the technologies of chemical metrology and quality
TRANSCRIPT
The Technologies of Chemical Metrology and
Quality Assurance of Measurement Results in
Food Analysis
Prof. Li Hongmei
National Institute of Metrology, China (NIM, China)
National Research Center of Certified Reference
Materials(NRCCRM)
Outline
1. Background
2. Metrological Traceability in Analytical Chemistry
Concept of metrological traceability
Key factors of measurement quality control
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
2
An inter-laboratory comparison held by EU in the year of 2000
Key factors for chemical
measurement
Measurement methods
Pre-preparation and reagent
Operator and environment
Measuring instrument
Reference material
Others
The measurement Results are accurate or not?
One time measurement
Globally effective
Primary Method
PRM
CRM
High Accuracy Method
Standard Method
analysis
SI unit
Chemical metrology system
Traceability: NMIs develop and establish the unbroken metrological traceability chain by providing the services of CRMs, PT and results assessment etc.
Comparability:The transverse connection of metrology, calibration and testing laboratory at different level
The Role of Chemical Metrology
Chemical Metrology vs. Free Trade
Test
Comparability
Traceability
One Test
Mutual Recognition
Global Recognition Free Trade
Sustainable Economic Development
Metrology Standard
Measurement Quality Assurance
specialized
production
Product
Consistency Product
Conformity
Precision Product
Quantification
Promoting trade Improving products
Sustainable Economic Development
product application
(market access)
product application
(consumer protection)
Conformity
Assessment
Reference Measurement Systems supports food safety
International Mutual
Recognition System:
International Organizations
Chemical
Metrology
System
CRM:
The key role
7
Grain food is a major nutrition source. Among 10 largest grain exporting countries in the world, 6 are
from APEC, such as the United states, Australia and Canada.
Grain safety main concerned with different contaminants, like mycotoxins, heavy metals,
pesticide residue, microorganism, etc.. Among them, mycotoxins and heavy metals are two
major harmful influence factors.
Grain safety is the basis of national economic security, and is the core of the production,
processing, trade, reserve and consumption balance.
Measurement and standards provide accurate and internationally recognized methods to assure
grain safety.
Harmonized global measurement and standards can improve quality control system in
developing countries, reduce economic loss and trade disputes.
The role of of measurement and standards in grain food
Outline
1. Background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
9
VIM definition:
Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.
The term “Traceability” is replaced by “Metrological traceability”
a new definition as property of a measurement result which can be related to a reference
an evidence of measurands tracing to the primary standards which can realize the SI units
a documented unbroken chain of calibrations
2.1 Metrological Traceability
10
Metrological Traceability
ISO/IEC Guide 99:2007, “International vocabulary of metrology — Basic and general concepts and associated terms”
11
Unbroken chain of calibrations
Results
Calibration
Calibration
Calibration Results
Measured
SI /Reference
Measurement standard
Measurement procedure
Measurement unit
Measurements uncertainty
Measurements value &
Document
Document
Document
Outline
1. Background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
12
13
2.2 Key factors in quality control of measurement
Chemical metrology
Method
CRM Reference value for PT
Primary methods
High accuracy methods
Pure / solution CRM
Matrix CRM
Measurement standards and tools for metrological traceability
Calibration CRM1
Sample
Measurement result1
Higher level reference
Common reference
Trac
eab
ility
Matrix CRM1
Bias
Matrix CRM2
Bias
Higher level reference
Calibration CRM2
Measurement result2
Sample
comparability
comparability
14
2.2 Key factors in quality control of measurement
Sample preparation techniques
Measurement characteristics
Measurement techniques
Advance material
Environment
Food safety
Medicine
Forensic science Security
Energy
Core capability principles in establishing chemical metrological traceability system
15
2.2 Key factors in quality control of measurement
Outline
1. Background
2. Traceability control in chemical metrology
Concept of metrology traceability
Key factors in traceability control
Method development
CRM production
Proficiency test
3. Traceability system establishment in mycotoxin
4. Summary
16
17
Water content The related
structure
impurities
VOCs Non-volatiles
Qualitative
analysis by GC-
MS, LC-MS
Quantitative
analysis by GC, LC,
GCMS,LCMS
Karl Fischer
titrator
Verify by TGA
headspace GC-
MS / headspace
GC-FID
Verify by q-
NMR,TGA
Ash residue
method, TGA or
ICP-MS
Verify by TGA
Purity assessment of organic compound-Mass Balance Approach
(MBA)
P=1-WRS-WW-Wv-WNV
2.3 Method development
18
Procedure
Selection of internal
standard
Selection of solvent
Selection of
quantitative peaks
Optimization of
qNMR paramemeters
Determination
Potential primary method
Traceability can be established to SI units
Universal to almost organic compounds
Simple pretreatment, which may decrease
uncertainty
No identification of impurities of water,
solvent, inorganic…
One peak from analyte and one peak from
internal standard is enough
Advantage
QNMR
Chemical components measurement result and influence factors on metrological traceability
Method of matrix sample
Definition of
measurement
Sampling
Sample measurement
data processing and uncertainty evaluation
Result and application
Inaccurate or incomplete definition of the
measurement
Matrix effects
Instability of chemical composition ;
Complicated sample transformation
measurement process
Complicated uncertainty components and
combination method
19
Mea
sure
me
nt
cal
ibra
tio
n
Isotope Dilution Mass Spectrometry --high accuracy method !!!
