Novel Approaches toOmega-3 Stability Testing
Performing the p-Anisidine Value (TAV) Test by a New HPLC-UV Method
Dr. Steve Li, MD, M.Sc. (Clin.Pharm)Director of Laboratory Operations
Diteba, a Nutrasource Diagnostics Inc. [email protected]
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p-Anisidine Value Analysis is for Determination of Oxidation Level of Oil Substance
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p-Anisidine Value Analysis Procedure Has Been Included in Many Official Methods
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1. The United States Pharmacopeia and the National Formulary (USP–NF)
2. European Pharmacopeia (EP)3. American Oil Chemists' Society (AOCS)4. Food Chemicals Codex (FCC)5. Association of Official Analytical Chemists
(AOAC)
p-Anisidine Test is One of the Three Common Analytical Tests
for Oil Oxidation
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• Acid Value• p-Anisidine Value
• Peroxide Value
Acceptable Limits for Oxidative Stability Parameters in Marine Oils
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(Recommended Reporting Threshold) ________________________________________
Acid Value NMT 3 mg KOH/Kg
Peroxide value (PV) NMT 5 mEq/Kg
Anisidine value (AV) NMT 20
TOTOX value NMT 26 (2 x PV + AV )
______________________________________________________
Oxidation Pathways of Oil Autooxidation
• Free radical formation starts the chain reaction of degradation to unsaturated fatty acid.
• The major initial oxidation products, ROOH hydroperoxide, form compounds responsible for off-flavors and odors.
Such secondary products include aldehyde and ketones, such as hexanal, pentanal, and malonaldehyde.
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Oxidation Pathways of Oil Autooxidation
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Traditional p-Anisidine Value Test
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1. The anisidine value is defined as 100 times the optical density measured in a 1 cm cell of a solution containing 1 g of the substance to be examined in 100 ml of a mixture of solvents and reagents.
2. Test solution (a). Dissolve 0.500 g of the substance to be examined in iso-octane and dilute to 25.0 ml with the same solvent.
3. Test solution (b). To 5.0 ml of test solution (a) add 1.0 ml of a 2.5 g/l solution of p-anisidine R in glacial acetic acid R, shake and store protected from light.
.
Traditional P-Anisidine Value Test
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4. Reference solution. To 5.0 ml of isooctane add 1.0 ml of a 2.5 g/l solution of p-anisidine in glacial acetic acid, shake and store protected from light.
5. Measure the absorbance of test solution (a) at the maximum at 350 nm using isooctane as the compensation liquid. Measure the absorbance of test solution (b) at 350 nm exactly 10 min after its preparation using the reference solution as the compensation liquid.
The p-anisidine value (p-A.V.) is given by the formula:
25 (1.2 As – Ab)pAV = -------------------------
m
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Why Do We Have Problems with the p-Anisidine Value Test?
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The Test Has No Problem to Evaluate and Compare the Oxidation Level of Simple
Marine Oil.
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Marine Oil Products Changed When they Became Important Natural Health Products
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The Challenge Comes From the Advanced Formulated Products Containing Marine Oil
and Other Additives
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New Ingredients Are Introduced
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• Colour additives• Flavour additives• Vitamin additives
• Others
The New Formulations Interfere
With p-Anisidine Tests
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Advanced Formulations Bring Big Challenges to the Traditional p-Anisidine Value Test
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1. Interference creates wrong p-anisidine results and generates misleading certificates;
2. Interference causes failed performance of the test method;
3. No Practical Alternative Test Available to replace p-Anisidine method for the combined oil formulations.
There should be a procedure available to solve this issue.
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1. A lot of research work on oil oxidation has been nicely done and available; True!
2. It should not be too difficult to develop an alternative test method; True!
How??
There are Two Groups of Analytical Methods
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Routine Test Methods
Advantages• Fast• Easy to be performed• Used in industry for century?• Cost effective• Common Apparatus or
InstrumentDisadvantages:• Not specific• Not directly quantitative• Easily Interfered
Research Methods
Advantages• Relatively Specific• Can be quantitativeDisadvantages:• Time consuming• Cost• Require instruments• Difficult to be used in QC
environment
Strategies
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Simple approach – new sample preparation to separate degradation products
Simple Procedure
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After several trials of different sample preparations.
