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Accred Qual Assur (2003) 8:21–24
DOI 10.1007/s00769-002-0549-9
© Springer-Verlag 2003
G. Anand Kumar
H.S. Sahoo
S.K. Satpathy
G. Swarnabala
Received: 3 April 2002
Accepted: 4 September 2002
G. Anand Kumar · H.S. Sahoo
S.K. Satpathy · G. Swarnabala (✉)
VIMTA Labs Ltd,
Hyderabad – 500 051, India
e-mail: [email protected]
Tel.: +91-40-7264141
Fax: +91-40-7263657
Interlaboratory quality audit program
for potable water – assessment of method
validation done on inductively coupled plasma
atomic emission spectrometer (ICP-AES)
Abstract In an effort to assess the
method validation done using ICPAES in our laboratory for potable
water, an Environmental Laboratory
Approval Program organized by
New York State Department of
Health, Wadsworth Center providing
the reference material has been undertaken for 14 trace elements and
seven other chemical constituents.
The certified means for the reference
material and the results obtained in
our laboratory are compared. The
comparisons helped us assess the
quality of our work. All the data
from the inductively coupled plasma
atomic emission spectrometer (ICPAES) fall into the ranges specified.
Introduction
Certain major, minor and trace elements tend to accumulate
causing toxicity in potable water. The quantitative measurement of these elements helps in diagnosis and treatment of
a range of disorders. Proficiency testing materials, when
studied by an analytical method, help in method improvement and validation and lead to better results, increasing
the confidence of the analysts in reporting the data to the
customers. Due to the complex nature of the material in
question, its variable compositions of the elements, the
need to validate the method of analysis is mandatory on the
part of the analyst. So the analysis can be authenticated
with the help of studies on proficiency testing materials,
thus increasing the confidence level for values reported.
In an effort to meet this demand, we have procured
proficiency testing material of potable water from the
Environmental Laboratory Approval Program being conducted by New York State Department of Health, Wads-
These data are intended to depict the
quality of chemical analysis being
conducted in our laboratory and to
increase the level of confidence of
our clientele in accepting our test reports. It should be further noted that
while the technique may not be new,
the model is new and the simultaneous detection of elements required
validation for those of our clientele
who are only familiar with sequential AAS and AES.
Keywords ICP-AES ·
Environmental Laboratory Approval
Program – New York Department
of Health, Wadsworth Center ·
Trace elements · Potable water
worth Center. The chief of this institute has initiated the
collaborative analysis program for analyzing the reference material for subsequent certification, with respect
to major, minor and trace element concentrations. The
whole study is used to analyze the waters of all kinds
[1–6] such as drinking water – IS: 10500/1991, packaged
natural drinking water – IS: 13428/1998, packaged
drinking water – IS: 14543/1998, and water for quality
tolerances for processed food industry – IS: 4251/1967.
The characterization of these materials includes different
sample preparation methods and analytical techniques
being used by all the laboratories worldwide. Our laboratory is participating from India with NABL accreditation. We have determined 14 constituents by ICP-AES
and seven by classical methods for the present study. The
aim of this paper is to highlight the potential of ICP-AES
in the generation of accurate analytical data for several
trace elements in potable water samples and increase the
confidence level of the customers who send us these
Interlaboratory quality audit program for potable water – assessment of method validation done on ICP-AES
Table 1 Validation data for potable water reference materials
– Environmental Laboratory
Approval Program analyzed for
the following elements by ICPAES
Sat, Satisfactory; Unsat, unsatisfactory.
Table 2 Validation data for potable water reference materials
– Environmental Laboratory
Approval Program analyzed for
the following chemical parameters on ICP-AES
TDS, Total dissolved salts; Sat,
satisfactory.
113
Parameter
(µg/L)
Result
APHA method
Study mean
Accept. limits
Score
Ag
As
Ba
Be
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Sb
Se
Zn
87.0
57.3
777
8.74
10.0
99.0
300
541
70.5
219
31
45.95
130.0
479
3120
3120
3120
3120
3120
3120
3120
3120
3120
3120
3120
3120
3120
3120
82.2
51.1
817.0
7.42
8.59
88.4
328.0
523.0
74.20
240.0
33.80
39.30
48.50
479.0
73.8–90.5
44.8–57.3
696.0–942.0
6.6–8.94
6.9–10.4
75.1–102.0
293.0–359.0
478.0–568.0
68.50–79.80
201.0–273.0
23.60–43.80
27.40–51.0
37.80–56.60
439.0–518.0
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Sat
Unsat
Sat
Parameter
(mg/L)
Result
APHA method
Study mean
Accept. limits
Score
Na
Nitrite
Chloride
Fluoride
NO3 as N
Sulfate
TDS
12.6
1.52
62.9
5.1
7.94
44.4
228
3500
4500
4500
4500
4500
4500
2540
12.50
1.51
59.10
5.46
7.91
48.4
244.0
11.30–13.70
1.28–1.74
55.10–63.10
4.94–6.04
7.19–8.79
43.4–53.4
162.0–326.0
Sat
Sat
Sat
Sat
Sat
Sat
Sat
samples. Since the programme had all the constituents
determined, the data for the classical methods is also
presented for completeness.
