UNDP/GEF Danube Regional Project

Preparation of Reference Materials for
Analytical Quality Control in the Water
Laboratories

Report on Homogeneity Tests of the Second
Sediment Reference Materials

October, 2003

VITUKI Plc.,
WATER RESOURCES RESEARCH CENTRE Plc.
H-1095 Budapest, Kvassay Jen út 1.
Hungary
Hungary

LIST OF CONTENT

A.
PROJECT OBJECTIVES..................................................................................1
B.
APPROACH OF WORK IN LINE WITH THE REQUIRED SERVICE..............1
Sediment RMs:.................................................................................................1
C.
HOMOGENIZATION .........................................................................................2
D.
HOMOGENEITY TESTING...............................................................................2
1. Bulk homogeneity test................................................................................2
2. Specific homogeneity test..........................................................................4
E.
EVALUATION OF HOMOGENEITY .................................................................5
F.
PROGRESS OF WORK....................................................................................8

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 pol utant 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 prograrmme 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:

Sediment 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, heavy metals, as well as selected determinands to
characterize organic contamination, e.g. total organic carbon (TOC), chlorinated
hydrocarbons, ((DDT, HCB, HCH (-, -, -), PAHs (fluoranthene,
benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indenopyrene,
benzo(g,h,i)perylene (Borneff PAHs)).

The compounds of interest in the sediment RMs will be in the range of
concentrations found in Danube sediments.

In the case of sediment reference materials all the preparation steps and tests are
specified. The procedure for producing powdered RMs is the following:

1

a) sampling
b) cleaning
c) air drying
d) grinding
e) sieving

fraction > 63 ľm

discarded
f) fraction < 63 ľm
g) homogenization
h) bulk homogeneity testing
i) storage
j) testing
k) transport

C.
HOMOGENIZATION

Homogenization of sediment (fraction < 63 ľm) was carried out by a special
equipment in VITUKI. Based on earlier experience (at the first sediment RM) the time
of homogenization at a constant rotating speed was longer, as before, eight days.

D.
HOMOGENEITY TESTING

1. Bulk homogeneity test

At the end production, sub-samples were taken from the bulk material to control the
homogeneity on three heavy metals: copper, lead, nickel, using a relatively fast and
accurate method (atomic absorption spectrometric method). The test results were
used as indicators of successful bulk homogenization.

2

Randomly selected four sub-samples were tested. Each sub-sample was analyzed in
six replicates. The results can be seen in Table 1-3.

Results of homogeneity test

Table 1.

Bottle-1
Bottle-2 Bottle-3 Bottle-4

Cu(mg/kg) Cu(mg/kg) Cu(mg/kg) Cu(mg/kg)

/1
143,05 135,15 137,24 135,17

/2
143,63 140,16 136,40 135,68

/3
143,37 137,72 139,71 136,84

/4
140,90 136,04 138,38 137,44

/5
143,42 134,26 137,59 136,50

/6
143,10 132,83 136,11 134,32

Minimum
140,90 132,83 136,11 134,32 132,83
Minimum
Maximum
143,63 140,16 139,71 137,44 143,63
Maximum
Median
143,24 135,60 137,42 136,09 136,75
Median
Average
142,91 136,03 137,57 135,99 138,13
Average
SD
1,01 2,61 1,33 1,15 1,53
SD
RSD (CVw)
0,71 1,92 0,97 0,85 1,11
RSD (CVb)
Uw
0,22 0,61 0,31 0,27 0,35
Ub
CVw+Uw
0,93 2,53 1,27 1,12 1,46
CVb+Ub
CVw-Uw
0,48 1,31 0,66 0,58 0,76
CVb-Ub

Table 2.

Bottle-1 Bottle-2 Bottle-3 Bottle-4

Ni(mg/kg) Ni(mg/kg) Ni(mg/kg) Ni(mg/kg)

/1 44,83 45,56 45,41 45,44

/2 46,21 46,38 45,46 45,91

/3 45,98 46,42 45,38 45,61

/4 45,10 45,18 46,44 45,31

/5 46,44 44,74 42,19 45,85

/6 45,32 44,78 44,53 44,60

Minimum
44,83 44,74 42,19 44,60
42,19
Minimum
Maximum
46,44 46,42 46,44 45,91
46,44
Maximum
Median
45,65 45,37 45,40 45,53
45,46
Median
Average
45,65 45,51 44,90 45,45
45,38
Average
SD
0,65 0,75 1,46 0,48
0,84
SD
RSD (CVw)
1,43 1,65 3,25 1,05
1,85
RSD (CVb)
Uw
0,45 0,52 1,03 0,33
0,58
Ub
CVw+Uw
1,88 2,17 4,28 1,38
2,43
CVb+Ub
CVw-Uw
0,98 1,13 2,22 0,72
1,26
CVb-Ub

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Table 3.

