Use of a Potentiostat
The use of potentiostats in the laboratory involves the application of potentials and the consequent passage of currents through solutions of electrolytes and as such the risks associated with the combination of an electrical appliance and a conducting fluid medium are always present. In many cases the potentiostat is computer driven and controlled, hence the positioning of this second electrical appliance must be evaluated. The use of conducting solutions of ions, many of which are transition heavy metal ions and whose solutions often need degassing, require the operator to be familiar with the relevant COSHH data and the use of and/or conveyance of compressed gas cylinders.
The main hazards are those encountered in the use of any electrical appliance but with the added complication of the presence of electrochemically active solutions namely:
- The cell design incorporates non-insulated contact points as well as exposed electrode surfaces hence electric shock is a major risk. Electric shock is the effect produced on the body and particularly on the nervous system by an electrical current passing through it. The effect depends on the current strength which itself depends on the voltage and body resistance i.e. path length and surface resistance of skin (which is much reduced when wet). Death can be the result of the normal voltage of 240 V causing currents of greater than 30 mA to flow through the body for more than 40 ms. Minor shocks may also cause injury following involuntary muscle contraction.
- Burns caused by the passage of heavy currents through the body.
- Explosion and fire caused by electrical sparks, short circuits or overload heating, old wiring in the presence of flammable material.
- The by-products of many electrochemical reactions are gaseous and occur in the confined volume of the cell. As a consequence injury from flying glass and other debris as well as the possible injury and contamination from the reaction media during an explosion exists.
- Electrochemical cells are designed to be opaque and glass is predominantly the preferred fabrication material hence cuts from damaged or broken glass and poisoning following cuts by contaminated glassware are possible.
The degassing of solutions prior to electrochemical investigation with an inert gas is a frequently employed operation. As such:
- Pressurised gas cylinders are very heavy and unstable objects and as such can present considerable danger to those handling them.
- They contain gas which may be toxic, asphyxiating or flammable and at high pressure.
- Apart from the chemical risk from these gases, serious physical damage can be caused by exposure to the full force of escaping gas.
- Gas cylinder valves are very robust but a broken valve can turn a cylinder into a lethal projectile.
Gas pressure regulators are much less robust and if damaged may allow the escape of gas.
The hazards associated with the use of computers include:
- Repetitive Strain Injury (RSI) a musculo-skeletal disorder, the symptoms of which include pain, swollen soft tissue, restricted joint movement, loss of function and possible permanent disability.
- Users of keyboards who are not trained typists are more susceptible to such problems.
- Eye Strain: Evidence indicates that using DSE is not associated with damage to the eyes or eyesight although uncorrected defects can increase the stress of working with such equipment.
- Fatigue and stress.
The operator should ensure the following:
- That the potentiostat, cell design and computer hardware all meet the relevant standards (for further details see the university code of practice "Electrical Safety" and the Risk assessment on Use of Standard Electrical Equipment). If in doubt check with the Electric Workshop personnel.
- That the wiring of the potentiostat to the cell assembly has been undertaken with due care and attention.
- That all wiring has been attached to the appropriate electrodes, that the connections have been checked for their ability to remain fast to the area of application and that no undue strain is placed upon them.
- Contact with any exposed electrically active areas is avoided once the experiment has been set in motion.
- That all excess solvents and solutions have been removed from the area in and around the working potentiostat to avoid spillage and resulting contamination and/or electrical shock as well as the danger of explosion and fire from sparks associated with the use of flammable solvents.
- That the cell is supervised to avoid the build up of pressure due to the evolution of gaseous products. If harmful by-products result the cell should be placed in a fume cupboard and the appropriate precautions observed.
- That s/he has familiarised themselves with all aspects of the degassing procedure including the use of the compressed gas cylinders and the risks associated with V.D.U. operation.
No specific training is required in the use of potentiostats, however the operator should familiarise themselves with the relevant references and user manuals.
There will always remain a risk from electrical injury and injury from sudden and unexpected gas release but with the correct operational procedures in place the dangers will be minimised.
- Switch off the power before touching the injured person.
- Never use water on an electrical fire.
Escape of gas
- If the gas escape is large follow the procedure described in the Department of Chemistry Safety Handbook for the escape of toxic materials:- remember even an inert gas can kill by asphyxiation. For small non-toxic leaks, inform a member of staff, ventilate, evacuate, seal and secure the room.
- If a cylinder falls over, NEVER attempt to catch it. It is much too heavy and will cause you serious injury. It is also very robust and is unlikely to be damaged although it may make a loud noise. Do not attempt to upright it by yourself but get competent help.
Cuts from Glassware
- Always treat cut and burns immediately. Apart from very minor injuries, call for First Aid treatment.