Experimental
follows: the ampoule temperature is adjusted to 20 °C prior to
analysis. Approximately 900 mL of reagent water is added to a
1-L volumetric flask. Reagent grade nitric acid (5.0 mL) is added
to the volumetric flask. The flask is swirled to mix. Ampoule ID
no. is recorded. The ampoule is broken and 10 mL of the sample is
transferred to the flask using a pipette. Then the flask is filled to
mark with Milli-Q water and thoroughly shaken. The 14 elements
are measured and the data are tabulated in Table 1.
Instrumentation
The ICP-AES used is a Varian-Radial Vista (Varian Instruments,
Australia) associated with a microcomputer, software operating
parameters, etc. as given in reference [7].
Materials
The water sample is obtained from the Environmental Laboratory
Approval Program. We have used ICP-AES multi-element Reference Standard supplied by E. Merck with Lot. No: 0C030033 for
standard calibration. These standards have certified data obtained
from NIST as third-generation traceability, assuring reasonable accuracy in the estimations (Certificate of Analysis, Certipur – Reference Material; 11355 ICP multielement standad IV made from
NIST standards reference materials, Lot No. 0C030033. Dr. Harald
Untenecker, Central Analytical Laboratory, Merck). An echellogram showing all the elements is attached.
Standard preparation
Aqueous standards are prepared from 1000 ppm E. Merck standard reference material supplied with NIST traceability. The standards are made up using 18 MΩ Milli-Q water with 1% v/v high
quality nitric acid 65%-Fluka Chemie.
The following calibration standards for a five-point calibration
curve have been made keeping in view the need to cover the range
of 10, 2, 1, 0.1, and 0.01-ppm concentrations:
Std. 1: Ag, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn.
Std. 2: Be.
Std. 3: As, Se, and Sb.
Rinse and calibration blank solutions were prepared from 18 MΩ
Milli-Q water with 5% HNO3 as per the instructions provided by
the approval program.
Sample procedure
Methods used for chemical analysis
To minimize the possibility of change in concentration, the ampoule is opened just before the analysis. The sample is prepared as
All the chemical analysis procedures are adopted from APHA
methods [8]. These are specified in Table 2 along with the analyte.
114
G.A. Kumar et al.
Fig. 1 Echellogram showing all the 23 elements in the standard
along with the wavelengths. The wavelengths for all the 23 elements are:
Ag
Bi
Co
Fe
Li
Ni
Zn
328.068
223.061
238.892
238.204
670.783
231.604
213.857
Al
Ca
Cr
Ga
Mg
Pb
396.152
317.933
267.716
294.363
279.553
220.353
B
Cd
Cr
In
Mn
Sr
249.772
214.439
357.868
230.606
257.610
407.771
Ba
Cd
Cu
K
Na
Tl
455.403
226.502
327.395
766.491
589.592
190.794
Results and discussion
ICP-AES offers rapid, multi-element determinations.
Its sensitivity is lower than that of either ICP-MS or
AA-GTA, but it can handle higher levels of total dissolved solids than ICP-MS and is much faster than
AA-GTA. The results obtained are in comparison with
all the equipment used by about 100 laboratories that
are participating in the Environmental Laboratory
Approval Program. The quality of the performance relating to equipment as well as the analyst in such international collaborative programs implies the use of certified reference materials for calibration and control
samples to ensure a certain level of traceability of the
measurements and finally the degree of assurance of reliability.
The use of reference standards for calibration minimized several analytical errors. However, our working
standards also gave results very similar to the reference
standards. The results obtained for the study in question
are summarized in Tables 1 and 2. The organizers collected the assigned value for individual elements and
provided us the mean or range of the submitted data for
over 100 laboratories using highly reliable statistical
procedures. The table gives the result, mean, method,
range and reliability of the parameter in question. A
careful observation of these data provides the precision
with which the experimental work has been conducted
in the present study. Figure 1 shows the Echellogram of
23 elements in the reference standard along with the
wavelengths.
