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Guidelines for sterility testing of therapeutic goods
Annex III. Composition and preparation of diluents
Diluent 1
| Peptic Digest of Animal Tissue | 1 g |
| Purified Water | 1000 mL |
| pH after sterilisation (measured at room temperature): | 7.1±0.2 |
Method of preparation
Mix the ingredients in the proportions specified above and heat to dissolve. If necessary, add sufficient 1 M sodium hydroxide or 1 M hydrochloric acid to bring the pH within the range specified for the diluent. Distribute into vessels that are closed against the access of micro-organisms, and sterilise the filled vessels by heating in an autoclave by the method described for sterilisation of media.
Sterilisation
If necessary, clarify the diluents by filtration, preferably through membrane filters, before sterilisation. Sterilisation should be performed within four hours of the start of preparation and should be by exposure of the whole of the contents of each vessel to 121°C for 20 minutes.
Diluent 2
| Peptic Digest of Animal Tissue | 1 g |
| Polysorbate 80 | 1 mL |
| Purified Water | 1000 mL |
| pH after sterilisation (measured at room temperature): | 7.1± 0.2 |
Method of preparation and sterilisation
Prepare and sterilise as above for Diluent 1.
Diluent 3
| Peptic Digest of Animal Tissue | 1 g |
| Disodium hydrogen phosphate, Na2HPO4 | 8.38 g |
| Sodium dihydrogen phosphate, NaH2PO4.2H20 | 1.62 g |
| Purified Water | 1000 mL |
| Penicillinase solution (15000 Levy Units/mL) | 100 mL |
| Final pH (measured at room temperature): | 7.5±0.2 |
Method of preparation
Proceed as in the preparation of Diluents 1 and 2. After the sterilised solution has cooled to between 20°C and 30°C, aseptically add the penicillinase.