Quantitative measurements in continuous flow HPLC/NMR

Two methods for the quantitative determination of compounds in continuous-now HPLC/NMR are described, The first method uses an internal standard (caffeine) of known concentration directly mixed into the mobile phase, while with the second method, a known amount of internal standard is injected onto the column during the chromatographic run. The latter method was validated using several nitroaromatic compounds and explosives, Deviations between the injected and calculated amounts of analytes are usually below 10% while the relative standard deviation ranges from 2% in the upper microgram range to 40% at the limit of detection.