Ion Exchange and Reversed Phase interactions in selective Bio-SPME extractions of designer drugs

Transcription

1 Ion Exchange and Reversed Phase interactions in selective Bio-SPME extractions of designer drugs Frank Michel, Craig R. Aurand, Robert E. Shirey, Yong Chen, Leonard M. Sidisky sigma-aldrich.com/analytical

2 Application of SPME for subsequent LC/MS Most of SPME applications for subsequent GC analysis SPME/HPLC hyphenation in the past only seldomly Manual process, no automation Swelling/Shrinking of fiber with polymeric coatings Development of bio-compatible Solid Phase Micro Extraction (Bio-SPME) fibers for subsequent HPLC analysis Coating with mixed mode hydrophobic and cation exchange particles Arrangement in a 96 tip array for high throughput 2

3 Bio-SPME Fiber Configuration Coated Fiber Pipette Tip 3

4 Adsorption Mechanism on Bio-SPME Extraction Metal Core Analyte Adsorption Embedded Functionalized Particles Biofluid well Extraction Time 4

5 Adsorption Mechanism on Bio-SPME Extraction Adsorption mechanism for Bio-SPME based on Flick s Law Partitioning of analyte depends on distribution constants between sample liquid and stationary phase (fiber) No exhaustive technique After given amount of time, an equilibrium of analytes is achieved between the matrix and the fiber coating for small sample volumes (2-5ml): n KV f C 0 V s s = KV f +V s at infinite volume of samle (V s >> V f ): n s = KV f C 0 K Distribution constant fiber/sample n s Amount analyte in stationary phase V f Volume of Stationary Phase V s Volume of Sample Concentration of analyte in sample C 0 5

6 Introduction Permanent release of new designer drugs of phenethylamine and cathinone compound class ( Bath Salts, Jewelry Cleaner or Plant Food ) Stimulating affects similar to methamphetamine, heroin and MDMA, bans on the sale of these compounds now in place Challenge in testing for these compounds in forensic testing facilities Normal ELISA testing methods do not work More selective LC/MS methods are necessary Sample prep is critical for reliable LC/MS methods of biological samples 6

7 Analytes investigated (Bath Salts) NH NH Butylone m/z = Da Ethylone m/z = Da NH C H 3 N MDPV m/z = Da NH Mephedrone m/z = Da H 3 C Methylone m/z = Da NH Methedrone m/z = Da NH CH3 F NH CH3 NH CH3 F 4-Fluoromethcathinone m/z = Da 3-Fluoromethcathinone m/z = Da Buphedrone 7

8 Analytes investigated (Bath Salts) Analyte Log D ph 3.0 Log D ph 7.0 pka 1 methylone -3,49-1,21 7,74 ethylone -2,98-0,71 7,75 butylone -2,98-0,7 7,74 methedrone -2,55-0,07 7,48 mephedrone -2,4 0,12 7,41 3-fluoromethcathinone -2,46 0,22 7,14 4-fluoromethcathinone -2,24 0,4 7,14 buphedrone -2,2 0,49 7,14 MDPV -0,67 1,01 8,41 Mixed mode Bio-SPME fibers capable for RP and IEX Analytes should be ionized for strongest interaction Low log D values at low ph postulate HILIC mode in HPLC 8

9 HILIC Separation of Bath Salts Analyte r T [min] MDPV 2.0 Buphedrone fluoromethcathinone 2.7 butylone 2.9 ethylone fluoromethcathinone 3.7 mephedrone 4.6 methylone 5.2 methedrone 6.0 System: Agilent 1290 Infinity w/ 6210 TF Column: Ascentis Express HILIC 100 x 2.1mm, 2.7um Mobile Phase: 5mM NH 4 formate (98:2 ACN:water) Flow: 0.6mL/min Temperature: 35 ºC System Pressure: 127bar Injection Vol: 1uL MS Detection: ESI+, m/z, Time (min) 9

