UNDP/GEF Danube Regional Project
Preparation of Reference Materials for
Analytical Quality Control in the Water
Laboratories
Report on the Stability Testing and Conclusions
November, 2003
VITUKI Plc.,
WATER RESOURCES RESEARCH CENTRE Plc.
H-1095 Budapest, Kvassay Jen út 1.
Hungary
LIST OF CONTENT
A.
PROJECT OBJECTIVES.........................................................................................................1
B.
APPROACH OF WORK IN LINE WITH THE REQUIRED SERVICE ..............................1
C.
REQUIREMENTS FOR REFERENCE MATERIALS ..........................................................2
D.
THE PROCEDURE FOR PRODUCING WATER RMS ........................................................3
E.
STABILITY TEST.....................................................................................................................4
CONCLUSIONS AND REMARKS .....................................................................................................30
Annex I.
A. PROJECT
OBJECTIVES
Objective: Ensure the reliability and comparability of monitoring results during the implementation of
the transnational water quality monitoring (TNMN) in the Danube river basin (DRB) by providing
appropriate reference materials (RM) for analytical quality Control (AQC).
Outputs: Ensure availability of homogenous reference samples (RM), as AQC sample, for analyzing
specified pollutant characteristics in water and sediment. The RMs shall be available for performance
testing (intercalibration) and intra-laboratory quality control.
This project output will assist DRB-countries to control the water quality monitoring results by
reference samples in their laboratories and to ensure sustainable quality work as well as to improve
their working quality as needed.
Implementation of the project will ensure the continuity of the quality assurance activities in the DRB
which have been developed and maintained since 1995 in the frame of different projects supported
from different financial sources, e.g. individual countries, PHARE program and the ICPDR.
B.
APPROACH OF WORK IN LINE WITH THE REQUIRED
SERVICE
In line with the Work Program of the MLIM Expert Groups, there is a need to ensure and maintain the
analytical quality control measures in the water laboratories in the DRB as a basic requirement of the
quality assurance in the trans-national monitoring. This Project provides significant quantities of water
and sediment RMs.
1. Water RMs:
based on earlier experience concerning the problem of determination of the different river quality
characteristics the target determinands include nutrients, i.e. nitrogen and phosphorus forms, as well as
heavy metals.
The compounds of interest in reference materials present in about the same concentration range (no
more than a factor of 5-10) as in the Danube samples which are usually analyzed.
The concentrates for analyses of nutrients contain:
-
ammonium-N,
-
nitrate-N,
-
phosphate-P,
-
total P.
The concentrates for analyses of heavy metals contain:
-
cadmium,
-
copper,
-
chromium,
-
lead,
-
nickel,
-
zinc,
-
mercury,
-
aluminum,
-
arsenic
C. REQUIREMENTS FOR REFERENCE MATERIALS
The basic requirements which a reference material must fulfill in order to be of any use, it should be:
-
representative,
-
homogeneous,
-
stable.
Representative:
The RM must represent water and/or sediment sample containing the range of determinands normally
expected in the normally tested sample.
Homogeneous:
In order to results obtained with reference samples will be reproducible the distribution of
determinands within the material must be homogeneous.
Stable:
The RM must also remain stable over a defined period of time, that is, the concentration of
determinands present must remain within defined limits. As water sample would not be stable, so
some means of preservation is required.
2
D. THE PROCEDURE FOR PRODUCING WATER RMs
In the case of water reference materials all the preparation steps and tests were specified. The
procedure was the following:
a) preparation of concentrates
b) analyses
c) bottling
d) sterilization + repeated analyses (in the case of nutrients only)
e) storage
f) testing
g) transport
preparation of concentrates:
analytical grade reagents were measured into an appropriate flask and diluted with
distilled water. After homogenization by mechanical stirring solutions were taken
into volumetric flasks and filled to the mark. The solutions were preserved according
to ISO 56667-3 Standard.
analyses:
were made according to Hungarian and ISO Standards
bottling:
reclosable bottles were filled manually
sterilization: bottles for nutrients were placed into autoclave to prevent any change due to
microorganisms
analyses:
after sterilization analyses were repeated
storage:
a/ in refrigerator ( 4° C)
b/ in room temperature ( 22° C)
testing:
stability had been tested between bottles. All samples were measured on the same day,
by the same technicians.
transport:
by courier post
The concentrated solutions should be enough to prepare one litre of water sample ready for analyses.
3
For practical reasons the first series of nutrients consist of five reclosable bottles for each laboratory to
make five dilutions at least.
Both nitrogen and phosphorus form are included in each bottle.
The first series of heavy metals consist of four reclosable bottles for each laboratory to make some
dilutions (at least five).
The second series of heavy metals consist of eight reclosable bottles, including five bottles for
mercury. As concentrate of mercury solution is rather low, it is advised to use the mercury reference
material concentrate once time after opening the small bottles and not to use again the remaining
content of the bottles (working instruction was attached to the distributed RMs).
