Practical Aspects of the Determination of Paralytic Shellfish Poisoning (PSP) Toxins by Liquid Chromatography-Fluorescence Detection

Transcription

1 Practical Aspects of the Determination of Paralytic Shellfish Poisoning (PSP) Toxins by Liquid ChromatographyFluorescence Detection

2 utline 1. Chemistry of PSTs structural characteristics 11sulfate ketoenol tautomery oxidation of PSTs hydrolysis of B and Ctoxins 2. Chromatography postcolumn derivatization retention sensivity. Parameters and hydrolysis: temperature, time their impacts oxidation: p column: temperature eluants: p injection: volume matrix effects, imposters 4. Alternative methods shima Lawrence 5. Conclusions

3 1. Chemistry of PSTs Saxitoxin Chemical Structure 2 Purine derivative 1 2 imino functions Acetal moiety Carbamoyl group caffeine

4 1. Chemistry of PSTs Chemical Structures Toxin R1 R2 R R4 R 4 R 1 STX E GTX1 S GTX2 S GTX S C 2 (Carbamoyl) 2 GTX4 S 2 B1= GTX5 B2= GTX6 C S C1 S C2 S CS (Sulfocarbamoyl) C4 S R 2 R dcstx dce (Decarbamoyl) dcgtx1 S STX = Saxitoxin E = eosaxitoxin GTX = Gonyautoxin dcgtx2 S dcgtx S dcgtx4 S

5 1. Chemistry of PSTs 11Sulfate KetoEnol Tautomery 2 GTX / 2 S + 2 S ketone enol S 2 2 GTX2 S + 2 S

6 1. Chemistry of PSTs 11Sulfate KetoEnol Tautomery Toxin R1 R2 R R4 R 4 R 1 2 R 2 R 2 The R 2 /R toxin isomers are given as sums, because the R 2 /R ratios are not stable (except for the equilibrium ratio) STX E GTX1 S GTX2 S GTX S GTX4 S B1= GTX5 B2= GTX6 C S C1 S C2 S C4 S dcstx dce dcgtx1 S dcgtx2 S dcgtx S dcgtx4 S C 2 (Carbamoyl) CS (Sulfocarbamoyl) (Decarbamoyl)

7 1. Chemistry of PSTs xidation of PSP Toxins 1. PSP toxin eluting from column showing neither UV nor fluorescence activity 2. xidation with 2 2 or periodic acid. Acidifying with acetic acid or nitric acid, products showing strong fluorescence (Ex: 0 nm, Em: 90 nm)

8 1. Chemistry of PSTs xidation of PSP Toxins STX B1 E B2 GTX2/ GTX C1/C2 Janeček, M. et al. (199) J. Chromat. 644, 211

9 1. Chemistry of PSTs ydrolysis of B and CToxins o Ctoxin standards are commercially available, Therefore (sulfocarbamoyl) toxins have to be desulfonated into carbamoyl toxins for quantitation S 2 R 1 2 R 2 R 2 2 R S 4 R 2 R ydrolysis conditions: 1 Cl, 15 min, 90 C

10 1. Chemistry of PSTs ydrolysis of B and CToxins Toxin R1 R2 R R4 STX E GTX1 S GTX2 S GTX S GTX4 S B1= GTX5 B2= GTX6 C S C1 S C2 S C4 S dcstx dce dcgtx1 S dcgtx2 S dcgtx S dcgtx4 S C 2 (Carbamoyl) CS (Sulfocarbamoyl) (Decarbamoyl) B1 > STX B2 > E C > GTX1 C1 > GTX2 C2 > GTX C4 > GTX4

11 2. Chromatography Ion pair chromatography with postcolumn oxidation and fluorescence detection

12 2. Chromatography Ion pair chromatography with postcolumn oxidation and fluorescence detection Krock B. et al. (2007) armful Algae. in press

13 2. Chromatography Postcolumn oxidation of PSP Toxins T=50 C Waste Pumps Periodate itric acid

