Azathioprine is an immunosuppressant agent which has been clinically applied in the inhibition of organ rejection for the past thirty [1]. But it has a pancreatitis and hepatic toxicity and suppresses the bone marrow, which makes the patients sensitive to infection. Therefore, determination of Azathioprine concentration in urine and plasma is essential [2]. According to our knowledge, no usage of LLME for the extraction and preconcentration of Azathioprine in plasma and urine samples has been reported thus far. Optimizing the effective factors was done in two stages. First, the effective factors were identified by PBD, then the meaningful factors were optimized by BBD