• Relative measurements, excellent precision and accuracy
compared with standard additions
• Ideal internal standard (the same compound) , Correction for
signal drift and matrix effects
• Quantitative separation processes are not required
• Once equilibration of the spike and analyte isotopes has
been achieved, the total recovery of the analyte is not
required
Isotope Dilution Mass Spectrometry
Optimizing chromatographic conditions
Preparation of stable isotope labeled
standard solution
Value
assignment
Matrix sample test
Ratios of analyte to isotopic internal standard
………
International
comparison
Matrix sample test
Yes
No
Optimizing mass spectrometry conditions
Yes No
CRM value assignment procedure by IDMS in organic targets
21
Matrix effect
sensitivity
selectivity
accuracy
Mass spectrum detection
Resolution
high throughput
high efficiency
Chromatographic Separation
Extraction recovery
Remove matrix
Interferences
concentration
Sample preparation
Key points of IDMS method
IDMS technique can effectively compensate the matrix effect in some
situation, matrix, instrumentation and other factors may still give rise to
variation of the peak area ratio of analyte to isotope and consequently lead to
unpleasant result.
22
Effect of composition of mobile phase and sample solvent on θ
40%
35%
30%
25%
0.80
0.85
0.90
0.95
1.00
1.05
30%
35%
40%
Th
e fa
cto
r o
f m
atr
ix e
ffec
t (θ
)
Ace
tonitr
ile in
disso
lutio
n sol
vent
Acetonitrile in mobile phase
When the content of acetonitrile in the mobile phase was increased, the
difference in ME of CAP and D5-CAP was getting smaller, or even disappeared. 23
Matrix effect -- Chromatographic Separation
Chloramphenicol in milk powder
Melamine 13C3-Melamine 15N3- Melamine 13C3-15N3-Melamine
N
N
N
NH2
H2N NH2
1 2
3 4
5
6 N
N
N
NH2
H2N NH2
13
13
13
15
1515
N
N
N
NH2
H2N NH2
13
13
13
N
N
N
NH2
H2N NH
2
15
1515
IS Increased mass Total mass The ratio( %)
13C3-melamine 3 39 7.69
13C3-15N3-melamine 6 84 7.14
15N3-melamine 3 45 6.67
ME of Melamine in Milk Powder
24
Matrix effect -- Mass spectrometry detection
Response Ratio of Melamine to Internal Standards
0.0 1.5 3.0 4.5 6.0 7.5 9.0
0.9
1.0
1.1
1.2
1.3
1.4
average:1.35
average:1.27
Th
e r
ati
o o
f th
e p
ea
k a
rea
The concentration of analyte,ug/kg
The ratio of peak area (melamine / 15
N3-melamine)
The ratio of peak area(melamine / 13
C3-
15N
3-melamine)
The ratio of peak area(melamine / 13
C3-melamine)
average:0.97
13C
13C-15N
15N
Different response ratio has been found in melamine to three internal standards
with same concentration, average values are 0.97, 1.27 and 1.35 respectively.
