Sample Preparation Strategies for Water Analysis Hannah White Waters Business Development Manager ©2007 Waters Corporation Outline Introduction Strategies Summary Appendix — Why sample Prep — Considerations o Choices of tools — Why SPE o Pre-Treatment — Traditional approaches — Modern approaches o Mixed Mode o Reverse phase ©2007 Waters Corporation 2 Why Sample Prep? 60% of the work activity and operating cost is spent on sample preparation for introduction into the analytical system Three Purposes: – Removes interferences from sample matrix – Concentrating analytes of interest – Improving analytical system performances For high sensitivity analyses, such as those employing LC/MS/MS, proper sample preparation can be critical for minimizing matrix effects and concentrating analytes of interest. ©2007 Waters Corporation 3 Sample Preparation Techniques Sample Preparation- The simplification of sample matrix and enrichment of target analyte(s) Types of Sample Prep include: — Dilution — Centrifugation — Filtration — Liquid/Liquid Extraction — Solid Phase Extraction ©2007 Waters Corporation 4 Some Considerations Solid samples — usually start with organic or aqueous extract of tissue or soil — initial extract is adjusted for optimal SPE enrichment and/or cleanup o pH adjustment o solvent adjustment • acetone/acetonitrile/IPA – suitable for aqueous dilution, Reversed-Phase and Mixed-Mode SPE • ethyl acetate/DCM/MTBE – can be exchanged to hexane for normal-phase SPE Aqueous samples (water, beverage, plasma/urine) — pretreatment may be appropriate o pH adjustment o filtration/centrifugation o protein precipitation — Usually, aqueous samples can be analyzed using Oasis® ReversedPhase or Mixed-Mode SPE ©2007 Waters Corporation 5 Pre-Treatment Prior to SPE Pre treatment: Solid samples (soil, tissue, etc.) — shake, sonicate or soxhlet o extract with polar organic solvent (methanol, acetonitrile); polars o extract with organic solvent + drying agent (DCM, acetone); nonpolars, multi-residue Non aqueous Liquid o if water soluble, dilute with water for reversed-phase (or mixedmode) SPE o if hexane soluble, dilute with or exchange to hexane for NP-SPE Wastewater — filter or centrifuge as necessary o filtered solids and filter may require analysis as solids ©2007 Waters Corporation 6 Why Solid Phase Extraction Isolation of the analyte(s) of interest from the matrix Sample Cleanup — removal of matrix interference — Increased sensitivity o Increased system uptime o Longer column lifetime Enrichment of analyte(s) of interest o Increased sensitivity Exchange to LC or GC compatible solvent SPE is also faster and more suitable for automation compared with liquid-liquid extraction ©2007 Waters Corporation 7 Short List of Sorbent Types for SPE Normal-Phase Sorbents (polar sorbents) — Silica, Alumina, Florisil®, Aminopropyl silica, Diol silica, GCB Reversed-Phase Sorbents (non-polar sorbents) — Oasis® HLB — C18, C8 etc (alkyl silica's) — Carbon based sorbents Ion Exchange — Accell Plus™ CM, QMA Mixed Mode (ion-exchange/reversed phase) — Oasis® MAX, Oasis WAX (strong and weak anion-exchange) — Oasis® MCX, Oasis WCX (strong and weak cation-exchange) ©2007 Waters Corporation 8 Outline Introduction Strategies Summary Appendix — Why sample Prep — Considerations o Choices of tools — Why SPE o Pre-Treatment — Traditional approaches — Modern approaches o Mixed Mode o Reverse phase ©2007 Waters Corporation 9 SPE Strategies 1. Approach #1 Retention, cleanup, elution 2. Approach #2 Pass-through 3. Approach #3 Dispersion ©2007 Waters Corporation 10 SPE Strategy 1 Retention-Cleanup-Elution 