8 Hour Stability

ELEMENT WAVELENGTH MDL MAXIMUM
(nm) (µg/L) LINEAR RANGE (mg/L)
Ag 328.289 0.5 10
Al 308.215 11.4 1000
As 189.042 2.1 50
B 208.959 2.2 10
Ba 455.403 0.7 50
Be 313.107 0.1 10
Ca 317.933 2.6 1000
Cd 214.438 0.1 20
Co 228.616 0.2 100
Cr 205.552 0.3 50
Cu 324.754 0.5 50
Fe 271.441 52 1000
K 766.491 30 500
Li 670.784 1.0 50
Mg 279.079 40 1000
Mn 257.610 0.1 20
Mo 202.030 0.5 20
Na 589.592 10 200
Ni 231.604 0.4 50
P 178.287 3.2 20
Pb 220.353 2.1 50
Sb 206.833 2.4 50
Se 196.090 2.8 50
Si 251.612 7.2 50
Sn 189.989 1.8 50
Ti 334.941 0.2 20
Tl 190.864 1.6 100
V 292.402 0.6 50
Zn 206.200 0.2 20
Table 4. Wavelengths, Method Detection Limits and Maximum Linear Range.
Linear Concentration Range
The upper limit of the linear dynamic range must be
established for each analyte and instrument configuration.
The upper range limit should result in an observed signal
no more than 10% below the level extrapolated from the
normal calibration curve. This check should be carried
out whenever instrument changes occur and at six
monthly intervals as a minimum.
This evaluation is very important when using interelement
correction since, if the linear range is exceeded for
the interfering element measurement, the calculated
correction factor will be incorrect and the analytical result
will be in error.
For some elements the plasma is viewed in radial
mode using a weaker line to improve the linear range.
This results in less chance of some samples being overrange
so that more accurate data is achieved. Table 4
shows the maximum linear range figures in mg/L.
Background Correction Points
Method 6010B requires that off-peak background
correction is used for trace element determinations. The
background was measured simultaneously by monitoring
the signal in pixels adjacent to the analyte peak position.
The ideal position of background correction points was
determined by examining spectra in subarrays for a
calibration blank, calibration standard and spiked matrix
solution. The points selected for analysis should take into
account any spectral interferences that may be present.
The documented data for all decisions related to
wavelength choice (where different to the EPArecommended
lines), background correction points,
interelement corrections and MDL’s must be kept on file
and be available for review by the data user or auditor.
4. Results and Discussion
4.1 Initial (ICV) and Continuing (CCV) Calibration
Verification
Method 6010B requires that a very strict quality control
procedure is followed to ensure validity of sample data.
Quality control checks are carried out following
instrument calibration, during sample analysis and at the
end of the analytical run. For the sample data to be
acceptable all checks must meet the required criteria.
The instrument was set up using the parameters shown in
Table 1 and allowed to stabilise for 30 minutes prior to
calibration.
Immediately after calibration, an Initial Calibration
Verification (ICV) solution, calibration blank and
Continuing Calibration Verification (CCV) solution were
run. The calibration blank value must be within 3 times
the Method Detection Limit (MDL) while the calibration
verification solution results must be within 10% of their
calibrated value. In addition, the standard deviation for a
minimum of 2 resamples must be less than 5% for the
data to be acceptable. Typical results are shown in Table 5
below.
Analysis of the CCV solution and calibration blank
was then repeated every 10 samples to ensure that the
instrument remained in calibration.
4.2 Interference Check Solutions
Prior to the start of each sample analysis, interference
check solutions were run to verify that the inter-element
correction factors and background correction points were
still valid.
Interference Check Sample A (ICSA) was prepared
containing 500mg/L Al, Ca, Mg and 200mg/L Fe.
Interference Check Solution AB was then prepared by
spiking this solution at concentrations of 0.05 to 1mg/L
for the analyte elements. The values measured for ICSAB
must be within 20% of the true value for the data to be
acceptable. Data is shown in Table 6 below.