The B-Bride Serum Estradiol Immunoassay kit uses a specifically generated antibody to measure estradiol in serum and plasma samples. This kit is more sensitive than our Estradiol EIA Kit (Cat # K3030-1 and K3030-5), which allows for the detection of free estradiol in serum and plasma samples. This kit uses a sheep antibody to estradiol and has a range of 3.75 pg/mL to 120 pg/mL.