Procedures of extraction and separation are too tedious and not feasible for QC methods.
Oops!
Advanced Technologies
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1. GC-Flame Ionization Detector. Too complicated to identify and quantify the oxidized compounds.
2. GC-MS. Features good identification. Too complicated to identify and quantify the oxidized compounds.
3. LC-UV. Too difficult to identify the oxidized compounds.
4. LC-MS. Too difficult of sample preparation and too expensive to quantify the oxidized compounds.
5. IR or FTIR (Fourier Transform Infrared spectroscopy). Very good test mechanism but very difficult to be a routine analytical method.
IR Spectrum for Oil Degradation Samples
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IR Spectrum for Oil Degradation Samples
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IR method seems working but...
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The method can not be used as a quality control method because there are no
appropriate control samples and the peak areas are not very reproducible, meaning
poor precision.
Chromatograms of p-Anisidine Value Test Preparations
Blank, Oil Sample and Reacted
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Channel @ PDA 245.0 nm; Acquired By yingluz
AU
0.00
0.02
0.04
0.06
0.08
Minutes
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00
Channel @ PDA 245.0 nm; Acquired By yingluzAU
0.00
0.02
0.04
0.06
0.08
0.10
Minutes
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00
Channel @ PDA 245.0 nm; Acquired By yingluz
isoo
ctan
e -
3.15
6
AU
0.00
0.02
0.04
Minutes0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 55.00 60.00
What do we need for this method?
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1. Simple routine method2. Economical and practical3. Relatively specific4. Relatively precise and accurate
All approaches explored are Not doable and Not All approaches explored are Not doable and Not affordable!affordable!
What else? Nothing!!
p-Anisidine HPLC-UV Method
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Chromatographic Conditions
HPLC column, 4.6 mm × 250 mmColumn Temperature: 25˚CDetection: UV at 254nm
Injection Volume: 10µL Flow Rate: 1.0 mL/minute
Run Time: 10 minutes Mobile Phase: Hexane: 2-Propanol (50:50)
p-Anisidine HPLC-UV Method
Specificity Chromatogram
Channel @ W2996 PDA 254.0 nm at 1.2
AU
-0.05
0.00
0.05
0.10
0.15
0.20
Minutes
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
Injection Peaks
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p-Anisidine HPLC-UV Method
Typical Chromatogram of QL(S/N=15, 3.162 µg/mL)
Channel @ W2996 PDA 254.0 nm at 1.2
3.30
5
p-A
nisi
dine
- 4.
855
AU
0.000
0.001
0.002
0.003
0.004
0.005
Minutes
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00
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p-Anisidine HPLC-UV MethodLinearity Study
(Range: 0.1002 to 0.5008 mg/mL)Equation Y = 8.49e+006 X - 7.06e+003R 2̂ 0.999889
R 0.999944 Cal Curve Id 5424
Norm Intercept/Slope -0.002770 Residual Sum of Squares 8.044077e+008
Calibration Plot
Are
a
0
1x106
2x106
3x106
4x106
5x106
Am ount
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
1
2
3
4
5
Mean
% RSD
Nam e X Value Response Calc. Value Manual Ignore RF
p-Anis idine
p-Anis idine
p-Anis idine
p-Anis idine
p-Anis idine
0.100200
0.200300
0.300500
0.400600
0.500800
857435.001071
1686026.997872
2530386.492799
3381242.004378
4259300.996942
2542878.298613
52.85
0.101871
0.199510
0.299008
0.399271
0.502740
No
No
No
No
No
No
No
No
No
No
8557235.539636
8417508.726270
8420587.330447
8440444.344429
8504994.003479
8468154.0
0.7
Peak: p-Anis idine
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p-Anisidine HPLC-UV MethodRepeatability Results
SampleNo.
