Development of DMS and Acetonitrile, and Formaldehyde gas standards. Gwi Suk Heo, Yong Doo Kim, Mi-Eon Kim, and Hyunjin Jin

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1 Development of DMS and Acetonitrile, and Formaldehyde gas standards Gwi Suk Heo, Yong Doo Kim, Mi-Eon Kim, and Hyunjin Jin

2 The amount of chemical substances in cylinder container Purity uncertainty Gravimetry uncertainty Check the amt of chemicals in gas phase Stability uncertainty

3 Uncertainty evaluation for preparation of low μmol/mol DMS CRM : Modeling Equation Modeling Equation C DMS ( n n DMS DMS n N 2 ) 10 6 f purity f Ads f Re f S Where, C DMS : Concentration of DMS (μmole/mole) n DMS : Mole of DMS in CRM (mole), n DMS =m DMS /M DMS m DMS : Amount of liquid DMS reagent in CRM (g) M DMS : Molecular weight of DMS (g/mole) n N2 : Mole of N2 in CRM(mole), f purity : Factor for purity of liquid DMS reagent f Ads :: Factor for adsorption loss of DMS in cylinder f Re : Factor for Preparation reproducibility of DMS CRM f S : Factor for stability of DMS in cylinder n N2 =m N2 /M N2 m N2 : Amount of N2 gas in CRM (g) M N2 : Molecular weight of N2 (g/mole)

4 Purity determination of DMS Measurement techniques: GC-FID, GC-SCD, FTIR, Karl-Fischer coulometer GC-FID was used for analysis of total impurity hydrocarbons (4,063 μmol/mol) GC-SCD was used for analysis of total sulfur (<1 μmol/mol) Karl-Fischer coulometer was used for analysis of moisture (1,471 μmol/mol) Therefore, total of 0.1% of uncertainty was assigned to DMS purity result of 99.5%.

5 Preparation Scheme of DMS CRM High purity chemical Purity Analysis (GC-FID,AED) WM of VOC Components UE for purity analysis WM = weight measurement Micro-gravimetry UE = Uncertainty Evaluation WM = Weight Measurement Cylinder cleaning Thermal high vacuum WM of Empty cylinder Gas balance- Gravimetry Introduction of VOCs to cylinder UE of Gravimetry Filling cylinder with Balance gas (N2) WM of Nitrogen Gas balance- Gravimetry Mixing gas mixture Analytical Method Homogeneity Test (GC-FID) UE of CRM preparation UE of Analysis Stability Test Checking loss of VOCs due to adsorption and reaction

6 Preparation reproducibility of low μmol/mol DMS Preparation reproducibility : 0.36 % Cylinder No. Conc. of preparation (μmol/mol) Means (± S.D) RSD (%) Response factor Difference (%) Date of preparation MD MD MB MD RSD(%) 0.36

7 DMS loss test due to reaction with cylinder : immediate reaction, short term stability Reaction with the inner surface of cylinder and cylinder valve Adsorption loss test of DMS during the preparation of CRMs Low μmol/mol CRM : Loss of DMS due to adsorption to inner surface of cylinder was evaluated by distributing equal amount of low micromole/mole DMS to other empty cylinder, then second cylinder again was distributed to another empty cylinder. The three cylinders were analyzed and compared their FID response factors to check the adsorption loss of DMS. Result : very small loss, 0.11 % loss at first distribution, 0.35 % loss at second distribution.

8 Stability of low μmol/mol DMS for 6 years Prepd by Syringe Method Stability : 0.18 % Cylinder No. Conc. of preparation (μmol/mol) Means (± S.D) RSD (%) Response factor Difference (%) Date of preparation MD MD MD RSD (%) 0.18

9 Consistency between syringe method and headspace method : Preparation of μmol/mol DMS CRM 10 μmol/mol level DMS CRM Relative Unc. : 1.3 % ± 0.5 % Headspace method (2010) Syringe method (2009)

10 Uncertainty evaluation for preparation of low μmol/mol DMS CRM : Uncertainty parameter contribution Concentration of DMS : μmol/mol Relative Expanded uncertainty : 1.3 % uncertainty parameter level of contribution (%) f_purity Factor for purity of liquid DMS reagent 2.3 f_ads Factor for adsorption loss of DMS in cylinder 2.8 f_re Factor for reproducability for manufacture of DMS CRM 29.7 f_s Factor for stability of DMS in cylinder 7.4 m_dms Amount of liquid DMS reagent in CRM 57.8

11 Sonic dilution system setup in KRISS: 10 umol/mol cyl std With 0.6 % rel u 1 ~ 10 nmol/mol std gas with 1 % rel u 1 ~ 10 nmol cyl std with 2 % rel u 1,000 ~ 10,000 times dilution with 0.6 % rel u

