Electrophoresis apparatus

1. Introduction

Electrophoresis apparatus may represent a significant electrical hazard in laboratories if used incorrectly. The potential for injury arises principally from the high levels of electrical energy involved, and from the supporting gel medium being immersed in aqueous solutions. Many workers mistakenly believe that there is little hazard associated with electrophoresis apparatus except when operating at higher voltages, such as might be required for procedures like DNA sequencing. However, even routine agarose gel electrophoresis operating at 100 volts (V) can cause a lethal shock at a current of 25 milliamps (mA) and minor leaks in gel tank devices can result in electric shock. 10-100mA direct (DC) current can cause muscular paralysis and cardiac problems, and such currents are within the output range of most electrophoresis power packs and typical of contacts made through wet skin. Minor shocks may also cause secondary injury due to involuntary muscle contraction, while handling chemicals or flammable reagents, for example. Other techniques such as electroporation and electrotransformation, which also apply electricity to biological materials, may present a similar electrical hazard. Departments should not underestimate the potential seriousness of an accident involving electrophoresis, or similar, apparatus.

The hazards associated with the use of electrophoresis apparatus may be controlled by a combination of design features on the equipment, strict adherence to a safe system of work, adequate training, and ongoing supervision. This Policy Statement outlines the basic requirements in each of these key areas.

2. Risk assessment

Supervisors are responsible for ensuring that electrophoresis procedures are risk assessed, with assistance from a person who is electrically competent, usually the Electrical Safety Supervisor (ESS), if necessary. In departments where there is no ESS appointed further advice may be sought from the Area Safety Officer or from the Safety Office.

The assessment should consider the apparatus being used during the procedure, ensuring that it is appropriate for the task and that all parts of the system are compatible, in accordance with Sections 3, 4 and 5. The results of the assessment should be recorded and used as part of training.

3. Power packs

(a)  All power supplies should be clearly labelled with their maximum output voltage.

(b)  Electrical supply to the power pack should be protected with a Residual Current Device (RCD). This will protect against faults with the main 230V AC electrical supply to the power pack.

(c)  All power packs must incorporate a safety device that disables the high voltage supply to the electrophoresis equipment when the cover of the gel tank is opened or removed.

(d)  It is recommended that power packs also have the following additional safety features. They should:

(i)  be isolated or ‘floating’, meaning that terminals are not referenced to the case (earth).

(ii)  have a load detection system, preventing power being supplied if there is no load on the output terminals.

(iii)  have a ‘reset on / turn on’ feature, meaning that if the electrical supply is turned off and then on, the apparatus must be reset to recommence the electrophoresis run.

(e)  Power packs capable of operating at 1000 volts and above must utilise 2mm shrouded connectors on the high voltage outlets so that they cannot be connected to apparatus which is not designed for this voltage range. However, a given supplier’s power pack, used exclusively with the same supplier's dual moulded 4mm plug connectors is regarded as satisfactory.

(f)  Multi-outlet powerpacks may be used with multiple electrophoresis devices, providing a safe system of work is followed. Departmental Safety Officers and Area Safety Officers should receive a copy of all risk assessments relating to such use.

(g)  Multi-purpose power packs are frequently purchased to fulfil a number of functions in the laboratory but their use must be strictly monitored by supervisors. Where, for example, a maximum voltage of 200 volts is required for a process it is inappropriate to use a power pack supplying 2000 volts. In such cases a low voltage power pack should be purchased for low voltage work.

Any new power packs purchased by a department should meet the above criteria. It is recommended that departmental Electrical Safety Supervisors are consulted by users before purchases are made.

4. Gel equipment

(a)  Gel equipment must be used with a cover in place such that neither electrodes nor buffer chambers are accessible.

(b)  Gel equipment should be interlocked with the power supply. Removable covers must be fitted with deep insulated sockets that engage with contact pins in the electrophoresis tanks and be so arranged that the current is cut off to the tank immediately the cover is removed. The live parts of the sockets must not be inadvertently accessible. An integrity check of the cover must be performed before use.

(c)  Apparatus that is not designed for use above 1000 volts must not be fitted with leads that can be plugged into a power pack capable of delivering more than 1000 volts. The use of adaptors which convert 4mm plugs to 2mm plugs is prohibited.

(d)  During operation all electrophoresis apparatus should have prominently displayed safety warning signs to indicate that the equipment is 'live'.

(e)  The use of customized or locally made electrophoresis devices is discouraged. Where modification is an absolute requirement then the work may only be done by a person who is electrically competent and the modifications must meet the requirements of this Policy Statement.

5. High voltage cables

(a)  All connecting cables between power packs and gel equipment must be fitted with shrouded connectors so that live parts are inaccessible. Stackable plugs must not be used. Both the cable and connectors must be correctly rated for the maximum voltage that the power pack can deliver in use.

(b)  Electrophoresis sets fitted with their own set of permanently attached connector leads that eliminate jacks and plugs entirely are acceptable.

(c)  Leads must be regularly inspected to ensure that there is no damage to insulation and that all parts of the conductor are covered.

(d)  Leads must never be left connected to power packs when the electrophoresis run is complete.

6. Training

Only trained individuals should be allowed to operate electrophoresis apparatus.

Supervisors are responsible for providing those under their supervision with appropriate instruction and training. Instruction should clearly identify the apparatus to be used, and its location, and include the manufacturer’s specific operating instructions and the safe systems of work to be followed throughout the process. These factors are in addition to the consideration of non-electrical hazards (e.g. chemicals), the requirement for personal protective equipment (lab coats, gloves, and eye protection), and any applicable emergency procedures.

Supervisors must ensure that these operational requirements are observed by routine checks on equipment and monitoring of procedures.

7. Departmental action

Departments should review the use of electrophoresis apparatus against the requirements of this policy. Particular attention should be paid to older equipment. Any equipment not conforming to this Policy Statement should be removed from service immediately.

Electrophoresis apparatus should be the subject of annual electrical testing and this should include testing of interlock function.

Supervisors must ensure that all electrophoresis apparatus has been risk assessed in accordance with Section 2. They must develop a safe system of work for electrophoresis procedures and ensure their staff are given adequate training. The appended guide is provided as a basis for safe working practices.

Further advice should be sought from the University Safety Office if difficulties in meeting the standards in this policy are experienced.

THIS STATEMENT FORMS PART OF THE UNIVERSITY’S SAFETY POLICY AND UNIVERSITY POLICY STATEMENT S9/96 IS SUPERSEDED.  PLEASE AMEND THE INDEX.

June 2007