Assay (%)
RepeatabilityIntermediate
Precision
1 86.0 84.1
2 85.6 83.4
3 85.0 85.8
4 83.6 84.9
5 85.1 86.6
6 84.4 83.7
Mean 85.0 84.8
%RSD 1.0 1.5
Mean of 12 Samples
84.9%
RSD 1.2%
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p-Anisidine HPLC-UV Method Summary of Accuracy Results
Concentration Level % Recovered Average
50%
99
99%RSD = 0%
99
99
100%
100
100%RSD =0 %
100
100
150%
101
101%RSD =1 %
101
102
Average of 9 samples = 100% RSD = 1%
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p-Anisidine HPLC-UV MethodSummary of System Suitability Study
Injection No.Retention
Time(Minutes)
Peak Area (μV*sec)
USP Tailing Factor
Theoretical Plate
Number
1 4.85 2111474 2.3 2858
2 4.85 2125521 2.3 2843
3 4.85 2127289 2.3 2831
4 4.86 2139357 2.3 2808
5 4.85 2131861 2.3 2842
6 4.85 2146601 2.3 2836
Mean 4.85 2130350 2.3 2836
%RSD 0.03 0.6 0.9 0.6
Overall %RSD N/A 0.6% N/A N/A
Check Std Recovery (%)
N/A 101.0% N/A N/A
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p-Anisidine HPLC-UV MethodSummary of System Suitability Study
Injection No.Retention
Time(Minutes)
Peak Area (μV*sec)
USP Tailing Factor
Theoretical Plate
Number
1 4.85 2111474 2.3 2858
2 4.85 2125521 2.3 2843
3 4.85 2127289 2.3 2831
4 4.86 2139357 2.3 2808
5 4.85 2131861 2.3 2842
6 4.85 2146601 2.3 2836
Mean 4.85 2130350 2.3 2836
%RSD 0.03 0.6 0.9 0.6
Overall %RSD N/A 0.6% N/A N/A
Check Std Recovery (%)
N/A 101.0% N/A N/A
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p-Anisidine HPLC-UV MethodCross Reference of Known AV values
and Specification Set-up
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p-Anisidine HPLC-UV MethodCross Reference of Known AV values
and Specification Set-up
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p-Anisidine HPLC-UV Method
Specification Set-up
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From the data collected from our current tests and stability studies the TAV acceptance
criteria has been recommended. Most of the oil samples with over anisidine values >20
give the TAV results around 69% to 72% anisidine % remaining . The range is very small and well correlated with p-Anisidine
results.
Conclusion1. The method is validated. It has
good specificity, good precision and accuracy.
2. The most important feature is that the method demonstrates very good correlation with traditional p-Anisidine value test.
3. The method shows good characteristics of a quality control method.
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© Nutrasource Diagnostics Inc.
Acknowledgements
Diteba Team Lucy Zhao
Linda ChangNutrasource Diagnostics Inc.
TeamKevin Yan
Martha Wlodek William RoweMike Wlodek
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© Nutrasource Diagnostics Inc.
Thank you!Thank you!
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© Nutrasource Diagnostics Inc.
p-Anisidine HPLC-UV MethodRecommended Test Criteria
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Flavoured Marine oil TAV p-anisidine
1. Marine oil containing Vitamin A yes no
2. Marine oil containing Vitamin A + D yes no
3. Marine oil containing orange Flavour yes no
4. Marine oil containing low level of orange flavour yes no
5. Marine oil containing Tangerine lime (concentration unknown) yes no
Biomedical Research Findings Support Its Usage with Important Indications
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1. Cardiovascular diseases (CVDs) are the number one cause of death globally
2. The most common disorders: hypertension (arteries), heart attacks (coronary arteries) and strokes (brain arteries). The changes are all related to blood vessels, a build-up of fatty deposits on the inner walls of the blood vessels, blood clots and bleeding
3. Importantly, these conditions are reversible and preventable4. Omega-3s EPA and DHA can help by lowering blood
triglycerides , preventing fatty deposits and reducing blood pressure
p-Anisidine Value test is to determine the secondary oxidation compounds in the oil products. This spectrophotometric test is
easy to be interfered.
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