Fuels & Lubricants Magazine

epeatability (r): 6 measurements on
each sample, at repeatable conditions
(same sample, same apparatus,
same operator, same laboratory,
short term period); b) in order to
evaluate laboratory reproducibility
(R): sample “DS” was measured,
at reproducible conditions (same
sample, same apparatus, different
operator, same laboratory, long term
period – different test conditions);
c) in order to evaluate accuracy (and
reproducibility (R)): measurement
of CRMs (supplier: PAC), measurement
of samples from interlaboratory
comparisons (RR) with a known
CN value according to the CFR
method (EN ISO 5165 / ASTM D
613), “on-line” participation in a RR
for the determination of DCN.
Different statistical methods and
tests [10] were applied for the evaluation
of results [11].
Results of Validation
Tables 1 – 3 show the results for the
evaluation of repeatability (r).
Table 1: Samples of diesel fuel without FAME
DCN
No. of
measurement
M1
M2
M3
M4
M5
M6
(2704/14) (1996/14) (1959/14) (1810/14) (3040/14) (2429/14)
1 53.79 50.55 51.56 52.06 51.14 53.52
2 53.30 50.34 51.86 51.83 51.31 54.06
3 53.11 50.40 51.97 52.06 50.97 53.66
4 53.31 50.12 51.49 51.87 51.08 53.66
5 53.55 50.37 51.36 52.21 50.96 53.48
6 53.43 50.29 51.60 52.11 51.09 53.85
x − 53.42 50.35 51.64 52.02 51.09 53.71
s 0.24 0.14 0.23 0.15 0.13 0.22
t tab (0.05, 5) 2.571 2.571 2.571 2.571 2.571 2.571
s · t tab 0.60 0.36 0.59 0.37 0.33 0.56
s ∙ t tab < r ✓ ✓ ✓ ✓ ✓ ✓
r (ASTM D7668) 0.64 0.58 0.61 0.61 0.60 0.65
Fuels&Lubricants No. 2 JUNE 2018 25