Sample Preparation Strategies for Water Analysis

©2007 Waters Corporation 

Sample Preparation Strategies 

for Water Analysis 

Hannah White 

Waters Business Development Manager

Outline 

Introduction 

— Why sample Prep 

— Considerations 

o Choices of tools 

— Why SPE 

o Pre-Treatment 

Strategies 

— Traditional approaches 

— Modern approaches 

o Mixed Mode 

o Reverse phase 

Summary 

Appendix 

©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. 


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 


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 ® Reversed- 

Phase or Mixed-Mode SPE 


Pre-Treatment 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 


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 


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) 


Outline 

Introduction 




— Why SPE 





o Mixed Mode 


Summary 

Appendix 


SPE Strategies 

1. Approach #1 

Retention, cleanup, elution 


Pass-through 


Dispersion 


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 

SPE Strategy 1 

Retention-Cleanup 

Retention Cleanup-Elution Elution 

1. load 2. wash 3. elute 



Pass-Through Pass Through Cleanup 

1. Sample is passed 

through sorbent 

and collected 

• no sample 

enrichment 

2. Matrix 

interferences are 

retained on 

sorbent 

pass through 



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 


Outline 

Introduction 




— Why SPE 





o Mixed Mode 


Summary 

Appendix 


Ion-Exchange Ion Exchange and Mixed-Mode 

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 


Why Mixed-Mode? 

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 


Oasis ® Family of Mixed-Mode 

Mixed Mode 

Sorbents: 

Reversed-Phase Reversed Phase Retention and Ion Exchange 


Oasis Mixed-Mode 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 


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 


UPLC-MS 

UPLC MS-MS MS System 

ACQUITY Ultra Performance LC 

— Using 1.7μm particles, and at elevated pressures up to 15,000 

psi 

Shorter Analysis Time 

Higher Resolution 

Broad selectivity options 

Quattro Premier XE 

— Fast acquisition rates 

— Sensitive detection 

Oasis sorbents 

— Cleaner samples 


Goals 

Develop an Acquity UPLC TM 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 


Structures of PFOS and PFOA 

PFOA and PFOS are Persistent Organic Pollutants of high interest 

worldwide. 

F 3C 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

F 

perfluorooctanoic acid 

PFOA 

pKa ~ 1 

O 

OH 

F 3C 

F 

F 

F 

F 

F 

F 

F 

F 

perfluorooctanesulfonate 

PFOS 

pKa

Oasis ® 2x4 Method 

For Acids, Bases, and Neutrals 

For Bases: 

pKa 2-10 

Use Oasis ® MCX 

For Strong Acids 

pKa 10 

Use Oasis ® WCX 

Protocol 2 

Prepare Sample 

Condition/Equilibrate 

Load Sample 

Wash: 

5% NH 4OH 

Elute 1: 

100% MeOH 

For Acids 

pKa 2-8 

Use Oasis ® MAX 

Elute 2: 

2% Formic Acid in MeOH 

Strong 

Bases 

Acids 


Optimized SPE Protocol 

for River Water 

Oasis ® WAX sorbent was 

selected for these analytes 

Logic: PFOA pKa ~1 

PFOS pKa < 1 

Oasis ® WAX 

N 

N 

H 

N O 

H 

N 

N 

H H 

mixed-mode weak anion-exchange 

pKa ~6 

+ 

+ 

Conditions for Oasis ® WAX 3 cc 60mg cartridges 

Oasis ® WAX 

Optimized Protocol 1 


pH 3 

Condition 

2 mL methanol/2 mL water 

Load 

200 mL 

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 

Samples were evaporated and 

reconstituted in 0.15 mL mobile phase 


SPE Protocol 

Oasis ® WAX 

Optimized Protocol 1 


pH 3 

Condition 

2 mL methanol/2 mL water 

Load 

200 mL 

Wash #1 

1 mL 2% formic acid 

Wash #2 

2 mL methanol 

Elute 2 

2 mL 1% conc. ammonia in 

10:90 methanol/MTBE 

@ pH 3 Sorbent, and analytes are fully charged 

(assures mixed-mode retention) 

Maximum load for good recovery 

of C3, C4 and PFBS 

Assures sorbent is charged 

Removes neutrals and bases retained 

by reversed-phase 

MTBE based eluent minimizes elution of 

any retained humic material 


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 ES- 

100 

TIC 

1.34e4 

% 

0 

% 

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 


100 

TIC 

1.34e4 

PFBS 

Blank 

Spiked River Water 

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 

PFOS 


C3-C7 C3 C7 in River Water 




100 

TIC 

9.38e4 

% 

0 

% 

0 

Blank 

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 


100 

TIC 

9.38e4 

C3 

C4 


C5 

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 

C6 

C7 


C8-C12 C8 C12 in River Water 



PFOS_082306AQC21x50C18_3 1: MRM of 5 Channels ES- 

100 

TIC 

1.61e5 

% 

0 

% 

0 

Blank 

2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 

PFOS_082306AQC21x50C18_4 1: MRM of 5 Channels ES- 

100 

C9 

TIC 

1.61e5 


C8 C10 

2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 

C11 

C12 


River Water Recoveries 

Spike Level 

μg/L 

PFBS PFOS PFOS C C3 C4 C4 C5 C5 C6 C6 C7 C8 C9 C10 C11 C12 

0.10 122 109 108 119 97 154 107 83 121 101 101 100 

0.30 110 117 95 132 105 110 119 126 137 118 94 95 

0.70 102 98 91 107 93 118 100 78 103 126 119 121 

1.0 113 94 128 106 98 130 100 88 100 110 117 87 

4.0 104 86 101 99 99 102 102 92 115 99 84 68 

10 104 100 98 101 100 87 89 82 103 99 101 66 


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 


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 


Acidic Herbicides 

Cl 

OCH 2COOH 

Cl 

2,4-D 

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. 

