LC/QTOF Discovery of Previously Unreported Microcystins in ... · LC/QTOF Discovery of Previously...
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LC/QTOF Discovery of Previously Unreported Microcystins in
Alberta Lake Waters
Ralph HindleVogon Laboratory Services Ltd.
Cochrane, Alberta, Canada
Xu ZhangDavid W. Kinniburgh
Alberta Centre for Toxicology
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Vogon Laboratory Services Ltd.Calgary, Alberta, Canada
Vogon Laboratory Services Ltd.Calgary, Alberta, Canada
Vogon Laboratory Services Ltd.Cochrane, Alberta, Canada
Kananaskis Provincial Park
1. Identify and quantitate targeted microcystins (7 compounds) in lake water
2. Identify unknown peak in lake waters:a) Lake Water A (corresponding to nominal mass of YR)b) Lake Water B (corresponding to nominal mass of LY)
Confirmation Request
General Microcystin StructureOver 70 microcystins have been identified in the literature
MicrocystinProvided by ACFT
X Z Formula Neutral Mass
LR Leucine Arginine C49H74N10O12 994.5488
Desmethyl LR Leucine Arginine C48H72N10O12 980.5331
RR Arginine Arginine C49H75N13O12 1037.5658
YR Tyrosine Arginine C52H72N10O13 1044.5280
LW Leucine Phenylalanine C54H72N8O12 1024.5270
LF Leucine Tryptophan C52H71N7O12 985.5161
HtyR Homotyrosine Arginine C53H74N10O13 1058.5437
OCH3
CH3
NH
H3CO
HN
COHO
NNH
O CH2
OCH3
H3CHN
O
OHN
O
CH3
CH3
CH3HN
OCHO O
NH
NH2
HN
Microcystin-LR Structure(Most common microcystin reported)
C49H74N10O12Mass = 994.5488
Arginine (R)
Leucine (L)
MeAsp
Ala
MdhaGlu
Adda
QQQ MRM Parametersa
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a These patterns are useful, as they show that all supplied MCs fragment to the same 2 diagnostic ions
b RR readily shows a doubly‐charged precursors. Depending on source conditions, other MCs can show either singly‐ or doubly‐charged ions.
Microcystin Precursor b(m/z)
Product Ion(m/z)
Collision Energy(V)
LR 995.6 135.2213.2
8080
Desmethyl-LR 981.5 135.2213.2
8080
RR 520.0 135.2213.2
3040
YR 1045.5 135.2213.2
8070
LW 1025.5 135.2213.2
8060
LF 986.5 135.2213.2
7050
HtyR 1059.5 135.2213.2
8070
Common Microcystin Fragmentsm/z = 135.2 and 213.2
C9H11O+
m/z = 135.0804
Glu + Mdha = C9H13N2O4+
m/z = 213.0870
LC-QTOF Instrumentation
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HPLC Mass Spectrometer1290 Binary Pump 6540B QTOF1200 Degasser Jet Stream Electrospray Source1290 Autosampler1290 TCC
TOF MSQ‐TOF MS/MSQQQ MS/MSSingle Q MSTrap MSn
Acquire DataLC/MS
Transforming Data
Fully or Partially AutomatedFully or Partially Automated
Find CompoundsMFE
Find Compounds
Find CompoundsAuto MS/MS
Find Compounds LMFE (Proteins)
Find CompoundsTargeted MS/MS
Find CompoundsBy Formula
Compare Compounds
Compare compoundsbetween samples
• Metabolite ID• Mass Profiler
Compare compoundsbetween 2 sample sets
• Mass Profiler• Mass Profiler Professional
Compare compoundsbetween >2 sample sets
• Mass Profiler Professional
Identify Compounds
Molecular Formula Generation(MFG)
• Via accurate mass MS andMS/MS
MS/MS Structural Correlation (MSC) via accurate mass
• Future Tools
Accurate Mass and RT(AMRT) Database Search• Endogenous Metabolites (METLIN)• Food, Forensics, Environmental
Protein DB Search• Spectrum Mill• Mascot• Others (via mzXML, mzData)
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Find By Formula Parameters
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Level 3 Calibrator (10 ng/mL)
Time of Flight MS Spectra
Database Score
Monoisotopic mass(varies in ppm)
Isotope spacing(varies in ppm)
Isotope distribution(varies in %) Score based on:
• Mass match – measured versus given.
• Abundance score – abundance pattern of measured isotope cluster compared withvalues predicted from the proposed formula.
