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1
Supplementary Comparison COOMET.QM-S4
“С2-С5 components in mixtures of liquified hydrocarbons”
Final report L.A. Konopelko1, Y.A. Kustikov1, A.V. Kolobova1, A. V. Meshkov1, O V Efremova1, M. Rozh-
nov2, D. Melnyk2, S. Kisel2, O. Levbarg2, S. Shpilnyi2, S. Yakubov2, A.M. Mironchik3, M.V.
Mokhnach3, V.N. Ananyin3.
1D.I.Mendeleyev Institute for Metrology, 19, Moskovsky pr., St-Petersburg, 190005, Russia.
2All-Ukrainian State Research and Production Center of Standardization, Metrology, Certifi-
cation and Consumers Rights Protection, 4, Metrologicheskaya str., Kiev, 03143, Ukraine. 3Belorussian State Institute for Metrology, Section for physico-chemical and optical measure-
ments, sector for standards and gas mixtures, 8, Serova st., Minsk, Belarus.
Field Amount of substance
Subject Comparison of the composition of liquefied petroleum gas (С2-С5 components)
Table of contents Field ............................................................................................................................ 1
Subject ........................................................................................................................ 1
Table of contents ........................................................................................................ 1
1 Introduction ............................................................................................................. 2
2 Design and organisation of comparison .................................................................. 2
2.1 Participants ……...................................................................................................2
2.2 Measurement standards………………………………………………………….2
2.3 The schedule……………………………………………………………………..3
2.4 Measurement methods and calibration procedures………………………..…….3
3 Results ..................................................................................................................... 4
4 Supported CMC claims ........................................................................................... 8
5 Discussion and conclusions ..................................................................................... 8
6 References ............................................................................................................... 8
Annex A – Purity data……………………………………………………………….9
Annex B - Calculation of reference values accounting for possible instability ……11
Annex C – Measurement reports from participants
Measurement report from BelGIM .................................................................. 15
Measurement report from Ukrmetrteststandard .............................................. 21
Measurement report from VNIIM ................................................................... 26
2
1 Introduction
The objective of the present supplementary comparison is assessment of the analytical capabilities of
laboratories for measuring the composition of a Liquid Petroleum Gas (LPG) mixtures when sampled in
the liquid phase from Constant Pressure Cylinders (CPCs).
This comparison was organized by VNIIM within Technical Committee 1.8 “Physical Chemistry”
COOMET.
In 2015 VNIIM participated in the similar CCQM comparison - CCQM-K119 «Liquified Petroleum
Gas»[1] and showed the equivalent results.
2 Design and organization of comparison
2.1 Participants
Table 1 lists the participants of the comparison.
Table 1: List of participants
Acronym Country Institute
VNIIM RU D.I.Mendeleyev Institute for Metrology, St-Petersburg, Rus-sia
Ukrmetrt-
eststandart
UA All-Ukrainian State Research and Production Center of Standardization, Metrology, Certification and Consumers Rights Protection, Kiev, Ukraine
BelGIM BY Belorussian State Institute for Metrology, Minsk, Belarus
2.2 Measurement standards
A suite of mixtures (4 travelling standards) has been prepared at VNIIM for this comparison. Table
2 shows the nominal composition of the mixtures (expressed as amount of substance fractions).
Table 2: Nominal composition of the mixtures
Component Amount fraction,
cmol/mol
Ethane 2
Propene 9
n-Butane 10
1-Butene 3
i-Butane 4
i-Pentane 1
Propane 71
The calculation procedures of ISO 6142-1[2] and ISO 19229[3] were used to calculate the amount-
of-substance fractions and associated standard uncertainties. These mixtures were prepared in constant
pressure cylinders (CPC), V=1 dm3, produced by Monitoring LTD (Russia). Components were added
to CPC in order of increasing boiling point. After filling the CPCs were pressurized with He to 2.0
MPa.
Purity analysis of the parent substances was carried out by GC- FID, TCD. Results of purity analysis
are shown in the Annex A.
The travelling standards were verified by establishing consistency within the suite and also were
compared to VNIIM Primary Reference Standard (PSM) - a liquid mixture with the same nominal
composition also prepared in a CPC (V=2 dm3).
From 2 to 5 measurements (GC-FID) were carried out before shipping depending on the shipping
date of the travelling standard. Measurements were performed also after return of the travelling stand-
ards to assess stability of mixtures.
3
Stability was estimated by measurements against VNIIM PSM and also by application of method of
internal normalization.
2.3 Measurement methods and calibration procedures
Measurement and calibration methods are summarized in the table 3.
Table 3 Measurement and calibration methods
Laboratory Measurement
method
Calibration
method
Total number of measure-
ments
Ukrmetrteststandart GC-FID linear model ISO
6143:2001
3 primary standard
gas mixtures, pre-
pared in house
4 measurements
4 sub-measurements
BelGIM GC-FID ISO 7941:1988
One point calibra-
tion
2 own standards of
LPG
3 measurements
3 sub-measurements
VNIIM GC-FID GOST R 54484-
2011
One point calibra-
tion
1 own standard
3 measurements
4-6 sub-measurements
2.4 The schedule
The schedule for the comparison is shown in table 4.
Table 4: The schedule for the comparison
Date Event
January 2017 Final protocol published
February - March 2017
Preparation and verification of mixtures
April 2017 Distribution of cylinders
May-June 2017 Analysis of the mixtures by participants
July - August 2017 Participants reports are sent to coordinator and return of the cylinders
September 2017 Reanalysis of the mixtures at VNIIM
October 2017 Resending the cylinder to Ukrmetrteststandart due to technical problems
January - May 2018 Analysis of the mixture in Ukrmetrteststandart
June 2018 Ukrmetrteststandart sent the report to VNIIM
August 2018 Return of the Ukrmetrteststandart cylinder to VNIIM
September 2018 Reanalysis of the Ukrmetrteststandart mixture at VNIIM
Осtober 2018 Draft A report available
January 2019 Draft B report available
Note – The initial schedule of the comparison has been moved significantly due to repeated ship-
ping of the travelling standard to Ukraine and delivery of travelling standard from RF to Ukraine
through a third country.
