159 / 302
3
Table 2. EQuan MAX chromatography conditions used
Table 3. Exactive Orbitrap MS operating conditions
Parameter
Setting
Scan range
m/z
150–1100
Resolving power
50,000 (FWHM at
m/z
200)
Polarity
Positive
Measured
m/z
995.5543 MC-LR
519.7898 MC-RR
1045.5344 MC-YR
825.4501 Nodularin
Ionization source
Electrospray
Spray voltage
4000 V
Capillary temperature
340 °C
Capillary voltage
37 V
Tube lens voltage
85 V
Skimmer voltage
22 V
Results and Discussion
High-Resolution Mass Spectra of Toxins
The standards were prepared at a concentration of 1 ng/mL
each and injected using a syringe pump to observe the
mass spectra. The molecular ion and carbon isotope
spectra of microcystin-LR, -RR, -YR, and nodularin are
shown in Figure 2a. Four carbon isotopes were observed
for most compounds. Using this isotopic pattern, it was
possible to match the experimentally recorded carbon
isotopic distribution ratios to the theoretical isotopic ratio
to provide confirmation of the toxin using the analysis
software. Meanwhile, molecular ions were observed in
nodularin at
m/z
825 and the isotopic pattern was
confirmed (Figure 2b).
Pump 1
Pump 2
Hypersil GOLD aQ
(preconcentration column)
Hypersil GOLD
(analytical column)
Time
%A
%B µL/min Time
%A
%B µL/min
0.00
98
2
1000
0.00
98
2
400
1.01
98
2
1000
1.00
98
2
400
1.20
98
2
100
2.00
2
98
400
3.50
98
2
100
3.50
2
98
400
4.00
98
2
1000
3.51
98
2
400
4.00
98
2
400
Mobile phase A: 0.1% formic acid in water
B: acetonitrile
Mobile phase A: 0.1% formic acid in water
B: acetonitrile
Column temperature: Ambient
Injection volume: 1000 µL