Atomic Absorption Spectroscopy is an affordable and reliable technique for trace metal estimations and has gained wide acceptance in laboratories across the world However, adequate precautions should be taken when operating the system due to inherent operational hazards.
- Flame or graphite furnace temperatures around 2000°C or above.
- Use of strong acids for sample digestions
- Corrosive and toxic fumes
- Presence of hot surfaces
The idea behind highlighting the hazards is to provide safety awareness and not to scare you from adopting the technique. In this article we shall take a look into different types of operational hazards and how to protect yourself and others from harm.
- Perform all operations involving use of acids wearing gloves and safety goggles
- Ensure that eye-wash station and safety shower are functional
- Never use perchloric acid alone as it is highly corrosive and also a strong oxidizing agent. Always use mixtures with other acids.
- Handle hydrofluoric acid with care as it is highly corrosive (never use glass containers as it attacks glass)
- High fat content samples can cause explosions when digested with nitric acid as nitroglycerine can form. Use alternate digestion methods.
- Carry all digestion operations involving use of acids in fume hood with exhaust fan running to vent out hot toxic and corrosive fumes
Instrument Operation Hazards
- Severe burns can result from touching burner head, graphite furnace or quartz cell immediately after use. Always allow sufficient time after cooling to room temperature before touching these parts.
- Do not look directly into deuterium lamp when it is on or nitrous oxide – acetylene flame to avoid exposure to UV radiation. Always use UV protection glasses
- Keep the burner chamber safety cover closed when flame is ignited
- Fume exhaust Hood should be switched on to permit venting of hot corrosive fumes during flame analysis
- Clean burner head regularly as clogging. can cause flame flashback
- Clean burner chamber when switching from organic to aqueous solutions and vice versa
- If high concentrations of copper, silver or mercury have been aspirated into acetylene flame unstable acetylides may form and if allowed to dry these compounds can cause explosions. Flush thoroughly the spray chamber with water after such analysis.
- Do not allow cyanide containing solutions to come in contact with acidic solutions in drain otherwise toxic hydrogen cyanide can form
- Gas tanks should be preferably kept outside the laboratory
- Never use copper tubing in acetylene supply lines as acetylide formation can result in explosions
- Do not exceed acetylene gas pressure above 15 psig as otherwise explosive decomposition can occur
- Never use nitrogen as purge gas when performing graphite furnace analysis as poisonous cyanogen can form at temperatures above 2300°C
- Use built-in heater on nitrous oxide gas regulator as cooling on expansion can lead to diaphragm jam due to freezing. This can cause erratic flame behaviour or even a flashback.
Proper care and adherence to safety guidelines can prevent accidents and loss of valuable time. Modern-day instruments have built-in safety interlocks which allow flame ignition only when all safety conditions are complied with. Atomic absorption spectroscopy is a well established technique capable of giving precise results. Make safety a habit and you will be able to prevent all mishaps.
Please share your experiences and leave your valuable comments.