There is an increasing public interest in the analysis of aromatic amines since this class of organic compounds includes many carcinogenic substances.

In recent years other sources of aromatic amines apart from tobacco smoke have gained more and more interest, for example, azo dyes (1). Therefore a fast and reliable method for the determination of aromatic amines in dyes like printer ink was developed. Five primary aromatic amines (PAAs) (aniline, 2-anisidine, 3-chloro-4methoxyanline, 2,4-dimethylaniline, o-toluidine) were chosen for this demonstration.

Method Parameters for Full Mass Scan Tests

The mass spectra of single compound standards are shown in Figure 1. The resulting m/z values manifest the fragmentation patterns of the PAAs. For every PAA the highest intensity was detected for the single charged quasi molecule ion [M+H]⁺. Therefore this mass was chosen for quantification in all cases.

Figure 1: Mass spectra of single standard.

With the calibrated m/z values the extracts of two printer inks were analysed in order to determine PAA composition and concentrations of these five PAAs.

Sample Preparation

Samples were prepared as cold water extracts according to EN 645:1993 from printed paper.

Instrument Configuration

This application was performed on a PLATINblue binary high pressure gradient UHPLC system equipped with degasser, autosampler, column thermostat and MSQ Plus mass detector.

UHPLC Parameters: Column: BlueOrchid 175–1.8 C18, 100 x 2 mm i.d.; Eluent A: water + 0.1% formic acid; Eluent B: methanol + 0.1% formic acid; Gradient: yes (details on request); Flow rate: 0.2 mL/min; Injection volume: 50 µL; Column temperature: 40 °C

MS Detection Parameters: Ionization mode: ESI, positive mode; Needle voltage: 1 kV; Cone voltage: 20 V; Probe temperature: 200 °C

Figure 2: SIC scans of two printer inks (P1 + P2) after sample preparation.

Conclusion

The UHPLC-ESI-MS method presented in this application demonstrates the fast and simultaneous separation, qualification and quantification of five PAAs usually found in printer ink. The limit of detection was in the range between 1 to 5 µg/L (S/N = 3). Only 7 min are required for the analysis of one sample, including a washing step and re-equilibration of the column. Therefore the method is well-suited for routine analyses. Due to the fast separation and low eluent flow rate of this method, only about 1.5 mL of eluent and less than 1 mL of methanol are needed for one run. Thus this method is both economical and environmentally acceptable.

Reference

(1) M.J. Zeilmaker, H.J van Kranen, M.P. van Veen and J. Janus, Cancer risk assessment of azo dyes and aromatic amines from tattoo bands, folders of paper, toys, bed clothes, watch straps and ink. Rijksinstituut voor Volksgezondheid en Milieu RIVM, 22-Feb-2000.

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