4
3 Results
The degree of equivalence (Dij) for each participating laboratory and each component is defined in
accordance with the equation:
refij, jiji xx=D -
(1)
Where, xij is the reported amount fraction of component j from laboratory i and xij,ref is the
comparison reference value of component j from the mixture delivered to laboratory i. The
combined standard uncertainty of Dij thus can be expressed as:
)x(u)x(u)x(u)x(u)x(u)D(u ver,ij
2
prep,ij
2
ij
2
ref,ij
2
ij
2
ij
2 ++=+== (2)
where u(xij) is the standard uncertainty of the reported by laboratory amount fraction of component j,
u(xij,prep) is the standard uncertainty in the amount of substance fraction from preparation and u(xij,ver)
is the uncertainty from verification.
The expanded uncertainty )U(D jiof Dij at a 95 % confidence level is calculated using the following
equation:
2
verij,
2
prepij,
2
ijij u+u+uk=)U(D (3)
where k is the coverage factor, (k=2).
In the comparison the stability of each component was monitored (before and after distribution) and
for one of the travelling standards (for Ukrmetrteststandart travelling standard (cylinder №1310), for
which the time period before and after distribution measurements was about a year) some trend was
registered for several components. This trend was tested for significance, and was found to be insig-
nificant as the slope (b) of time dependence of concentration satisfied to inequality (4)
b t0,95,k-2s(b) (4)
where s(b) is the standard deviation of b, t0,95,n-2 - Student coefficient for f=n-2 degrees of freedom and
P=0.95.
For other travelling standards trend was not observed within the accuracy of measurements.
Thus gravimetric values were adopted as reference values for all the comparison travelling standards.
Another approach for reference values which accounts for some instability is shown in the Annex B,
which also contains results of calculations for inequality (4).
5
Lab/
Cylinder № Component
xij,ref
(xij,prep),
cmol/mol
uij,ref,
cmol/mol
xij,
cmol/mol
u(xij),
cmol/mol
Dij,
cmol/mol
U(Dij),
cmol/mol Dij rel,%
U(Dij)
rel,%
BelGIM/
1066
Ethane 2,0030 0,0078 1,99 0,02 -0,013 0,043 -0,65 2,14
Propene 8,8186 0,0121 8,82 0,03 0,001 0,065 0,02 0,73
n-Butane 10,0732 0,0228 10,10 0,03 0,027 0,075 0,27 0,75
1-Butene 3,0054 0,0062 3,01 0,02 0,005 0,032 0,15 1,08
i-Butane 4,0606 0,0132 4,07 0,02 0,009 0,048 0,23 1,18
i-Pentane 0,9951 0,0048 1,00 0,01 0,002 0,022 0,19 2,23
Propane 71,031 0,053 71,0 0,15 -0,03 0,32 -0,04 0,45
Ukrmetrt-
eststandart/
1310
Ethane 2,0144 0,0067 2,026 0,018 0,012 0,038 0,58 1,91
Propene 9,4211 0,0098 9,444 0,031 0,023 0,065 0,24 0,69
n-Butane 9,9599 0,0288 9,953 0,045 -0,007 0,107 -0,07 1,07
1-Butene 3,0694 0,0078 3,047 0,014 -0,022 0,032 -0,73 1,05
i-Butane 4,0532 0,0087 4,055 0,018 0,002 0,039 0,04 0,97
i-Pentane 0,9873 0,0045 0,986 0,010 -0,001 0,022 -0,13 2,22
Propane 70,482 0,033 70,49 0,25 0,01 0,50 0,01 0,72
VNIIM/
1306
Ethane 2,0173 0,0055 2,016 0,009 -0,001 0,021 -0,06 1,02
Propene 8,8798 0,0094 8,867 0,014 -0,013 0,033 -0,14 0,37
n-Butane 10,0778 0,0244 10,13 0,025 0,052 0,070 0,52 0,69
1-Butene 2,9782 0,0046 2,983 0,006 0,005 0,015 0,16 0,50
i-Butane 4,0218 0,0078 4,038 0,008 0,016 0,023 0,40 0,56
i-Pentane 0,9985 0,0037 0,996 0,005 -0,003 0,012 -0,25 1,19
Propane 71,014 0,033 70,97 0,072 -0,044 0,158 -0,06 0,22
Table 5 Results of COOMET.QM-S4
The results are presented graphically in the figures 1-7.
6
Figure 1. Results for Ethane
Figure 2. Results for Propene
Figure 3. Results for n-Butane
-5-4,5
-4-3,5
-3-2,5
-2-1,5
-1-0,5
00,5
11,5
22,5
3
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce v
alu
e, %
Ethane
-2
-1,6
-1,2
-0,8
-0,4
0
0,4
0,8
1,2
1,6
2
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve d
evia
tion
fro
m
refe
ren
ce v
alu
e, %
Propene
-2
-1,6
-1,2
-0,8
-0,4
0
0,4
0,8
1,2
1,6
2
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce
va
lue,
%
n-Butane
7
Figure 4. Results for 1-Butеne
Figure 5. Results for i-Butane
Figure 6. Results for i-Pentane
-2
-1,6
-1,2
-0,8
-0,4
0
0,4
0,8
1,2
1,6
2
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce v
alu
e, %
1-Butеne
-2
-1,6
-1,2
-0,8
-0,4
0
0,4
0,8
1,2
1,6
2
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce v
alu
e, %
i-Butane
-5
-4
-3
-2
-1
0
1
2
3
4
5
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce v
alu
e, %
i-Pentane
8
Figure 7. Results for Propane
4 Supported CMC claims
The results of this supplementary comparison can be used to support CMC claims for ethane, pro-
pane, propene, i-butane, n-butane, 1-butene and i-pentane in the liquid phase in CPCs with a matrix
of propane, n- butane or i-butane.
The support of CMC claims is described in more detail in the GAWG strategy for comparisons and
CMC claims.[4]
5 Conclusions
The results in this supplementary comparison demonstrate good comparability between laboratories
within the stated uncertainties.
References
[1] M.L. Downey, P.J. Brewer, R.J.C. Brown, A.S. Brown, Milton MJT, A.M.H. van der
Veen, E.T. Zalewska and others, International comparison CCQM-K119 “Liquefied petroleum
gas”, Final report, KCDB BIPM (2017).
[2] ISO 6142-1:2015, Gas analysis -- Preparation of calibration gas mixtures -- Part 1: Grav-
imetric method for Class I mixtures, (2015).
[3] ISO 19229:2015, Gas analysis -- Purity analysis and the treatment of purity data, (2015).
