In this work, headspace-single-drop microextraction has been used in combination with microvolume
UV–vis spectrophotometry to enhance the determination of trimethylamine-nitrogen (TMA-N) in fish
samples. TMA-N is often used for monitoring fish freshness, but due to the low analytical sensitivity usually
achieved, its determination must be performed after certain time of storage in some fish species. The
proposed methodology, based on the extraction and subsequent complexation of volatile TMA-N onto a
picric acid-containing xylene microdrop exposed to the headspace, involves an important improvement
of sensitivity (detection limit 6 104 mg TMA-N per 100 g of fish), a miniaturization of the AOAC Official
Method (971.14) and a simple approach for routine labs. This method is well suited to determination of
TMA-N in different species of frozen and fresh fish samples from markets and to study the evolution of
TMA-N concentration in farmed turbot at the earliest stages of deterioration.