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TARGETED AND NON-TARGETED APPROACHES TO THE DETERMINATION OF MICROCYSTINS AND OTHER CYANOTOXINS IN WATER

Xavier Ortiz2, Eva Korenkova

2, Karen MacPherson

2, Eric Reiner

2, Julie Degryse

3, Adam Ladak

4, Lauren Mullin

4, Claude Mallet

4, Stuart Oehrle

4, Marijn Van Hulle

5, Simon Hird

1

1 Waters Corporation, Wilmlsow, UK, 2 Ontario Ministry of Environment and Climate Change, Canada, 3 Watergroep, Heverlee, Belgium, 4 Waters Corporation, Milford, USA, 5 Waters Corporation, Brussels, Belgium

METHODS UPLC-MS/MS

50 µL aliquots of drinking and surface water samples were injected as supplied without any further preparation onto a system comprising an ACQUITY UPLC I-Class coupled with a Xevo TQ-S with electrospray in positive ion mode

4.

UPLC-QToF

Samples of lake water were lysed (freeze/thaw), filtered and diluted with water before injecting (10 µL) onto a system comprising an ACQUITY UPLC I-Class with a Xevo G2-XS with electrospray in positive ion mode. Data was acquired using full spectral acquisition with alternating high- and low-collision energy (MS

E)5.

2D-UPLC-QToF

Samples of water, prepared as per UPLC-QTof above, were injected (100-500 µL) onto a system comprising an ACQUITY UPLC I-Class configured for 2D-UPLC trap and elute with at column dilution with a Xevo G2-XS with electrospray in positive ion mode. Data was acquired using MS

E mode.

RESULTS AND DISCUSSION UPLC-MS/MS (Xevo TQ-S)

Excellent sensitivity, selectivity and precision was demonstrated by the response for each of the 10 analytes detected from the direct analysis of water. All compounds could be easily detected at the 0.025 µg/L level, well below the WHO provisional guideline value for MC-LR of 1 μg/L without the need for on-line enrichment.

INTRODUCTION Cyanobacteria (blue-green algae), photosynthetic organisms

found in both marine and freshwater environments, produce

secondary metabolites including microcystins, some of

which are toxic to higher organisms after ingestion or

contact with water, causing sickness and public concern1,2

.

Over 100 different microcystins have been reported to date

of which microcystin-LR (MC-LR) is the most common.

AA1

AA2

AA3AA4

AA5

AA6AA7

AA1 AA2 AA3 AA4 AA5 AA6 AA7

Ala (H4)Y MeAsp Aba Adda Glu Mdha

Gly Aha Asp Ala (6Z)Adda Glu(OMe) Dha

Leu Ala Apa ADMAdda Glu(C3H7O) Dhb

Ser Arg Arg DMAdda dihydro

Glu Butyrine EtAdda MeAla

Glu(OMe) Glu(OMe) MeLan

Hil Har MeSer

Hph His Ser

hR hR

Hty Hty

Leu Leu

M(O) M(O)

Phe Met

Trp Phe

Tyr Trp

Val Tyr

Tyr(OMe)

Val

Figure 1. Microcystin structure showing the many variants

The WHO provisional guideline value for MC-LR (1 μg/L) has

been adopted as a basis for national standards or guideline

values for drinking water in many countries3. Some countries

also set limits for microcystins in water-bodies used for

recreation and these tend to be at higher concentrations.

Other cyanotoxins are regulated in some countries by the

use of guidance values/health alert limits.

To check compliance with these limits, water testing

laboratories have turned to using LC-MS/MS on tandem

quadrupole (TQ) instruments for the determination of a range

of cyanotoxins. These methods provide fast and reliable

determination of targeted cyanotoxins in surface and

drinking water samples.

However, the scope of such LC-MS/MS methods is limited to

the toxins for which reference standards are commercially

available. LC-MS using quadrupole-time of flight mass

spectrometry (Q-Tof), in some cases in combination with ion

mobility, provides an opportunity for non-targeted analysis

and the detection of a much greater number of cyanotoxins

in water samples and algal blooms. To gain additional

sensitivity, automated extraction and cleanup of water

samples can be achieved on-line using a 2D-UPLC set up.

Oasis HLB 2.1 mm x 30 mm x 20 µm

HSS T3 2.1 mm x 150 mm x 1.8 µm

Figure 2. Schematic of the workings of the 2D-UPLC system

UPLC-IMS QToF

An extract from an algal bloom was injected into a system comprising an ACQUITY UPLC I-Class with a Vion with electrospray in positive ion mode. Data was acquired using full spectral acquisition with alternating high- and low-collision energy, aligned with ion mobility drift time (HDMS

E).

