Patent ID: 8415944

Claim:
A method for stabilizing ac magnetic susceptibility of a magnetic fluid, comprising the following steps: (A) preparing two reagents of known magnetic concentration, including a first one in a mixture of an x C1 micro liter, m 1 -emu/ml magnetic fluid and a y C1 micro liter Phosphate Buffer Saline solution and a second one in a mixture of an x C2 micro liter, m 2 -emu/ml magnetic fluid and a y C2 micro liter Phosphate Buffer Saline solution, in addition to a to-be-detected reagent in a mixture of an x S micro liter, m S -emu/ml magnetic fluid and a y S micro liter Phosphate Buffer Saline solution, in which the two reagents of known magnetic concentration are respectively referred to as C1 and C2, and the to-be-detected reagent is referred to as S, while meeting with the following requirements: m 1 x C1 >m S x S >m 2 x C2 ; (B) detecting alternatively χ ac,o signals, denoting mixed-frequency ac magnetic susceptibility χ ac before association between magnetic nanoparticles and bio-particles, of each of background, being without any reagent, and the above-said three reagents in a predetermined sequence of time intervals so as to obtain average values of detected χ ac,o signals during each interval, which are referred to as χ ac,o,B , χ ac,o,C1 , χ ac,o,S , χ ac,o,C2 for background, C1, S, and C2, respectively; (C) calculating a new χ ac,o value, i.e. χ ac,cal , for S, a to-be-detected reagent via χ ac , cal = χ ac , o , S - χ ac , o , C ⁢ ⁢ 1 χ ac , o , C ⁢ ⁢ 2 - χ ac , o , C ⁢ ⁢ 1 × m 2 ⁢ x C ⁢ ⁢ 2 - m 1 ⁢ x C ⁢ ⁢ 1 m s + m 1 m s ⁢ x C ⁢ ⁢ 1 ; and (D) repeating steps (B) and (C) to find the χ ac,cal for a next run, and then finding a time dependent χ ac,cal for S.