The separated concentrates for heavy metals are the following:
Cd, Cr, Cu
Pb, Ni, Zn
Hg
Al, As
Expiration period of water RMs is one year after the preparation.
Assigned values: in the case of nutrients sub-samples were tested in three replicates per day during a
week and the assigned values were calculated from these data. Nominal concentrations were
considered as assigned values for the artificially prepared heavy metals samples.
The assigned values of water RMs are attached in Annex 1.
E.
STABILITY TEST
The most common approach to stability testing is to expose the RM to conditions that are likely to lead
to degradation or transformation of the analyte. Such changes in analyte concentration can be due to
many sources, e.g., thermal degradation or conversion, microbiological activity, photo-degradation.
For stability testing selected bottles for
nutrients were sterilized to negligate any degradation due to microbiological activity and
stored at room temperature (22 °C), as well as at 4 °C, where no significant changes are
expected.
In parallel not sterilized samples were also storage at 4 oC comparing any changes into concentration
to sterilized samples.
Heavy metals samples were stored at:
the normal room temperature (22 oC)
at a temperature, where no changes are expected ( 4 oC).
Stability was evaluated by analysing samples stored at different temperatures. The time steps: 0.5, 1, 3
month.
Independent analyses were carried out in triplicate for each storage temperature and time.
4
The evaluation makes use of the ratio RT, which is based on the mean values (xT) of three
determination made after storage at room temperature, divide by the mean value for three
measurements of samples stored at the safe temperature (X-s):
RT= XT/Xs
.
RT was calculated for each storage interval.
In order to minimise the day-to day variation, the mean values that were used for the calculation RT,
were obtained from analyses that were performed on the same day.
In the case of "ideal" stability, the ratios RT should be equal to 1.00, but due to the uncertainty of the
measurements there may be some random variations.
The uncertainty (UT) was obtained from the coefficient of variation (CV) of three measurements
obtained at each temperature:
U
2
o
T=(CVT +CV24 C)1/2 * RT
No instability can be concluded when the values 1 are comprised between the respective ranges: RT±
UT.
The mean values for the analyses at the different times and for the two storage temperatures are
together with the respective standard deviations and variation coefficients presented in Table 1- 10.
Results compared sterilized and not sterilized samples are summarized in Table 11-12.
Graphical presentations of the stability test results can be seen on Fig.1-12.
5
Table 1. Evaluation of stability testing using the safe temperature ratios
Nutrients (RM-1)
Storage at + 22 o C
Storage at + 4 o C
mg/l
NH +
-
3-
+
-
3-
4 -N NO3 -N PO4
-P TP NH4 -N NO3 -N PO4 -P TP
t = 0,5
0,462
1,83
0,127 0,230
0,464
1,82 0,131
0,233
month
0,463
1,81
0,133 0,228
0,467
1,83 0,131
0,228
0,461
1,82
0,128 0,229
0,465
1,84 0,130
0,230
mean
0,462
1,82
0,129 0,229
0,465
1,83 0,131
0,230
S.D.
0,001
0,010
0,003 0,001
0,002
0,010
0,001 0,003
CV
0,216
0,549
2,485 0,437
0,328
0,546
0,442 1,093
t = 1
0,465
1,80
0,131 0,225
0,464
1,83 0,130
0,228
month
0,460
1,82
0,127 0,230
0,465
1,83 0,132
0,231
0,460
1,80
0,133 0,231
0,465
1,82 0,131
0,232
mean
0,462
1,81
0,130 0,229
0,465
1,83 0,131
0,230
S.D.
0,003
0,012
0,003 0,003
0,001
0,006
0,001 0,002
CV
0,625
0,639
2,344 1,406
0,124
0,316
0,763
0,90
t = 2
0,465
1,81
0,131 0,230
0,465
1,82 0,128
0,232
months
0,456
1,79
0,129 0,229
0,463
1,84 0,133
0,228
0,459
1,82
0,129 0,229
0,466
1,83 0,131
0,229
mean
0,460
1,81
0,130 0,229
0,465
1,83 0,131
0,230
S.D.
