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Determination of rosin-size retention in wet-end process by quantifying the resin acid content in paper products

In this paper, we report an approach for determining the rosin-size retention in wet-end process, by comparing the agent content in a ton of paper with the agent consumption, in which the resin acid compounds (RAs) were used as the indicating species. The sample was pretreated by disintegration, dissolution in NaOH/urea/thiourea aqueous solution, and rosin ultrasonic extraction using methyl tert-butyl ether. The extraction medium was analyzed by HPLC with a UV detector. It was found that RAs were good indicating compounds for rosin. Under the used HPLC conditions, these RAs could not be separated from each other and only one peak appeared in the chromatogram. This makes the RAs quantification much simpler. The analyte was quantified by an external calibration, in which an excellent linearity (r = 0.9992) in the concentration range of 1 to 100 μg/ml was achieved. The results showed that the method had a good measurement precision and accuracy. The relative standard deviations were within 3.41% and the spiked recoveries were in the range of 88.0 to 99.2%. The limit of quantification of the method was 1 mg/kg. The present method is simple, feasible and suitable to be used for the determination of the rosin-size retention in the wet-end process.