Archived | Amplified DNA Product Separation for Forensic Analysts | Troubleshooting

Troubleshooting Guide
Issue	Possible Cause	Action
Poor mobility and reproducibility	Temperature fluctuation	Check instrument oven Check environment temperature
	Blocked, dirty capillary	Change capillary
	Sample-wall interaction	Rinse capillary with polymer
	Ion depletion of buffers	Replace buffers
Buffer siphoning	Buffer reservoir levels not equal	Equalize buffer levels
Poor sensitivity	Not enough amplified product in sample	Reamplify or add more amplified product
	Bubble in sample tube, capillary exposed to bubble	Reinject
	Poor laser power	Service call, possible laser replacement
	Ion competition during electrokinetic injection	Check quality of formamide Compare results of sample to positive control included in kit - if okay, then evaluate extraction and sample preparation
	Poor matrix	Rerun matrix
Gradual change in current	Different cathode/anode buffers and/or concentration	Confirm buffers
Current fluctuations	Bubbles in the system	Conduct a visual check for bubbles and clear by flushing with fresh polymer.
No current	Plugged capillary	Flush with polymer Replace capillary
No current	Wrong buffer	Confirm buffers
Noisy baseline	Poor matrix	Rerun matrix
Flat baseline	Capillary not aligned in detector window	Realign capillary
	No voltage	Confirm voltage settings Ensure capillary ends are immersed in buffer
	Sample not injected	Confirm the following: Sample in vial Sample is thoroughly mixed with formamide and is not on the side of the tube Capillary end in sample solution Injection time
	Laser not functioning	Service call, possible laser replacement
	Clogged capillary	Replenish with fresh polymer Replace capillary
Electrical arcing	Buffer spill in high voltage areas	Clean autosampler tray with distilled water and wipe dry
Poor peak shape	Incorrect current causes: peak distortion tailing [low current]	Replace buffer
Poor peak shape	Capillary failure	Replenish capillary with fresh polymer Replace capillary

Back Forward

Additional Online Courses

See additional NIJ-sponsored training

Date Created: July 21, 2023