Twist protection for reagent vessels

A system for positioning and reading identification marks on storage vessels, said system comprising:

• an analytical instrument having at least one holding position with an upper portion, a lower portion, a slot and a slit for holding storage vessels therein, said analytical instrument including a reading device for reading identification marks on the storage vessels;
• at least one storage vessel disposed in said at least one holding position, said at least one storage vessel including an identification mark thereupon and also including a closure which is snapped onto the storage vessel, wherein an outer wall surface of the closure and an inner wall surface of the storage vessel include corresponding projections which engage each other, thereby preventing a twisting of the closure relative to the storage vessel, said closure having a notch projection thereon, the notch projection configured such that said notch projection and said slot cooperate to prevent a twisting of the storage vessel within the holding position, and the identification mark is accessible through said slit.

A system recited in clam 12, wherein the bar code is a two-dimensional bar code.