1. Sample is loaded onto SPE sorbent • Analyte(s) of interest are retained on sorbent 2. Matrix interferences are washed off sorbent 3. Analytes are eluted from sorbent 1. load 2. wash 3. elute ©2007 Waters Corporation 11 SPE Strategy 2 Pass-Through Cleanup 1. Sample is passed through sorbent and collected • no sample enrichment 2. Matrix interferences are retained on sorbent pass through ©2007 Waters Corporation 12 SPE Strategy 3 Dispersion Cleanup Bulk sorbent is added to sample with agitation Sample is filtered or centrifuged Supernatant is collected for analysis This is similar to pass-through cleanup, but less effective - Dispersion SPE is a one stage (one theoretical plate) cleanup - Pass-through SPE is a multi-stage cleanup ©2007 Waters Corporation 13 Outline Introduction Strategies Summary Appendix — Why sample Prep — Considerations o Choices of tools — Why SPE o Pre-Treatment — Traditional approaches — Modern approaches o Mixed Mode o Reverse phase ©2007 Waters Corporation 14 Ion-Exchange and Mixed-Mode Ionizable Compounds Many compounds of environmental interest are weak acids (i.e. dinoseb) or weak bases (i. e. aniline). — weak acids can be ionized at high pH — weak bases can be ionized at low pH Some compounds are strong acids (i.e. PFOA) or strong bases (i.e. chlorhexidine) that are ionic except at extreme pH values A few of these compounds are quaternary amines (i.e. paraquat), ionic at all pH ©2007 Waters Corporation 15 Why Mixed-Mode? Mixed-Mode SPE extends pH range for good retention of acids or bases Retention can be by reversed-phase, ion-exchange or both — Chose retention mode by adjusting pH — ion-exchange allows for good retention in strong solvent o acids can be retained by anion-exchange while bases/neutrals are washed off with strong solvent o bases can be retained on cation-exchange while acids/neutrals are washed off with strong solvent For environmental analysis, mixed-mode SPE allows simultaneous retention of acids and bases ©2007 Waters Corporation 16 Oasis® Family of Mixed-Mode Sorbents: Reversed-Phase Retention and Ion Exchange ©2007 Waters Corporation 17 Oasis Mixed-Mode Sorbents Strategies for Isolation and Enrichment of Individual Compounds or Compound Classes Oasis® 2x4 method PFOS, PFOA (perfluoroacids and related compounds) — Oasis WAX Acidic Herbicides — Oasis MAX Quats — Oasis WCX Pharmaceuticals/pesticides (organic bases) — Oasis MCX ©2007 Waters Corporation 18 Introduction Perfluorinated compounds (PFCs) such as perfluorooctanesulfonate and perfluorooctanoic acid are persistent organic pollutants (POPs) PFCs have been identified in environmental samples worldwide — PFOS can be detected at low PPT levels in most humans — PFOS commonly found in arctic fauna There is need for reliable analytical methods for PFCs in food, drinking water, tissue, plasma and blood In this presentation we will discuss sample preparation for UPLC-MS determination of PFCs in water and tissue samples ©2007 Waters Corporation 19 UPLC-MS-MS System ACQUITY Ultra Performance LC™ — Using 1.7μm particles, and at elevated pressures up to 15,000 psi ¾ Shorter Analysis Time ¾ Higher Resolution ¾ Broad selectivity options Quattro Premier™ XE — Fast acquisition rates — Sensitive detection Oasis sorbents — Cleaner samples ©2007 Waters Corporation 20 Goals Develop an Acquity UPLCTM separation based on a recently published method* Adapt or modify the SPE protocol for UPLC — River Water sample — Chicken Liver tissue sample Lower the quantification limits to under 1 ppb in Chicken Liver tissue, and Low ppt level in River Water sample *S. Taniyasu