Notes: (+)-Norpropoxyphene-d5 (maleate) (Item No. 15838) is an analytical reference standard intended for use as an internal standard for the quantification of norpropoxyphene (Item No. 15291) by GC- or LC-MS. Norpropoxyphene is categorized as an opioid.{43162} It is a metabolite of propoxyphene (Item Nos. 22769/ ISO60184).{43138} This product is intended for research and forensic applications.