Flame Atomic Absorption Maintenance And Safety

Flame Atomic Absorption Maintenance and Safety

Objectives • Outline a suitable protocol for routine maintenance covering: – Gas supplies – Atomization system – Instrument body – Key accessories • Maintain instrument performance • Review safety considerations

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Results of Poor Maintenance • Degradation of performance • Unsafe operation

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Basic Flame Maintenance Light Sources Gas Supplies Burner Nebulizer Assembly Instrument Body Accessories

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Maintain Written Logbook

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Acetylene • MUST be Stabilized • NEVER Operate with cylinder pressure below 700 kPa (100 psig) • Or line pressure above 105 kPa (15 psig) • NEVER use copper lines or fittings

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Nitrous Oxide Regulator • It may FREEZE! • NEVER Lubricate “O” rings with grease • It is stored as liquid Cylinder pressure does NOT indicate contents!

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Check Delivery Pressure Normal

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Gas Flow and Burning Velocity

Flame Burning Down

Gas flowing Up

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Nitrous Oxide - Acetylene Gas Flow Acetylene

Nitrous Oxide

2.0 5

1.8

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Varian AA Gas Flow Region

1.6 1

Fuel/Oxidant Ratio

1.4

10

Flash Back Region

1.2 1.0

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0.8 5

0.6

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0.4 0.2

1

0.0 0.0

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5.0

10.0

15.0 Total Gas Flow Litre/Min

20.0

25.0

30.0

Maintenance Tasks Check Exhaust System Clean Burner Compartment & Instrument Clean Windows

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Daily Maintenance Tasks • Empty waste container • Check exhaust system • Clean burner compartment & instrument • Check the gas delivery pressures & cylinder contents • Check the nebulizer uptake rate

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Check Exhaust

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Clean Spills

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Measure Uptake Rate

Listen to the sound of the nebulizer it should hiss! And there should be a change in pitch when sample is aspirated 15

Low Uptake Rate



6 mL/min

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

3.4 mL/min

Mini-Vacuum Cleaner Lint or sample particle blockages Lint or sample particle blockages

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Aspirate D.I. Water

distilled water

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Rinse regularly and at the end of a set of samples +/- 200ml

Recommended Procedures at End of the day 1. Aspirate distilled water for a few minutes before shutting off flame (200 mL) 3. Allow burner to cool 5. Remove burner and clean by running tap water through it 7. Dry burner by shaking 9. Pour half a litre of water into spray chamber, through burner socket 11. Replace burner 13. Empty waste vessel 19

Periodic Maintenance Tasks • Check condition of O rings in atomization system • Check condition of the impact bead • Clean burner • Clean windows in sample compartment

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Check O-rings Lubricate with water or Nonionic detergent ie Triton X-100 ONLY

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Clean Burner Keep slot clean and polished

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Clean Windows YES, YOU MUST DO THE WINDOWS!

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SIPS Operation

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SIPS Pump Maintenance • Clean Rollers and Band regularly – Use Alcohol and tissue • Clean and rinse T piece • Replace capillary tubing if blocked • Wipe down case with damp cloth • Ensure adequate ventilation around control unit

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The SIPS pump head

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Autosampler Maintenance Check interconnecting tubing and probe capillary in good condition Clean any spills

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Capillary Connections Capillary to Nebulizer Connection Free of Dead Volume

Capillary to Autosampler or SIPS

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Vapor Generation System Maintenance Clean up spills Check pump tubing Check pump Rollers

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Stretched Tubing

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Pump Roller Clips

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Check for Gas Leaks

Overnight Leak Check 5:00 PM

Watch the PRIMARY Gauge! 33

8:00 AM

Grease O-rings DO NOT use grease on “O” rings in spray chamber HiVacuu m Grease TOO MUCH GREASE!!!!!!!!!!!!

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AA Maintenance Guide Useful reference guide to maintenance provided on the CD See document called AA Maintenance Guide

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Summary • Check gas supplies • Check exhaust system • Check uptake rate • Clean dirty components & spills • Maintain accessories • Empty waste container • Aspirate 200 mL D.I. water after analysis

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How do you prove that an instrument is working ok? Validation

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