0,005
0,015
0,001 0,001
0,002
0,010
0,003 0,002
CV
0,996
0,845
0,891 0,252
0,329
0,546
1,926 0,906
t = 0,5
RT 0,99
0,99
0,99
0,99
month
UT 0,00
0,01
0,02
0,01
RT+UT 1,00
1,00
1,01
1,01
RT-UT 0,99
0,99
0,96
0,98
t = 1
RT 0,99
0,99
0,99
0,99
month
UT 0,01
0,01
0,02
0,02
RT+UT 1,00
1,00
1,02
1,01
RT-UT 0,99
0,98
0,97
0,98
t = 2
RT 0,99
0,99
0,99
1,00
months UT 0,01
0,01
0,02
0,01
RT+UT 1,00
1,00
1,01
1,01
RT-UT
0,98
0,98
0,97
0,99
6
Table 2. Evaluation of stability testing using the safe temperature ratios
Nutrients (RM-2)
Storage at + 22 o C
Storage at + 4 o C
mg/l
NH +
-
3-
+
-
3-
4 -N NO3 -N PO4 -P
TP
NH4 -N NO3 -N PO4 -P
TP
t = 0,5
0,695
2,24
0,214 0,316
0,703
2,35
0,213 0,319
month
0,700
2,53
0,213 0,320
0,706
2,43
0,215 0,318
0,706
2,27
0,217 0,321
0,699
2,28
0,217 0,322
mean
0,700
2,35
0,215 0,319
0,703
2,35
0,215 0,320
S.D.
0,006
0,159
0,002 0,003
0,004
0,075
0,002 0,002
CV
0,786
6,796
0,970 0,829
0,500
3,189 0,930
0,651
t = 1
0,697
2,26
0,212 0,317
0,703
2,35
0,212 0,321
month
0,706
2,45
0,214 0,322
0,701
2,37
0,216 0,319
0,703
2,29
0,216 0,319
0,703
2,31
0,214 0,322
mean
0,702
2,33
0,214 0,319
0,702
2,34
0,214 0,321
S.D.
0,005
0,102
0,002 0,003
0,001
0,031
0,002 0,002
CV
0,653
4,378
0,935 0,788
0,164
1,304 0,935
0,476
t = 2
0,701
2,27
0,210 0,315
0,703
2,32
0,209 0,323
months
0,706
2,39
0,217 0,329
0,704
2,41
0,210 0,318
0,704
2,27
0,211 0,310
0,699
2,28
0,219 0,321
mean
0,704
2,31
0,213 0,318
0,702
2,34
0,213 0,321
S.D.
0,003
0,069
0,004 0,010
0,003
0,067
0,006 0,003
CV
0,358
2,999
1,780 3,097
0,377
2,849 2,590
0,785
t = 0,5 RT 1,00
1,00
1,00
1,00
month UT 0,01
0,07
0,01
0,01
RT+UT 1,01
1,07
1,01
1,01
RT-UT 0,99
0,92
0,99
0,99
t = 1
RT 1,00
1,00
1,00
1,00
month UT 0,01
0,05
0,01
0,01
RT+UT 1,01
1,04
1,01
1,01
RT-UT 0,99
0,95
0,99
0,99
t = 2
RT 1,00
0,99
1,00
0,99
months UT 0,01
0,04
0,03
0,03
RT+UT 1,01
1,03
1,03
1,02
RT-UT
1,00
0,95
0,97
0,96
7
Table 3. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-1)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Cd Cr Cu Cd Cr Cu
t = 0,5
1,97
15,50
15,00
1,99
15,40
15,02
month
1,99
15,20
15,00
2,00
15,35
15,00
2,03
15,30
14,99
2,02
15,35
14,99
mean
2,00
15,33
15,00
2,00
15,37
15,00
S.D.
0,031
0,153
0,006
0,015
0,029
0,015
CV
1,530
0,996
0,038
0,762
0,188
0,102
t = 1
1,96
15,50
15,00
1,98
15,40
15,01
month
2,04
15,10
15,00
2,03
15,25
15,00
1,97
15,30
14,98
2,02
15,45
14,99
mean
1,99
15,30
14,99
2,01
15,37
15,00
S.D.
0,04
0,200
0,012
0,03
0,10
0,010
CV
2,19
1,307
0,077
1,32
0,68
0,067
t = 2
1,98
15,50
15,08
2,04
15,40
15,06
months
2,02
15,30
15,04
2,01
15,25
15,00
2,00
15,40
14,96
1,96
15,45
15,00
mean
2,00
15,40
15,03
2,00
15,37
15,02
S.D.
0,02
0,10
0,061
0,04
0,10
0,035
CV
1,00
0,65
0,407
2,02
0,68
0,231
t = 0,5 RT
1,00
1,00
1,00
month UT 0,02
0,01
0,00
RT+UT 1,01
1,01
1,00
RT-UT 0,98
0,99
1,00
t = 1
RT 0,99
1,00
1,00
month UT 0,03
0,01
0,00
RT+UT 1,02
1,01
1,00
RT-UT 0,96
0,98
1,00
t = 2
RT 1,00
1,00
1,00
month UT 0,02
0,01
0,00
RT+UT 1,02
1,01
1,01
RT-UT
0,98
0,99
1,00
8
Table 4. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-2)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Cd Cr Cu Cd Cr Cu
t = 0,5
1,00
6,06
8,00
1,00
6,00
8,04
month
0,99
6,00
7,99
1,01
6,05
7,99
1,00
6,04
8,00
1,00
6,01
8,00
mean
1,00
6,03
8,00
1,00
6,02
8,01
S.D.
