PERMEATIVE AMINE OR ACID INTRODUCTION FOR VERY WEAK ACID DETECTION IN ION CHROMATOGRAPHY

摘要

A permeative amine/acid introduction device (PAID) is placed after a conventional KOH eluent suppressed conductometric anion chromatography (SCAC) system. The PAID converts the suppressed eluites from the acid form to the corresponding salt. For example, when the analytes are acids, they are converted to the corresponding ammonium salt (NR₂H+HX→NR₂H₂⁺+X⁻) and allows very weak acids HX (pK_a≧7.0) that cannot normally be detected by SCAC to be measured by a second conductivity detector following the PAID. Permeative reagent introduction is dilutionless, can be operated without pumps and provides good mixing with low band dispersion (as small as 30 μL). An exemplary amine is diethylamine (DEA), which was chosen as the amine source due to its low pK_b value (pK_b 3.0), high vapor pressure, and low toxicity and low odor.