A fluid collection assembly and method for use thereof is provided including a barrel with a plunger rod slidably inserted is disclosed. The assembly and method are particularly useful in the collection of arterial blood. The plunger rod includes a proximal portion, a distal portion with a stopper, and a breakable connector between the proximal and distal portions. In use, the assembly is primed with a liquid anticoagulant, the breakable connection is broken, and a fluid sample is collected with the arterial pressure causing the distal portion of the plunger rod to travel in a proximal direction along the barrel and contact an annular flange extending within the barrel. After collection, a tip cap can be applied to the assembly to prevent any spillage of the fluid sample during handling, storage, and transportation.