0,01
0,03
0,01
0,01
0,03
0,03
CV
0,58
0,51
0,07
0,58
0,44
0,33
t = 1
1,00
6,01
8,10
0,99
5,99
7,90
month
0,99
6,10
7,98
1,02
6,15 8,05
1,00
5,94
8,00
1,00
6,00
8,00
mean
1,00
6,02
8,03
1,00
6,05
7,98
S.D.
0,01
0,08
0,06
0,02
0,09
0,08
CV
0,58
1,33
0,80
1,52
1,48
0,96
t = 2
0,98
6,12
8,09
1,01
6,15
7,95
months
1,02
5,95
8,00
0,99
5,94
8,02
1,03
5,96
7,95
1,02
5,99
8,00
mean
1,01
6,01
8,01
1,01
6,03
7,99
S.D.
0,03
0,10
0,071
0,02
0,11
0,036
CV
2,62
1,59
0,885
1,52
1,82
0,451
t = 0,5
RT
0,99
1,00
1,00
month UT
0,01
0,01
0,00
RT+UT 1,00
1,01
1,00
RT-UT 0,99
1,00
0,99
t = 1
RT 0,99
1,00
1,01
month
UT 0,02
0,02
0,01
RT+UT 1,01
1,01
1,02
RT-UT 0,98
0,98
0,99
t = 2
RT 1,00
1,00
1,00
months UT 0,03
0,02
0,01
RT+UT
1,03
1,02
1,01
RT-UT
0,97
0,97
0,99
9
Table 5. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-1)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Ni Pb Zn Ni Pb Zn
t = 0,5
9,90
9,90
80,10
10,15
10,13
80,00
month
9,99
9,70
79,91
9,98
9,89
79,99
10,03
10,05
79,90
9,98
9,85
80,00
mean
9,97
9,88
79,97
10,04
9,96
80,00
S.D.
0,07
0,18
0,11
0,10
0,15
0,01
CV
0,67
1,78
0,14
0,98
1,52
0,01
t = 1
9,92
10,10
81,00
10,05
10,05
80,40
month
10,09
9,97
80,02
10,02
10,00
79,59
9,99
9,80
79,56
9,99
9,97
80,05
mean
10,00
9,96
80,19
10,02
10,01
80,01
S.D.
0,09
0,15
0,74
0,03
0,04
0,41
CV
0,85
1,51
0,92
0,30
0,40
0,51
t = 2
9,92
10,06
80,40
10,00
10,35
80,10
months
9,98
9,94
81,00
10,00
9,90 80,00
10,02
9,98
79,50
9,98
9,94
80,00
mean
9,97
9,99
80,30
9,99
10,06
80,03
S.D.
0,05
0,06
0,755
0,01
0,25
0,058
CV
0,50
0,61
0,940
0,12
2,47
0,072
t = 0,5
RT
0,99
0,99
1,00
month
UT 0,01
0,02
0,00
RT+UT 1,01
1,02
1,00
RT-UT 0,98
0,97
1,00
t = 1
RT 1,00
1,00
1,00
month UT 0,01
0,02
0,01
RT+UT 1,01
1,01
1,01
RT-UT 0,99
0,98
0,99
t = 2
RT 1,00
0,99
1,00
months
UT 0,01
0,03
0,01
RT+UT 1,00
1,02
1,01
RT-UT
0,99
0,97
0,99
10
Table 6. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-2)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Ni Pb Zn Ni Pb Zn
t = 0,5
5,06
8,00
10,02
5,00
7,99
10,00
month
5,00
7,85
10,00
5,01
7,89 10,00
5,00
7,90
10,00
5,01
7,95
10,00
mean
5,02
7,92
10,01
5,01
7,94
10,00
S.D.
0,03
0,08
0,01
0,01
0,05
0,00
CV
0,69
0,96
0,12
0,12
0,63
0,00
t = 1
5,02
7,93
9,99
5,03
8,02
10,03
month
5,04
7,99
9,98
5,04
7,97
10,02
4,99
7,90
10,00
5,00
7,95
9,98
mean
5,02
7,94
9,99
5,02
7,98
10,01
S.D.
0,03
0,05
0,01
0,02
0,04
0,03
CV
0,50
0,58
0,10
0,41
0,45
0,26
t = 2
5,05
7,99
10,15
5,06
8,35
10,08
months
5,06
7,85
10,01
5,01
7,86 10,02
4,98
7,89
10,00
5,01
7,85
9,98
mean
5,03
7,91
10,05
5,03
8,02
10,03
S.D.