[4] Brewer PJ, van der Veen AMH, GAWG strategy for comparisons and CMC claims,
CCQM Gas Analysis Working Group, (2016).
Date: 03/10/2018
-2
-1,6
-1,2
-0,8
-0,4
0
0,4
0,8
1,2
1,6
2
VNIIM BelGIM Ukrmetrteststandart
Di,
rel
ati
ve
dev
iati
on
fro
m
refe
ren
ce v
alu
e, %
Propane
9
Annex A
Purity data
Table A1 - Purity data for ethane
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
ethane 99.99988 -
n-butane 0.00012 0.00003
Table A2 - Purity data for propene
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
propene 99.97184 —
propane 0.0209 0.0025
nitrogen 0.0070 0.0021
i-butane 0.00026 0.00008
Table A3 - Purity data for n-butane
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
n-butane 99.97095 —
neo-pentane 0.0244 0.0020
i-butane 0.0031 0.0005
trans-2-butene 0.00088 0.00026
cis-2-butene 0.00037 0.00011
propane 0.00030 0.00009
Table A4 - Purity data for 1-butene
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
1-butene 99.4508 —
n-butane 0.243 0.017
i-butene (2-methylpro-
pene) 0.124 0.025
i-butane 0.093 0.007
nitrogen 0.059 0.018
trans-2-butene 0.0103 0.0021
oxygen 0.010 0.003
propene 0.0058 0.0007
propane 0.0017 0.0005
1,3- butadiene 0.0014 0.0004
cis-2-butene 0.0010 0.0003
10
Table A5 - Purity data for i-butane
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
i-butane 99.97725 —
n-butane 0.012 0.003
propane 0.0102 0.0012
i-butene 0.00055 0.00017
Table A6- Purity data for i-pentane
Component Amount fraction
cmol/mol
Expanded uncertainty
(k=3)
cmol/mol
i-pentane 99.6822 -
n-pentane 0.2546 0.0764
neo-pentane 0.043 0.013
toluene 0.0072 0.0022
n-heptane 0.0030 0.0009
n-hexane 0.0027 0.0008
1-hexene 0.0016 0.0005
2-methyl-1-butene 0.0016 0.0005
cyclohexane 0.00115 0.00004
1-pentene 0.00057 0.00017
n-butane 0.00051 0.00015
n-nonane 0.00047 0.00014
cyclopentane 0.00029 0.00009
3-methyl-1-butene 0.00020 0.00006
2,2-dimethylbutane 0.00018 0.00005
2-methyl-2-butene 0.00014 0.00004
benzene 0.00012 0.00004
n-octane 0.00010 0.00003
trans-2-pentene 0.00010 0.00003
2-methylpentane 0.00009 0.00003
3-methylpentane 0.000077 0.000023
Table A7 - Purity data for propane
Component Amount fraction
cmol/mol
Expanded uncertainty (k=3)
cmol/mol
propane 99.9957 —
n-butane 0.0029 0.0004
propene 0.00076 0.00019
ethane 0.00035 0.00011
i-butane 0.00025 0.00007
11
Annex B
Calculation of reference values accounting for possible instability
The approach for calculation of reference values considering some instability was applied only for
cylinder №1310 (Ukrmetrteststandart travelling standard) for which the time period before and after
distribution measurements was about a year. The corrections were determined from linear regression
of the time dependance of the results of measurements.
In this case the reference values xij,ref have been calculated according to the equation:
stab,ijprep,ijrefij, xxx += (1B)
where xij,prep is the amount of substance fraction from preparation, xij,stab is a drift correction for j
component determined from its regression at the time when it was analysed by the participant
The appropriate combined standard uncertainty of Dij - u (Dij) was calculated in accordance with (2B)
)x(u)x(u)x(u)x(u)D(u stab,ij
2
ver,ij
2
prep,ij
2
ij
2
ij
2 +++== (2B)
where u(xij,stab) is the standard uncertainty of the drift correction.
Table 1B provides the reference values and results from the comparison in accordance with this ap-
proach.
12
Lab/
Cylinder № Component
xij,prep, cmol/mol
xij,stab xij,ref uij,ref,
cmol/mol
xij,
cmol/mol
u(xij),
cmol/mol
Dij,
cmol/mol
U(Dij),
cmol/mol Dij rel,% U(Dij)rel,%
BelGIM/
1066
Ethane 2,0030 - 2,0030 0,0078 1,99 0,02 -0,013 0,043 -0,65 2,14
Propene 8,8186 - 8,8186 0,0121 8,82 0,03 0,001 0,065 0,02 0,73
n-Butane 10,0732 - 10,0732 0,0228 10,10 0,03 0,027 0,075 0,27 0,75
1-Butene 3,0054 - 3,0054 0,0062 3,01 0,02 0,005 0,032 0,15 1,08
i-Butane 4,0606 - 4,0606 0,0132 4,07 0,02 0,009 0,048 0,23 1,18
i-Pentane 0,9951 - 0,9951 0,0048 1,00 0,01 0,002 0,022 0,19 2,23
Propane 71,031 - 71,031 0,0529 71,0 0,15 -0,031 0,318 -0,04 0,45
Ukrmetrt-
eststandart/
1310
Ethane 2,0144 -0,0335 1,9809 0,0207 2,026 0,018 0,045 0,055 2,27 2,77
Propene 9,4211 0,0071 9,4282 0,0421 9,444 0,031 0,016 0,105 0,17 1,11
n-Butane 9,9599 -0,0845 9,8754 0,0173 9,953 0,045 0,078 0,096 0,79 0,98
1-Butene 3,0694 -0,0068 3,0626 0,0678 3,047 0,014 -0,016 0,139 -0,51 4,52
i-Butane 4,0532 -0,0045 4,0487 0,0216 4,055 0,018 0,006 0,140 0,16 3,47
i-Pentane 0,9873 -0,0099 0,9774 0,0097 0,986 0,010 0,009 0,028 0,88 2,85
Propane 70,482 0,1448 70,6268 0,1334 70,49 0,25 -0,137 0,567 -0,19 0,80
VNIIM/
1306
Ethane 2,0173 - 2,0173 0,0055 2,016 0,009 -0,001 0,021 -0,06 1,02
Propene 8,8798 - 8,8798 0,0094 8,867 0,014 -0,013 0,033 -0,14 0,37
n-Butane 10,0778 - 10,0778 0,0244 10,13 0,025 0,052 0,070 0,52 0,69
1-Butene 2,9782 - 2,9782 0,0046 2,983 0,006 0,005 0,015 0,16 0,50
i-Butane 4,0218 - 4,0218 0,0078 4,038 0,008 0,016 0,023 0,40 0,56
i-Pentane 0,9985 - 0,9985 0,0037 0,996 0,005 -0,003 0,012 -0,25 1,19
Propane 71,014 - 71,014 0,0326 70,97 0,072 -0,044 0,158 -0,06 0,22
Table 1B. Results of COOMET.QM-S4
13
Figures 1B and 2B show the graphs for the results of measurements for cylinder №1310 during
the comparison period
The data for the graphs are shown below in the table 2B.
