closed end of the tube thus the separator 70 is positioned initially atop the testing reagents 44 and spaced from the closed end of the tube as shown in fig2 in use a liquid sample a is delivered to the tube by a needle that penetrates closure 50 in upper well area 60 for purposes of illustration only the liquid sample is blood the liquid sample is introduced into the evacuated space between the closure and the safety separator the separator 70 effectively blocks movement of the testing reagent 44 into the evacuated space during blood collection this prevents back flow of the reagents towards the patient this feature allows blood collection and testing in a closed system i e there is no need to open the tube to introduce the testing reagent after blood collection the separator 39 s position atop the testing reagents 44 preloaded in the bottom of the tube 30 and spaced from the closure provides easy direct loading of the fluid sample on the separator thus the fluid sample is easily delivered into the tube without exposing the fluid sample needle to the test reagents reducing back flow to almost zero after collection the needle 16.