A flow cytometer apparatus is provided herein including (a) a flow cell, (b) a fluidic pathway having a second end coupled to a first end of the flow cell, (c) a probe coupled to a first end of the fluidic pathway, (d) a sensor configured to detect one or more properties of a fluid in the fluidic pathway and positioned between the probe and the first end of the flow cell, (e) a processor in communication with the sensor, and (f) a non-transitory computer readable medium having stored therein instructions that are executable to cause the processor to perform functions including: (i) receiving, via the processor, the one or more properties of the fluid in the fluidic pathway detected by the sensor, and (ii) determining, based on the detected one or more properties of the fluid in the fluidic pathway, a presence of a separation gas in the fluid in the fluidic pathway.