the 1955 aas paper a. walsh, "the application of atomic absorption spectra to chemical...

The 1955 AAS paper

A. Walsh, "The application of atomic absorption spectra to chemical analysis", Spectrochimica Acta, 1955, 7, 108-117.

Reprinted from Spectrochimica Acta, Vol 7, A. Walsh, The application of atomic absorption spectra to chemical analysis, Pages 108-117, © (1955), with permission from Elsevier.

Constructivism: effective learning

Engagement and understandingLink VCE physics (science) to topical events

2005 = 50th anniversary of paper of Victorian invention

Multiple teachers running in the same direction

Integrated curriculum Themes crossing curriculum boundaries Each discipline offers different insights

Electromagnetic spectrum: Figure 6.4, Brown, Lemay, Bursten, Burdge, Chemistry the Central Science (9e), Prentice-Hall, 2003.

Electromagnetic spectrum

Electromagnetic spectrum: Figure 6.4, Brown, Lemay, Bursten, Burdge, Chemistry the Central Science (9e), Prentice-Hall, 2003.

Light passing through a prism: Figure 6.10, Brown, Lemay, Bursten, Burdge, Chemistry the Central Science (9e), Prentice-Hall, 2003.

Light passing through a prism: Figure 6.10, Brown, Lemay, Bursten, Burdge, Chemistry the Central Science (9e), Prentice-Hall, 2003.

Light passing through a prism

Sodium atomic emission spectrum

Wavelength, λ

, Intensity

I

Solar spectrum: 400 to 700 nm

Solar spectrum: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF<http://www.noao.edu/image_gallery/images/d5/suna.jpg>

Absorption spectroscopy

Solar flare image: NSO/AURA/NSF<http://www.noao.edu/image_gallery/images/d1/02245b.jpg>

Light source

DetectorSample

IoutIinit

€

I init,Iout=lightintensity

€

Absorbance=log10I init

Iout

Solar spectrum


http://www.shef.ac.uk/physics/teaching/phy103/solspec72.gif

Atomic spectroscopy

Energy

~100% population

Emission Absorption

~0% population

Atomic spectroscopy

Boltzmann distribution

€

population(j)population(0)

=N j

N0=exp

−E j

kT⎧ ⎨ ⎩

⎫ ⎬ ⎭

=exp−E j

RT⎧ ⎨ ⎩

⎫ ⎬ ⎭

Atomic energy Molecular energy

WavelengthAtom Nj /N0 at 3000 K

589.0 nmNa 5.88 10-4

422.7 nmCa 3.69 10-5

213.9 nmZn 5.58 10-10

852.1 nmCs 7.24 10-3

Light sources

Wide spectrum (thermal) light sources

Narrow spectrum light sources


Atomic spectroscopy

Atomic emission Zero background (noise)

Atomic absorption Bright background (noise) Measure intensity change More signal than emission Trace detection

The 1955 AAS paper


Reprinted from Spectrochimica Acta, Vol 7, A. Walsh, The application of atomic absorption spectra to chemical analysis, Pages 108-117, © (1955), with permission from Elsevier.

The 1955 AAS paper


Remove bright background > Hollow cathode lamp

Measure intensity change> Light chopper

Atomic spectra> Flame atomisation

Photo of Sir Alan Walsh. © Australian Academy of Science. Reproduced from Historical Records of Australian Science vol. 13 (P. Hannaford, 2000) by permission of CSIRO Publishing and Australian Academy of Science.

Hollow cathode lamp

Electron and ionic impact on cathodeM(s) M(g)M(g) M*(g)M*(g) M(g) + h

The black "getter" spot

Thin lay of cathode material

Pictures of hollow cathode lamp, © Varian inc.Reproduced with permission from Varian Australia.

low-pressure inert gas

Flame burner: D. C. Harris, Quantitative Chemical Analysis, 6th Edn., W.H. Freeman and Company, New York, 2002,

from Figure 21-2.