0,04
0,07
0,084
0,03
0,29
0,050
CV
0,87
0,91
0,834
0,57
3,56
0,502
t = 0,5
RT
1,00
1,00
1,00
month
UT
0,01
0,01
0,00
RT+UT 1,01
1,01
1,00
RT-UT 1,00
0,99
1,00
t = 1
RT 1,00
0,99
1,00
month UT 0,01
0,01
0,00
RT+UT 1,01
1,00
1,00
RT-UT 0,99
0,99
1,00
t = 2
RT 1,00
0,99
1,00
months
UT 0,01
0,04
0,01
RT+UT
1,01
1,02
1,01
RT-UT
0,99
0,95
0,99
11
Table 7. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-1)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Al As Al
As
t = 0,5
9,90
9,89
9,96
10,01
month
9,95
9,99
9,99
9,90
10,10
9,98
10,10
10,00
mean
9,98
9,95
10,02
9,97
S.D.
0,10
0,06
0,07
0,06
CV
1,04
0,55
0,74
0,61
t = 1
9,79
10,05
9,98
9,93
month
10,12
9,95
9,99
10,10
10,05
9,95
10,03
9,90
mean
9,99
9,98
10,00
9,98
S.D.
0,17
0,06
0,03
0,11
CV
1,74
0,58
0,26
1,08
t = 2
9,94
9,77
10,15
10,10
months
10,10
10,15
10,05
10,03
9,98
9,98
9,99
9,95
mean
10,01
9,97
10,06
10,03
S.D.
0,08
0,19
0,08
0,08
CV
0,83
1,91
0,80
0,75
t = 0,5
RT 1,00
1,00
month
UT 0,01
0,01
RT+UT 1,01
1,01
RT-UT 0,98
0,99
t = 1
RT 1,00
1,00
month UT 0,02
0,01
RT+UT 1,02
1,01
RT-UT 0,98
0,99
t = 2
RT 0,99
0,99
months
UT 0,01
0,02
RT+UT 1,01
1,01
RT-UT 0,98
0,97
12
Table 8. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-2)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Al As Al
As
t = 0,5
8,40
14,20
8,50
14,57
month
8,50
14,60
8,60
15,00
8,50
14,50
8,52
14,00
mean
8,47
14,43
8,54
14,52
S.D.
0,06
0,21
0,05
0,50
CV
0,68
1,44
0,62
3,45
t = 1
8,60
14,49
8,65
14,43
month
8,30
14,62
8,45
14,60
8,40
13,99
8,48
14,45
mean
8,43
14,37
8,53
14,49
S.D.
0,15
0,33
0,11
0,09
CV
1,81
2,32
1,26
0,64
t = 2
8,40
14,80
8,52
14,38
months
8,55
14,20
8,49
14,54
8,45
14,40
8,46
14,55
mean
8,47
14,47
8,49
14,49
S.D.
0,08
0,31
0,03
0,10
CV
0,90
2,11
0,35
0,66
t = 0,5
RT 0,99
0,99
month UT 0,01
0,04
RT+UT 1,00
1,03
RT-UT 0,98
0,96
t = 1
RT 0,99
0,99
month
UT 0,02
0,02
RT+UT 1,01
1,02
RT-UT 0,97
0,97
t = 2
RT 1,00
1,00
months UT 0,01
0,02
RT+UT 1,01
1,02
RT-UT 0,99
0,98
13
Table 9. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-1)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Hg Hg
t = 0,5
1,96
1,98
month
1,97
1,99
1,99
1,98
mean
1,97
1,98
S.D.
0,02
0,01
CV
0,77
0,29
t = 1
1,94
1,95
month
1,92
1,97
1,90
1,98
mean
1,92
1,97
S.D.
0,02
0,02
CV
1,04
0,78
t = 2
1,90
1,97
months
1,92
1,95
1,89
1,96
mean
1,90
1,96
S.D.
0,02
0,01
CV
0,80
0,51
t = 0,5
RT 0,99
month UT 0,01
RT+UT 1,00
RT-UT 0,99
t = 1
RT 0,98
month
UT 0,01
RT+UT 0,99
RT-UT 0,96
t = 2
RT 0,97
months UT 0,01
RT+UT 0,98
RT-UT 0,96
14
Table 10. Evaluation of stability testing using the safe temperature ratios
Heavy metals (RM-2)
Storage at + 22 o C
Storage at + 4 o C
µg/l
Hg Hg
t = 0,5
2,84
2,85
month
2,85
2,87
2,79
2,82
mean
2,83
2,85
S.D.
0,03
0,03
CV
1,14
0,88
t = 1
2,84
2,85
month
2,81
2,83
2,80
2,84
mean
2,82
2,84
S.D.
0,02
0,01
CV
0,74
0,35
t = 2
2,80
2,86
months
2,84
2,80
2,80
2,86
mean
2,81
2,84
S.D.
