Click here to view printable Application Sheet Notes: Diphenhydramine (DPH) is an antihistaminic drug mainly used as a sedative, hypnotic and antiemetic most know by the trade name, Benadryl®. It is available over-the-counter in many countries and is very common. Generally regarded as a harmless drug, there have been sixty-eight non-fatal and 55 fatal poisonings with DPH or in combination with other drugs were investigated in the last 10 years.

Method Conditions Column Cogent Diamond Hydride™, 4µm, 100A Catalog No. 70000-15P Dimensions 4.6 x 150 mm Solvents A: DI water + 10 mM pyridine B: acetonitrile + 10 mM pyridine Mobile Phase Isocratic 25%B Flow rate 0.4 mL/min. Peaks diphenhydramine 256 m/z (M - H)- RT = 3.49 min 50 ng/mL prepared in 50%A/50%B Detection ESI – neg - Agilent 6210 MSD TOF mass spectrometer Discussion: When a mobile phase containing 80%B (with 10 mM pyridine in solvent A and B) was used diphenhydramine hydrochloride (DPH) was fully retained on the column. After the mobile phase was changed to the one described above, the DPH peak eluted at 3.5 minutes. This wide range of retention time can give analysts many possibilities of developing methods for quantitative analysis of formulations, drugs and also on column SPE methods for isolation of DPH from complex matrices. The method above is very reproducible and sensitive with a lower limit of quantitation (LLOQ) of 5 ng/mL for DPH, with good linearity in the range 1- 500 ng/mL (r2 > 0.9990).