Flame burner

Flame burner: D. C. Harris, Quantitative Chemical Analysis, 6th Edn., W.H. Freeman and Company, New York, 2002, from Figure 21-2.

Mn+(aq) + anion(aq) salt(s)salt(s) salt(g)salt(g) atoms (g)M*(g) M(g) + hn

Light chopper

Emission only

Light chopper

Emission and

transmitted light

Reprinted from Spectrochimica Acta Part B, Vol 54, A. Walsh, The development of the atomic absorption spectrophotometer, Pages 1943-1952, © (1999), with permission from Elsevier.

The original 1954 AAS instrument

Reprinted from Spectrochimica Acta Part B, Vol 54, A. Walsh, The development of the atomic absorption spectrophotometer, Pages 1943-1952, © (1999), with permission from Elsevier.

The first commercial prototype

Pictures of Varian AA280 flame instrument, © Varian inc.Reproduced with permission from Varian Australia.

Hollow cathode lamps

Modern commercial AAS instrument

Flame atomiser Sample inlet

Element Flame AAS Flame AESAg 3 20Ca 1 0.1Cd 1 2000Fe 6 50K 2 3

Mg 0.2 5Mn 2 15Na 0.2 0.1Ni 3 600Pb 5 200Zn 1 200

Detection limits (ppm = ng mL-1)

Data compiled by D. A. Skoog, D. M. West, F. J. Holler and S. R. Crouch,Fundamentals of Analytical Chemistry, 8th Edn., Brooks/Cole, Belmont (CA), 2004.

First-year chemistry exercise at Deakin University.

Student determination of Fe

Fe: 0.05

mg mL-1

50.00 mL volumetric flasks

1.00 mL pipette

2 mL1 mL 3 mL 4 mL 5 mL

Actual student data from first-year chemistry exercise at Deakin University.

Student determination of Fe

Calibration curve for absorbance of Fe

y = 0.2093x + 0.001

0

0.5

1

1.5

0 1 2 3 4 5 6

Fe concentration / ppm

Absorbance

Classroom use of atomic absorption

AAS idea 3 AAS idea 5previewsreviews

VCE topic

AAS idea 4

VCE topic VCE topic

VCE Physics Unit 1 (Light and waves)

Key knowledge and skills describe mathematically connections between wavelength,

frequency, period and speed of travel of waves; identify visible light as a particular region of a spectrum of

transverse electromagnetic radiation; describe the colour components of white light …; describe colour dispersion in prisms and lenses

VCE Physics Unit 2 (Astrophysics)

Light is the basic tool of astrophysicists and … the nature of the nuclear atom is the same throughout the Universe.

Key knowledge and skills describe characteristics of the Sun as a typical star,

including size, mass, energy output, colour and information obtained from the Sun’s radiation spectrum;

VCE Physics Unit 4 (… light and matter)

Outcome 1 On completion of this unit the student should be able to use

wave and photon models to explain interactions of light and matter and the quantised energy levels of atoms.

Key knowledge and skills interpret atomic absorption and emission spectra in terms

of a quantised energy level model of the atom, including calculations of the energy of photons … E = hf

VCE Physics Unit 4 (3.2: Photonics)

Key knowledge and skills explain the production of light by incoherent light sources,

in terms of> thermal motion of charged particles in materials for

wide spectrum light sources, including the Sun…> transitions between quantised energy states of atoms

for narrow spectrum light sources, including metal vapour lamps

VCE Chemistry Unit 3 (Analytical chem.)

Key knowledge: … analytical procedures … including … flame tests and …

atomic absorption spectroscopy

Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka

Reprinted from Ecotoxicology and Environmental Safety, Vol. 50, G. Allinson, et al., Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka, Pages 197-202 , © ( 2002), with permission from Elsevier.

Determination of Hg in fish

Locations of the reservoirs from which tilapia samples were obtained. Cities: Cl, Colombo; G, Galle. Reservoirs: C, Chandrikewewa; R, Ridiyagama; M, Meegahanjandura; B, Badagiriya; K, Kirribanwewa.

c UN FAO PWTDI (Provisional Tolerable Weekly Intake).d UN FAO PMTDI (Provisional Maximum Tolerable Daily Intake). All calculations assume an average male adult body weight of 70 kg.