Step 1 – characterize analytes 

they are acids pKa 3-6 

For Acids 

pKa 2-8 

Select 

Oasis ® MAX 


Oasis ® 2x4 Method: Method 

Starting Protocols For Acids and Bases 

For Bases: 

pKa 2-10 



pKa 10 


Protocol 2 




Wash: 

5% NH 4OH 

Elute 1: 

100% MeOH 

For Acids 

pKa 2-8 


Elute 2: 


Strong 

Bases 

Acids 


Oasis ® 2x4SM 2x4SM 

Method 

Choose Starting Protocol 

Cl 

OCH 2COOH 

Cl 

2,4-D 

For Acids 

pKa 2-8 


Protocol 2 




Wash: 

5% NH 4OH* 

Elute 1: 

100% MeOH 

Elute 2: 


Acids 

The Oasis MAX cartridge 

was chosen for retention 

of acid herbicides 

Logic: 2,4-D and other 

acid herbicides 

pKa 3-6 


Oasis ® MAX SPE Method 

Acidic Herbicides 1µg/kg 1 g/kg in River Water 

Oasis MAX 

Protocol 2 


Condition 

3 mL methanol/ 3 mL water 

Load 

300 mL sample 

Wash #1 

3 mL 5% NH 4OH 

Elute 1 (Wash #2) 

3 mL methanol 

Elute 2 

4 mL 2% Formic Acid in MeOH 

Evaporate and Reconstitute 

Conditions for 6 cc cartridges 

1 2 

3 

4 

5 

Waters XTerraMS C 18 , 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 

Waters ZQ, ESI-, SIR mode 

6 

7,8 9 

1 ppb in river water 

1. picloram 

2. chloramben 

3. 4-nitrophenol 

4. bentazon 

5. 2,4-D 

6. MCPA 

7. dichlorprop 

8. 2,4,5-T 

10 

11 

12 

13 

14 

9. MCPP 

10. DCB 

11. acifluorfen 

12. 2,4,5-TP 

13. 2,4-DB 

14. dinoseb 

15. pentachlorophenol 

15 

20 min 


Paraquat/Diquat 

For Quats 

Select 

Oasis ® WCX 

CH 3 

+ 

The Oasis WCX cartridge was 

chosen for these analytes 

Logic: quats are 

cationic at all pH 

values 

+ 

N N CH 3 

quats can be eluted 

from Oasis WCX with 

acidic solvent 

N 

paraquat diquat 

+ 

N + N 


Retention Factor (k’) 

% Eluted 

Retention and Elution of Paraquat 

on Mixed-Mode Mixed Mode Sorbents 

Retention 

Oasis ® MCX 

Oasis ® WCX 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 

pH 

Elution 

Oasis ® WCX 

Oasis ® MCX 

note: quats are eluted from 

Oasis WCX at low pH 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 

pH of elution solvent (80:20 acetonitrile/water) 



Optimized Oasis MCX Protocol 

For Quats 

Select 

Oasis ® WCX 

Protocol 2 




Wash1: 

5% NH 4 OH in water 

Wash2: 

100% MeOH 

Elute : 

1.5 mL ACN/water/TFA 84:14:2 

optimized elution solvent 

acetonitrile/water/TFA 


Optimized SPE Protocol 


Oasis ® WCX SPE Method 


Conditions for 3 cc cartridges 


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 


LC-MS LC MS Conditions 

paraquat/diquat 

MS Conditions 

Instrument: Waters Quattro micro API 

Paraquat: cone 40 V 

MRM 171 → 77 (CID (CID 35 eV) 

171 → 155 (CID 35 eV 

cone 15 V 

MRM 93* → 77 (CID 30 eV) 

Diquat: cone 40 V 

MRM 183 → 157 (CID 30 eV) 

183 → 168 (CID 35 eV) 

cone 15 V 

MRM 92* → 85 (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) 

Column Temp: 30 o C 

Sample Temp: 5 o C 

Injection: 10 µL 

100 

1 

100 

0.20 µg/L Spiked Sample 

diquat 

paraquat 

1 

2 3 4 5 6 7 8 


0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

r2 r = 0.998 

2 = 0.998 

0 2 4 6 

Validation 

Performance was demonstrated 

from 0.1 to 5 µg/L using 20 mL 

samples of Sudbury River 

water. 