A typical example of the requirements for IS:
14543/1998 (4) are Ba, 1.0; Cu, 0.05; Fe, 0.1; Mn, 0.1;
Zn, 5.0; Ag, 0.01; Al, 0.03; Se, 0.01; Ca, 75.0; Mg, 30.0;
Na, 200.0; Hg, 0.001; Cd, 0.01; As, 0.05; Pb, 0.01; Cr,
0.05; Ni, 0.02; Sb, 0.005; B, 5.0 µg/L separately. Routinely all the samples are checked for the requirements before
reporting. VISTA software has a built in program with
USEPA requirements [9, 10] for the aspirating of standard reference solution; instrument check standard solution; interference check standard solution and QC standard solution for the laboratory QC control. Continuing
calibration verification is done every ten analytical samples run on Auto Sampler, a facility that is not available
when using the manual runs of the samples. We have
adopted the Varian instruments instructions to calibrate
the equipment to find the instrument detection limits and
the method detection limits. The former values were obtained by aspirating on consecutive three days for all the
standards and the latter values were obtained for consecutive seven runs on the same day for all the standards.
These are also reconfirmed using “CHEMSW” software
program available for the calculation of detection limits.
The original “K-style” glass concentric nebulizer is used
to obtain the raw-data with best possible sensitivity. For
our method validation, we have adopted a seven-point
calibration range for almost all the elements ranging between 10–0.01 mg/L. The accuracy in the recovery of the
standards ranged from 95%–105% with a precision at
1 µg/L as ±12%. Matrix spiking results in the recoveries
range between 75%–%125% as per USEPA/APHA. Vapour-generation accessory (VGA 77), is used for
Hg measurements. Three standards 0.001; 0.005, and
0.01 µg/L are used for linearity or calibration. Stannous
chloride (25%) and HCl (Fluka) are being used for the reduction in the cold-vapour generation.
Conclusions
It may be concluded that the observed data for 13 elements (except for the selenium) and the seven other constituents specified for potable water are in concurrence
with all the laboratories whose data is submitted to Environmental Laboratory Program, New York State Department of Health. [After the constructive criticism from the
reviewers, the unsatisfactory results for the Ag, Cd, Sb
and Se elements were repeated. Cd values have improved
by changing the wavelength from 217 to 226 nm. For antimony we have used a new standard and the value improved. For silver the number of washings before aspiration was tripled and the result improved. The selenium
range is still not very satisfactory, but our efforts to improve upon this are in progress and we are positive about
it.] The method detection limits, RSD’s, and the instru-
Interlaboratory quality audit program for potable water – assessment of method validation done on ICP-AES
mental detection limits obtained for our instrument and
also the method validation done using this data confirms
the validity of the method being adopted. Thus the use of
instruments simultaneously for routine analysis imparts a
high degree of excellence to the data being reported.
115
Acknowledgements G.S. is grateful to Dr. S. P. Vasireddi, Founder, Chairman and Managing Director, VIMTA Labs Ltd for giving permission to publish this work. We would like to thank the
Environmental Laboratory Approval Program organized by New
York State Department of Health, Wadsworth Center for permitting us to publish these data.
References
1. APHA (2000) Standard methods for
the examination of water and waste
water analysis, 20th edn. APHA.
2. (1991) IS 10500 – Drinking water
3. (1998) IS 13428 – Packaged natural
mineral water
4. (1998) IS 14543 – Packaged drinking
water (other than the packaged natural
mineral water)
5. (1992) IS 1070 – Reagent-grade water
6. (1967) IS 4251 – Quality tolerances
from water for processed food industry
7. Satyanarayana KVS, Ravi Kumar Ch,
Swarnabala G (2002) Atomic Spectrosc (submitted)
8. APHA (2000). Methods – 3120, 3500,
4500 and 2540. In: Standard methods
for the examination of water and waste
water analysis, 20th edn. APHA
9. USEPA (1994) Determination of metal
and trace elements in water and wastes
by inductively coupled plasma–atomic
emission Sspectrometry – Method
200.7, USEPA, Environmental Monitoring and Support Laboratory, Cincinnati, OH, May 1994. USEPA Washington, DC
10. Bridger S, Knowles M (2000) ICPAES at work – ICP-29. A complete
method for environmental samples by
simultaneous axially viewed ICP-AES
following USEPA guidelines. Varian
Australia Pty Ltd.
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