Trace determination of aromatic hydrocarbons in paraffins by two-wavelength spectrophotometry

The possibility of decreasing the detection limit of the procedure for dete rmining aromatic hydrocarbons in paraffins of the fraction 190-365 degrees C according to GOST (State Standard) 27808-88 to a level of 0.0005 wt % is discussed. It is demonstrated that single-wavelength spectrophotometry, whi ch is used in the GOST procedure, provides the detection limit 0.005 wt %. The necessity of using two-wavelength spectrophotometry within the GOST pro cedure is justified. Recommendations are given for the selection of wavelen gths for three concentration ranges: 0-0.005 wt %, 0-0.01 wt %, and 0-0.02 wt %. Improved computational equations are presented for the determination of aromatic hydrocarbons in paraffins.