Soumya,
In order to do this, you could create a helper entity with an association to Loans (many to many). After your first retrieve, create a new object with your helper entity and set the association to Loans with the list from your first retrieve. Now you can perform a second retrieve using the helper entity (and its association to Loans) and the other Xpath constraints you want to use.
Hope that helps,
Mike
**edit**
That depends on what you are filtering on. If you are filtering attributes on the Loans entity, you can do that with a List operation. If it is associations, you cannot do that with a List operation. A couple of additional notes: