There are various in-office teeth whitening options to choose from (Zoom whitening, Britesmile, Lumibrite, Opalescence, etc.), each of which ranges somewhat in price. Costs for in-office treatment may also depend on the dentist performing the treatment. That said, the national average cost of in-office teeth whitening is approximately $650.
I have read, but can not substantiate, that urine can be kept in a cool room temperature environment for 24 hours. Refrigerating and/or freezing can kill the bacteria that the urine test is supposed to detect and unless recommended by your doctor is not something you want to do.
How accurate is the test? The test is fairly sensitive to the presence of drugs in the urine. This means that if drugs are present, you will usually get a preliminary positive result. If you get a preliminary positive result, you should send the urine sample to the laboratory for a second, more accurate test. It is very important to send the urine sample to the lab, because the drug of abuse urine screening may give positive results when no drugs are actually present.