10 Bio-SPME Extraction Conditions from Buffer Impact of ph on recovery (n=4) Fiber: Conditioning: Sample ph3 Sample ph7 Extraction: Desorption: Drying step: Reconstitution: Mixed mode: SCX/C18 silica in tippets 15 30min in 50% methanol-water Buffer solution ph 3 water ph adjusted to ph 3.2 with formic acid, spiked to 200ng/mL with Bath Salts Buffer solution ph 7 10mM ammonium formate ph 7, spiked to 200ng/mL with Bath Salts 15min from 96well plates 1mL volume, 750µl of sample per well 60min in 150µl methanol with 0.5% NH4H (28% solution) in 300ul volume 96 well plate 60min at 40 C under a blanket of nitrogen 50µl of MeH and mixed for 2 min on plate shaker, high speed 10

11 Bio-SPME Extraction from Buffer Impact of ph on recovery (n=4) 11

12 Summary ph study Strong impact of ph on extraction efficiency At neutral conditions (ph = 7) analytes are partially charged resulting in lower extraction efficiency (hydrophobic interactions) Under the acid conditions (ph = 3) all Bath Salts are fully ionized resulting in higher extraction efficiency (hydrophobic plus ionexchange interactions) Extraction time of 15 minutes demonstrated reproducible recovery results, while being pre-equilibrium condition. Next step: extraction of the Bath Salts from plasma samples. 12

13 Bio-SPME Extraction Conditions from Plasma Recovery of analytes and matrix monitoring (n=4) Plasma ph3 Plasma ph7 Extraction: Desorption: Drying step: Rat plasma ph adjusted with phosphoric acid, spiked to 50ng/mL bath salts Rat plasma ph adjusted with 1M sodium phosphate buffer ph 7 (10mM final), spiked to 50ng/mL bath salts 15min from 96well plates 1mL volume, 750µl of sample per well 60min in 150µl methanol with 0.5% NH4H (28% solution) in 300ul volume 96 well plate 60min at 40 C under a blanket of nitrogen Reconstitution: 50µl of methanol and mixed for 2 min on plate shaker, rapid speed As additional sample prep technique protein precipitation (3:1 ratio of 1% formic acid acetonitrile to plasma) was performed on plasma samples for comparison of analyte response and matrix monitoring 13

14 Bio-SPME Extraction from Plasma Recovery of analytes (n=4) 14

15 Bio-SPME Extraction from Plasma Matrix monitoring (n=4) 2X increase in response as compared to protein precipitation Bio-SPME Mixed Mode ph 3.0 In both samples, plasma spiked at 50ng/mL of bath salts Protein Precipitated Plasma 15

16 Bio-SPME Extraction from Plasma Matrix monitoring (n=4) 1/10 th phospholipids as compared to PPT Bio-SPME Mixed Mode ph 3.0 HPLC conditions for Matrix Monitoring: Ascentis Express C18, 50 x 2.1mm, 2.7 µm 5mM NH 4 formate (95:5 MeH:H 2 ) 0.3mL/min 55 C ESI, positive mode, SIM Protein Precipitated Plasma 16

17 Direct in vivo SPME n site sampling No blood withdrawal The extraction phase comes into concentration equilibrium with the chemicals in the surrounding sample matrix. Slide Courtesy of Ines DeLannoy-NoAb BioDiscoveries 17

18 in-vivo PK Study: SPME Extracts of Plasma Carbamazepine from Mice Whole Blood CBZ Concentration (ng/ml) SPME 1 mouse Terminal blood draw Plasma from 3 mice Time (min) Slide Courtesy of Ines DeLannoy-NoAb BioDiscoveries 18

19 Summary Bio-SPME studies demonstrated the capability of analyzing sub 10ng/mL concentration levels of Bath Salts in plasma Mixed mode chemistry ideal for extraction of polar basic compounds Bio-SPME provides 10x reduction in matrix as compared to standard precipitation techniques Increased analyte response Binding process for mixed mode particles on fiber provides a shielding affect to prevent binding of proteins and other large molecules 96 well format of tippets allows for high throughput applications 19

20 Thank you! Craig R. Aurand Robert E. Shirey Yong Chen Leonard M. Sidisky 20