4-Nitrophenyl b-L-arabinofuranoside is a fluorogenic substrate for the aminoglycoside and fluoroquinolone antibiotics. It is used in the detection of these drugs in food, water, and soil samples. 4-Nitrophenyl b-L-arabinofuranoside has been shown to conjugate with the antibiotic chloramphenicol to form a fluorescent compound that can be detected using a luminometer. The enzyme substrate has also been used for diagnostic purposes to measure bacterial activity.