Determination of EU-Banned Disperse Dyes by LC/MSD TOF

Accurate mass measurements are used to both confirm the presence of a compound and help identify unknowns. Furthermore, high-mass accuracy enables the user to generate very narrow extracted ion chromatograms, enabling excellent quantitation. This application note describes the use of the Agilent liquid chromatograph/ mass selective detector time-of-flight (LC/MSD TOF) instrument to identify and quantitate the disperse dyes used in textiles. This is regulated by the European Commission (EC), which is the trade regulatory arm of the European Union (EU). Introduction Disperse dyes were originally developed for the dyeing of cellulose acetate. They are substantially Determination of EU-Banned Disperse Dyes by LC/MSD TOF Application water insoluble. The dyes are finely ground in the presence of a dispersing agent, then sold as a paste or spray, dried and sold as a powder. They can also be used to dye nylon, triacetate, polyester, and acrylic fibers. The general structure of disperse dyes is small, planar, and non-ionic, with attached polar functional groups like -NO2 and -CN. The shape makes it easier for the dye to slide between the tightlypacked polymer chains, and the polar groups improve both the water solubility and the dipolar bonding between dye and polymer, affecting the color of the dye. However, their small size means that disperse dyes are quite volatile, and tend to sublime out of the polymer at sufficiently high temperatures. Increasingly, liquid chromatography/mass spectrometry (LC/MS) is being used for the analysis of many polar dyes of the EU Directives, as passed down by the European Commission (EC), and is rapidly becoming an accepted technique in dye residue analysis for regulated monitoring. In particular, LC/MS works well on the new families of disperse dyes that are polar and thermally labile. Thus, LC/MS methods are often preferred over the older, established GC/MS techniques, which have often required derivatization for analysis or the liquid chromatography/ultraviolet (LC/UV) methods, which are less sensitive and less selective. As a result, LC/MS is an emerging technology for the analysis of dyes, and here we present the results of using the Agilent time-of flight instrument, or LC/MSD TOF, for the accurate mass and high resolution analysis of dyes. Environmental Disperse dye Molecular formula Structure Mono-isotopic mass 1 Disperse Blue 1 C14H12N4O2 2.68.2744 [2475-45-B] 2 Disperse Blue 3 C17H16N2O3 296.325 [2475-46-9] 3 Disperse Blue 7 C18H18N2O6 358.35 [3179-90-6] 4 Disperse Blue 26 C16H14N2O4 298.2934 [3860-63-7] 5 Disperse Blue 35 C15H12N2O4 284.27 [12222-75-2] 6 Disperse Blue 102 C14H17N5O3S 335.38 [12222-97-8] 7 Disperse Blue 106 C15N16N6O2S 344.39 [12223-01-7] 8 Disperse Blue 124 C16N19N5O4S 377.11 [61951-51-7] 2 Experimental The work undertaken in this study was performed on an Agilent 1100 LC system consisting of a binary pump, autosampler, thermostatted column compartment, and the LC/MSD TOF. The compounds analyzed are shown in Table 1. Table 1. The 20 Disperse Dyes Studied, Including Chemical Abstract Services Number (in brackets), Chemical Structure, and Theoretically Calculated Exact Mass