et. al. J. Chrom. A., 1093 (2005) pp89-97 ©2007 Waters Corporation 21 Structures of PFOS and PFOA PFOA and PFOS are Persistent Organic Pollutants of high interest worldwide. F F F F F F O F F F F F F OH F3C perfluorooctanoic acid PFOA pKa ~ 1 F F F F F F F O S O- F3C F F F F F F F O perfluorooctanesulfonate PFOS pKa<<1 ©2007 Waters Corporation 22 Oasis® 2x4 Method For Acids, Bases, and Neutrals For Bases: pKa 2-10 Use Oasis® MCX For Strong Acids pKa <1.0 Use Oasis® WAX For Strong Bases pKa >10 Use Oasis® WCX For Acids pKa 2-8 Use Oasis® MAX Protocol 1 Protocol 2 Prepare Sample Prepare Sample Condition/Equilibrate Load Sample Condition/Equilibrate Load Sample Wash: 2% Formic acid Wash: 5% NH4OH Elute 1: 100% MeOH Elute 2: 5% NH4OH in MeOH Bases Strong Acids Neutrals Elute 1: 100% MeOH Elute 2: 2% Formic Acid in MeOH Strong Bases Acids ©2007 Waters Corporation 23 Optimized SPE Protocol for River Water Oasis® WAX sorbent was selected for these analytes Conditions for Oasis® WAX 3 cc 60mg cartridges Oasis® WAX Optimized Protocol 1 Logic: PFOA pKa ~1 PFOS pKa < 1 Prepare Sample pH 3 Condition 2 mL methanol/2 mL water Load Oasis® WAX 200 mL N H N+ N H N+ H H N O Wash #1 1 mL 2% Formic acid Elute 1 (Wash #2) 2 mL methanol Elute 2 2 mL 1% conc. ammonia in 10:90 methanol/MTBE mixed-mode weak anion-exchange pKa ~6 Samples were evaporated and reconstituted in 0.15 mL mobile phase ©2007 Waters Corporation 24 SPE Protocol Oasis® WAX Optimized Protocol 1 Prepare Sample pH 3 @ pH 3 Sorbent, and analytes are fully charged (assures mixed-mode retention) Condition 2 mL methanol/2 mL water Load 200 mL Wash #1 1 mL 2% formic acid Wash #2 2 mL methanol Maximum load for good recovery of C3, C4 and PFBS Assures sorbent is charged Removes neutrals and bases retained by reversed-phase Elute 2 2 mL 1% conc. ammonia in 10:90 methanol/MTBE MTBE based eluent minimizes elution of any retained humic material ©2007 Waters Corporation 25 PFBS/PFOS in River Water 100 ng/L (ppt) 200mL river water 6cc WAX _200uL recon _BK PFOS_082306AQC21x50C18_3 Sm (SG, 1x1) 2: MRM of 3 Channels ESTIC 1.34e4 Blank % 100 0 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 PFOS_082306AQC21x50C18_4 Sm (SG, 1x1) 5.50 5.75 2: MRM of 3 Channels ESTIC 1.34e4 100 Spiked River Water PFOS % PFBS 0 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 ©2007 Waters Corporation 26 C3-C7 in River Water 100 ng/L (ppt) 200mL river water 6cc WAX _200uL recon _BK PFOS_082306AQC21x50C18_3 Sm (SG, 1x1) 1: MRM of 5 Channels ESTIC 9.38e4 100 % Blank 0 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 PFOS_082306AQC21x50C18_4 Sm (SG, 1x1) 4.20 C7 Spiked River Water % 4.00 3: MRM of 5 Channels ESTIC 9.38e4 100 C5 3.80 C6 C4 C3 0 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 ©2007 Waters Corporation 27 C8-C12 in River Water 100 ng/L (ppt) 200mL river water 6cc WAX _200uL recon _BK PFOS_082306AQC21x50C18_3 1: MRM of 5 Channels ESTIC 1.61e5 100 % Blank 0 2.50 3.00 PFOS_082306AQC21x50C18_4 3.50 4.00 4.50 100 5.50 6.50 7.00 C11 C9 C8 6.00 C10 7.50 8.00 1: MRM of 5 Channels ESTIC 1.61e5 % Spiked River Water 5.00 C12 0 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 ©2007 Waters Corporation 28 River Water Recoveries Spike Level μg/L PFBS 0.10 0.30 0.70 1.0 4.0 10 122 110 102 113 104 104 PFOS C3 109 117 98 94 86 100 108 95 91 128 101 98 C4 C5 C6 C7 C8 C9 C10 C11 C12 119 97 154 107 83 132 105 110 119 126 107 93 118 100 78 106 98 130 100 88 99 99 102 102 92 101 100 87 89 82 121 137 103 100 115 103 101 118 126 110 99 99 101 100 94 95 119 121 117 87 84 68 101 66 ©2007 Waters Corporation 29 Observations/Recommendations