• Spacing match – how the m/z spacingbetween the lowest m/z ionand the A+1 and A+2 ions compared withthe values predicted from the proposed formula.
Score Evaluation for Find by Formula
RT Name Mass m/z Score Diff from Tgt (ppm) Ions Flags (Tgt)
Flag Severity (Tgt)
4.60 HtyR 1058.5429 1059.5505 98.4 ‐0.7 14 Pass
4.62 YR 1044.5275 1045.5347 99.3 ‐0.5 18 Pass
4.68 LR 994.5487 995.5560 99.2 ‐0.1 15 Pass
4.80 RR 1037.5654 519.7900 99.2 ‐0.4 16 Pass
4.87 dm‐LR 980.5332 981.5404 99.7 ‐0.1 13 Pass
5.27 LW 1024.5265 1025.5340 99.3 ‐0.5 8 Pass
5.40 LF 985.5159 986.5232 99.8 ‐0.2 12 Pass
• Scores range from 98.4 – 99.8• Mass error all < 1 ppm; up to 18 ions found to help confirm molecular formula• MassHunter table includes Flags and Severity ratings to help interpret results (no flags
identified in this data)
Compounds-at-a-Glance (20 uL)
HtyR
YR
LR
RR
0.1 ng/mL 1 ng/mL 10 ng/mL
Calibration Curves
Calibration Accuracies
Creating a Quant method is easy:• Review the data in Qual• Export a Compound Exchange Format (CEF) file• Select “New Method from File” in Quant• Add calibration levels• That’s it!
Water Sample Results – Lake A
Cal 1
Cal 2
Cal 3
Lake A
Lake B
HtyR YR LR RR
Lake A – YR Investigation in Qual
• The raw spectrum shows that the unknown contains a distinct A ion at 1045.5342• This is ‐0.5 ppm mass error and score of 99.4 for YR formula: C52H72N10O13• Because RT is wrong, suspect structural isomer• Run Targeted MS/MS on each sample (next slide)
YR vs Unknown Compound: MS/MS
• Notable ions missing from Lake A compound:• 127.0862• 155.0803• 157.1094• 213.0864
• Notable ions present in Lake A compound:• 150.0904• 361.1730
• Conclusion: Unknown peak is not YR
Zoom in on common MC fragments - 135
135.0804 = C9H11O+
• De‐methylation is common in microcystins• Two 135 ions are present in both YR and in
unknown compound in Lake A, from 2 different fragments
• Indicates that Adda group is intact and not de‐methylated
OCH3
CH3
NH
H3CO
HN
COHO
NNH
O CH2
OCH3
H3C
X
O
Z
O
CH3HN
CHO O135.1168 = C10H15
+
Zoom in on common MC fragments - 213
• De‐methylation can also occur on Mdha group
• 213.0870 ion is very low in Lake A unknown
• Indicates a de‐methylated microcystin
Glu + Mdha = C9H13N2O4+
m/z = 213.0870
Zoom in on common MC fragments - 199• Predict: C8H11N2O4
+ fragment ion from [Mdha – CH2] de‐methylation• Result: Found in Unknown, not in YR• Des‐methyl HtyR has same formula as YR, and so is a strong
candidate• If 1045.5 ‐> 213.1 is monitored as qualifier ion by QQQ, ratio will be
low compared to YR standard
Additional unknowns detected – Lake A
• MS‐only• PCD of 52 microcystins (in‐house)• Mass Tolerance: 5 ppm• Min Score: 70• H+ adduct required
Additional unknowns detected – Lake B
• MS‐only• PCDL of 52 microcystins (in‐house)• Mass Tolerance: 5 ppm• Min Score: 70• H+ adduct required
1. All calibrators were detected at 0.1 ng/mL on 6540 QTOF2. Calibration curves were linear (R2 > 0.998)3. Microcystins confirmed:
1. Lake A: dm-LR = 15.8 ng/mL2. Lake B: LR = 0.4 ng/mL
4. Identify unknown peak in lake waters:I. Lake Water A
i. HtyR tentatively identified, corresponding to nominal mass of YRii. 7 additional MCs were tentatively identified
II. Lake Water Bi. suspected LY confirmed to be different compoundii. 7 additional MCs were tentatively identified
5. In-house PCDL of 52 compounds was created from WHO list and used to tentatively identify previously unreported microcystins
Summary
Acknowledgements
• ACFT sample prep staff