AA Light Sources

2

Hollow Cathode Lamp Design

BaseGraded Seal

QuartzEnd Window

Pyrex Envelope

Anode

Cathode

Getter

Alignment Pin

Electrical Contacts

Lamp Element Code Contacts

Lamp CodeCircuit

GlassShield

3

HCL Operation

Hollow Cathode

Anode

Atom Atom

e-

Electrical DischargeNe+ + e-

Sputtering

EmissionExcitationRelaxation

PhotonSpecific toExcited Atom

En

Eo

En

Eo

4

Self-Reversal

Cloud of Ground State Atoms

Normal OutputOutputafter Reversal

5

Choosing an Analytical Wavelength

Sample ConcentrationPrecisionDillution FactorsWavelength

• Calibration CurvatureRelative Sensitivity

• Concentration & DilutionRelative Intensity

• Signal to noise

6

Lamp Data

Element Maximum Current

mA

Recommended Current

mA

Wavelength Slit nm Relative Sensitivity

Relative Intensity

Ni 10 4 232.0 0.2 1 5352.5 0.2 5 100351.5 0.2 10 30362.5 0.2 500 10

Cu 10 4 324.8 0.5 1 100327.4 0.5 2 50217.9 0.2 8 3218.2 0.2 10 2222.6 0.2 40 5244.2 1 270 15

7

Multi Element Lamps

Available for:

Ag-Cd-Pb-ZnAg-Cr-Cu-Fe-NiCa-MgCa-Mg-AlCo-Mo-Pb-ZnCu-Fe-Mn-ZnCu-Fe-Si-ZnCu-ZnFe-Co-Ni-Mn-Cu-CrNa,K

8

Using Multi Element Lamps

Use all normal recommended wavelengths

Refer to Data Sheet for recommended slit width

Refer to Data Sheet for recommended lamp currentThe SAME current is used for ALL elements in the lamp – may need to change in the method

9

Multi Element Lamps

AdvantagesMore elements can be run without changing lampsLower initial cost

DisadvantagesMore complex emission profileSome secondary lines cannot be usedSome changes in sensitivity observedOperating current may be higherLine intensities may be lower

10

How Can We Make LampsMore Intense?

We could increase the lamp current - but this results in the following undesirable changes

• The atom cloud extends beyond excitation region and cools down

• Atoms in the atom cloud may absorb light from the lamp (self-reversal)

• This causes broadening of the emission line and increased calibration curvature

11

The High Intensity UltrAA Lamp

12

The Varian UltrAA Lamp

QuartzWindow

Glass Shield

CathodeBoost Filament

Discharge Guide

AnodeBoost Anode

Glass EnvelopeShields

13

UltrAA Lamp Operation

2 anodes are fitted inside the UltrAA lamp:• one for the normal HCL discharge• the second for a separate boost discharge which is directed

across the cathodeElectrons emitted by a heated filament are passed through the atom plume to re-excite the atoms by collisionThis increases the emission intensity of the lamp

14

UltrAA Lamps - Elements Available

Single Element UltrAA LampsSb Cu Mn SiAs Ge Ni TeBi Au Pd TlB Fe Pt SnCo Pb Se

Multi Element UltrAA LampsAg-Cr-Cu-Fe-Ni Cu-Fe-Mn-ZnAg-Cd-Pb-Zn Cu-Fe-Si-ZnAs-Cu-Fe Cu-ZnCa-Mg-Al Fe-Co-Ni-Mn-Cu-CrCo-Mo-Pb-Zn Ni-Se

15

UltrAA Lamps

Varian's boosted discharge lamps provide: • Improvements in intensity• Extended lifetime• Improved sensitivity• Improved calibration linearity

16

Lead Lamp Comparison

0

0.5

1

1.5

2

2.5

0 10 20 30 40 50 60 70 80 90 100Concentration

Abso

rban

ce

UltrAA Lamp

Normal HCl Lamp

17

Advantages of UltrAA Lamps

Reduced baselinenoise

Peak to peak baseline noise forSe is 0.013 Abs.for the conventionalHCL compared with0.008 Abs. for theUltrAA Lamp

18

UltrAA Lamp Increased Sensitivity

Increased sensitivity• Typical signals for 75

µg/L Se are illustratedUltrAA Lamp

Conventional HCL

Abs

orba

nce

Tem

pera

ture

Bac

kgro

und

25000.50

0.50

Time (sec)

0.00 0

72.00 74.60

19

Advantages of UltrAA Lamps

Enhanced calibration linearity• Typical calibrations for

Se using standards of 25, 50 and 75 ug/L Se are illustrated

20

Advantages of UltrAA Lamps

Improved Characteristic Concentrationsand Detection Limits

Element Wavelength UltrAA Conventionalnm Lamp HCL

Characteristic Concentration (in µg/L with 20µL sample)As 193.7 0.25 - 0.3 0.31Pb 283.3 0.15 - 0.26 0.26Se 196.0 0.49 - 0.5 0.85 - 2.2

Detection Limits (3 sigma in µg/L with 20µL sample)As 193.7 0.35 - 0.7 0.3 - 1.4Pb 283.3 0.18 - 0.23 0.8Se 196.0 0.28 - 0.57 1.1 - 3.1

21

Gold Lamp Comparison

0.0

0.5

1.0

1.5

2.0

2.5

0 20 40 60 80 100

Concentration

Abs

orba

nce

Boosted Lamp

Normal Lamp

22

Comparison of Gold UltrAA and Normal Lamps at Detection Limit Levels

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.00 0.01 0.10 1.00 10.00

Concentration mg/L

Prec

isio

n %

242.8nm UltrAA Lamp 267.6nm UltrAA

242.8nm HCl 267.6nm HCl

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Lifetime of UltrAA Lamps

350

400

450

500

550

0 2000 4000 6000 8000

Operating Time Hours in mA-Hours

Phot

omul

tiplie

r Vol

ts

Lead

Selenium

Arsenic

24

Key Benefits of the UltrAA Lamp

Improved analytical performance• Lower baseline noise levels• Increased sensitivity• Lower detection limits• Enhanced calibration linearity

Greater reliabilityLonger lamp lifetimes