Fluorocarbon parts, tubing, etc. are potential sources of interferences — UPLC fluidic lines were conditioned with 2% TFA in propanol followed with 4% conc. ammonia in water (4 hours each step) Polypropylene (PP) lab ware may be best for sample prep — Do not use Teflon!! (possible positive interference) — Analytes may adsorb to glass (possible negative interference) C3-C5 analytes are highly volatile — Evaporative losses are possible, much more so at very low pH Samples in glass vials may show loss of some analytes with time — Analyze within 24 hrs of sample prep ©2007 Waters Corporation 30 Conclusions • Oasis® WAX SPE method is effective for isolation and enrichment of C4-C8 perfluorosulfonic acids and C3-C12 perfluorocarboxylic acids from water and tissue • Acquity UPLC™ provides significantly reduced analysis time and improved chromatographic behavior for these compounds compared with traditional HPLC The Quattro Premier XE™ API mass spectrometer, operated in MRM mode, provides outstanding sensitivity and selectivity for these compounds ©2007 Waters Corporation 31 Acidic Herbicides OCH2COOH Cl Cl 2,4-D Step 1 – characterize analytes they are acids pKa 3-6 For Acids pKa 2-8 Select Oasis® MAX These herbicides, such as 2,4-D, are used in cultivated agriculture, in pasture and rangeland applications, forest management and home and garden. Also in aquatic applications. ©2007 Waters Corporation 32 Oasis® 2x4 Method: Starting Protocols For Acids and Bases For Bases: pKa 2-10 Use Oasis® MCX For Strong Acids pKa <1.0 Use Oasis® WAX For Acids For Strong Bases pKa 2-8 pKa >10 Use Oasis® WCX Use Oasis® MAX Protocol 1 Protocol 2 Prepare Sample Prepare Sample Condition/Equilibrate Load Sample Condition/Equilibrate Load Sample Wash: 2% Formic acid Wash: 5% NH4OH Elute 1: 100% MeOH Elute 2: 5% NH4OH in MeOH Bases Strong Acids Neutrals Elute 1: 100% MeOH Elute 2: 2% Formic Acid in MeOH Strong Bases Acids ©2007 Waters Corporation 33 Oasis® 2x4SM Method Choose Starting Protocol For Acids pKa 2-8 Use Oasis® MAX OCH2COOH Protocol 2 Prepare Sample Cl Condition/Equilibrate Load Sample Cl 2,4-D Wash: 5% NH4OH* The Oasis MAX cartridge was chosen for retention of acid herbicides Logic: 2,4-D and other acid herbicides pKa 3-6 Elute 1: 100% MeOH Elute 2: 1% Formic Acid in MeOH Acids ©2007 Waters Corporation 34 Oasis® MAX SPE Method Acidic Herbicides 1µg/kg in River Water 3 Oasis MAX Protocol 2 Waters XTerra™MS C18, 2.1 x 100 mm A: 15mM ammonium formate (pH 3.5), B: acetonitrile 25% B to 60% B in 9 min, hold 5 min, to 90% B in 16 min Prepare Sample Waters ZQ, ESI-, SIR mode Condition 15 3 mL methanol/ 3 mL water 4 Load 300 mL sample Wash #1 3 mL 5% NH4OH 1 6 2 7,8 9 12 10 13 5 14 11 Elute 1 (Wash #2) 3 mL methanol 20 min 1 ppb in river water Elute 2 4 mL 2% Formic Acid in MeOH Evaporate and Reconstitute Conditions for 6 cc cartridges 1. picloram 2. chloramben 3. 4-nitrophenol 4. bentazon 5. 2,4-D 6. MCPA 7. dichlorprop 8. 2,4,5-T 9. MCPP 10. DCB 11. acifluorfen 12. 2,4,5-TP 13. 2,4-DB 14. dinoseb 15. pentachlorophenol ©2007 Waters Corporation 35 Paraquat/Diquat The Oasis WCX cartridge was chosen for these analytes For Quats Logic: Select Oasis® WCX quats are cationic at all pH values quats can be eluted from Oasis WCX with acidic solvent + + N+ N CH3 CH3 N N+ paraquat diquat ©2007 Waters Corporation 36 Retention and Elution of Paraquat on Mixed-Mode Sorbents Retention Factor (k’) Retention Oasis® MCX Oasis® WCX 0 1 2 3 4 5 % Eluted Elution 6 7 pH 8 9 10 11 12 13 14 note: quats are eluted from Oasis WCX at low pH Oasis® WCX Oasis® MCX 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH of elution solvent (80:20 acetonitrile/water) ©2007 Waters Corporation 37 Paraquat/Diquat Optimized Oasis MCX Protocol Protocol 2 For Quats Prepare Sample Select Oasis® WCX Condition/Equilibrate Load Sample Wash1: 5% NH4OH in water Wash2: 100% MeOH optimized elution solvent acetonitrile/water/TFA Elute : 1.5 mL ACN/water/TFA 84:14:2 ©2007 Waters Corporation 38 Optimized SPE Protocol Paraquat/Diquat Oasis® WCX SPE Method Paraquat/Diquat Conditions for 3 cc cartridges Prepare Sample adjust to pH 7 Condition 1mL methanol/ 1 mL water Load up to 25 mL sample Wash 1 mL pH 7 buffer/1mL methanol Elute 1.5 mL ACN/water/TFA 84:14:2 Evaporate and Reconstitute 0.5 mL mobile phase 50:1 sample enrichment ©2007 Waters Corporation 39 LC-MS Conditions paraquat/diquat MS Conditions Instrument: Waters Quattro micro API™ Paraquat: cone 40 V MRM cone 15 V MRM Diquat: cone 40 V MRM cone 15 V MRM 171 → 77 (CID 35 eV) 171 → 155 (CID 35 eV 93* → 77 (CID 30 eV) LC Conditions Column: Waters Atlantis™ HILIC, 2.1 x 150 mm Flow: 0.4 mL/min Mobile Phase: 40% acetonitrile 60% aqueous buffer pH 3.7 (200 mM ammonium formate) o Column Temp: 30 C Sample Temp: 5 oC Injection: 10 µL 0.20 µg/L Spiked Sample 183 → 157 (CID 30 eV) 183 → 168 (CID 35 eV) 100 92* → 85 (CID 30 eV) paraquat 1 100 1 1 diquat 2 3 4 5 6 7 8 ©2007 Waters Corporation 40 Validation Performance was demonstrated from 0.1 to 5 µg/L using 20 mL samples of Sudbury River water. 0.9 0.8 Paraquat Intraday Results (1 µg/L) Day 1 1.08 µg/L (8.1% RSD) Day 4 1.10 µg/L (8.0% RSD) Day 5 0.95 µg/L (7.1% RSD) 0.7 0.6 0.5 0.4 r2 = 0.998 0.3 0.2 Overall (n=15) 1.04 µg/L (9.8% RSD) 0.1 0 0 2 4 6 ©2007 Waters Corporation 41 Advantage of Oasis® WCX for Paraquat/Diquat No Salts required for elution — Eluent can be evaporated and reconstituted in mimimal volume — Method is more compatible with API mass spectrometry — Method is more compatible with ion-pair chromatography — Method is more compatible with on-line SPE ©2007 Waters Corporation 42 Oasis® 2x4 Method: Starting Protocols For Acids and Bases For Bases: pKa 2-10 Use Oasis® MCX For Strong Acids pKa <1.0 Use Oasis® WAX For Strong Bases pKa >10 Use Oasis® WCX For Acids pKa 2-8 Use Oasis® MAX Protocol 1 Protocol 2 Prepare Sample Prepare Sample Condition/Equilibrate Load Sample Condition/Equilibrate Load Sample Wash: 2% Formic acid Wash: 5% NH4OH Elute 1: 100% MeOH Elute 2: 5% NH4OH in MeOH Bases Strong Acids Neutrals Elute 1: 100% MeOH Elute 2: 2% Formic Acid in MeOH Strong Bases Acids ©2007 Waters Corporation 43 Pharmaceuticals/Pesticides/Industrial Chemicals (Organic Bases, pKa 2-10) Example: Aniline (pKa ~ 4) + NH3 NH2 pH 2 Protocol 1 For Bases pKa 2-10 Select Oasis® MCX Prepare Sample Condition/Equilibrate Load Sample Wash: 2% Formic acid Elute 1: 100% MeOH Elute : 5% NH4OH in MeOH To recover acids and neutrals, analyze Elute 1 for GC, use 90:10 MTBE/methanolic ammonia for elute 2 ©2007 Waters Corporation 44 Pharmaceuticals/Pesticides/Industrial Chemicals (Organic Bases, pKa 2-10) GC-NPD Conditions COMPOUND Agilent 5890 series II 30 m x 0.25 mm (ID) RTX 5 (0.25 µm) EPA 8270C bases, 20 ug/L 200 mL tap water/Oasis MCX protocol 2 uL inject (20 µg/L Tap Water) 3 29 16 1 17 2 9 22 23 11 10 13 19 20 24 10 20 Minutes 30 NPD 30 25 26 28 31 27 0 % RECOVERY± RSD 40 1. pyridine 2. picoline 3. aniline 9. o-toluidine 10. phentermine 11. chloroaniline 13. phenylenediamine 61 (17) 77 (16) 90 (11) 82 (12) 73 (18) 82 (11) 93 (15) 16. 2 -nitroaniline 17. 3 -nitroaniline 19. 1 -aminonaphthalene 20. 2 -aminonaphthalene 22. 2 -methyl - 5-nitroaniline 23. 