0,02
0,03
CV
0,82
1,22
t = 0,5
RT 0,99
month UT 0,01
RT+UT 1,01
RT-UT 0,98
t = 1
RT 0,99
month UT 0,01
RT+UT 1,00
RT-UT 0,98
t = 2
RT 0,99
months UT 0,01
RT+UT 1,01
RT-UT 0,98
15
Table 11. Comparing results of not-sterilized and sterilized samples stored
at 4 oC
Nutrients (RM-1)
Without sterilization
Sterilized
mg/l
NH +
-
3-
+
-
3-
4 -N NO3 -N PO4 -P
TP
NH4 -N NO3 -N PO4 -P
TP
t = 0,5
0,466
1,86
0,068 0,232
0,464
1,82
0,131 0,233
month
0,470
1,89
0,070 0,230
0,467
1,83
0,131 0,228
0,471
1,87
0,070 0,229
0,465
1,84
0,130 0,230
mean
0,469
1,87
0,069 0,230
0,465
1,83
0,131 0,230
S.D.
0,003
0,015
0,001 0,002
0,002
0,010
0,001 0,003
CV
0,564
0,815
1,665 0,663
0,328
0,546 0,442
1,093
t = 1
0,464
1,85
0,070 0,223
0,464
1,83
0,130 0,228
month
0,460
1,80
0,072 0,229
0,465
1,83
0,132 0,231
0,459
1,84
0,072 0,224
0,465
1,82
0,131 0,232
mean
0,461
1,83
0,071 0,225
0,465
1,83
0,131 0,230
S.D.
0,003
0,026
0,001 0,003
0,001
0,006
0,001 0,002
CV
0,574
1,446
1,619 1,427
0,124
0,316 0,763
0,90
t = 2
0,462
1,75
0,059 0,213
0,465
1,82
0,128 0,232
months
0,467
1,62
0,063 0,217
0,463
1,84
0,133 0,228
0,463
1,79
0,061 0,214
0,466
1,83
0,131 0,229
mean
0,464
1,72
0,061 0,215
0,465
1,83
0,131 0,230
S.D.
0,003
0,089
0,002 0,002
0,002
0,010
0,003 0,002
CV
0,570
5,168
3,279 0,970
0,329
0,546 1,926
0,906
t = 0,5 RT 1,01
1,02
0,53
1,00
month UT 0,01
0,01
0,01
0,01
RT+UT 1,01
1,03
0,54
1,01
RT-UT 1,00
1,01
0,52
0,99
t = 1
RT 0,99
1,00
0,54
0,98
month UT 0,01
0,01
0,01
0,02
RT+UT 1,00
1,02
0,55
0,99
RT-UT 0,99
0,99
0,53
0,96
t = 2
RT 1,00
0,94
0,47
0,93
months UT 0,01
0,05
0,02
0,01
RT+UT 1,01
0,99
0,48
0,95
RT-UT
0,99
0,89
0,45
0,92
16
Table 12. Comparing results of not-sterilized and sterilized samples stored
at 4 oC
Nutrients (RM-2)
Without sterilization
Sterilized
mg/l
NH +
-
3-
+
-
3-
4 -N NO3 -N PO4 -P
TP
NH4 -N NO3 -N PO4 -P
TP
t = 0,5
0,654
2,15
0,109 0,290
0,703
2,35
0,213 0,319
month
0,701
2,15
0,106 0,290
0,706
2,43
0,215
0,318
0,680
2,16
0,108 0,291
0,699
2,28
0,217 0,322
mean
0,678
2,15
0,108 0,290
0,703
2,35
0,215 0,320
S.D.
0,024
0,006
0,002 0,001
0,004
0,075
0,002 0,002
CV
3,471
0,268
1,419 0,199
0,500
3,189
0,930 0,651
t = 1
0,673
2,33
0,103 0,224
0,703
2,35
0,212 0,321
month
0,678
2,28
0,104 0,235
0,701
2,37
0,216
0,319
0,675
2,33
0,102 0,234
0,703
2,31
0,214 0,322
mean
0,675
2,31
0,103 0,231
0,702
2,34
0,214 0,321
S.D.
0,003
0,029
0,001 0,006
0,001
0,031
0,002 0,002
CV
0,373
1,248
0,971 2,633
0,164
1,304
0,935 0,476
t = 2
0,664
2,45
0,100 0,214
0,703
2,32
0,209 0,323
months
0,659
2,39
0,101 0,209
0,704
2,41
0,210 0,318
0,661
2,29
0,103 0,214
0,699
2,28
0,219 0,321
mean
0,661
2,38
0,101 0,212
0,702
2,34
0,213 0,321
S.D.
