Sample separation device and sample separation method

1. A sample separation device used to introduce a sample to be separated to an inside of the sample separation device, centrifuge the sample, and collect a desired liquid after separation, the sample separation device comprising:

a sample introducing portion configured to introduce the sample to be separated into the sample separation device;

a liquid surface defining portion connected to the sample introducing portion;

a first separating portion disposed below the liquid surface defining portion and connected to the liquid surface defining portion;

a second separating portion connected to the first separating portion;

a third separating portion disposed above the second separating portion and connected to the second separating portion; and

a liquid extracting portion including the third separating portion and connected to the second separating portion,

wherein a tubular flow path is formed by at least the first separating portion and the second separating portion,

wherein an opening of the sample introducing portion and an opening of the liquid extracting portion are oriented in a same direction,

wherein the first separating portion is configured so that gravity and a capillary force generated in a direction opposite to a gravity act on the sample after separation,

wherein the liquid surface defining portion has a horizontal cross-sectional area which is larger than a horizontal cross-sectional area of the first separating portion,

such that an action of the capillary force on the sample after the separation is reduced when the sample after the separation reaches a lowermost portion of the liquid surface defining portion due to the capillary force,

wherein the third separating portion has a horizontal cross-sectional area which is larger than a horizontal cross-sectional area of the second separating portion,

wherein a horizontal cross-sectional area of a connecting portion between the second separating portion and the third separating portion is the smallest in the third separating portion, and

wherein a maximum value of the horizontal cross-sectional area of the liquid surface defining portion is equal to or larger than a minimum value of the horizontal cross-sectional area of the third separating portion.

2. The sample separation device according to claim 1 , wherein the third separating portion constitutes a part of the liquid extracting portion, and occupies a part of the liquid extracting portion from a connecting portion with the second separating portion to a height of a liquid surface of the sample after the separation,

wherein a height of the lowermost portion of the liquid surface defining portion is located between an uppermost portion and a lowermost portion of the liquid extracting portion,

wherein the height of the lowermost portion of the liquid surface defining portion is the same as the height of the liquid surface of the sample after the separation, which is an uppermost portion of the third separating portion, and

wherein, when a volume of the sample introducing portion is V, a volume of the first separating portion is A, a volume of the second separating portion is B, and a volume of the third separating portion is C, A+B+C is substantially equal to V.

3. The sample separation device according to claim 1 , wherein a U-shaped or J-shaped flow path is formed by at least the first separating portion and the second separating portion.

4. The sample separation device according to claim 2 ,

wherein the sample is blood, and

wherein the sample after the separation extracted from the liquid extracting portion is plasma.

5. The sample separation device according to claim 4 , wherein when a blood cell volume ratio is a, a relationship of (B+C)×α≤B is satisfied.

6. The sample separation device according to claim 5 , wherein α is 0.518, 0.57, 0.62, or 0.67.

7. The sample separation device according to claim 1 , wherein the third separating portion is configured such that a horizontal cross-sectional area is gradually reduced toward a connecting portion between the third separating portion and the second separating portion.

8. The sample separation device according to claim 1 , wherein the liquid surface defining portion is configured such that a horizontal cross-sectional area is gradually reduced from at least a part of the liquid surface defining portion to the lowermost portion.