Usefulness of the evaporative light scattering detector for direct screening of biological fluids Original Research Article

This paper reports a fast, simple procedure for the direct screening of biological fluids by using a flow configuration coupled on-line to an evaporative light scattering detector with no chromatographic separation. The potential of this coupling was exemplified for paracetamol. The configuration adopted permits selective retention of paracetamol and its metabolites from dilute urine or serum samples on a LiChrolut®EN sorbent column located in the loop of a high pressure injection valve. Retained paracetamol is eluted with acetonitrile and driven directly to the evaporative light scattering detector. Some analytical features are: detection limit 0.3 μg ml−1, quantitation interval 1–100 μg ml−1, repeatability, as RSD, 1.0%. The reliability of the method was studied at three concentration levels of paracetamol spiked to urine or serum blanks (1, 2 and 4 times the detection limit) yielding 0% of false positives and negatives, thanks to the high precision of the method. Finally a comprehensive study of 50 real urine samples (paracetamol free) obtained from different individuals (healthy, drug addicts and patients from a hospital) provided 4% of false positives and 0% false negatives for the threshold limit established.