An optical measuring device (1; 1′; 1″; 41; 61) configured for being connected in a flow path, said optical measuring device (1; 1′; 1″; 41; 61) comprising:—a first and a second flow path connector (5, 7; 5′, 7′; 5″, 7″);—at least one flow cell part (3; 3a, 3b; 3a, 3b, 3c, 3d) provided in between the first and second flow path connectors (5, 7; 5′, 7′; 5″, 7″) such that a flow in a flow path in which the optical measuring device (1; 1′; 1″; 41; 61) can be arranged will flow through the first flow path connector (5; 5′; 5″), the at least one flow cell part (3; 3a, 3b; 3a, 3b, 3c, 3d) and through the second flow path connector (7; 7′; 7″); and—at least one releasable connection device (9) arranged for releasably connecting the at least one flow cell part (3; 3a, 3b; 3a, 3b, 3c, 3d) in between the first and second flow path connectors (5, 7; 5′, 7′; 5″, 7″).