12 Work Ongoing and next Plan: Work Ongoing: International Key Comparison of 10 umol/mol DMS cylinder standard (will be finished this year, 2012) - Participating Labs: NPL, VSL, VNIIM, NIMC, KRISS* Establishing 10 nmol/mol DMS standard by dynamic dilution - 1,000 ~ 10,000 times dilution system is setup by Sonic nozzle dilution system Next Plan: Developing transfer standard of cylinder at 1 ~ 10 nmol/mol level - Certify the nmol std with the dynamic dilution standard

13 Establishing KRISS gas standards for acetonitrile

14 1.327 Preparation reproducibility test of CH 3 CN CRMs Preparation reproducibility of CH 3 CN gas standards was checked by GC-FID Analytical Conditions Column : Carrier gas : 6 ml/min, pa 140 FID1 A, (0608\D D) CP-SIL 5CB, 30 m x 0.53 mm x 5 μm, 120 Injection : Split ratio 2 : 1, Sample loop ml, Sample flow : 100 ml/min 60 GC oven Temp. : 100 (2.2min) Detector : FID, Temp. 250 Sample valve temp. : Analysis Chromatogram of CH 3 CN min

15 Preparation reproducibility of low 10 μmol/mol CH 3 CN Preparation reproducibility : 0.31 % Cylinder No. Conc. of preparation (μmol/mol) Means (± S.D) RSD (%) Response factor Difference (%) Date of preparation D D D RSD(%) 0.31

16 CH 3 CN loss test due to reaction with cylinder : immediate reaction, short term stability Reaction with the inner surface of cylinder and cylinder valve Adsorption loss test of CH 3 CN during the preparation of CRMs 10 μmol/mol CRM : Loss of CH 3 CN due to adsorption to inner surface of cylinder was evaluated by distributing equal amount of 10 μmole/mole CH 3 CN to other empty cylinder.. The two cylinders were analyzed and compared their FID response factors to check the adsorption loss of CH 3 CN. Result : very small loss, 0.18 % loss at first distribution.

17 Development and preparation of CH 3 CN CRM Preparation of acetonitrile CRM by gravimetry (ISO 6142) Preparation reproducibility 100 μmol/mol was checked by preparation four CH 3 CN CRMs : < 0.21% 10 μmol/mol was checked by preparation three CH 3 CN CRMs : < 0.31% >> 10 μmol/mol CH 3 CN CRM manufactured by gravimetric dilution with 100 μmol/mol CH 3 CN CRM and N 2 gas. Stability test is in progress.

18 Uncertainty evaluation for preparation of 10 μmol/mol CH 3 CN CRM : Modeling Equation Modeling Equation C CH 3CN CH 3CN N 2' N 2 6 CH 3CN 10 f Ads f Re mch 3CN mn 2 n CH 3CN n M n M CH 3CN CH 3CN n N 2' m CH 3CN n M N 2 M n N 2 M N 2 Where, C CH3CN : Concentration of CH 3 CN (μmole/mole) n CH3CN : Mole of CH 3 CN in CRM (mole) m CH3CN : Amount of liquid CH 3 CN reagent in CRM (g) M CH3CN : Molecular weight of CH 3 CN (g/mole) n N2 : Mole of N 2 in 100 μmol/mol CRM (mole) M N2 : Molecular weight of N 2 (g/mole) m N2 : Amount of N 2 gas in CRM (g) n N2 : Mole of N 2 in CRM (mole) n N2 Mole of N 2 in CRM (g) f Ads :: Factor for adsorption loss of CH 3 CN in cylinder f Re : Factor for Preparation reproducibility of CH 3 CN CRM

19 Uncertainty evaluation for preparation of 10 μmol/mol CH 3 CN CRM : Uncertainty parameter contribution Concentration of CH 3 CN : μmol/mol Relative Expanded uncertainty : 0.93 % uncertainty parameter level of contribution (%) n_ch3cn Mole of CH 3 CN in CRM 40.4 f_ads Factor for adsorption loss of CH 3 CN in cylinder 15.0 f_re Factor for reproducability for manufacture of CH 3 CN CRM 44.6

20 Relative Response Stability of CH 3 CN CRM Year of Preparation

21 Next Plan: Establishing 1 ~ 10 nmol/mol MeCN standard by dynamic dilution - 1,000 ~ 10,000 times dilution system setup by Sonic nozzle Developing transfer standard of cylinder or other container - Certify with the dynamic dilution standard

22 Establishment of Formaldehyde Gas Standard

23 Generation of HCHO std gas from Paraformaldehyde permeation tube using MSB dynamic mixing system n HCHO + m H2O Establishing HCHO gas standard by gravimetric generation of HCHO gas HCHO gas standard was established using micro-gravimetric permeation method. The established standard was corrected for moisture emission with precise moisture control and measurement.