4 -nitroaniline 24. diphenylamine 95 (7.2) 103 (8.5) 87 (5.1) 88 (8.5) 104 (6.2) 106 (8.7) 93 (4.4) 26. aminobiphenyl 30. dimethylaminoazobenzene 31. dimethylbenzidine 33. dichlorobenzidine 105 (4.2) 100 (3.9) 64 (8.9) 111 (6.0) 33 32 50 ©2007 Waters Corporation 45 Summary Sample Preparation is necessary to obtain the best analytical results SPE is a very versatile and cost efficient sample preparation technique for environmental samples. Waters provides strategies which combine sorbents, formats and methodologies resulting in optimal SPE protocols. Whether for analysis by LCMS or GCMS; Waters analytical solutions, including SPE, cover a wide range of sample matrices and compounds classes ©2007 Waters Corporation 46 Oasis® Mixed-Mode Sorbents Strategies for Multiresidue Isolation and Enrichment (acids, bases and neutrals together) Mixed-Mode strong ion-exchange sorbents (Oasis MCX and Oasis MAX) can simultaneously retain polar acids and bases better than the best reversed-phase sorbents such as Oasis HLB — Oasis® MCX, sample adjusted to low pH o acids/neutrals retained by reversed-phase o bases retained by mixed-mode cation-exchange — Oasis® MAX, sample adjusted to high pH o acids retained by mixed-mode anion-exchange o bases/neutrals retained by reversed-phase ©2007 Waters Corporation 47 SPE of Acids and Base/Neutrals Reversed-Phase Logic Consider: Aniline, phenol and benzyl alcohol on Reversed-Phase SPE NH2 OH OH At pH 2: Aniline is cation – not retained Phenol is protonated – retained Benzyl alcohol is neutral – retained At pH 11 Aniline is neutral – retained Phenol is ionized – not retained Benzyl alcohol is neutral – retained ©2007 Waters Corporation 48 SPE of Acids and Base/Neutrals Mixed-Mode Logic Consider: Aniline, phenol and benzyl alcohol on Mixed-Mode SPE NH2 OH OH At pH 2 on Oasis® MCX: Aniline is cation –retained Phenol is neutral – retained Benzyl alcohol is neutral – retained At pH 11 on Oasis® MAX: Aniline is neutral – retained Phenol is anion – retained Benzyl alcohol is neutral – retained ©2007 Waters Corporation 49 Multi residue Analysis Oasis® MCX Method for GC Oasis® MCX Optimized Protocol Prepare Sample pH 2 Condition 2 mL DCM, 2 mL methanol, 2 mL water Load 250 mL sample Wash 2 mL 5 % MeOH/water Elute 4 mL of 0.7 M NH4OH in 90:10 DCM/MeOH Dry over Sodium Sulfate Evaporate to Final Volume prepare reagent using anhydrous ammonia in methanol (Aldrich) Micro K-D ©2007 Waters Corporation 50 SPE for Base/Neutrals and Acids Oasis® MCX GC Protocol COMPOUND % RECOVERY ±RSD (20 µg/L Tap Water) 7,8 6 1. 2. 3. 4. 5. 6. 12 FID 4 5 14 18 21 15 3 29 16 1 17 2 9 22 23 11 10 13 19 20 24 25 26 28 31 27 0 10 20 Minutes NPD 30 30 bases, acids, neutrals 40 33 pyridine picoline aniline phenol benzyl alcohol o-cresol 61 77 90 65 75 91 (17) (16) (11) (14) (25) (8.6) 7,8. m,p-cresol 9. o-toluidine 10. phentermine 11. chloroaniline 12. dichlorophenol 13. phenylenediamine 91 82 73 82 57 93 (8.9) (12) (18) (11) (6.2) (15) 14. 15. 16. 17. 18. 19. 2-methylnaphthalene trichlorophenol 2-nitroanili ne 3-nitroanili ne dibenzofuran 1-ami nonaphthalene 81 (8.0) 54 (10) 95 (7.2) 103 (8.5) 80 (5.4) 87 (5.1) 20. 21. 22. 23. 24. 25. 2-ami nonaphthalene tetrachlorophenol 2-methyl-5-nitroaniline 4-nitroanili ne diphenylamine phenacetin 88 (8.5) 35 (17) 104 (6.2) 106 (8.7) 93 (4.4) 85 (7.3) 26. 27. 28. 29. 30. 31. aminobi phenyl dinoseb nitroqui noline oxide methapyril ene dimethylaminoazobenzene dimethylbenzidine 105 (4.2) 90 (7.1) 100 (6.5) 105 (5.5) 100 (3.9) 64 (8.9) 32 50 32. acetamidofluorene 33. dichlorobenzidi ne 135 (5.4) 111 (6.0) ©2007 Waters Corporation 51
© Copyright 2024