Rapid in situ quantitation of photoinitiators in packaging by two-points kinetic calibration of liquid microjunction surface sampling-mass spectrometry

Yu Mei; Qian Wu; Shiwen Zhou; Zhiguo Wang; Qiuju Liang; Youmei Li; Hongmei Lu

doi:10.1016/j.talanta.2020.121017

Rapid in situ quantitation of photoinitiators in packaging by two-points kinetic calibration of liquid microjunction surface sampling-mass spectrometry

Talanta. 2020 Aug 15:216:121017. doi: 10.1016/j.talanta.2020.121017. Epub 2020 Apr 9.

Authors

Yu Mei¹, Qian Wu², Shiwen Zhou¹, Zhiguo Wang³, Qiuju Liang³, Youmei Li¹, Hongmei Lu¹

Affiliations

¹ College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China.
² College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan, 410083, PR China. Electronic address: qianwu@csu.edu.cn.
³ Technology Center of China Tobacco Hunan Industrial Co. Ltd, Changsha, Hunan, 410007, China.

PMID: 32456927
DOI: 10.1016/j.talanta.2020.121017

Abstract

Absolute quantitation is always a challenge for in situ analysis of solid samples with ambient liquid extraction mass spectrometry due to unknown sampling efficiencies of analytes from complex solid matrices such as commercial packaging materials. Standards were usually dropped onto the sample surface for signal calibration, but the mass transfer of standards would not be the same as analytes distributed in samples. In this work, an in situ quantitation method via liquid microjunction sampling (LMJSS) coupled with mass spectrometry (MS) for photoinitiators (PIs) in packaging was developed without standard spiking. For direct in situ quantitation, mass transfer kinetic model for LMJSS of solid surface was proposed and validated. Results showed that the detection data well fitted the mass transfer model with adjusted R² mostly in the range of 0.8-0.9 for 12 PIs in both lab-made mimetic positive samples and commercial packaging samples. According to the mass transfer kinetic model, two-point kinetic calibration method was proposed for calculation of the absolute concentration of PIs in solid samples by LMJSS of the same sample area for two times. The conditions of LMJSS including extraction solvent composition and solvent flowrate were optimized. With the optimized LMJSS-MS method and new calibration method, in situ analysis was done within only 2 min, and detection limits and quantitation limits of 15 PIs in mimetic samples were in the range of 0.06-1.5 mg/m² and 0.34-6 mg/m² respectively with relative standard deviation (RSDs) in the range of 2%-26%. The quantitation accuracy by the new calibration method for 13 PIs was in the range of 61%-162%. The method was applied to the quantitation of PIs in commercial packaging samples. 6 PIs were detected and identified in four commercial packaging materials, and the quantitation results were comparable with that by traditional solvent extraction-LC-MS method (relative recovery, 63%-127%).

Keywords: In situ quantitation; Kinetic calibration; Liquid microjunction surface sampling; Packaging; Photoinitiators.