You can enter the PayPal Email for a separate Micropayments account in Seller Admin > Payment Preferences, so all order totals under $12.00 would be paid to that account rather than your main PayPal Email.
Bear in mind the selection of PayPal Payments Standard vs. PayPal Payments Pro on that Payment Preferences screen affects the checkout behavior for your cart regardless of order total. This means that your regular PayPal account and Micropayments PayPal account must both be set up using PayPal Payments Standard or both set up using PayPal Payments Pro.
I.e., if you want to use PayPal Payments Pro for your main PayPal account and also want to use Micropayments, then your PayPal Micropayments account must also be enrolled with PayPal Payments Pro and integrated with E-junkie as a PayPal Payments Pro account. Conversely, if your Micropayments account has to be a PayPal Payments Standard account, then you could only use your main PayPal account for PayPal Payments Standard checkouts as well, so in this case you'd need to select PayPal Payments Standard in your E-junkie Payment Preferences.