Quantitative analysis of morphine in urine by gas chromatography-chemical ionization-mass spectrometry, with (N-C2H3)morphine as an internal standard.

A highly sensitive and specific method is described for quantitative determination of morphine in urine. Used in the method is a gas chromatograph and a computerized, quadrupole mass spectrometer operated under chemical ionization conditions. Morphine concentrations as low as 5 ng/mI can be measured by selected ion monitoring, with N-trideuteromethyl morphine as the internal standard. The sensitivity and specificity of the method is illustrated by the detection and quantitation of morphine in urine after ingestion of cough medicine containing codeine.