Surface Acoustic Wave Nebulisation Mass Spectrometry for the Fast and Highly Sensitive Characterisation of Synthetic Dyes in Textile Samples

Abstract

Surface acoustic wave nebulisation (SAWN) mass spectrometry (MS) is a method to generate gaseous ions compatible with direct MS of minute samples at femtomole sensitivity. To perform SAWN, acoustic waves are propagated through a LiNbO₃ sampling chip, and are conducted to the liquid sample, which ultimately leads to the generation of a fine mist containing droplets of nanometre to micrometre diameter. Through fission and evaporation, the droplets undergo a phase change from liquid to gaseous analyte ions in a non-destructive manner. We have developed SAWN technology for the characterisation of organic colourants in textiles. It generates electrospray-ionisation-like ions in a non-destructive manner during ionisation, as can be observed by the unmodified chemical structure. The sample size is decreased by tenfold to 1000-fold when compared with currently used liquid chromatography-MS methods, with equal or better sensitivity. This work underscores SAWN-MS as an ideal tool for molecular analysis of art objects as it is non-destructive, is rapid, involves minimally invasive sampling and is more sensitive than current MS-based methods. Graphical Abstract ᅟ.

Keywords: Ambient mass spectrometry; Art; Conservation; Restoration; Surface acoustic wave nebulisation; Synthetic dyes; Textiles.

Graphical Abstract

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Figure 1

a Experimental setup, b chip and chip holder and c surface acoustic wave nebulisation (SAWN) controller and Android tablet with the software to run the system. MS mass spectrometer, SAW surface acoustic wave

Figure 2

a SAWN mass spectrometry (MS) spectrum and b SAWN-MS/MS spectrum of 1-mm textile fibre dyed with basic violet 3 (BV 3) in MeOH–H₂O (1:1 v/v) (collision energy 65 eV). BV 1 basic violet 1, 1-PA monomethyl pararosaniline, 2-PA bimethyl pararosaniline, 3-PA trimethyl pararosaniline, 4-PA tetramethyl pararosaniline

Figure 3

a SAWN-MS spectrum and b SAWN-MS/MS spectrum of 1-mm textile fibre dyed with acid red 88 (AR 88) in MeOH–H₂O (1:1 v/v) (collision energy 150 eV). AO 6 acid orange 6, AR 18 acid red 18, DR 28 direct red 28

Figure 4

SAWN-MS spectrum of 1-mm textile fibre dyed with acid violet 7 (AV 7);AO 6 acid orange 6, AO 7 acid orange 7, AR 13 acid red 13, AR 18 acid red 18, AR 26 acid red 26, AR 88 acid red 88, DR 28 direct red 28, P 3R ponceau 3R