Detection of carbohydrates using surface-assisted laser desorption/ionization mass spectrometry with HgTe nanostructures

Abstract

We have optimized a previously developed method, combining surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) with HgTe nanostructures, for the detection of sucrose, cyclodextrins, pullulan, and dextran without the need for derivatization. For these analytes, [M + Na]⁺ ions were the dominant species detected in the mass spectra. We adjusted several parameters, including the concentration of the HgTe nanostructures, the pH and salt concentration of the sample matrices, to optimize the sensitivity of the detection of the analytes. This SALDI-MS approach allowed quantitative determination of the concentrations of sucrose, α-cyclodextrin (CD), β-CD, γ-CD, PL-6k, and PL-10k over the ranges 0.5–25, 0.5–50, 0.5–50, 0.5–75, 0.01–5, and 0.05–10 μM, respectively, with limits of detection (at a signal-to-noise ratio of 3) of 100, 28, 30, 22, 8.5, and 25 nM, respectively. The MS profiles of PL-6k and PL-10k were symmetric, revealing the absence of degradation during the SALDI-MS analysis process. From the MS data, we determined the polydispersity indices (PDIs) of PL-6k and PL-10k to be 1.03 and 1.05, respectively. The spot-to-spot and sample-to-sample variations for these analytes were both less than 13%; for example, they were less than 6 and 9%, respectively, for PL-6k. This simple, sensitive, accurate, and reproducible SALDI-MS approach using HgTe nanostructures allows determination of the molecular weights of polysaccharides up to 12 000 Da and quantitative determination of neutral carbohydrates.