References 1. Schmidt JR, Wilhelm SW, Boyer GL (2014). The Fate of Microcystins in the Environment and Challenges

for Monitoring. Toxins 6:3354-3387

2. Testai E et al., (2016). Review and analysis of occurrence, exposure and toxicity of cyanobacteria toxins in food. EFSA Supporting Publication 2016; 13(2):EN-998, 309 pp

3. WHO (2003). Cyanobacterial toxins: Microcystin-LR in drinking-water. Background document for prepara-tion of WHO Guidelines for drinking-water quality. Geneva, World Health Organization (WHO/SDE/

WSH/03.04/57)

4. Degryse J et al. (2017). Analysis of Cyanotoxins, Including Microcystins, in Drinking and Surface Waters by Liquid Chromatography-Tandem Mass Spectrometry. Waters Application Note 720005939en

5. Mullin L et al. (2017). Targeted and Untargeted Screening of Microcystins in Lake Water Samples Using High Resolution Mass Spectrometry. Waters Application Note 720006016en

Time0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

2

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00 5.20 5.40 5.60 5.80 6.00 6.20 6.40 6.60 6.80

%

0

100

CYL

ANA

MC-DeRR

MC-RR

NOD

MC-YR

MC-LR

MC-LY

MC-LW

MC-LF

Figure 3. Chromatograms showing cyanotoxins from analysis of a standard prepared at 0.025 µg/L in drinking water

As the concentrations measured from the analysis of spiked water samples were underestimated and highly variable, indicating the presence of ion suppression due to matrix effects, standard addition was used for quantification. Known amounts of standard were added directly to test portions of an Aquacheck proficiency test lake water sample in an automated manner using the Auto Addition feature in the ACQUITY Sample Manager driver.

Concentration of MC-LR in PT sample = 724 ng/L

Figure 4. Results in Targetlynx XS from analysis of the PT sample

However, methods based upon TQ are restricted in scope to the compounds for which reference standards are commercially available. Untargeted acquisition using QTof, combined with intelligent data processing workflows, offers a practical alternative.

UPLC-QTof (Xevo G2–XS) and UNIFI workflows

QTof carries out full spectral acquisition but with sufficient sensitivity for monitoring purposes. High mass resolving power provides selectivity and the unbiased acquisition mode, MS

E,

generates a comprehensive dataset for retrospective interrogation.

Figure 5. Extracted ion current chromatogram for MC-LR from the analysis of a standard at 0.1 µg/L (100 ppt) in HPLC water (20 µl)

Solutions of 12 available microcystins were analysed and information on retention time and theoretical exact masses of protonated molecular ions, addducts and fragment ions were added to the Scientific Library. Data from the analysis of water samples was componentised and a search was made for a target list of the 12 microcystins from the Scientific Library. Including the 12 standards in the analysis of the sample facilitated quantification of those analytes and demonstrated sensitivity (Figure 5).

Raw data

Organise

Componentisation

Analyse

Workflows

Interrogate

Report results

Peak

componentisationOnly needs to be

done once

Performed in parallel

with data acquisition

Speedy

application

processing Through setting

various questions via

the application of

filters that are

combined into a

workflow

Figure 7. Results in UNIFI 1.8 from analysis of a contaminated lake water sample shown to contain MC-LR

Extra sensitivity can be achieved by injecting more sample. Using 2D-UPLC, 500 µL of sample was injected onto a trap column, where the microcystins were automatically concentrated prior to elution onto an analytical column. At column dilution with an aqueous solvent permits transfer of large volumes of strong elution solvents from the trap column without deterioration of analytical peak shape.

Figure 6. Extracted ion current chromatogram for MC-LR from the analysis of a standard at 0.001 µg/L (1 ppt) in drinking water

The move to 2D-UPLC set up improved the capacity of the MOECC laboratory 3-fold, reduced the size of the water sample required but maintained the MDL. The on-line clean-up reduced the matrix effects so removed the need for standard addition.

Results of a search using the target list from the analysis of a lake water sample gave a confident match for MC-LR (Figure 7). The auto in-silico fragmentation tool helped support the assignment by matching partial structures to the fragment ions observed.

The target list was extended to 100 microcystins based upon knowledge of molecular formulae of the additional microcystins only. Using this approach MOECC were able to detect ca. 70 microcystins in water samples. If the compound is not present in the library, a search can be made of external databases (e.g. Chemspider) for assignment of likely structures to the empirical formulae proposed by the UNIFI software. Prior to the search, the large number of possible candidates detected can be reduced to a more manageable number by user-defined filters.

UPLC-IMS QToF (Vion) and UNIFI workflows

The addition of ion mobility provides selectivity orthogonal to UPLC and MS. The cleaner, drift-time aligned mass spectra makes interpretation of the data more straightforward. The use of collision cross section (CCS) information also reduces errors in compound identification. Figure 8 shows the impact of a filter that includes the range of CCS values typical for microcystins.

High energy spectrum

Low energy spectrum

• 98.5% of the initial candidates were discarded

• Filtered final candidates with cleaner spectra after IMS

Figure 8. Reducing the number of candidates for further investigation by the application of intelligent user-defined filters

CONCLUSION Direct analysis of water samples using ACQUITY UPLC I-

Class coupled to a Xevo TQ-S TQ provides fast and reliable quantitation, using standard addition, of the presence of specific cyanotoxins in water samples, without the need for extraction, at concentrations well

below the WHO guideline value for MC-LR of 1 μg/L

Direct analysis of water using ACQUITY UPLC I-Class coupled to a Xevo G2-XS QTof can also be used to quantify microcystins at concentrations that meet regulatory limits with the added benefit of retrospective data review and the opportunity to search for a wider

range of other microcystins using in-silico tools.

The addition of ion mobility provides spectral clean up

and CCS values to further aid interpretation of the data

Significant improvements in sensitivity and degree of automation can be achieved using the ACQUITY UPLC I-

Class in a 2D-UPLC configuration

Evaluation of this data to identify novel microcystins is ongoing.

Assigned value = 720 ng/L