All reagents, including solvents, used in tests and assays must be of appropriate quality. They should be purchased from reputable manufacturers or dealers, preferably in small factory-filled containers suitable for laboratory use. Stocks stored in greater bulk are more vulnerable to contamination and degradation. Appropriate safety regulations should be drawn up and rigorously implemented wherever toxic or flammable reagents are stored or used. Those subject to poison regulations or to the controls applied to narcotic and psychotropic substances should be clearly marked as “Poison” and kept separately from other reagents in locked cabinets. A register of these substances must be maintained by the responsible member of staff. The head of each unit must accept personal responsibility for the safe-keeping of any of these reagents kept in the workplace.
Reagents made up in the laboratory should be prepared according to prescribed procedures and, when applicable, to published pharmacopoeial or other standards. Each label should clearly specify the contents, the manufacturer, the date received, and, as appropriate, the concentration, standardization factor, shelf-life, and storage conditions. Volumetric solutions made up by dilution should be labelled with the name of the manufacturer of the concentrate, the date of preparation, and the initials of the responsible technician.
Responsibility for making up reagents in the laboratory should be clearly assigned. Standardization of procedures is more readily implemented when this work is supervised by one person, even when the same reagents are used in several units. However, the reagents should not be moved unnecessarily from unit to unit and should be transported, whenever possible, in their original containers. When they are subdivided, they should always be transferred into scrupulously clean, fully labelled containers.
Whatever routine precautions are taken to ensure the adequacy of volumetric solutions, they should be checked whenever they are used in a test which indicates that a sample is not in compliance with specifications and the results of the check should be attached to the analytical worksheet.
Distilled water and deionized water should also be regarded as reagents and precautions should be taken to avoid contamination during their supply and distribution. Stocks should be checked at least once a month to ensure that they meet quality requirements: the specific conductance at 20 °C should not be greater than 2.0 × 10-6 ohm-1 cm-1 and the chloride ion content should meet current pharmacopoeial requirements for purified water.
All reagent containers should be inspected to ensure that seals are intact both when they are delivered to the reagent store and when they are distributed to the units. These inspections should be recorded by initialling and dating the labels. Reagents that appear to have been tampered with should be rejected except in rare instances when their identity and purity can be confirmed by testing. Maintaining stocks of reagents in a central store promotes safety and continuity of supplies, particularly for substances that need to be ordered long in advance of delivery.
In a large laboratory the storage area should provide separate rooms for flammable substances, for fuming acids, including concentrated hydrochloric acid, nitric acid, and bromine, and for ammonia and volatile amines. Self-igniting materials, such as metallic sodium and potassium, should also be stored separately. All storage areas should be located and equipped in accordance with fire regulations. To promote safety and to reduce contamination of the laboratory environment, these reagents should never be stored elsewhere in the laboratory without good reason.
The store should be kept stocked up with the clean bottles, vials, spoons, funnels, and self-adhesive labels required for dispensing reagents from larger to smaller containers. Special equipment may be needed for the transfer of larger volumes of corrosive liquids. The storekeeper should be trained to handle chemicals with the necessary care and safety.