14 2. Chromatography Retention under Ion Pair Conditions Ion pair chromatography: rganic anions are added to the mobile phase to form neutral complexes ( ion pairs ) with kations, or vice versa STX GTX C2 Retention: C2 < GTX < STX

15 2. Chromatography Retention under Ion Pair Conditions

16 2. Chromatography Ctoxins Retention under Ion Pair Conditions A. tamarense (0.0 M Ac) GTX E STX GTX E STX A. tamarense (1 Cl, 15 min, 90 C) GTX2

17 2. Chromatography Sensivity PLCFLD LCMS/MS (API 4000 QTrap) Limit of Quantitation (LQ) Limit of Quantitation (LQ) Toxin (S/=5) [pg] (S/=5) [pg] GTX GTX dcgtx dcgtx GTX B GTX 67 5 E dcstx STX 61 14

18 . Parameters and their impacts ydrolysis of B and CToxins: Time 100% 80% 60% 40% 20% C/4 C1/2 B2 B1 dcgtx2/ dcstx GTX 2/ GTX 1/4 E STX 0% 15min, 90 C 0min, 90 C 60min, 90 C

19 . Parameters and their impacts 100% ydrolysis of B and CToxins: Temperature 90% 80% 70% 60% 50% 40% 0% 20% C/4 C1/2 B2 B1 dcgtx2/ dcstx GTX 2/ GTX 1/4 E STX 10% 0% 15min, 90 C 15min,100 C

20 . Parameters and their impacts xidation: p GagoMartínez, A. et al. (2001) J. Chromat. A 905, 5157

21 . Parameters and their impacts Column: Temperature Column temperature: 20 C Column temperature: 25 C GTX STX GTX STX

22 . Parameters and their impacts Eluants: p Eluant A: p 6.9 Eluant A: p 7.0 GTX1 GTX GTX1 GTX

23 . Parameters and their impacts Injection: Volume Injection volume: 20 µl Injection volume: 0 µl Injection volume: 40 µl Injection volume: 50 µl

24 . Parameters and their impacts Matrix Effects A. minutum extract A. minutum extract 1:2 dilution A. minutum extract 1: dilution A. minutum extract 1:5 dilution Standard

25 . Parameters and their impacts Imposters Baker T.R. et al. (200) Toxicon 41() 947.

26 4. Alternative methods shima method (postcolumn oxidation) column flow Inertsil C85, 4.6x150mm 0.8 ml/min Cgroup: 1 mm TBAP, adjusted to p 5.8 with Ac GTXgroup:2 mm a 1heptanesulfonate in 10 mm ( 4 ) 2 P, p 5.8 STXgroup:2 mm a 1heptanesulfonate in 0 mm ( 4 ) 2 P, p 7.1:AC = 10:5 shima, Y. (1995) Manual on armful Marine Microalgae, IC Manuals and Guides o.. G. M. allegraeff, D. M. Anderson and A. D. Cembella. Paris, UESC: 8194.

27 4. Alternative methods Lawrence method (precolumn oxidation)

28 4. Alternative methods Lawrence method (precolumn oxidation) ot validated for decarbamoyl toxins (except for dcstx) 1hydroxylated PSTs have to be purified by 2 subsequent SPE steps Quilliam M.A. et al. (199) Rapid Commun. Mass Spectrom. 7,

29 4. Alternative methods Lawrence method (precolumn oxidation) Complex toxin profile cannot be resolved Quilliam M.A. et al. (199) Rapid Commun. Mass Spectrom. 7,

30 5. Conclusions 1. Ion pair chromatography with postcolumn oxidation and fluorecence detection is highly selective and sensitive method for PSP determination 2. B and C toxins can indirectly be determined by acidic hydrosis. 11sulfate toxins (C1/C2, C/C4, GTX1/GTX4, GTX2/GTX, dcgtx1/dcgtx4, dcgtx2/dcgtx) should be given as sums only due to their easy interconvertability 4. PLC and oxidation parameters have to be carefully controlled in order to keep retention times and molecular response constant 5. Despite of high selectivity signals have to be confirmed by experiments or inddependent methods

31 Thanks to Annegret Müller, AWI and for your attention!