Figure 1B
Figure 2B
Note – range of sdandard deviation for each day measurement is shwn in the Table 2B.
y = -7E-05x + 2,0093
y = -0,0001x + 9,4648
y = 4E-06x + 4,0446
y = -6E-05x + 9,895
y = 9E-06x + 3,057
y = -3E-05x + 0,9769
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
8,00
9,00
10,00
11,00
0 100 200 300 400 500 600
Mea
sure
d a
mo
un
t fr
acti
on
, cm
ol/
mo
l
Days after preparation
Stability data for cylinder №1310
n-butane
propene
i-butane
butene-1
ethane
i-pentane
y = 0,0003x + 70,596
65,00
66,00
67,00
68,00
69,00
70,00
71,00
72,00
0 100 200 300 400 500 600
Mea
sure
d a
mo
un
t fr
acti
on
, cm
ol/
mo
l
Days after preparation
Stability data for cylinder № 1310, propane
propane
14
Measured amount fraction, cmol/mol SD for each
day measure-
ment, % rel Date 27.03.2017 15.05.2017 05.07.2017 19.09.2017 20.09.2018
Number of days
Component 1 51 102 178 543
Ethane 2,0144 1,9867 2,0271 1,9855 1,9733 0,3-0,75
Propene 9,4211 9,4652 9,5069 9,4343 9,3926 0,1-0,4
i-Butane 4,0532 4,0487 4,0227 4,0545 4,0475 0,2-0,45
n-Butane 9,9599 9,8960 9,8066 9,8829 9,8795 0,4-0,7
1-Butene 3,0694 3,0712 3,0288 3,0572 3,0667 0,2-0,4
i-Pentane 0,9873 0,9690 0,9746 0,9638 0,9641 0,2-1,0
Propane 70,482 70,5986 70,7584 70,6729 70,7227 0,1-0,2
Table 2B. Stability data for cylinder №1310
Table 3B contains data on the assessment of the significance of the slope of the depend-
ence of the amount of substance on time
Component |b| s(b) t0,95,n-2 s(b)
(t0,95,k-2=3,18)
Conclusion
Ethane 710-5 4,510-5
14,310-5 b t0,95,k-2 S(b)
the slope is insignificant
Propene 0,00012 0,000095 0,00030
b t0,95,k-2 S(b)
the slope is insignificant
n-Butane 5,610-5 1410-5 4510-5 b t0,95,k-2 S(b)
the slope is insignificant
1-Butene 9,310-6 4,710-5
14,810-5
b t0,95,k-2 S(b)
the slope is insignificant
i-Butane 3,810-6 3,510-5 11,110-5 b t0,95,k-2 S(b)
the slope is insignificant
i-Pentane 2,910-5 1,9810-5 6,2910-5 b t0,95,k-2 S(b)
the slope is insignificant
Propane 0,00030 0,00024
0,00076
b t0,95,k-2 S(b)
the slope is insignificant
Table 3B. Testing of the slope b, (cmol/mol)/day, of time dependence of amount of substance
for significance
15
Annex C
Reports submitted by participating laboratories
Report of BelGIM
COOMET No 622/RU/13 Supplementary comparison
«C3-C5 components in mixtures of liquefied hydrocarbons»
REPORT ON THE RESULTS OF THE STUDY
I. Results of experimental studies
Laboratory: Belarus, BelGIM, Section for physicochemical and optical measurements, sector for standards and gas mixtures, 8, Serova st., Minsk.
Cylinder No: 1066
Measurement No 1
Component Date
dd/mm/yy
Result, 10-2 mol/mol
Standard deviation, % relative
Number of replicates,
n
Ethane 28/04/17 1,9946 0,027 4
Propene 28/04/17 8,816 0,012 4
n-Butane 28/04/17 10,102 0,05 4
1-Butene 28/04/17 3,012 0,05 4
iso-Butane 28/04/17 4,069 0,04 4
iso-Pentane 28/04/17 0,9964 0,08 4
Propane 28/04/17 71,009 0,011 4
Measurement No 2
Component Date
dd/mm/yy
Result, 10-2 mol/mol
Standard deviation, % relative
Number of replicates,
n
Ethane 04/05/17 1,9958 0,009 4
Propene 04/05/17 8,813 0,015 4
n-Butane 04/05/17 10,097 0,03 4
1-Butene 04/05/17 3,008 0,029 4
iso-Butane 04/05/17 4,068 0,019 4
iso-Pentane 04/05/17 0,9988 0,03 4
Propane 04/05/17 71,019 0,005 4
16
Measurement No 3
Component Date
dd/mm/yy
Result, 10-2 mol/mol
Standard deviation, % relative
Number of replicates,
n
Ethane 17/05/17 1,9919 0,04 4
Propene 17/05/17 8,821 0,018 4
n-Butane 17/05/17 10,106 0,020 4
1-Butene 17/05/17 3,010 0,027 4
iso-Butane 17/05/17 4,074 0,014 4
iso-Pentane 17/05/17 0,9948 0,07 4
Propane 17/05/17 71,003 0,005 4
Final results:
Component Result,
10-2 mol/mol Coverage factor
Expanded uncertainty, 10-2 mol/mol
Ethane 1,99 2 0,04
Propene 8,82 2 0,06
n-Butane 10,10 2 0,06
1-Butene 3,01 2 0,03
iso-Butane 4,07 2 0,04
iso-Pentane 0,997 2 0,010
Propane 71,0 2 0,3
17
II. Description of the study
Equipment
Gas chromatograph Trace GC Ultra with FID, 6-port gas sampling valve with 0.125 ml sampling
loop, column TG-BOND Alumina (KCl) 50 m × 0,53 mm × 10 µm.
