Determination of specific absorbance (A¦) for four designer benzodiazepines

Specific absorbance (A¦) is a unitless value defined as the absorbance of a 1% (w/v) solution measured at a 1 cm path length. Establishing reliable specific absorbance values allows forensic toxicology laboratories to verify the concentration of analytical stock solutions. Designer benzodiazepines have appeared with increasing frequency in forensic casework but often lack validated reference values. This study determined specific absorbance values for bromazolam, etizolam, flualprazolam, and flubromazepam using ultraviolet-visible spectroscopy in an aqueous acidic solution. Measurements were collected in duplicate at three concentrations across three days at the wavelength of maximum absorbance for each compound. Inter-run and intra-run variability were evaluated using the coefficient of variation, and the reliability of the values was classified according to Clarke's Analysis of Drugs and Poisons criteria. The experimentally derived values reported here provide reference information that may assist laboratories in verifying analytical standards for emerging benzodiazepines.