There are two pickups in 'Purge', pickups are small black squares.
1. Level 4.4 @0:04
After you pass through the 3rd checkpoint the pickup will be to the right under the second block with spikes on it to the right, its hard to see so if you miss it land on the spikes below to retry (As I do in the video)
2. Level 4.8 @0:46
Immediately upon starting the level press
/
to switch to Claire (Blue) and move left
to place Claire next to the spike wall for John (Yellow) to jump on and jump to the pickup which is
right next to the spike wall so you will die.
Here's a video