Carrier gas: He grade 6.0.
High purity hydrogen and compressed air for FID.
Data collection: Software Xcalibur 2.1.
Liquid sample vaporization manifold PerkinElmer Model Arnel 4085 for sample gasification.
Calibration standards (CS)
Calibration was performed using two reference mixtures of liquefied hydrocarbons similar in com-
position to the sample for comparison. CSs were prepared in constant pressure (piston) cylinders
(CPC) model CP-2GM with a volume of 1 liter (Welker, USA). CPCs were equipped with tracker
magnet, gravity mixer, two manometers for the pressure control in the sample chamber and in
the working gas chamber, three valves.
CS composition was calculated from the gravimetric preparation process according to
ISO 6142-1:2015 and was verified according to ISO 7941:1988 and using measurement proce-
dure developed in BelGIM. CS preparation was carried out by direct mixing of the initial compo-
nents in a previously evacuated CPC. Components were added in CPC in order of increasing
boiling point. All initial components were purity analyzed before use by GC-FID according to
ISO 7941:1988 and using measurement procedure developed in BelGIM.
Composition of CSs are given in table 1.
18
Table 1 – RMLH composition
Component
CS1 (CPC No 32279) CS2 (CPC No 32280)
Amount frac-tion,
10-2 mol/mol
Relative ex-panded uncer-
tainty (k=2, P=0,95), %
Amount frac-tion,
10-2 mol/mol
Relative ex-panded uncer-
tainty (k=2, P=0,95), %
Ethane 4,37 2,0 2,15 2,0
Propene 8,82 0,5 8,91 0,5
n-Butane 9,74 0,5 10,06 0,5
1-Butene 3,000 1,0 3,18 1,0
iso-Butane 3,92 1,0 4,04 1,0
iso-Pentane 1,034 1,0 0,989 1,0
Propane 69,10 0,3 70,67 0,3
GC calibration
Molar fraction of each component j in the sample for comparison was calculated by the internal
normalization technique according to ISO 7941:1988. Molar correction factor 𝐾𝑗 for each compo-
nent j was established by GC calibration with CS1 и CS2.
Sequence of measurements:
1) CS1 – sample for comparison – CS2
2) CS2 – sample for comparison – CS1
3) CS1 – sample for comparison – CS2
Since preparation of each sample and its measurement required more than 8 hours, calibration,
measurement and re-calibration were carried out for three days day after day.
The chromatograms of each CS were recorded at least three times.
For each chromatogram, the molar correction factor 𝐾𝑗 was calculated by the formula
𝐾𝑗 =𝐴𝐶3𝐻8𝑟𝑒𝑓
∙ 𝑋𝑗𝑟𝑒𝑓
𝑋𝐶3𝐻8𝑟𝑒𝑓
∙ 𝐴𝑗𝑟𝑒𝑓
(1)
where
𝐴𝐶3𝐻8𝑟𝑒𝑓
– peak area of propane, counts;
𝑋𝑗𝑟𝑒𝑓
– molar fraction of the component j in the CS, 10-2 mol/mol;
𝑋𝐶3𝐻8𝑟𝑒𝑓
– molar fraction of propane in the CS, 10-2 mol/mol;
𝐴𝑗𝑟𝑒𝑓
– peak area of the component j, counts.
To calculate the measurement result, the arithmetic mean of the molar correction factor values
established by CS1 and CS2 was used.
19
Sample handling
Before calibration (measurements) CPC with CS and the sample for comparison were kept at
room temperature for at least 24 hours. Helium was injected into the working gas chamber of
CPC to a pressure of 1.6 MPa.
CSs were homogenized with a gravity mixer.
A sample of a 20 ml CS (sample for comparison) was taken to a previously evacuated vaporiza-
tion manifold Arnel 4085 and was kept until complete evaporation and homogenization for at least
18 hours. The helium pressure in the working gas chamber of CPC during sample collection into
the vaporization manifold was maintained at 1.6 MPa.
During calibration (measurements) gas sample was fed into 6-port gas sampling valve via re-
strictor and stainless steel tube at a flow rate of 20 ml/min.
Uncertainty calculation
Molar fraction of the component j in the sample for comparison 𝑋𝑗, 10-2 mol/mol, was calculated
by the formula
𝑋𝑗 =𝐾𝑗 ∙ 𝐴𝑗
∑ 𝐾𝑗 ∙ 𝐴𝑗𝑚𝑗=1
∙ 100 (2)
where
𝐾𝑗 – molar correction factor of the component j;
𝐴𝑗 – peak area of the component j, counts;
𝑚 – number of components in the sample for comparison.
Relative summary standard uncertainty of measurement of molar fraction of component j in the
sample for comparison 𝑢𝑜(𝑋𝑗), %, was calculated by the formula
𝑢о(𝑋𝑗) = √[𝑢(𝑋𝑗)𝑜𝐴]2 + [𝑢(𝐾𝑗)𝑜𝐴]
2 + [𝑢(𝐾𝑗)𝑜𝐵]2, (3)
where
𝑢(𝑋𝑗)𝑜𝐴 – experimental relative standard deviation of the measurements results of the compo-
nent j, %;
𝑢(𝐾𝑗)𝑜𝐴 – experimental relative standard deviation of the molar correction factor of the compo-
nent j, %;
𝑢(𝐾𝑗)𝑜𝐵 – relative standard uncertainty of the molar correction factor of the component j due to
the uncertainty of the CS, %,
𝑢(𝐾𝑗)𝑜𝐵 = √[𝑢(𝑋𝑗𝑟𝑒𝑓
)𝑜]2+ [𝑢(𝑋𝐶3𝐻8
𝑟𝑒𝑓)𝑜]
2, (4)
where
20
𝑢(𝑋𝑗𝑟𝑒𝑓
)𝑜 – relative standard uncertainty of the molar fraction of the component j of the CS, %;
𝑢(𝑋𝐶3𝐻8𝑟𝑒𝑓
)𝑜 - relative standard uncertainty of the molar fraction of propane of the CS, %.
Total standard uncertainty of the molar fraction of the component j in the sample for comparison
𝑢(𝑋𝑗), 10-2 mol/mol, was calculated by the formula
𝑢(𝑋𝑗) =𝑢о(𝑋𝑗) ∙ 𝑋𝑗
100%. (5)
где 𝑋𝑗 – measurement result, 10-2 mol/mol.
