Abstract: [Object] An object is to provide a sulfonated fine cellulose fiber having excellent transparency, a sulfonated pulp fiber suitable for the sulfonated fine cellulose fiber, a method for producing these fibers, and a derivative pulp containing the sulfonated pulp fiber. [Means for achieving the object] The sulfonated pulp fiber of the present invention is a pulp fiber comprising a plurality of cellulose fibers, wherein a part of hydroxyl groups of the cellulose fibers of the pulp fiber is substituted with sulfo groups, an introduction amount of sulfur attributable to the sulfo groups is adjusted to be higher than 0.42 mmol/g while maintaining a fiber shape, and a water retention value of the pulp fiber is adjusted to 150% or more. Since the sulfonated pulp fiber has a predetermined water retaining property or more while maintaining the fiber shape, the degree of flexibility in handling can be improved.

Abstract: [Object] An object is to provide a sulfonated fine cellulose fiber having excellent transparency a sulfonated pulp fiber suitable for the sulfonated fine cellulose fiber, a method for producing these fibers, and a derivative pulp containing the sulfonated pulp fiber. [Means for achieving the object] The sulfonated pulp fiber of the present invention is a pulp fiber comprising a plurality of cellulose fibers, wherein a part of hydroxyl groups of the cellulose fibers of the pulp fiber is substituted with sulfo groups, an introduction amount of sulfur attributable to the sulfo groups is adjusted to be higher than 0.42 mmol/g while maintaining a fiber shape, and a water retention value of the pulp fiber is adjusted to 150% or more. Since the sulfonated pulp fiber has a predetermined water retaining property or more while maintaining the fiber shape, the degree of flexibility in handling can be improved.

Abstract: An analysis tool for use in optical analysis, comprising a detection unit 10 having through-holes 10h penetrating through the surface and the rear side of a base material 11, the detection unit 10 comprising, inside of the base material 11, a plurality of voids 11h that allows a liquid to pass through by capillary action and that communicate with the through-holes 10h, and the through-holes 10h being formed with a size that enables a liquid to be held by surface tension. Therefore, by irradiating the detection unit 10 with light, it is possible to obtain transmitted light L2 that has been transmitted through a liquid film Lf. By analyzing the transmitted light L2, a target component in a sample L can be appropriately quantified.

Abstract: [Object] An object is to provide a sulfonated fine cellulose fiber having excellent transparency, a sulfonated pulp fiber suitable for the sulfonated fine cellulose fiber, a method for producing these fibers, and a derivative pulp containing the sulfonated pulp fiber. [Means for achieving the object] The sulfonated pulp fiber of the present invention is a pulp fiber comprising a plurality of cellulose fibers, wherein a part of hydroxyl groups of the cellulose fibers of the pulp fiber is substituted with sulfo groups, an introduction amount of sulfur attributable to the sulfo groups is adjusted to be higher than 0.42 mmol/g while maintaining a fiber shape, and a water retention value of the pulp fiber is adjusted to 150% or more. Since the sulfonated pulp fiber has a predetermined water retaining property or more while maintaining the fiber shape, the degree of flexibility in handling can be improved.