Selected elements (g) in 60 g tilapia

Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka

Reprinted from Ecotoxicology and Environmental Safety, Vol. 50, G. Allinson, et al., Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka, Pages 197-202 , © ( 2002), with permission from Elsevier.

Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka Average diet: 60 g tilapia day-1

Provisional tolerable weekly intake (PTWI)Hg ~15% of PTWIAs ~6% of PTWICd < 0.1% of PWTI

Provisional maximum tolerable daily intake (PMTDI) Cu and Zn < 1% of PMTDI

~ 15% of the required daily intake of Fe

G. Allinson, M. Nishikawa, S. S. De Silva, L. J. B. Laurenson, and K. De Silva. Ecotoxicology and Environmental Safety, Vol. 50, pp. 197-202 (2002).

Metal intake in Sri Lankan fish diet

VCE Math Methods Units 3, 4

This area of study will include: Coordinate geometry

> graphs of inverse functions derived from graphs of original functions;

Algebra> one-to-one and many-to-one functions, conditions for

existence of inverse functions;

Calibration curves Often curved Linear if concentration range is carefully chosen

Calibration curves

Concentration, c

VCE Chemistry Unit 1 (Corrosion)

This area of study will include: reactions of metals in the atmosphere; corrosion of metals; corrosion minimisation, including passive, sacrificial and

cathodic measures.

Black "getter" spot Material from anode Reductant scavenges oxygen from lamp gas

Hollow cathode lamp

The black "getter" spot

Thin lay of cathode materialPictures of hollow cathode lamp, © Varian inc.

Reproduced with permission from Varian Australia.


Engagement and understandingLink VCE physics (science) to topical events

2005 = 50th anniversary of paper of Victorian invention

Multiple teachers running in the same direction

Integrated curriculum Themes crossing curriculum boundaries Each discipline offers different insights


Extends VCE Physics study design Related to topics in VCE Physics SD Extension topics

> Critically evaluate knowledge> apply knowledge

Connections to other study designs> Reinforce/review learning> Deeper understanding

Acknowledgements

Support, time release etc:

Deakin University Loyola College, Watsonia

Permission to use material

Thank you to:

Dr Graeme Allinson (Deakin University) Australian Academy of Science CSIRO Publishing Elsevier National Optical Astronomy Observatory /

Association of Universities for Research in Astronomy / National Science Foundation (USA)

Varian Australia / Varian Inc.

Reading list


A. Walsh, "The development of atomic absorption methods of elemental analysis 1952-1962", Analytical Chemistry, 1991, 63, 933A-941A.

A. Walsh, "The development of the atomic absorption spectrophotometer", Spectrochimica Acta Part B, 1999, 54, 1943-1952.

P. Hannaford, "Alan Walsh 1916-1998", Historical Records of Australian Science, 2000, 13, 45-72 <http://www.science.org.au/academy/memoirs/walsh2.htm>.

Reading list

G. Allinson, M. Nishikawa, S.S. De Silva, L.J.B. Laurenson and K. De Silva, "Observations on metal concentrations in tilapia (Oreochromis mossambicus) in reservoirs of south Sri Lanka", Ecotoxicology and Environmental Safety, 2002, 51, 197-202.

D. A. Skoog, D. M. West, F. J. Holler and S. R. Crouch,Fundamentals of Analytical Chemistry, 8th Edn., Brooks/Cole, Belmont (CA), 2004.

D. C. Harris, Quantitative Chemical Analysis, 6th Edn., W.H. Freeman and Company, New York, 2002.

Reading list

More information about Australian science and scientists can be found at

Australian Academy of Science <http://www.science.org.au/academy/>

Historical Records of Australian Science http://www.publish.csiro.au/journals/hras

the 1955 aas paper a. walsh, "the application of atomic absorption spectra to chemical...

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