Evaluation of measurement uncertainty is given in table 2.
Table 2
Compo-nent
Components of uncertainty Total rela-tive stand-ard uncer-
tainty 𝑢о(𝑋𝑗),
%
Total stand-ard uncer-
tainty 𝑢(𝑋𝑗),
10-2 mol/mol
Coverage factor
Expended uncer-tainty 𝑈(𝑋𝑗),
10-2 mol/mol
𝑢(𝑋𝑗)𝑜𝐴,
%
𝑢(𝐾𝑗)𝑜𝐴,
%
𝑢(𝐾𝑗)𝑜𝐵,
%
Ethane 0,03 0,03 1,0 1,0 0,020 2 0,04
Propene 0,01 0,03 0,3 0,3 0,03 2 0,06
n-Butane 0,02 0,03 0,3 0,3 0,03 2 0,06
1-Butene 0,03 0,04 0,5 0,5 0,015 2 0,03
iso-Butane 0,02 0,03 0,5 0,5 0,020 2 0,04
iso-Pen-tane
0,06 0,07 0,5 0,5 0,005 2 0,010
Propane 0,005 - 0,21 0,21 0,15 2 0,30
21
Report of Ukrmetrteststandart
COOMET.QM-S4 Supplementary comparison
«Liquefied Petroleum Gas»
MEASUREMENT REPORT
I. Results of the study
Laboratory: Ukrmetrteststandart, Kiev, Ukraine
Cylinder number: 1310
Measurement
No 1
Date
dd/mm/yy Result, cmol/mol
Relative standard devia-
tion, %
Number of repli-
cates,
n
Ethane C2H6 21.05.2018 2,031 0,16 4
Propene C3H6 21.05.2018 9,444 0,09 4
n-Butane n-C4H10 21.05.2018 9,961 0,16 4
Butene 1-C4H8 21.05.2018 3,049 0,21 4
iso-Butane i-C4H10 21.05.2018 4,059 0,21 4
iso-Pentane i-C5H12 21.05.2018 0,9889 0,19 4
Propane C3H8 21.05.2018 70,468 0,11 4
Measurement
No 2
Date
dd/mm/yy Result, cmol/mol
Relative standard devia-
tion, %
Number of repli-
cates,
n
Ethane C2H6 22.05.2018 2,0330 0,07 4
Propene C3H6 22.05.2018 9,448 0,05 4
n-Butane n-C4H10 22.05.2018 9,958 0,02 4
Butene 1-C4H8 22.05.2018 3,047 0,05 4
iso-Butane i-C4H10 22.05.2018 4,056 0,03 4
iso-Pentane i-C5H12 22.05.2018 0,9898 0,04 4
Propane C3H8 22.05.2018 70,467 0,03 4
Measurement
No 3
Date
dd/mm/yy Result, cmol/mol
Relative standard devia-
tion, %
Number of repli-
cates,
n
Ethane C2H6 23.05.2018 2,0087 0,02 4
Propene C3H6 23.05.2018 9,439 0,03 4
n-Butane n-C4H10 23.05.2018 9,942 0,04 4
Butene 1-C4H8 23.05.2018 3,045 0,06 4
iso-Butane i-C4H10 23.05.2018 4,046 0,04 4
iso-Pentane i-C5H12 23.05.2018 0,9767 0,06 4
Propane C3H8 23.05.2018 70,544 0,03 4
22
Measurement
No 4
Date
dd/mm/yy Result, cmol/mol
Relative standard devia-
tion, %
Number of repli-
cates,
n
Ethane C2H6 24.05.2018 2,031 0,1 4
Propene C3H6 24.05.2018 9,447 0,1 4
n-Butane n-C4H10 24.05.2018 9,951 0,16 4
Butene 1-C4H8 24.05.2018 3,048 0,08 4
iso-Butane i-C4H10 24.05.2018 4,060 0,15 4
iso-Pentane i-C5H12 24.05.2018 0,9891 0,07 4
Propane C3H8 24.05.2018 70,473 0,07 4
Final results
Component
Mole fraction, cmol/mol
Coverage factor Expanded uncertainty,
cmol/mol
Ethane C2H6 2,026 2 0,036
Propene C3H6 9,444 2 0,062
n-Butane n-C4H10 9,953 2 0,090
Butene 1-C4H8 3,047 2 0,027
iso-Butane i-C4H10 4,055 2 0,036
iso-Pentane i-C5H12 0,986 2 0,019
Propane C3H8 70,49 2 0,49
II. Description of the study
Principle
Sample of the LPG mixture to be analysed (of mass about 14 g) was transferred from the
constant pressure cylinder to the evacuated gas cylinder, where it was vaporised and diluted with
pure nitrogen (of mass about 160 g). The resulting gas mixture was analysed using gas chromato-
graph by comparison with the primary standard gas mixtures of similar composition. Analysis
results were normalised to 100 % of hydrocarbons.
Instrumentation
Balance used for primary standard gas mixtures (PSGM) preparation by gravimetric
method: Mettler Toledo XP26003L electronic balance (max. load 26,1 kg; min. 0,2 g; standard
deviation 0,003 g), with mass pieces traceable to PTB.
Measurement data were collected automatically.
Instruments for purity analysis of parent gases: Agilent 6890N gas chromatographs with
helium ionization detector (HID), flame ionization detector (FID), thermal conductivity detector
(TCD) and mass spectrometric detector (MSD), and gas analysers.
Gas mixture was analysed using Agilent 6890N gas chromatograph with FID. Capillary
column GS-ALUMINA, 50 m, 0,530 mm. Split mode 10:1. Carrier gas – helium, flow rate
5,2 cm3/min. tdetector = 110 ºС.
Calibration Standards
Composition of the calibration standards – primary standard gas mixtures (PSGM) used
for measurements by comparison method is given in the table below
23
Component
PSGM -1
Cylinder No 61032
PSGM -2
Cylinder No 27277
PSGM -3
Cylinder No 13746327
x, % u(x), % x, % u(x), % x, % u(x), %
Ethane C2H6 0,0990 0,0003 0,1051 0,0003 0,1142 0,0003
Propene C3H6 0,45472 0,00023 0,47165 00023 0,50734 00023 n-Butane n-
C4H10 0,47494 0,00017 0,49964 0,00017 0,53802 0,00017
Butene 1-
C4H8 0,14004 0,00017 0,15087 0,00017 0,16713 0,00017
iso-Butane i-
C4H10 0,19151 0,00016 0,20266 0,00016 0,22172 0,00016
iso-Pentane i-
C5H12 0,04826 0,00013 0,05303 0,00013 0,05552 0,00013
Propane C3H8 3,3533 0,0003 3,5285 0, 0003 3,7712 0, 0003
Nitrogen N2 balance balance balance
Note: x – mole fraction, u(x) – absolute standard uncertainty
Purity tables for parent gases used for PSGM preparation for are given below.