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) 

Overall (n=15) 1.04 µg/L (9.8% RSD) 


Advantage of Oasis® 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 


Oasis ® 2x4 Method: Method 

Starting Protocols For Acids and Bases 

For Bases: 

pKa 2-10 



pKa 10 


Protocol 2 




Wash: 

5% NH 4OH 

Elute 1: 

100% MeOH 

For Acids 

pKa 2-8 


Elute 2: 


Strong 

Bases 

Acids 


Example: Aniline (pKa ~ 4) 

NH 2 

pH 2 

Pharmaceuticals/Pesticides/Industrial 

Chemicals 

(Organic Organic Bases, pKa 2-10) 10) 

NH 3 

Protocol 1 


+ 



Wash: 

2% Formic acid 

Elute 1: 

100% MeOH 

Elute : 

5% NH 4OH in MeOH 

For Bases 

pKa 2-10 

Select 

Oasis ® MCX 

To recover acids and neutrals, 

analyze Elute 1 

for GC, use 90:10 

MTBE/methanolic ammonia 

for elute 2 


GC-NPD Conditions 

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 

1 

2 

3 

9 

Pharmaceuticals/Pesticides/Industrial 

Chemicals 

(Organic Organic Bases, pKa 2-10) 10) 

10 

11 

13 

16 

0 10 20 Minutes 30 40 50 

17 

19 20 

22 23 

24 

25 26 

27 

28 

29 

30 

31 

32 

NPD 

33 

COMPOUND % RECOVERY ±RSD ±RSD 

(20 µg/L Tap Water) 

1. pyridine 61 (17) 

2. picoline 77 (16) 

3. aniline 90 (11) 

9. o-toluidine 82 (12) 

10. phentermine 73 (18) 

11. chloroaniline 82 (11) 

13. phenylenediamine 93 (15) 

16. 2 -nitroaniline 95 (7.2) 


19. 1 -aminonaphthalene 87 (5.1) 

20. 2 -aminonaphthalene 88 (8.5) 

22. 2 -methyl -5-nitroaniline 104 (6.2) 


24. diphenylamine 93 (4.4) 

26. aminobiphenyl 105 (4.2) 

30. dimethylaminoazobenzene 100 (3.9) 

31. dimethylbenzidine 64 (8.9) 

33. dichlorobenzidine 111 (6.0) 


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 


Oasis ® Mixed-Mode 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 


SPE of Acids and Base/Neutrals 

Reversed-Phase Reversed Phase Logic 

Consider: 

Aniline, phenol and benzyl alcohol on Reversed-Phase SPE 

NH 2 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 



SPE of Acids and Base/Neutrals 

Mixed-Mode Mixed Mode Logic 

Consider: 

Aniline, phenol and benzyl alcohol on Mixed-Mode SPE 

NH 2 OH OH 

At pH 2 on Oasis ® MCX: Aniline is cation –retained 

Phenol is neutral – retained 


At pH 11 on Oasis ® MAX: Aniline is neutral – retained 

Phenol is anion – retained 



Multi residue Analysis 

Oasis ® MCX Method for GC 

Oasis ® MCX 

Optimized Protocol 


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 

Micro K-D 

prepare reagent using 

anhydrous ammonia in 

methanol (Aldrich) 


SPE for Base/Neutrals and Acids 

Oasis ® MCX GC Protocol 

1 

2 

3 

4 

5 

6 

7,8 

9 

10 

12 

11 

13 

14 

15 

16 

0 10 20 Minutes 30 40 50 

17 

18 

19 20 

22 23 

24 

25 26 

bases, acids, neutrals 

21 

27 

28 

29 

30 

FID 

31 

32 

NPD 

33 

COMPOUND % RECOVERY ±RSD 

(20 µg/L Tap Water) 

1. pyridine 61 (17) 

2. picoline 77 (16) 

3. aniline 90 (11) 

4. phenol 65 (14) 

5. benzyl alcohol 75 (25) 

6. o-cresol 91 (8.6) 

7,8. m,p-cresol 91 (8.9) 

9. o-toluidine 82 (12) 

10. phentermine 73 (18) 

11. chloroaniline 82 (11) 

12. dichlorophenol 57 (6.2) 

13. phenylenediamine 93 (15) 

14. 2-methylnaphthalene 81 (8.0) 

15. trichlorophenol 54 (10) 

16. 2-nitroaniline 95 (7.2) 


18. dibenzofuran 80 (5.4) 

19. 1-aminonaphthalene 87 (5.1) 

20. 2-aminonaphthalene 88 (8.5) 

21. tetrachlorophenol 35 (17) 

22. 2-methyl-5-nitroaniline 104 (6.2) 


24. diphenylamine 93 (4.4) 

25. phenacetin 85 (7.3) 

26. aminobiphenyl 105 (4.2) 

27. dinoseb 90 (7.1) 

28. nitroquinoline oxide 100 (6.5) 

29. methapyrilene 105 (5.5) 

30. dimethylaminoazobenzene 100 (3.9) 

31. dimethylbenzidine 64 (8.9) 

32. acetamidofluorene 135 (5.4) 

33. dichlorobenzidine 111 (6.0)

Sample Preparation Strategies for Water Analysis

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