A disposable set (100) includes a tube; and a sensing member (104) press-fittingly insertable into the tube, the sensing member including: a first end (106) having a first diameter and including at least one through hole (112) positioned along a perimeter of the first end; a second end (108) having a second diameter and including at least one through hole positioned along a perimeter of the second end, the first diameter and the second diameter being substantially equal to an interior diameter of the tube; and a middle portion (110) located between the first end and the second end having a diameter that is less than the first diameter, the middle portion including at least one SERS sensing element (114), wherein the through holes in the first and second ends enable fluid to pass through the sensing member.