Purity table for propane C3H8
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
C3H8 999677 13
C2H6 254 12
n-C4H10 10,1 0,5
iso-C4H10 8,0 0,4
N2 41 4
O2 10 1
Purity table for ethane C2H6
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
C2H6 999996 0,4
CH4 0,31 0,03
C3H8 0,37 0,04
N2 2,2 0,4
O2 1,0 0,2
Purity table for propene C3H6
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
C3H6 995568 118
C3H8 3831 115
C2H6 460 23
C2H4 127 6
CH4 3,2 0,2
N2 8,2 0,8
O2 2,4 0,5
24
Purity table for n-butane n-C4H10
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
n-C4H10 995249 85
C3H8 240 12
C2H6 12,0 2,4
iso-C4H10 2450 74
iso-C5H12 17,0 0,8
neo-C5H12 680 34
C6H14 299 15
CH4 90 5
O2 43 4
N2 920 18
Purity table for iso-butane iso-C4H10
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
iso-C4H10 994523 108
C3H8 2800 84
C2H6 495 25
n-C4H10 2100 63 1-C4H8 41 2
CH4 18,0 0,9
iso-C5H12 1,0 0,1
СO2 22 2,2
Purity table for iso-pentane iso-C5H12
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
iso-C5H12 995390 220
n-C5H12 4400 220
neo-C5H12 210 10
Purity table for 1-butene 1-C4H8
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
1-C4H8 990340 192
iso-C4H8 2120 64
iso-C4H10 1710 51
n-C4H10 5830 174
25
Purity table for nitrogen N2
Component Mole fraction, µmol/mol Standard uncertainty,
µmol/mol
N2 999864 6
O2 3,0 0,3
CO2 0,10 0,03
Ar 132 6
H2O 1,3 0,1
Calibration and measurement
Gas chromatograph was calibrated according to ISO 6143 with the PSGMs (PSGM-1,
PSGM-2, PSGM-3). Analysis functions to determine the analytes content in the sample were taken
linear:
x(y) = b1y + b0
The gas mixture was analysed by comparison method according to ISO 6143. Four com-
parisons were made in reproducibility conditions (on different days).
Measurement sequence:
PSGM-1 х 4;
PSGM-2 х 4;
COOMET mixture (diluted with nitrogen) х 4;
PSGM-3 х 4.
Thus, each measurement included 4 replicates.
Sample handling
Gas mixtures were handled in accordance with ISO 16664.
The cylinders had been kept for 24 hrs at the room where the measurements were made.
The room was thermostatted at t = (20 ± 2) ºС.
Uncertainty evaluation
Composition of the gravimetrically prepared primary standard gas mixtures and its uncer-
tainty were calculated according to ISO 6142-1 and ISO 19229.
Results of analysis by comparison method and their uncertainty were calculated according
to ISO 6143, taking into account the uncertainties of the measuring system response, analysis
functions and primary standard gas mixtures. Calculations were made with B_LEAST software.
Uncertainties of components mole fractions normalised to 100 % of the hydrocarbons were
calculated according to ISO 6974-2.
For uncertainty evaluation the typical relative standard deviations in measurements by
comparison method were taken as they are more representative than smaller deviations obtained
in this comparison. Besides, the values of combined uncertainty were increased with regard to
possible influence of LPG sample evaporation procedure.
Participants: M. Rozhnov, D. Melnyk, S. Kisel, O. Levbarg, S. Shpilnyi, S. Yakubov
26
Report of VNIIM
КООМЕТ № 622/RU/13)
Supplementary comparison “С2-С5 components in mixtures of liquified hydrocar-
bons”
MEASUREMENT REPORT
I. Results of study
Laboratory:D.I. Mendeleyev Institute for Metrology (VNIIM)
Cylinder number: 1306
Measurement № 1
Date dd/mm/yy
Result (mol/mol) Standard deviation
(% relative)
Number of sub meas-urements,
n
Ethane 29/03/2017 2,0097 0,421 4
Propene 29/03/2017 8,8584 0,103 4
n-Butane 29/03/2017 10,1344 0,221 4
1-Butene 29/03/2017 2,9846 0,137 4
i-Butane 29/03/2017 4,0397 0,114 4
i-Pentane 29/03/2017 0,9985 0,463 4
Propane 29/03/2017 70,975 0,063 4
Measurement № 2
Date dd/mm/yy
Result (mol/mol) Standard deviation
(% relative)
Number of sub meas-urements
n
Ethane 02/04/2017 2,0329 0,293 7
Propene 02/04/2017 8,8912 0,067 7
n-Butane 02/04/2017 10,0562 0,151 7
1-Butene 02/04/2017 2,9751 0,114 7
i-Butane 02/04/2017 4,0216 0,126 7
i-Pentane 02/04/2017 0,9900 0,184 7
Propane 02/04/2017 71,032 0,041 7
Measurement № 3
Date
dd/mm/yy Result (mol/mol)
Standard deviation
(% relative)
Number of sub meas-
urements
n
Ethane 04/04/2017 2,0040 0,129 5
Propene 04/04/2017 8,8502 0,057 5
n-Butane 04/04/2017 10,1989 0,143 5
1-Butene 04/04/2017 2,9887 0,109 5
i-Butane 04/04/2017 4,0537 0,078 5
i-Pentane 04/04/2017 1,0003 0,280 5
Propane 04/04/2017 70,9043 0,043 5
27
Final results:
Component
Result
(assigned value),
cmol/mol
mol/mol
Coverage factor
Assigned expanded uncer-
tainty
cmol/mol
Ethane 2,016 2 0,018
Propene 8,867 2 0,028
n-Butane 10,130 2 0,050
1-Butene 2,983 2 0,012
i-Butane 4,038 2 0,016
i-Pentane 0,996 2 0,010
Propane 70,97 2 0,14
II. Description of study Instrument
The measurements were performed on GC system «Crystal-5000.2» (Chromatec, Russia) Data collection: Software “Chromatec Analytic 2.6” Detector: FID
Column: Restek Rt-Alumina, 30 m 0,53 mm Carrier gas: He Gas flow:10 ml/min Injected dose: 0.25 µl