Bottle-1 Bottle-2 Bottle-3 Bottle-4

Pb(mg/kg) Pb(mg/kg) Pb(mg/kg) Pb(mg/kg)

/1
130,40 131,11 134,18 131,22

/2
138,11 134,04 136,40 133,13

/3
136,40 135,17 134,10 133,29

/4
133,79 134,52 132,67 133,87

/5
135,27 132,23 124,55 132,95

/6
134,88 130,24 131,56 129,24

Minimum
130,40 130,24 124,55 129,24
124,55
Minimum
Maximum
138,11 135,17 136,40 133,87
138,11
Maximum
Median
135,08 133,14 133,39 133,04
133,26
Median
Average
134,81 132,89 132,24 132,28
133,06
Average
SD
2,61 1,99 4,11 1,74 2,61
SD
RSD (CVw)
1,94 1,50 3,11 1,31 1,96
RSD (CVb)
Uw
0,61 0,47 0,98 0,42 0,62
Ub
CVw+Uw
2,55 1,97 4,09 1,73 2,58
CVb+Ub
CVw-Uw
1,33 1,02 2,12 0,90 1,34
CVb-Ub

2. Specific homogeneity test

After homogenization specific homogeneity both for between-units and within-unit
was tested.

Between-units homogeneity

It was necessary to check using a reasonable number of samples if the
differences between-units stay within acceptable limits.

The selected analytical method was atomic absorption spectrometric method, which
was applied under the best repeatable conditions: all samples were measured on the
same day, with the same instrument, by the same operator, against the same
calibrates.

Five representative replicate samples were selected from each bottle in order to
verify their homogeneity. All the representative samples were analyzed by VITUKI.

Within-unit homogeneity

Within-unit homogeneity was calculated from the five replicates per bottle (unit).

The analytical results are presented in Table 1-3.

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E.
EVALUATION OF HOMOGENEITY

The coefficients of variation (relative standard deviation) were obtained from the
between-unit and within-unit homogeneity tests (CVB and CVW respectively).

Their respective uncertainties UCV, are defined as follows:

UCV CV/ 2n , where n = number of replicates.

No inhomogeneity is detected when the uncertainty ranges of the two coefficients of
variation overlap, or when
CVB ą UCV, and CVW ą UCV show overlap.

Variation coefficients and uncertainties are also presented in Table 2-7 based on
copper, nickel and lead analytical results.

The evaluated values from between-unit and within-unit homogeneity test are
summarized in Table 4.

The bolded values inside the range (CVB ą UCV) indicate the homogeneity of
sediment RM and it is plotted in Fig. 1-3.

The requirement of homogeneity namely the uncertainty ranges of the two
coefficients of variation shall be overlapped is achieved.

Table 4. Evaluation of homogeneity test results

Copper Nickel Lead
CVB ą UCV CVW ą UCV CVB ą UCV
CVW ą UCV CVB ą UCV CVW ą UCV
w1 0,48-0,93
w1 0,98-1,88
w1 1,33-2,55
w2 1,31-2,53 w2 1,13-2,17
w2 1,02-1,97
0,76-1,46
1,26-2,43
1,34-2,58
w3 0,66-1,27
w3 2,22-4,28 w3 2,12-4,09
w4 0,58-1,12
w4 0,72-1,38
w4 0,90-1,73

5

Cu

3

2,5

2

t
1,5

uni
CV

e
e
n-
ą UB

1
t
w
CV

be
0,5

0

B-1
B-2
B-3
B-4

CVw-Ucv
within-unit

CVw+Ucv

Figure 1. Graphical representation of homogeneity of sediment RM

Ni

4,5

4

3,5

3

2,5

i
t
n
CV
-u
U
2

ą

e
e
n
B
1,5

e
tw
CV
b
1

0,5

0

B-1
B-2

B-3
B-4
CVw-Ucv

within-unit

CVw+Ucv

Figure 2. Graphical representation of homogeneity of sediment RM

6

Pb

4,5

4

3,5

3

t
2,5

ni
CV

-
u
U
2

e
e
n
ą B
t
w
1,5

CV

be
1

0,5

0

B-1
B-2

B-3
B-4
CVw-Ucv
within- unit
CVw+Ucv

Figure 3. Graphical representation of homogeneity of sediment RM

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F.
PROGRESS OF WORK

The Project goes forward nearly according to the work plan (Annex 2: paragraph E).
The second set of the water RMs for nutrients (ammonium-N, nitrate-N, phosphate-
P, total P) and heavy metals (cadmium, copper, chromium, lead, mercury, nickel,
aluminum arsenic) were prepared in September.

To prepare the second set of sediment RMs bulk sediment was collected in the
Ráckeve-Soroksár Danube Branch. The sediment was processed according to the
flow chart of sediment RM preparation (cleaning, drying, grinding, sieving and
homogenization). After homogenization the sediment was bottled and between- and
within-units homogeneity tests were carried out. As the evaluated results of
homogeneity tests showed homogeneity, the sediment RMs will be delivered
together with water RMs.

The reference material samples have been 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, 20/10/2003

Dr. Jolan Schneider

team leader

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