Sangil LEE, Mi Eon KIM, Sang Hyub OH, Jin Seog KIM. Center for Gas Analysis Korea Research Institute of Standards and Science (KRISS) Daejeon, Korea

Transcription

1 Determination of physical adsorption loss of primary reference gas mixtures in cylinders using cylinder-to-cylinder division Lee et al., 2017 Metrologia 54 L26) Sangil LEE, Mi Eon KIM, Sang Hyub OH, Jin Seog KIM Center for Gas Analysis Korea Research Institute of Standards and Science KRISS) Daejeon, Korea Advancing the State of the Art in Measurement Science CCCQM-GAWG Workshop CENAM, Querataro, Mexico 10 October 2018

2 Preparation of primary reference gas mixtures v Static gravimetric method v Dynamic method Dynamic dilution method PRM PRM diluent gas Dynamic gravimetric method

3 Major uncertainty sources v Static gravimetric method o balance/mass pieces o component gases o gas cylinder v Dynamic Method Dynamic dilution method o balance/mass pieces o component gases o a parent PRM in cylinder) o dilution system Dynamic gravimetric method o Balance/mass pieces o component gases o dilution system o time

4 Uncertainty sources of static gravimetric method

5 Traceability chain of primary reference gas mixtures SI Atomic Weights/ Molar Masses Purity Analysis Gravimetric Method Primary Reference Gas Mixtures PRMs) CCQM/RMO Key Comparisons assessing equivalence) Verification/ Stability Assessment Dissemination of Measurement Standards Certified Reference Gas Mixtures CRMs)

6 Impacts on amount-of-substance fractions Without adsorption loss With adsorption loss! " =! $%&'$! "! $%&'$

7 When was issued? DRAFT MINUTES OF THE SIXTH MEETING of the CCQM WORKING GROUP ON GAS ANALYSIS WGG) HELD on 28 TH JANUARY 2002 at NMi, DELFT Present APMP QM K4 120 μmol/mol ethanol in air) Dr Kato presented the Draft B report. Jin Seog Kim KRISS), Sang Hyub Oh KRISS), Airan Hahn KATS), Alejandro Pérez Castorena CENAM), Angelique Botha CSIR NML), Kenji Kato NMIJ), Robert Kaarls CCQM), Laurie Besley NML - CSIRO), Stanislav Musil SMU), Rob Wessel NMi), Ed de Leer NMi Chair), Janneke van Wijk NMi), Jean-Francois Perrochet METAS), Tatiana Mace LNE), Michela Sega IMGC), Adriaan van der Veen NMi), Annarita Baldan NMi), Maite Lopez CEM), Robert Wielgosz BIPM), Joële Viallon BIPM), Martin Milton NPL-minutes), Franklin Guenther NIST), Hans-Joachim Heine BAM), Anneliese Medem UBA) Dr Kato also described an experiment carried out at NMIJ to determine the extent of absorption on the walls of a cylinder. The experiments used passivated cylinders that had been pre-treated by exposure to ethanol/ air. Dr Heine said that he had experience of this type of decant experiment, and had found that it was necessary to heat the source cylinder in order to achieve a valid result. Dr van Wijk presented the results of similar experiments carried out by NMi. They had heated the exchange tubing to 60 degrees and had managed the transfer over a period of 4 hours. The mother cylinder had an initial pressure of 120 bar. Dr Milton presented the results of similar experiments carried out by NPL. They had observed reductions in ethanol content between 0.1 and 2% and concluded that this was a result of a number of effects that were highly sensitive to the exact conditions used for the experiment. There was considerable discussion about the relevance of these observations. Dr Besley agreed to coordinate the work of laboratories in investigating these effects.

