Ion‐pairing high‐performance liquid chromatography‐mass spectrometry of impurities and reduction products of sulphonated azodyes

Abstract

Ion-pairing high-performance liquid chromatography-mass spectrometry of impurities and reduction products of sulphonated azodyes An HPLC separation method with triethylammonium acetate mobile phase additive developed for the analysis of impurities in polysulphonated azo dyes provides good separation selectivity and compatibility with electrospray ionisation (ESI) mass spectrometry. The negative-ion ESI mass spectra containing only peaks of deprotonated molecules [M -H] -for monosulphonic acids, [M -xH] x -, and sodiated adducts [M -(x + y)H + yNa]x -for polysulphonic acids allow easy molecular mass determination of unknown impurities. Based on the knowledge of the molecular masses and of the fragment ions in the MS/MS spectra, probable structures of trace impurities in commercial dye samples are proposed. To assist in the interpretation of the mass spectra of complex polysulphonated azodyes, additional information can be obtained after chemical reduction of azodyes to aromatic amines. The structures of the non-sulphonated reduction products can be determined by reversed-phase HPLC/MS with positive-ion atmospheric pressure chemical ionisation and of the sulphonated products by ion-pairing HPLC/MS with negative-ion ESI.

Effects of functional groups on the fragmentation of dyes in electrospray and atmospheric pressure chemical ionization mass spectra

“…Triethylamine and dihexylamine (purity > 99%) were purchased from Aldrich (Milwaukee, WI, USA) and acetic acid from Sigma (St. Louis, MO, USA). Triethylammonium acetate (TEAA) or dihexylammonium acetate (DHAA) was prepared by mixing of equimolar amounts of triethylamine (or dihexylamine) and acetic acid and used as an ion-pairing reagent in HPLC/MS experiments [7,16,27,30].…”

“…In connection with soft ionization techniques, tandem mass spectrometry (MS/MS) or multiple-stage tandem mass spectrometry (MS n ) is essential, because of the lack of fragment ions in the first-order mass spectra [16,21,25]. The HPLC methods for the analysis of medium and low polar dyes employ the common reversed-phase C18 column packing and mobile phases consisted of aqueous methanol or acetonitrile.…”

Photocatalytic activity of Fe-modified bismuth titanate pyrochlores: Insights into its stability, photoelectrochemical, and optical responses

“…Broad area EDAX analysis confirms the MO is a complex organic molecule that is often used as a textile dying agent. MO has been chosen as a standard model-dye to verify the photocatalytic performance of various synthesized catalysts since its degradation using different photocatalysts have been well researched and its degradation products are well characterized [26][27][28][29]. The effect of catalyst loading on the photo-conversion of the MO was examined at a dye concentration of 10 M. 5 mL aliquots of the dye were removed from the slurry reactor and the absorbance was checked at regular time intervals.…”

Photocatalytic degradation of methyl orange using ZnO/TiO2 composites

“…Recently, liquid chromatography separation techniques coupling with mass spectrometry (LC-MS) have been established for the separation and detection of dyes and their degradation products [12][13].…”