Analysis of Amygdalin in Various Matrices Using Electrospray Ionization and Flowing Atmospheric-Pressure Afterglow Mass Spectrometry

Abstract

Amygdalin is a natural cyanogenic compound that plants produce in the fight against insects and herbivores. Excessive amounts of amygdalin by animals and humans can potentially lead to fatal intoxication. However, studies confirm that amygdalin has antitumor properties, including the ability to inhibit the proliferation of cancer cells and to induce their apoptosis. The analysis of amygdalin in various matrices is an important analytical problem today. The publication presents the methodology of direct determination of amygdalin in water, sewage, and biological materials using electrospray ionization mass spectrometry (ESI-MS) and a new analytical method using flowing atmospheric-pressure afterglow mass spectrometry (FAPA-MS). The methods of analyte pre-concentration using a magnetic, molecularly imprinted polymer (mag-MIP) and the influence of interferents on the recorded spectra were discussed. Analytical parameters in ESI-MS and FAPA-MS methods were established. The linearity range was 4.5 µg L^-1-45 mg L^-1 in positive mode ESI-MS and FAPA-MS. The limit of detection (LOD) for ESI-MS was 0.101 ± 0.003 µg L^-1 and the limit of quantification (LOQ) was 0.303 ± 0.009 µg L^-1. In FAPA-MS, the LOD was 0.050 ± 0.002 µg L^-1 and the LOQ was 0.150 ± 0.006 µg L^-1. The content of amygdalin in various matrices was determined.

Keywords: ESI-MS; FAPA-MS; amygdalin; mag-MIP.

Figure 1

Amygdalin structural formula.

Figure 2

Scheme of V-FAPA (flowing atmospheric-pressure afterglow) ambient plasma source.

Figure 3

The measuring system: plasma torch, heated sample holder, and amaZon SL mass spectrometer.

Figure 4

The electrospray ionization mass spectrometry (ESI-MS) spectrum of amygdalin performed in a buffer solution of pH 7.0 (disodium hydrogen phosphate and citric acid): (a) positive mode, (b) negative mode.

Figure 5

The ESI-MS spectrum of amygdalin performed in a buffer solution of pH 2.0 (hydrochloric acid, sodium chloride, and aminoacetic acid): (a) positive mode, (b) negative mode.

Figure 6

The ESI-MS spectrum of amygdalin performed in a buffer solution of pH 10.0 (boric acid, potassium chloride, and sodium hydroxide): (a) positive mode, (b) negative mode.

Figure 7

The ESI-MS spectrum of amygdalin performed in solutions with the addition of various ions: (a) Cu²⁺, (b) Pb²⁺, (c) Ca²⁺, (d) Na⁺, (e) K⁺.

Figure 7

The ESI-MS spectrum of amygdalin performed in solutions with the addition of various ions: (a) Cu²⁺, (b) Pb²⁺, (c) Ca²⁺, (d) Na⁺, (e) K⁺.

Figure 8

The positive mode FAPA-MS spectrum of amygdalin in 45 mg L^-1 aqueous solution.

Figure 9

Dependence of signal intensity vs. amygdalin concentration in the sample.

Figure 10

HPLC-diode array chromatogram of amygdalin solution (0.5 mg mL⁻¹).

Figure 11

UV spectrum of amygdalin, HPLC retention time t_R = 6.33 min.

Figure 12

Full scan spectrum of amygdalin, HPLC retention time t_R = 6.33 min, m/z 456 [M − H]⁻, m/z 950 [2M + Cl]⁻, m/z 492 [M + Cl]⁻, m/z 475 [M + Na]⁺, m/z 496 [M + K]⁺, and m/z 938 [2M + Na]⁺.

Figure 13

Dependence of signal intensity vs. amygdalin concentration in the sample.

Figure 14

Scheme of Fe₃O₄@SiO₂@VIN@MIP synthesis.

Figure 15

Release and binding of amygdalin in Fe₃O₄@SiO₂@VIN@MIP-amygdalin/Fe₃O₄@SiO₂@VIN@MIP.

Figure 16

X-ray fluorescence (XRF) spectrum of Fe₃O₄@SiO₂@VIN@MIP.

Figure 17

The concentration of amygdalin over time in solution after addition of Fe₃O₄@SiO₂@VIN@MIP. C₀ = 45 mg L⁻¹ (a), 0.45 mg L⁻¹ (b), and 4.5 μg L⁻¹ (c).

Figure 18

The amount of amygdalin released over time in solution after addition Fe₃O₄@SiO₂@VIN@MIP-amygdalin.

Figure 19

FAPA-MS² fragmentation spectrum of the m/z 313 ion observed for amygdalin.

Figure 20

FAPA-MS spectrum of amygdalin in human serum at 200 °C.

Figure 21

FAPA-MS spectrum of amygdalin in human serum at 340 °C.