8 Physical adsorption loss was estimated v CCQM-K41, APMP.QM-K41 10 μmol/mol hydrogen sulfide in nitrogen v CCQM-K46 10 μmol/mol ammonia in nitrogen v CCQM-K μmol/mol ethanol in nitrogen v CCQM-K94 10 μmol/mol dimethyl sulfide in nitrogen v CCQM-K nmol/mol monoterpenes in nitrogen Ratio Daughter/Mother CCQM-K121) n-hexane α-pinene 3-carene R-limonene 1,8-cineole Figure 5. Mother-daughter analysis of APE Each data point represents the ratio of the response of the daughter cylinder to that of the mother cylinder. Error bars represent expanded uncertainties, k = 2. However, there is no detailed information about the method

9 Physical adsorption Loss component/ balance gas Filling Without adsorption loss With adsorption loss Empty cylinder! " =! $ = % &$ % '$ Therefore, the gravimetrically determined amount-of-substance fraction actual amount-of-substance fraction if any adsorption loss exits! $ = % &$ % '$!: amount-of-substance fraction mol/mol) % & : amount of a component gas mol) % ' : amount of a balance gas mol)! " >! $ % &$ > % &$ )

10 How to estimate physical adsorption loss v PRMs in cylinders) vs PRMs in cylinders without adsorption loss) v PRMs in cylinders) vs PRMs from dynamic gravimetric or dilution) method v Cylinder-to-cylinder division! $! "! "%! "! "%! $! " =! $! "% =! $! $ >! "! $ >! " >! "%

11 Cylinder-to-cylinder division v A PRM cylinder is connected to a new vacuumed cylinder with a T-shape SS tube The transfer tube o should be as short as possible to minimize additional adsorption loss and dead volume o its internal surface should be checked for any defects and be treated if possible) o should be cleaned by purging and heating prior to the division o better to be heated during transfer v Transfer gas mixtures from the PRM cylinder into the vacuumed cylinder by opening the valves slowly Equilibrium o Two cylinders should remain connected by keeping the valves open until those are thermally equilibrated e.g., 3-4 hours) v Evaluate any adsorption loss by analyzing two cylinders Analysis o should be done right after the division

12 Cylinder-to-cylinder division Case I: cylinders of the same type Case II: the first mother cylinder without adsorption loss Lee et al., 2017)

13 Cylinder-to-cylinder division Case I: cylinders of the same type If there is no adsorption loss, / 9 = / & = / & = / ) = / )* / + = / +* = /, = /,* assumed that the amount of substance of a component gas! ", mol) adsorbed on the internal surface, # $", is equal for the same type, lot, internal volume, and internal surface area of cylinders o thus, the amount of substance of the adsorption loss is the same at each division # $" =! "&! "& =! ")! ")* =! "+ =! ", )! "+*! ",* changes in the amount-of-substance fraction o # -. = / & / & at gravimetric preparation o # -0 = / ) / )* at i th division as the total amount of substance is divided into two cylinders, o # -1 = 2 $ 3 # -. where 2 $ =! 436)) /! 43! 436)),! 43 total amount of substance in a cylinder

14 Cylinder-to-cylinder division Case I: cylinders of the same type assumed that analytical sensitivity is constant changes in the analytical response o! "# = % & % & at gravimetric preparation o! ") = % * % *+ at i th division as the total amount of substance is divided into two cylinders, o! ", = -. /! "# since analytical sensitivity is constant, % & 1 & = % & o & = 1 3 " ) & " 4 ) 52 3 " 4 4 ) 6" )7 1 & o 8 1 & = 1 & :< # ) > :" + 4 ) ) < # " 4 ) > + :2 > 3) :" 4 + ) 52 3 " 4 ) 6" 4 )7 ) 2 3 " 4 ) 52 3 " 4 4 ) 6" )7 >

15 Cylinder-to-cylinder division Case I: cylinders of the same type generalized equations #! # ' # ) " " =! "%& ) # " + ' ) # # for 1 2) " ) ", 5! " # =! " # # 5! "%& ) #! "%& 7 + 5) " # ) ) " # 7 + 5' ) ' 7 + 5) " # + ' ) " # ) ", # ) ) " # + ' ) " # ) ", # 7

16 Cylinder-to-cylinder division Case II: the first cylinder without adsorption loss changes in the amount-of-substance fraction o! "# = % & % & at gravimetric preparation o! ") = % * % *+ at 1 st division o! "6 = % 7 % 7+ at i th division as the total amount of substance is divided into two cylinders, o! "6 = 8 7 9! "# for = 1) o! "6 = 8 7@* 9! ") for = 2)

