A data frame containing reported results for lead (in mg/kg) from
CCQM Key Comparison CCQM-K30.
Usage
Pb
Format
A data frame containing 11 reported results with uncertainty data:
lab
Factor giving abbreviated laboratory identifier
value
The reported value for lead (mg/kg)
u
Standard uncertainty (mg/kg). The values in Pb were calculated from
the reported expanded uncertainty U and coverage factor k using u=U/k.
k
Coverage factor. Conventionally, the coverage factor is set to a suitable
quantile of Student's t based on the Welch-Satterthwaite effective degrees of freedom
or simply set to 2 for approximately 95% confidence. In this data set, labs all quoted
k for approximately 95% confidence.
U
Expanded uncertainty as reported by labs.
method
Factor indicating general measurement methodology:
IDMS
Isotope dilution mass spectrometry
ICP
Inductively coupled plasma spectrometry
GFAAS
Graphite furnace atomic absorbtion spectrometry
include
logical; Whether the reported result was included in the calculation
of the Key Comparison Reference Value for the study.
Details
The study involved circulation of a homogeneous set of samples of wine for analysis for lead (Pb) content
by a number of National Measurement Institutes.
The Key Comparison Reference Value, or assigned value for the lead content, was
set at 2.99 mg/kg with expanded uncertainty 0.06 mg/kg.
Source
Hearn, R., Santamaria-Fernandez, R. and Sargent, M. (2008)
Final report on key comparison CCQM-K30: Determination of lead in wine.
Metrologia45, 08001, 2008