After authorizing IFTTT to connect to your Buffer account, you'll be prompted to choose which social channel you’d like posts to be sent to. It's not possible to select multiple channels, which means that only one channel can be connected to your IFTTT account.
This means that any applets you create, where Buffer is the action service, can only add posts to one of your queues. The channel that you choose is tied to your IFTTT account as opposed to be tied to a specific applet that you create. Therefore, it is not possible to create separate applets where a different channel is chosen. The only workaround for this would be to set up completely separate IFTTT accounts under different email addresses.
We have found this to be one of the key reasons that some customers choose to use Zapier instead of IFTTT. When creating Zaps, you'll also only be able to choose one channel. However, you're then able to duplicate your Zap and edit the channel to create a new version, thus being able to send posts to multiple queues.