17 Cylinder-to-cylinder division Case II: the first cylinder without adsorption loss assumed that analytical sensitivity is constant changes in the analytical response o! "# = % & % & at gravimetric preparation o! ") = % * % *+ = % & % *+ at 1 st division o! ", = % - % -+ at i th division as the total amount of substance is divided into two cylinders, o! ", =. / -0*! ") for 5 2) since analytical sensitivity is constant, % * o : & = ; # < = " >. / % * % * + % *+ ) ) % *+ : * = : *+ : & = : & B; # ) C B" + > ) ) ; # " > ) C + B< C =) B< + = " > ) 0" > ) D" > C )E ) < = < = " > ) 0" > > ) D" )E

18 Cylinder-to-cylinder division v the difference between! " # and! " =! & ) due to physical adsorption loss! =! &! " # I. If! +! & ),! & is valid, and no further action might be needed II. If! > +! & -./! +!),! & is valid, but the difference can be used to estimate uncertainty and then combined with other uncertainties III. If! > +! & -./! > +!),! & is not valid,! & can be corrected with using equations suggested by Lee et al. 2017) or passivate cylinders, find other proper cylinders, or develop surface treatment methods +! & )! & +!& ) I II III!!!

19 Actual applications 6 nmol mol -1 propane in nitrogen Table 3. Changes in amount-of-substance fraction of propane at 6 nmol mol 1 level in electrolytically polished aluminium gas cylinders due to adsorption loss during cylinder-to-cylinder divisions for cylinders of the same type case 1). Division Preparation 1st division 2nd division Amount-of-substance fraction, nmol mol 1 x 0 ) x 0 ) Amount-of-substance fraction, nmol mol 1 x 1 ) x 1d ) Analytical response r 1 ) r 1d ) Amount-of-substance fraction, nmol mol 1 x 2 ) x 2d ) Analytical response r 2 ) r 2d ) x 0 x 0 = x 1 x 1d = x 2 x 2d Amount-of-substance fraction, nmol mol Expanded uncertainty k = 2), nmol mol

20 Actual Applications 6 nmol mol -1 propane in nitrogen

21 Actual Applications Table 4. Changes in amount-of-substance fraction of benzene at 6 nmol mol 1 level in electrolytically polished aluminium gas cylinders due to adsorption loss during cylinder-to-cylinder divisions for cylinders of the same type case 1). Division 6 nmol mol -1 benzene in nitrogen Preparation 1st division 2nd division Amount-of-substance fraction, nmol mol 1 x 0 ) x 0 ) Amount-of-substance fraction, nmol mol 1 x 1 ) x 1d ) Analytical response r 1 ) r 1d ) Amount-of-substance fraction, nmol mol 1 x 2 ) x 2d ) Analytical response r 2 ) r 2d ) x 0 x 0 = x 1 x 1d = x 2 x 2d Amount-of-substance fraction, nmol mol Expanded uncertainty k = 2), nmol mol L x0 L x1 L x2 Adsorption loss estimated by using analytical responses, nmol mol Expanded uncertainty k = 2), nmol mol Adsorption loss estimated by using equation 3), L xi = fn i L x0, nmol mol Expanded uncertainty k = 2), nmol mol

22 Actual Applications amount-of-substance fraction, nmol/mol nmol mol -1 benzene in nitrogen! " =! $! % % $ =! &! % &' =!%! % '

23 Summary provides detailed method procedures for cylinder-to-cylinder division describes how to estimate the adsorption loss, and the corrected amount-of-substance fraction and its uncertainty o correct the amount-of-substance fraction and its uncertainty o introduce estimated change in the amount-of-substance fraction due to the physical adsorption loss) as an uncertainty very useful for developing PRMs on reactive gases to find optimum cylinders if there is no adsorption loss at lower amount-of-substance fractions, no further evaluation might not be necessary for higher levels if there is adsorption loss at lower amount-of-substance fractions, further evaluation might be needed for higher levels