 This difference in composition gives the different types of hemoglobin different chemical properties (in addition to the higher affinity HbF has for dissolved blood oxygen over HbA, allowing baby to extract oxygen from the mother's blood).Fetal hemoglobin is resistant to alkali (basic) denaturation, whereas adult hemoglobin is susceptible to such denaturation.Therefore, exposing the blood specimen to sodium hydroxide (NaOH) will denature the adult but not the fetal hemoglobin.