To remove items from inventory select
Inventory--> Items--> View/edit (New item pages)
Inventory--> Items--> Search(Old item pages)
Search for the item to delete and then select the Delete link to remove a single item. To delete multiple items at once check the box on the right most column for each item to delete and then press the "Delete Selected" button given at the bottom of the page. Once an item is deleted it cannot be restored.