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Jan 30, 2010
© 2009 PerkinElmer
Environmental contaminants in finished drinking water and raw
source water : carbonyl compounds by EPA method 556
Dr. Padmaja Prabhu Application Specialist-Chromatography, India.
Andrew Tipler, Chromatography R&D Manager, Shelton, CT.
March 14, 2012
'Super sand' to help clean up dirty drinking water, By Katia Moskvitch Technology reporter, BBC News In many countries around the world, access to clean drinking water and sanitation facilities is still limited
Shale gas drilling 'contaminates drinking water‘, By Mark Kinver Science and environment reporter, BBC News Shale gas drilling operations increase the risk of nearby drinking water becoming contaminated
with methane, a study has suggested.
Water rates to rise by 10% in Alderney Water rates in Alderney will rise by 10% to help pay for cleaner drinking water, the island's
States has agreed.
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Pure drinking water is a major CONCERN in many countries
Emerging Substances of Concern Global Organic Contaminants Pharmaceuticals and Personal Care Products Endocrine Modulating Chemicals Nanoparticles Industrial Chemicals (new and recently recognized) Biological Metabolites and Toxins
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The concern………..
Choice of Samples
4 Take Away Here
Carbonyl compounds may be formed in water during ozonization and chlorination of natural organic matter
Hazardous pollutants released from diverse sources including motor vehicles and industrial emissions, have been shown to have adverse effects on human health.
EPA method 556 addresses this issue of carbonyl compounds in detail and suggests methodologies for its determination
We chose to examine:
• Bottled drinking water
• Well water
Method 556
A gas chromatographic method – ECD detector
Carbonyl compounds are derivatized to pentafluorobenzyloximes using (pentafluorobenzylhydroxylamine) PFBHA
Oxime derivatives were extracted in hexane Only 4 ml of hexane was used for the extraction, Micro extraction helps in reducing pollution
and ensures easy waste management
Analysed on capillary GC with ECD
5
Challenge with the method
Getting low background levels of formaldehyde and acetaldehyde Usually present in laboratory atmosphere, water , glassware and other reagents Aldehyde free water can be achieved by exposure to UV or distillation from permanganate Avoid exposure of reagents used to laboratory atmosphere as much as possible Glassware can be cleaned by detergent, hot water, tap water and distilled water rinses
A good skill level in liquid-liquid extractions and derivatization procedure is needed
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Carbonyl compounds in water - Analytical Method Summary…
Gas Chromatograph PerkinElmer Clarus 580
Analytical Column PerkinElmer Elite-5 (30 meter, 0.53 mm i.d., 0.5 µm df)GC column Flow 3.5 mL/min helium in constant flow modeGC inlet temperature 220 ºCSplit ratio 5:1Oven temperature programme
50ºC hold for 1.0 min, 4 ºC/min to 220 ºC and hold for 1.0 min, 20 ºC/min to 250 ºC and hold for 5.0 min, runtime is 56 minutes
Detector ECD at 375 º CMake-up Flow 30 mL/min
Extraction procedure The analytes are derivatized at 35 ºC for 2 hours with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBHA) reagent. The derivatives are extracted in water with hexane. The extract is finally processed through an acidic wash step.
Injection volume 1.0 µL
PerkinElmer Clarus 580
Sensitive and selective
Responds to halogen-containing compounds (Cl, F, Br, I), as well as other electron capturing substances
Ideal choice for pesticide residue analysis
Trace analysis (example: PCBs)
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Collector
63Nickel foil
Make-up gas in
Column connection
Carbonyl compounds for EPA method 556 in drinking water and raw source water
9 Take Away Here
# Analyte # Analyte
1. Formaldehyde 9. Nonanal
2. Acetaldehyde 10. Decanal
3. Propanal 11. Cyclohexanone
4. Butanal 12. Crotonaldehyde
5. Pentanal 13. Benzaldehdye
6. Hexanal 14. Glycoxal (ethanedial)
7. Heptanal 15. Methyl Glyoxal
8. Octanal
Calibration
Stock Solution: All the aldehydes standards were procured from Alfa aeasar. Ten mg of each of the aldehydes were weighed in 10 ml flask and diluted to volume with acetonitrile, to make 1000 μg/mL of each of the aldehydes.
