It’s not really a “General Purchase” as this code is used for those items that are consumed on a short term basis to generate profit for your business (i.e. a cost of sale).
If they have material value (typically £100) and several years of useful life, you could treat them as an asset (e.g. office equipment).
Otherwise it would need to be expensed, if that’s the case it’s better to create a new nominal code under the expense category and post it there.
Disclaimer: I’m not an accountant so would also recommend seeking a professional opinion.