Method and apparatus of automatically isolating and purifying nucleic acid

1. A method of automatically isolating and purifying nucleic acid from a nucleic acid-containing specimen, the method comprises:

a) injecting a liquid into a cartridge for isolation and purification of a nucleic acid including at least two openings from one opening of the at least two openings, in which the cartridge includes a container having the at least two openings and containing a nucleic acid-adsorbent solid phase;

b) passing the liquid through the nucleic acid-adsorbent solid phase by a pressure difference generated by a pressure generation means for generating a pressure difference between the inside and outside of the container; wherein a pressure generated in the inside of the container by the pressure generation means is measured and a pressure change velocity and a pressure change acceleration are calculated on the basis of the value of the measured pressure, and

c) discharging the liquid from the other opening of the container to the outside of the container by a pressure difference generated by the pressure generation means, wherein the timing of completion of discharge of the liquid from the container is determined by use of a temporal change pattern of a measured pressure selected from the group consisting of

(1) when the pressure of the inside of the container reaches a set value in the middle of pressurizing the inside of the cartridge by the pressure generation means, the pressurization by the pressure generation means is stopped, and a point of time when the pressure change acceleration in said container is minimized after the stop of pressurization is determined as the timing of completion of discharge of the liquid from the container;

(2) when the pressure of the inside of the container does not reach a set value in the middle of pressurizing the inside of the cartridge by the pressure generation means, at least one of a point of time when the pressure in the container is maximized and the pressure change velocity in the container becomes zero or less and a point of time when the pressure in the container is maximized and the pressure change acceleration in the container is minimized, is determined as the timing of completion of discharge of the liquid from the container; and

(3) when the pressure of the inside of the container does not reach a set value and is not maximized in the middle of pressurizing the inside of the cartridge by the pressure generation means, a point of time when the pressure change velocity in the container becomes lower than a threshold value, is determined as the timing of completion of discharge of the liquid from the container.

2. The method according to claim 1 , which comprises:

(1) injecting and pressurizing a nucleic acid-containing specimen liquid into the container through one of the at least two openings, and discharging the nucleic acid-containing specimen liquid from the other opening to thereby adsorb a nucleic acid contained in the nucleic acid-containing specimen liquid to the nucleic acid-adsorbent solid phase;

(2) dispensing and pressurizing a washing liquid into the container through one of the at least two openings, and discharging the washing liquid from the container through the other opening to remove impurities; and

(3) dispensing and pressurizing an elution liquid into the container through one of the at least two openings to isolate and discharge the nucleic acid adsorbed to the nucleic acid-adsorbent solid phase from the container through the other opening together with the elution liquid to thereby collect nucleic acid.

3. The method according to claim 2 , wherein in response of the determined timing of completion of discharge of the liquid, the subsequent step is performed.