Primary dilution standard (PDS) : 2.5 mL of each of Stock solution was then mixed in a 50 mL flask and made up to volume with acetonitrile (50 μg/mL)
Calibration spiking solution (CSS): Four mL of PDS was diluted to 10 mL with acetonitrile, to make a mixture 20 μg/mL of each of the analyte. This CSS solution was further used to prepare calibration solutions of the analytes.
Internal standard solution : 40 mg of 1,2 dibromopropane was diluted to 100 mL with hexane. Further 0.1 mL of this was again diluted to 100 mL with hexane to make a solution containing 0.4 μg/mL of IS. This solution was used for the extraction of the aldehyde oximes from water.
Surrogate Standard solution : 50 mg of 2,4,5 trifluoroacetophenone was diluted to 100 mL with acetonitrile. Further 0.4 mL of this was again diluted to 100 mL with acetonitrile to make a solution containing 2.0 μg/mL of SS. 0.2 μL of this solution was spiked in each of the calibration and recovery levels.
PFBHA solution : Freshly prepared 15 mg/mL solution in reagent water was used for derivatizing the analytes in samples and standard.
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Cal level no. Conc.of each analyte (ppb) CSS added (µL) Final volume (mL)
1 2 2 20
2 5 5 20
3 10 10 20
4 20 20 20
5 30 30 20
6 40 40 20
Summary of calibration experiment
# Analyte Linearity r2 LOQ level LOD level
1. Formaldehyde 2-40 ng/mL 0.997 2 ng/mL0.5 ng/mL
2. Acetaldehyde 2-40 ng/mL 0.993 2 ng/mL0.5 ng/mL
3. Propanal 2-40 ng/mL 0.992 2 ng/mL1.0 ng/mL
4. Butanal 2-40 ng/mL 0.993 2 ng/mL0.5 ng/mL
5. Pentanal 2-40 ng/mL 0.993 2 ng/mL0.5 ng/mL
6. Hexanal 2-40 ng/mL 0.996 2 ng/mL0.5 ng/mL
7. Heptanal 2-40 ng/mL 0.993 2 ng/mL0.5 ng/mL
8. Octanal 2-40 ng/mL 0.992 2 ng/mL1.0 ng/mL
9. Nonanal 5-40 ng/mL 0.988 5 ng/mL1.0 ng/mL
10. Decanal 5-40 ng/mL 0.990 5 ng/mL0.5 ng/mL
11. Cyclohexanone 2-40 ng/mL 0.998 2 ng/mL0.5 ng/mL
12. Benzaldehdye 2-40 ng/mL 0.998 2 ng/mL0.5 ng/mL
13. Glyoxal (ethanedial) 5-40 ng/mL 0.994 5 ng/mL0.5 ng/mL
14. Methyl Glyoxal 2-40 ng/mL 1.000 2 ng/mL0.5 ng/mL
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Typical calibration curve for some aldehydes……………….
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0 5 10 15 20 25 30 35 40 45
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
f(x) = 80487.5695049947 x + 137144.66162308R² = 0.99670812798973
formaldehyde Linearity
Series1Linear (Series1)
0 5 10 15 20 25 30 35 40 45
0
100000
200000
300000
400000
500000
600000
700000
800000
f(x) = 17131.6747606258 x + 19860.4682419192R² = 0.993330325350983
Acetaldehyde Linearity
Series1Linear (Series1)
0 5 10 15 20 25 30 35 40 45
0
200000
400000
600000
800000
1000000
1200000
f(x) = 24628.722861653 x + 12997.2763749884R² = 0.993141189387633
Butanal Linearity
Series1Linear (Series1)
0 5 10 15 20 25 30 35 40 45
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
f(x) = 20675.2357051644 x − 13665.2889706432R² = 0.992504253007601
Pentanal Linearity
Series1Linear (Series1)
0 5 10 15 20 25 30 35 40 45
0
100000
200000
300000
400000
500000
600000
700000
f(x) = 16542.1168226369 x − 11962.8381797189R² = 0.991709970808848
Octanal Linearity
Series1Linear (Series1)
0 5 10 15 20 25 30 35 40 45
0
200000
400000
600000
800000
1000000
1200000
f(x) = 28980.9496489492 x − 9799.14348270651R² = 0.998096057338135
Benzaldehyde Linearity
Series1Linear (Series1)
Typical chromatogram for aldehyde mixture
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Elution order
1. Formaldehyde 3. Propanal 6. Hexanal 9. Nonanal 12. Benzaldehyde
2. Acetaldehyde 4. Butanal 7. Heptanal 10. Decanal 13. Glycoxal
5. Pentanal 8. Octanal 11. Cyclohexanone 14. Methyl Glyoxal
Sample preparation
Samples were collected from a local Mumbai market. Bottled water samples were collected at random from the market. Raw water samples were collected from some wells in the vicinity of our laboratory. These samples were extracted as per the following extraction procedure.