0,003
0,081
0,002 0,003
0,003
0,067
0,006 0,003
CV
0,381
3,401
1,507 1,360
0,377
2,849
2,590 0,785
t = 0,5
RT 0,97
0,92
0,50
0,91
month UT 0,03
0,03
0,01
0,01
RT+UT 1,00
0,94
0,51
0,91
RT-UT 0,93
0,89
0,49
0,90
t = 1
RT 0,96
0,99
0,48
0,72
month UT 0,00
0,02
0,01
0,02
RT+UT 0,97
1,01
0,49
0,74
RT-UT 0,96
0,97
0,47
0,70
t = 2
RT 0,94
1,02
0,48
0,66
months UT 0,01
0,05
0,01
0,01
RT+UT 0,95
1,06
0,49
0,67
RT-UT
0,94
0,97
0,46
0,65
17
Figure 1. Graphical presentations of the stability test results
Nutrients (RM-1)
Stability (storage + 22 o C)
2,000
1,500
NH4+-N
N03--N
1,000
PO43--P
0,500
TP
concentration (mg/l) 0,000
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
2,00
1,50
NH4+-N
N03--N
1,00
PO43--P
0,50
TP
concentration (mg/l) 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
NH4+-N
N03--N
0,60
RT
PO43--P
0,40
TP
0,20
0,00
0,5 month
1 month
2months
time
18
Figure 2. Graphical presentations of the stability test results
Nutrients (RM-2)
Stability (storage + 22 o C)
2,50
g/l) 2,00
m
NH4+-N
1,50
ion (
N03--N
r
at 1,00
PO43--P
TP
0,50
concent 0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
2,50
g/l) 2,00
m
NH4+-N
1,50
ion (
N03--N
r
at 1,00
PO43--P
TP
0,50
concent 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
NH4+-N
N03--N
0,60
RT
PO43--P
0,40
TP
0,20
0,00
0,5 month
1 month
2months
time
19
Figure 3. Graphical presentations of the stability test results
Heavy metals (RM-1)
Stability (storage + 22 o C)
18,00
16,00
14,00
12,00
Cd
10,00
8,00
Cr
6,00
Cu
4,00
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
18,00
16,00
14,00
12,00
Cd
10,00
8,00
Cr
6,00
Cu
4,00
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Cd
0,60
RT
Cr
0,40
Cu
0,20
0,00
0,5 month
1 month
2months
time
20
Figure 4. Graphical presentations of the stability test results
Heavy metals (RM-2)
Stability (storage + 22 o C)
10,00
8,00
6,00
Cd
Cr
4,00
Cu
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
10,00
8,00
6,00
Cd
Cr
4,00
Cu
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Cd
0,60
RT
Cr
0,40
Cu
0,20
0,00
0,5 month
1 month
2months
time
21
Figure 5. Graphical presentations of the stability test results
Heavy metals (RM-1)
Stability (storage + 22 o C)
90,00
80,00
70,00
60,00
Ni
50,00
40,00
Pb
30,00
Zn
20,00
10,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
90,00
80,00
70,00
60,00
Ni
50,00
40,00
Pb
30,00
Zn
20,00
10,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Ni
0,60
RT
Pb
0,40
Zn
0,20
0,00
0,5 month
1 month
2months
time
22
Figure 6. Graphical presentations of the stability test results
Heavy metals (RM-2)
Stability (storage + 22 o C)
12,00
10,00
8,00
Ni
6,00
Pb
4,00
Zn
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
12,00
10,00
8,00
Ni
6,00
Pb
4,00
Zn
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Ni
0,60
RT
Pb
0,40
Zn
0,20
0,00
0,5 month
1 month
2months
time
23
Figure 7. Graphical presentations of the stability test results
Heavy metals (RM-1)
Stability (storage + 22 o C)
12,00
10,00
8,00
Al
6,00
As
4,00
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
12,00
10,00
8,00
6,00
Al
4,00
As
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Al
0,60
RT
As
0,40
0,20
0,00
0,5 month
1 month
2months
time
24
Figure 8. Graphical presentations of the stability test results
Heavy metals (RM-2)
Stability (storage + 22 o C)
16,00
14,00
12,00
10,00
Al
8,00
As
6,00
4,00
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
16,00
14,00
12,00
10,00
8,00
Al
6,00
As
4,00
2,00
concentration (µg/l)
0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
Al
0,60
RT
As
0,40
0,20
0,00
0,5 month
1 month
2months
time
25
Figure 9. Graphical presentations of the stability test results
Heavy metals (RM-1)
Stability (storage + 22 o C)
4,00
3,00
Hg
2,00
1,00
concentration (µg/l) 0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
4,00
3,00
2,00
Hg
1,00
concentration (µg/l) 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
0,60
RT
Hg
0,40
0,20
0,00
0,5 month
1 month
2months
time
26
Figure 10. Graphical presentations of the stability test results
Heavy metals (RM-2)
Stability (storage + 22 o C)
4,00
3,00
Hg
2,00
1,00
concentration (µg/l) 0,00
0,5 month
1 month
2months
time
Stability (storage + 4 o C)
4,00
3,00
2,00
Hg
1,00
concentration (µg/l) 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
0,60
RT
Hg
0,40
0,20
0,00
0,5 month
1 month
2months
time
27
Figure 11. Graphical presentations of the stability test results
Nutrients (RM-1)
Without sterilization
2,00
1,50
NH4+-N
N03--N
1,00
PO43--P
0,50
TP
concentration (mg/l) 0,00
0,5 month
1 month
2months
time
Sterilized
2,00
1,50
NH4+-N
N03--N
1,00
PO43--P
0,50
TP
concentration (mg/l) 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
NH4+-N
N03--N
0,60
RT
PO43--P
0,40
TP
0,20
0,00
0,5 month
1 month
2months
time
28
Figure 12. Graphical presentations of the stability test results
Nutrients (RM-2)
Without sterilization
2,00
1,50
NH4+-N
N03--N
1,00
PO43--P
0,50
TP
concentration (mg/l) 0,00
0,5 month
1 month
2months
time
Sterilized
2,00
1,50
NH4+-N
N03--N
1,00
PO43--P
0,50
TP
concentration (mg/l) 0,00
0,5 month
1 month
2months
time
Stability (ratio RT X+22/X+4)
1,20
1,00
0,80
NH4+-N
N03--N
0,60
RT
PO43--P
0,40
TP
0,20
0,00
0,5 month
1 month
2months
time
29
CONCLUSIONS AND REMARKS
As the role of certified reference materials (CRMs) is very important in the internal quality controls
but most of laboratories cannot bear the costs of CRMs.
