4. Montaño, M.; Ranville, J.; Badiei, H.; Bazargan, S. Improvement in the detection and characterization of engineered nanomaterials using spICP-MS with microsecond dwell times. Environmental Science: Nano. Submitted 2014.

5. Borovinskaya, O.; Hattendorf, B.; Tanner, M.; Gschwind, S.; Günther, D. A prototype of a new inductively coupled plasma time-of-flight mass spectrometer providing temporally resolved, multi-element detection of short signals generated by single particles and droplets. Journal of Analytical Atomic Spectrometry, 2013, 28, pp. 226-233.

6. Panáček, A.; Kvitek, L.; Prucek, R.; Kolář, M.; Večeřová, R.; Pizúrová, N.; Sharma, V.; Nevěčná, T.; Zbořil, R. Silver Colloid Nanoparticles: Synthesis, Characterization, and Their Antibacterial Activity. Journal of Physical Chemistry B, 2006, 110, pp. 16248-16253.

7. Benn, T.; Westerhoff, P. Nanoparticle Silver Released into Water from Commercially Available Sock Fabrics. Environmental Science and Technology, 2008, 42, pp. 4133-4139.

8. Vigneshwaran, N.; Ashtaputre, N.; Varadarajan, P.; Nachane, R.; Paralikar, K.; Balasubramanya, R. Biological synthesis of silver nanoparticles using the fungus Aspergillus flavus. Materials Letters, 2007, 61, pp. 1413-1418.


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