24 Micro-Gravimetric System for HCHO Gas Std Generation High precision micro-gravimetric system(msb) and moisture measurement system (CRDS) were used for establishing HCHO gas standard.

25 Micro-Gravimetric System for HCHO Gas Std Generation

26 Model Equation for conc. calculation of HCHO std gas generated from permeation dynamic system x HCHO : HCHO mole fraction (μmol/mol) P : Permeation rate (ng/min) m HCHO : Weight loss of permeation tube (measured on MSB) (g) t : Measurement period (min) V m : Molar volume (L/mol) F T : Gas flow rate (ml/min) M HCHO : HCHO molar mass, (g/mol) x H2O : H 2 O mole fraction (μmol/mol) or other impurity M H2O : H 2 O molar mass, (g/mol) or other impurity

27 Purity Measurement of HCHO std gas generated from permeation tube at MSB system (by GC-AED) (from the HCHO gas standard using permeation tube) Excess Vent GC-AED Vent N 2 Cyl. Outlet : 60 psig MFC (500 ml/min) Permeation device in Chamber oven 110 Back pressure regulator 30 psig Loop (500 μl) 100 MFC (50 ml/min) VI inlet 100 Spilt ratio 4:1 CP-Sil 5CB, 50 m 530 μm 5 μm Carrier gas flow 4 ml/min Oven 30 (8 min) 5 /min 200 Valve 0.05 min injection / 0.55 min load

28 Other emission impurity measurement (from the HCHO gas standard using permeation tube) Counts AED3 A, Carbon 193 ( D) HCHO from permeation tube HCHO AED3 A, Carbon 193 ( D) Counts Counts AED3 A, Carbon 193 ( D) Counts Artifact from valve switching No other VOC impurities detected from the emitted HCHO gas standard AED3 A, Carbon 193 ( D) min Counts AED3 A, Carbon 193 ( D) HCHO from cylinder gas 85 Counts CO 2 HCHO AED3 A, Carbon 193 ( D) But, some unknown impurities were detected min form the HCHO cylinder standard gas. min min Unknown Trimer Unknown min min

29 h2o (ppb) Moisture as impurity in HCHO std gas generated from MSB-permeation system Generate HCHO std gas under pressurized condition, measure H2O at the same conditions Moisture Determination from HCHO std gas generation system (permeation tube method) h2o System blank of measuring system was maintained below 1 nmol/mol of H2O CRDS were used for H2O determination in HCHO gas standard time (hr)

30 Moisture emission measurement (from HCHO permeation tube) Ratio of conc of H2O vs total emission conc : 94 / 6061 * 100 = 1.5 % In paraformaldehyde, mole ratio H 2 O:CH 2 O = 1 : 65 About 1.5 % of water contained in CH 2 O gas std generated from paraformaldehyde n HCHO + m H2O n = 65 HCHO m = 1 H2O

31 Variation of HCHO Concentration over 25 Days Measurement Period : ~ Variation of HCHO Concentration over 25 days : RSD 0.40 %

32 Variation of HCHO Concentration over 4 Days Measurement Period : ~ Variation of HCHO Concentration over 4 days : RSD 0.15 %

33 Uncertainty Modeling Equation x HCHO : HCHO mole fraction (μmol/mol) P : Permeation rate (ng/min) m HCHO : Weight loss of permeation tube (measured on MSB) (g) t : Measurement period (min) V m : Molar volume (L/mol) F T : Gas flow rate (ml/min) M HCHO : HCHO molar mass, (g/mol) x H2O : H 2 O mole fraction (μmol/mol) M H2O : H 2 O molar mass, (g/mol)

34 Uncertainty Tree V m : Molar volume (L/mol) P : Permeation rate (ng/min) t : Measurement period (min) m HCHO : Weight loss of permeation tube (g) x HCHO : HCHO mole fraction (μmol/mol) M H2O : H 2 O molar mass (g/mol) M HCHO : HCHO molar mass (g/mol) x H2O : H 2 O mole fraction (μmol/mol) F T : Gas flow rate (ml/min)

35 Major Uncertainty factors HCHO Mole Fraction 5.90 μmol/mol Relative Expanded Uncertainty 1.4 % (coverage 95 %, k=2) Quantity Definition Distribution (%) F_T Gas flow rate (ml/min) 76.6 f_t Factor for temperature variability 8.5 f_p Factor for pressure variability 8.5 x_h2o H 2 O mole fraction (μmol/mol) 3.7 Δm_HCHO Weight loss of permeation tube (measured on MSB) (g) 2.2 t Measurement period (min) 0.6

36 Work Ongoing - Improve measurement uncertainty < 1% Uext - Develop portable formaldehyde standard in gas cylinder

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