Although TNMN laboratories (especially NRLs) do have adequate equipment, the high costs of
operating materials, RMs, hamper optimal operation.
To avoid problems with obtaining relevant RMs the present project provided two series of water and
sediment reference materials for participating laboratories in the QualcoDanube intercalibration
comparison.
Assigned values:
-
nominal concentrations were considered as assigned values for the artificially
prepared heavy metals samples (and confirmed by analyses)
-
measured values were accepted as assigned values not "theoretical" values for
nutrients because of concentration changing during sterilization.
-
as the sediment RMs are "real-world" materials, before using them for internal
quality control the assigned values for the target compounds should be established
based on results of intercomparison test.
After preparing of water RMs, stability tests were carried out.
The results obtained from samples stored at the safe temperature of 4 °C, show a rather similar
pattern to the 22 °C data. By calculating the ratios RT of the means it appears (Fig. 1-12) that there is
no problems of instability, but there is significant difference in phosphate concentration comparing
sterilized samples to not sterilized samples (Table 11-12).
Materials, prepared and analysed by the earlier mentioned process, can be used as in-house RMs for a
relatively long time.
Remarks:
- period for implementation of present project to prepare reference materials from two
matrices (water and sediment) for the TNMN laboratories, to check homogeneity and stability
was rather short. Sediment preparation all the steps and tests - takes a long time and it was
relatively long in the case of the first sediment RM's preparation, when inhomogeneity was
detected and repeated homogenization and tests were necessary,
- evaluation of the analytical data for sediment RMs will be finished over the project as the
sediment RMs are "real-world" materials and before using them for internal quality control
the assigned values for the target compounds should be established based on results of
intercomparison test of a group of experienced laboratories .,
- in the case of water concentrates for nutrients the samples should be sterilized to prevent
activity of microorganisms and any changes into concentration.
- it is known from experience and it was confirmed again that concentration of phosphorous
forms inspite of preservation and sterilization has been changed, as it can be seen in Table
11-12 and Fig. 11-12.
It is expected that date of expiry will be shorter than a year in the case of phosphorous forms.
Unfortunately there was not any long term investigation before.
30
The reference material samples were prepared and tested according to the "Practical Manual for
Production of Laboratory Reference Materials" as well as ISO Guide 34,1996. Quality system
guidelines for the production of reference materials. Ibid.
Budapest, 26/11/2003
Dr. Jolán Schneider
team leader
31
Annex I
Assigned value of RM-1 water
Determinands Unit
Value
Nutrients
NH +
4 -N mg/l
0,465
NO -3-N mg/l
1,83
PO 3--
4
P mg/l
0,13
TP mg/l
0,23
Heavy metals
Cd
µg/l
2
Cr
µg/l
15
Cu
µg/l
15
Pb
µg/l
10
Ni
µg/l
10
Zn
µg/l
80
Hg
µg/l
2
Al
µg/l
10
As
µg/l
10
Assigned values of RM-2 water
Determinands Unit
Value
Nutrients
NH +
4 -N mg/l
0,70
NO -3-N mg/l
2,35
PO 3--
4
P mg/l
0,215
TP mg/l
0,32
Heavy metals
Cd
µg/l
1,0
Cr
µg/l
6,0
Cu
µg/l
8,0
Pb
µg/l
8,0
Ni
µg/l
5,0
Zn
µg/l
10,0
Hg
µg/l
2,85
Al
µg/l
8,5
As
µg/l
14,5