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20 mL of sample in a Test tube
200 mg Potassium Hydrogen Phthalate
One mL of freshly prepared PFBHA solution
Keep the tubes in water bath at 35ºC for 2 hours, remove
and cool at RT
0.05 mL of concentrated sulphuric acid
4 mL of hexane containing IS
shaken for 3 min.
3 mL hexane layer + 3 mL of 0.2N sulfuric
acid shake
1 µL injected to GC/ECD
Results of sample analysis
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# Name of aldehyde Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample raw source water
Concentration in ng/mL
1. Formaldehyde 22.46 21.00 23.50 18.47 10.74 8.772. Acetaldehyde 30.55 42.58 86.81 52.30 1.04 4.673. Propanal ND ND ND ND ND ND4. Butanal 0.80 0.81 0.64 0.72 ND 1.425. Pentanal 1.03 1.25 1.14 ND ND 0.986.
Hexanal 2.17 2.08 2.40 1.65 ND 1.507.
Cyclohexane 2.45 2.32 1.44 2.07 ND 0.698.
Heptanal 0.66 1.08 1.16 0.54 0.17 0.909.
Octanal 1.31 1.55 1.77 ND ND ND10.
Benzaldehyde 2.30 1.07 1.28 ND ND ND11.
Nonanal 5.58 4.96 5.51 4.39 ND 3.3212.
Decanal 12.31 9.72 8.62 3.77 0.79 4.9113.
Glyoxal 10.78 5.93 15.14 2.02 2.93 3.9014.
Methyl Glyoxal ND 0.56 0.73 ND ND 1.19
Precision and Accuracy Results
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# Name of aldehyde Fortified conc. (µg/mL)
Mean Conc. found(µg/mL) RSD % Mean Recovery (%)
1. Formaldehyde 20.0 18.7 4.61 94
2. Acetaldehyde 20.0 19.4 9.66 97
3. Propanal 20.0 19.8 3.74 99
4. Butanal 20.0 19.7 4.55 98
5. Pentanal 20.0 19.5 4.43 98
6. Hexanal 20.0 19.8 3.29 99
7. Cyclohexane 20.0 20.5 1.46 102
8. Heptanal 20.0 19.0 9.37 95
9. Octanal 20.0 19.1 6.94 95
10. Benzaldehyde 20.0 20.1 2.70 100
11. Nonanal 20.0 19.3 3.30 97
12. Decanal 20.0 21.5 7.69 108
13. Glyoxal 20.0 20.6 3.85 103
14. Methyl Glyoxal 20.0 20.7 0.94 103
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Results and Conclusion
There is a very strong need to control the aldehyde contaminants in water.
Sulfuric acid added during solvents extraction prevents extraction of reagent, which may cause chromatographic interferences.
The method uses a micro-extraction procedure which requires very small quantities of organic solvents, reducing the need for waste management.
Formaldehyde and acetaldehyde were seen in all the drinking water samples at varying levels
Take Away Here
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References
1. EPA method 556. Determination of carbonyl compounds in drinking water by pentafluorobenzylhydroxylamine derivatisation and capillary gas chromatography with electron capture detection.
Take Away Here
