Page 24 - Shimadzu Journal vol.8 Issue2

Hydrocarbon Processing Industry

Table 2. Method specifications and actual operating parameters for analysis.

Specification ASTM D4294 Requirement ISO 8754 Requirement Actual Measurement Parameters

Temperature Not Specified Not Specified Room temperature (25°C)
Normal Ambient Condition
Humidity Not Specified Not Specified
(~50% RH)
Atmospheric Pressure Not Specified Not Specified Normal Ambient Condition

“whenever possible the instrument is
Warm-up Time “Continuously Switched On” ≥15 minutes
left on…”
Polyester, Polypropylene, Polycarbonate, “Normally 6 μm polyester,
Sample Film 5 μm Polypropylene
Polyimide films, “usually <10 μm” polypropylene, or polycarbonate”
Ambient Air and Helium
Atmosphere Air and Helium Not Specified
(99.999% purity)
100 to 300 seconds, 100 to 200 seconds,
Analysis Time Not Specified
concentration dependent concentration dependent

Several factors were assessed for method compliance, including re- For ASTM D4294, repeatability was assessed by analyzing one
peatability (r), reproducibility (R), blank measurement, and a lower sample 20 times on the same instrument and performed by the
limit of detection (LLD). same operator. Reproducibility was assessed by analyzing one
sample 20 times on one instrument in one laboratory, and then
For both test methods, calibration curves were generated using oil- the same sample was analyzed a further 20 times on a different
based standards of known concentration. An example concentra- instrument (of the same model) and in a different laboratory by a
tion curve is provided in Fig. 5 different operator. The result is the magnitude of the range of re-
sults for the 20 replicated about the true value and the results were
then compared to the calculated, statistical limit as per the method
specifications, calculated based on equations 1 and 2. The blank
was assessed by analyzing a blank sample 20 times. The blank
measurement must be below 2 ppm. When analyte concentrations
were ≥500 ppm, analysis was conducted with the analytical cham-
ber purged with He and under standard atmospheric conditions.
At concentrations <500 ppm, analysis was conducted only with the
chamber purged with He.

Equation 1: Repeatability (r), in ppm, according to ASTM D4294 for base oil
(a) and diesel fuel (b). The target concentration is represented as S.

Figure 5. Example calibration curve of known samples Equation 2: Reproducibility (R), in ppm, according to ASTM D4294 for
using a helium-purged sample chamber. base oil (a) and diesel fuel (b). The target concentration is represented as S.

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