Matrix effect -- Mass spectrometry detection
Uncertainty evaluation
Instrumental
optimization
Matrix effect
Balance
linearity Balance
calibration
Sample weighing
CAP in milk powder
efficiency
weighing
SPE evaluation
separation
Pretreatment, chromatography separation, Sample solution
repeatability
Matrix removal enrichment Clean up
efficiency
Column evaluation
components matrix
extraction
separation
transfer
Method
parameter
Volumetric
flask
Standard
solution CAP dilution
Temperature D5-CAP dilution
MS condition
calibration
Calibration solution Uncertainty account for :57%
Uncertainty account for :43%
Purity
matrix solvents
instrument
Linear
range
26
Chloramphenicol in milk powder
57%
Uncertainty evaluation--chloramphenicol in milk powder
27
Uncertainty evaluation
Outline
1. Background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
28
29
Value-Assignment of Calibrant
High pure substance
Identification analyte in calibrant
Purity /calibrant assignment method
Sample Analysis Competencies
Identification of analytes in sample
Extraction of analytes
Cleanup - separation of analytes
Transformation – conversion of analytes
Calibration approach for value-assignment of analytes in matrix
Verification method for value-assignment of analytes in sample
2.4 CRM production
Core competency
Food matrix CRMs in NIM
Till Sep. 2016,food related CRM: 451,pure & solution: 391;matrix: 60
0
2
4
6
8
10
12
14
16
18
20
Matrix type 19
15
12
9
7
5
3 3 2
0
5
10
15
20
25
30
35
40
45
Measurands
42
8 6
4 4 4 3 2 1 1
0
20
40
60
80
100
120
140
160
pesticide additive nutrient hormone packing contact
drug elements species
phthalate clinical
Pure CRM
137
77 68
36
20 20
8 8 6
30
Uncertainty
evaluation
Validation
Quantitation
Sample 1-chloramphenicol in milk powder
Chromatography
separation
Sample
preparation
MS
optimization
Xiu Qin Li, Qing He Zhang, Hong Mei Li,Analytica Chimica Acta, 807 (2014) 75– 83
Value(μg/kg) U(μg/kg)(k=2)
<0.004 --
0.915 0.067
31
Relative CRMs
CRMs No. Mass fractions U (%) k=2
purity of melamine GBW10058 99.5 % 0.5
melamine in milk powder
GBW10059 0.45 mg/kg 16
GBW10060 3.47mg/kg 14
GBW10061 16.5mg/kg 10
32
Outline
1. Background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
33
Specially designed inter-laboratory comparisons was
combined with external QC activities of field laboratories
and promote the establishment and spread of valid
national metrological traceability system.
Providing customized multi-level blind samples
Providing independent reference values
Providing technical analysis in aspects of reference materials used,method performance, measurement uncertainties and risk in
compliance assessment like false negative or positive results.
2.5 Proficiency test
34
PT on food safety organized by NIM
35
Year Name number of
participants
2010 Determination of chloropropanol in soy sauce 23
2011 Determination of benzo[a]pyrene in edible oil 25
2011 Determination of sodium thiocyanate in liquid milk 25
2012 Determination of lead and chromium in solution 31
2012 Determination of lead and chromium in milk powder 31
2012 Determination of lead and chromium in tea 31
2012 Determination of pigments in wine 130
2012 Determination of cadmium in rice 510
2013 Determination of aluminum in vermicelli 40
2013 Determination of 16 kinds of phthalate acid esters in Chinese spirit 15
2013 Determination of aflatoxin in liquid milk 15
2014 Determination of 16 kinds of phthalate acid esters in chinese spirit 37
2014 Determination of lead in infant powder 37
2014 Determination of aflatoxin M1 in milk 33
2015 Determination of clenbuterol in pork 8
2015 Determination of progesterone and methyltestosterone in milk 8
16 food safety related PTs cover 11 food matrix, about 13 kinds of measurands
Multi-targets and sample transfer means
•Performance of measurement methods
•Measurement capability of testing
laboratories
•Accuracy of the property value
of reference materials
•Preparation capabilities
•Certification capabilities
pilot laboratory
…
pilot laboratory
Lab1
Lab2
Lab3
Lab n
Lab1
Lab2 Lab3
Lab n
… 36
• Primay data analysis
•Regressed value for multi-point comparison
•Standard deviation estimate
•Performance evaluation
•Histogram
•Kernel density
•Normal distribution test
•Ordinary linear least square method → linear regression with errors in both axes
• Intercept ≠ 1 and slope ≠ 1 significantly:
• Big errors in the nominal property values of evaluated RMs
• Commutability
• Systematic error
•Standard deviation estimate of uncertainty weighed mean from expert
laboratories
•Standard deviation estimate of robust median from participants
•Shortest coverage interval
• Method performance
• Laboratory performance
• Analytical method dependence
• Matrix effect and commutability
• Technical advices
Integrated statistical and technical analysis
37
10
23
3
1
11
14
718
20
9
17
8
6
25
22
24
15
122
19
13
-6
-4
-2
0
2
4
-5 -4 -3 -2 -1 0 1 2 3 4 5
95%置信概率 系列2 99%置信概率
0
20
40
60
0.9 1 1.1
Traceability control
Priority in selecting reference value
1. Measured or gravimetric prepared value by pilot laboratory
2. consensus value from collaborative expert laboratories
3. Consensus value from participants
4. Other methods
Tra
ce
ab
ilit
y
Ve
rifi
ca
tio
n
38
Priority in selecting measurement method
1) national primary apparatus or primary methods;
2) High accurate methods, the accuracy of them has been proved through the international measurement
comparisons;
3) reference laboratory system established through inter-laboratory study;
4) high precision methods using PRM or metrological traceable to provide measurement traceability.
