Determination of nonnitrogenous organic acids and inorganic anions in sugarcane molasses and molasses alcohol waste by ion chromatography with solid-phase extraction
固相萃取-离子色谱法测定甘蔗糖蜜及糖蜜酒精废液中的非氮有机酸和无机阴离子

A method was established for the determination of main nonnitrogenous organic acids (including acetic, lactic, succinic, maleic, tartaric, oxalic, fumaric, citric, and aconitic acids) and three inorganic anions (Cl~, SO2~4 and PO3~4) in sugarcane molasses and molasses alcohol waste by ion chromatography with solid-phase extraction. The diluted sample solution was purified by strong anion exchange (SAX) solid-phase extraction (SPE) in a small packed column to remove most of sugar, pigment and other interfering matrices. The eluate obtained from the column was rinsed with diluted KOH solution and filtered through a 0.45 μm inorganic membrane, finally separated on an anion column of IonPac AS15 with the gradient elution of KOH solution and determined with a suppressed conductivity detector. The pretreatment and procedures of SPE for separating organic acids and inorganic anions from their matrix were investigated. The detection limits were less than 0.20 mg/L. The relative standard derivations were less than 6.7%. The organic acids and inorganic anions in three real samples (two sugarcane molasses samples and an alcohol waste sample) were determined, the recovery ranges were from 94% to 109%. The method shows good precision and linearity.