Injector temperature: 50C
Temperature of the cooling zone of the injector: 10C
Detector temperature: 300C
Temperature program of the column thermostat: 40C – 5 min, 7C/min, 130C – 5 min. Calibration Standards
Preparation of LPG calibration mixtures (liquid) was carried out by gravimety in constant pressure cylinders (floating piston cylinders, 2 dm3). Every component was added directly from a conventional cylinder to a piston cylinder, except iso-pentane, which was transferred to the piston cylinder with a syringe. In the case of propane (major component) the cylinder was slightly heated during transferring in order to maintain enough vapour pressure. Before and after addition of each component the piston cylinder was weighed accurately on RAYMOR HCE-25G balance against a tare cylinder. After filling the piston cylinders were pressurized with He to 2.0 MPa. Purity analysis of the parent substances was carried out by GC- FID, TCD 1 Primary Reference Standard (PSM) was used for calibration. Composition of calibration standard is shown in the table 1. Table 1
Cylinder N 2316
Component
Amount of sub-stance fraction, cmol/mol
ugrav, cmol/mol (k=1)
Ethane 2,2647 0,0007
Propene 9,1447 0,0005
n-Butane 9,9547 0,0004
1-Butene 3,061 0,0005
i-Butane 4,0289 0,0004
i-Pentane 0,9890 0,0004
Propane 70,5443 0,0009
28
Purity data for parent gases is shown ithe tables 2-8 Table 2 - Purity data for ethane
Cylinder N4877
Component Amount fraction
cmol/mol Standard uncertainty (k=1)
cmol/mol
ethane 99,99988 -
n-butane 0,00012 0,00001
Table 3- Purity data for propene
Cylinder N4142
Component Amount fraction
cmol/mol Standard uncertainty (k=1)
cmol/mol
propene 99,97184 —
propane 0,0209 0,0008
nitrogen 0,0070 0,0007
i-butane 0,00026 0,00003
Table 4 - Purity data for n-butane
Cylinder N 3405
Component Amount fraction
cmol/mol
Standard uncertainty (k=1)
cmol/mol
n-butane 99,97095 —
neo-pentane 0,0244 0,0007
i-butane 0,0031 0,0002
trans-2-butene
0,00088 0,00009
cis-2-butene 0,00037 0,00004
propane 0,00030 0,00003
Table 5 - Purity data for 1-butene
Cylinder N 4142
Component Amount fraction
cmol/mol
Standard uncertainty (k=1)
cmol/mol
1-butene 99,4508 —
n-butane 0,243 0,006
i-butene (2-methylpro-pene)
0,124 0,008
i-butane 0,093 0,002
nitrogen 0,059 0,006
trans-2-butene 0,0103 0,0007
oxygen 0,010 0,001
propene 0,0058 0,0002
propane 0,0017 0,0002
29
1,3- butadiene 0,0014 0,0001
cis-2-butene 0,0010 0,0001
Table 6 - Purity data for i-butane
Cylinder N4874
Component Amount fraction
cmol/mol Standard uncertainty (k=1)
cmol/mol
i-butane 99,97725 —
n-butane 0,012 0,001
propane 0,0102 0,0004
i-butene 0,00055 0,00006
Table 7- Purity data for i-pentane
Cylinder N 8027-1
Component Amount fraction
cmol/mol
Standard uncertainty (k=1)
cmol/mol
i-pentane 99,6822 -
n-pentane 0,255 0,015
neo-pentane 0,043 0,004
toluene 0,0072 0,0007
n-heptane 0,0030 0,0003
n-hexane 0,0027 0,0003
1-hexene 0,0016 0,0002
2-methyl-1-butene 0,0016 0,0002
cyclohexane 0,00115 0,00001
1-pentene 0,00057 0,00006
n-butane 0,00051 0,00005
n-nonane 0,00047 0,00005
cyclopentane 0,00029 0,00003
3-methyl-1-butene 0,00020 0,00002
2,2-dimethylbutane 0,00018 0,00002
2-methyl-2-butene 0,00014 0,00001
benzene 0,00012 0,00001
n-octane 0,00010 0,00001
trans-2-pentene 0,00010 0,00001
2-methylpentane 0,00009 0,00001
3-methylpentane 0,000077 0,000008
30
Table 8 - Purity data for propane
Cylinder N 3889
Component Amount fraction
cmol/mol
Standard uncertainty (k=1)
cmol/mol
propane 99,9957 —
n-butane 0,0029 0,0001
propene 0,00076 0,00006
ethane 0,00035 0,00004
i-butane 0,00025 0,00003
Instrument Calibration
Single point calibration method was used to determine components mole fraction in the LPG mixture to be investigated (mathematical model – у=ax). Measurement sequence was in the order: Calibration mixture - Comparison mixture - Calibration mixture Analysis results were normalised to 100 %.
Sample Handling
The cylinders had been kept for at least 24 hrs at room temperature (t = (20 ± 2) ºС) before
measurements.
The injection of the sample was carried out by sampling valve for liquefied gases, which enables to maintain single-phase state for mixtures of liquefied hydrocarbons with saturated vapor pressure higher than atmospheric. Pressure in the injection system is provided by pressure in a working chamber of the piston cylinder (2.0 MPa).
Uncertainty evaluation
Component
Measurement result, cmol/mol
ugrav
(purity+weighing),
cmol/mol
uanal
(between and within day
measurements), cmol/mol
u (combined standard
uncertainty), cmol/mol
U (expanded uncertainty,
k=2), cmol/mol
U0 (relative expanded
uncertainty), %
Ethane 2,016 0,0008 0,009 0,009 0,018 0,9
Propene 8,867 0,0006 0,014 0,014 0,028 0,3
n-Butane 10,130 0,0005 0,025 0,025 0,05 0,5
1-Butene 2,983 0,0004 0,006 0,006 0,012 0,4
i-Butane 4,038 0,0004 0,008 0,008 0,016 0,4
i-Pentane 0,996 0,0004 0,005 0,005 0,010 1,0
Propane 70,97 0,0010 0,072 0,072 0,14 0,20