CCQM-K24 Cadmium in rice
CCQM-P64,K56 Trace elements (calcium,
iron, zinc and copper) in whole fat soybean
powder
CCQM-K59 Nitrite in water
CCQM-K103 melamine in milk powder
CCQM- K106 Pb, As and Hg in cosmetic
material
CCQM- K89 Trace and Essential Elements in
Herba Ecliptae (As,Ca,Cd,Pb,Zn)…
Cd in rice with two levels of concentration
PT- nutritious elements in whole fat soybean powder
Quality evaluation of reference materials :nitrite in
water
Method performance assessment of rapid testing
methods for melamine in milk
PT- Hg in cosmetic material with two levels of
concentrations
PT- Cd,Pb,Cu in white atractylodes rhizome…
Median: 0.216 mg/kg
NIM value:
0.214mg/kg
Traceability control
International
comparison PT
PT International
comparison
Traceability control
39
GC-HRMS
LC-PDA
Raman Microscope
LC-MS-MS
奶粉5(16.3mg/kg) Z比分数
24 0610
6614 02
4965 71
42 64 51 7377 21
5552 7539 76 59 35 58 16 17 13 03 45 40 53 85 04 41 70 31 79 25 87 63 29 78 09 15 67 30 86 12 23 44 11 18 34 05 38 74 80 48 61 69 37 68
83 07 19 36 26 32 89 54 43 22 72 88 08 81 56 8250
84 28
-8.00
-7.00
-6.00
-5.00
-4.00
-3.00
-2.00
-1.00
0.00
1.00
2.00
实验室代码
Z比分数
|Z|< 2 82%
2<|Z|< 3 7.2%
| Z | > 3 10.8%
Melamine in milk powder
CCQM-K103 & P145
Melamine in liquid milk and milk powder 40
41
PT -- Aflatoxin M1 in milk
33 Labs 0.2 μg/kg
NIM prepared the PT sample and certified the reference value using
LC-IDMS
The certified value has good consistency with the medium value
26 of 33 labs got favorable results
Median Reference value
Outline
1. Background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
42
43
Laula Anfossi, Recent patents on food, nutrition & agriculture, 2010, 2,140-153
3 Establishment of the global measurement system in mycotoxins
44
3 Establishment of the global measurement system in mycotoxins
•Secondment
•Training
•PT
•Calibration solution
•Food matrix
•Calibration solution
•Matrix CRM
• Purity assessment
• High accuracy method
• Standard method Method
development CRM
Knowledge transfer, PT
Comparison
Calibrations:Aflatoxin B1,
Zearalenone, Patulin,
Deoxynivalenol,etc.
Matrix:Cereal, Dairy product,
apple juice, oil, nuts, meat
Collaboration with BIPM and other metrology institutes, to develop metrological
capacity and the metrology infrastructure in mycotoxin:
• To quantify mycotoxins in food accurately
• To support standardization in mycotoxin
• To realize world-wide free trade in food
Regional Metrology Organizations (RMOs)
APMP
NIM
ACRM
Polarity:
High Polarity(-2 4)
Low Polarity(-8 -2)
Molecular weight:
Low MW(0 ~ 300)
Medium MW(300 500)
High MW(500 800)
Priorities in Mycotoxins – Matrix CRM
Patulin
Zearalenone
Aflatoxin B1
Aflatoxin M1 Deoxynivalenol
Ochratoxin A
Fumonisim B
0
100
200
300
400
500
600
700
800
-6 -5 -4 -3 -2 -1 0 1 2 3
MW
PKow
MW vs. Polarity
Company Logo
Ochratoxin A in cereal etc.
Fumonisim B in maize etc.
Zearalenone in maize etc.
Deoxynivalenol in rice flour
Aflatoxin M1 in milk powder
Aflatoxin B1 in oil
Patulin in juice
Ochratoxin A in meat etc.
Aflatoxin B1 in peanut
Outline
1. General background
2. Metrological Traceability in Analytical chemistry
Concept of metrological traceability
Key factors in quality control of measurement
Method development
CRM production
Proficiency test
3. Establishment of the global measurement system in
mycotoxins
4. Summary
47
1. Delivery service by CRMs and PT from NMIs are the important approach of
establishing metrology traceability system
2. The national measurement technical system is established through the
international mutual recognition to the core competency achieved by study on
features of analytical techniques, typical matrix and the characteristics of
analytes. It is the technical insurance of the formulating of standards and
laboratory accreditation.
3. High accuracy techniques of chemical metrology could evaluate the accuracy of
measurement results of testing as well as ensure their reliability and validity. It is
primary importance to the improvement of technical progress of advanced
measurement technologies in the field of food safety.
4. The establishment of Metrological Traceability system in Mycotoxin sustains
world-wide free trade.
4 Summary
Acknowledgement
Funded by the Ministry of Science and Technology of China
The technical group:
Dr. Li Xiaomin, Dr. Zhang Qinghe, Dr. Li Xiuqin,
Dr. Lu Xiaohua, Dr. Lu Hai, Mr. Guo Zhen, Dr. Huang Ting,
50