Human embryonic stem cell-derived midbrain dopaminergic (mDA) neurons could be the next generation of in vitro models for neuropsychiatric disorders like schizophrenia. A hallmark feature of this disorder is a dysregulation of dopaminergic neurotransmission in the midbrain. Present in vitro models of schizophrenia are confounded by the fact that the influence of system bias and observational bias are excluded from the experimental design and analysis. Our system may be an improved model for studying schizophrenia since mDA neurons are likely to express receptors and contain intracellular signal transduction mechanisms that are relevant to neurons in vivo; thus reducing system bias. In order to reduce the impact of observational bias, we developed a liquid chromatography-tandem mass spectroscopy method to quantify changes in dopamine concentration in the culture media of mDA neurons. We found that the state of maturity of developing cultures correlated strongly to the concentration of dopamine in the culture media. We then showed that changes in the maturation media have a profound influence on the phenotype of neurons even during late stages of maturation. Finally, mDA cultures were used to study the effect of chronic haloperidol administration on gene expression in order to probe its effect on cells.