Highly sensitive ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry detection method for levoglucosan based on Na+ enhancing its ionization efficiency

Abstract

The sensitive determination of levoglucosan in aqueous samples has great significance for the study of biomass burning. Although some sensitive high-performance liquid chromatography/mass spectrometry (HPLC/MS) detection methods have been developed for levoglucosan, there are still plenty of shortcomings, such as complicated sample pre-treatment procedures, large-amount sample requirements, and poor reproducibility. Herein, a new method for the determination of levoglucosan in the aqueous sample was developed using ultra-performance liquid chromatography with triple quadrupole mass spectrometry (UPLC-MS/MS). In this method, we firstly found that compared with H⁺, Na⁺ could effectively enhance the ionization efficiency of levoglucosan, even though the content of H⁺ is higher in the environment. Moreover, the precursor ion m/z 185.1 [M + Na]⁺ could be used as a quantitative ion to sensitively detect levoglucosan in aqueous samples. Only 2 μL of un-pretreated sample is required for one injection in this method, and great linearity was obtained (R² = 0.9992) using the external standard method when the concentration of levoglucosan was 0.5–50 ng mL⁻¹. The limit of detection (LOD) and quantification (LOQ) were 0.1 ng mL⁻¹ (0.2 pg absolute mass injected) and 0.3 ng mL⁻¹, respectively. Acceptable repeatability, reproducibility, and recovery were achieved. This method has the advantages of high sensitivity, good stability, good reproducibility, and simple operation, which could be widely used for the detection of different concentrations of levoglucosan in various water samples, especially for the detection of samples with low content such as ice core or snow samples.