CCQM-K7 was placed in the KCDB archives on 18 September 2023
MEASURAND : Amount-of-substance fraction of benzene, toluene, ethylbenzene, m-xylene and o-xylene in a nitrogen balance
| NOMINAL VALUES : | benzene |
50 nmol/mol |
| toluene |
80 nmol/mol |
|
| ethylbenzene |
70 nmol/mol |
|
| m-xylene |
90 nmol/mol |
|
| o-xylene | 60 nmol/mol |
Degrees of equivalence Di = (xi - xigrav) and expanded uncertainty Ui, both expressed in nmol/mol, for each analyte
Click on the graphs for a closer view
 |
 |
|
 |
 |
|
 |
||
CCQM-K7 was placed in the KCDB archives on 18 September 2023
MEASURAND : Amount-of-substance fraction of benzene, toluene, ethylbenzene, m-xylene and o-xylene in a nitrogen balance
The following table gives the degrees of equivalence Di and expanded uncertainty Ui, both expressed in nmol/mol.
| Metrology area, Sub-field | Chemistry and Biology, Gases |
| Description | Benzene, Toluene and Xylene (BTX) in Nitrogen at levels higher than regulatory levels |
| Time of measurements | 1999 |
| Status | Approved for equivalence |
| Final Reports of the comparisons | |
| Measurand | Amount-of-substance fraction: Benzene (50 nmol/mol), Toluene (80 nmol/mol), Ethylbenzene (70 nmol/mol), m-Xylene (90 nmol/mol), o-Xylene (60 nmol/mol) |
| Transfer device | Calibrated gas cylinder measured by gravimetry |
| Comparison type | Key Comparison |
| Consultative Committee | CCQM (Consultative Committee for Amount of Substance) |
| Conducted by | CCQM (Consultative Committee for Amount of Substance) |
| Comments | CCQM-K7 was placed in the KCDB archives on 18 September 2023 Results published on 11 July 2002. Benzene, Toluene, Ethylbenzene, m-Xylene and o-Xylene in a nitrogen balance Levels higher than regulatory levels |
| Pilot institute |
NIST
National Institute of Standards and Technology United States |
| Contact person | F. Guenther +1 301 975 3939 |
| Pilot laboratory | |
|---|---|
| NIST |
National Institute of Standards and Technology, United States, SIM |
| KRISS |
Korea Research Institute of Standards and Science, Korea, Republic of, APMP |
| NMIJ AIST |
National Metrology Institute of Japan, Japan, APMP |
| NPL |
National Physical Laboratory, United Kingdom, EURAMET |
| UBA |
Umweltbundesamt, Federal Environment Agency, Germany, EURAMET |
| VNIIM |
D.I. Mendeleyev Institute for Metrology, Rosstandart, Russian Federation, COOMET |
This page proposes print-out on A4 paper (portrait) of the comparison details (best printed out using a black and white printer).
Please, select items to be printed out, then click on "OK" :
CCQM-K7 was placed in the KCDB archives on 18 September 2023
MEASURAND : Amount-of-substance fraction of benzene, toluene, ethylbenzene, m-xylene and o-xylene in a nitrogen balance
| NOMINAL VALUES : | benzene |
50 nmol/mol |
| toluene |
80 nmol/mol |
|
| ethylbenzene |
70 nmol/mol |
|
| m-xylene |
90 nmol/mol |
|
| o-xylene | 60 nmol/mol |
| Key comparison reference value: there is no single reference value for this comparison, the value xigrav is taken as the reference value for laboratory i. |
| The degree of equivalence of each laboratory with respect to the reference value is given by a pair of terms: Di = (xi - xigrav) and Ui, its expanded uncertainty both expressed in nmol/mol, where Ui = k(ui2 + uigrav2)1/2, k = 2 for all laboratories except UBA, k = 3 for UBA (see pages 4 and 5 of the Final Report) |
| The degree of equivalence between pairs of laboratories are not explicitely given in the Final Report. They may be computed using Dij = Di - Dj and Uij, its expanded uncertainty, with Uij = (Ui2 + Uj2)1/2 for any pairs of laboratories excluding UBA. Calculation of the degrees of equivalence between two laboratories involving UBA cannot be computed using the above equations (see page 5 of the Final Report) |
CCQM-K7 was placed in the KCDB archives on 18 September 2023
MEASURAND : Amount-of-substance fraction of benzene, toluene, ethylbenzene, m-xylene and o-xylene in a nitrogen balance
| NOMINAL VALUES : | benzene |
50 nmol/mol |
| toluene |
80 nmol/mol |
|
| ethylbenzene |
70 nmol/mol |
|
| m-xylene |
90 nmol/mol |
|
| o-xylene | 60 nmol/mol |
xi : result of measurement carried out by laboratory i
ui : combined standard uncertainty of xi
xigrav : gravimetric value of the gas amount-of-substance fraction in the cylinder received by laboratory i
uigrav : combined standard uncertainty of xigrav
Note that the participants declared their uncertainties as expanded uncertainties at a 95% level of confidence. They all declared a coverage factor k = 2, except UBA which declared a coverage factor k = 3.
The ui values are obtained by dividing the declared expanded uncertainties by the declared k values.
