corr_mbf: Correcting instrumental mass bias.
In andreabz/pbratios: Processing Pb isotope ratio data

Description Usage Arguments Details Value See Also Examples

The function corrects Pb isotope ratio for mass bias using the standard bracketing approach.

1	corr_mbf(data)

data

A data.table produced by the calc.ratios function and containing average Pb isotope data. The dataset must have a column sample containing the sample ID, the columns Pb208207, Pb206207, Pb208206 and Pb207206 containing the measured Pb isotope ratio values for 208Pb/207Pb, 206Pb/207Pb, 208Pb/206Pb and 207Pb/206Pb, respectively. For each ratio also a columns Pb20x20y.se, containing standard errors are required. Bracketing standards must be labelled as “SRM981” and are assumed to be diluted solutions of NIST SRM 981. Certificate values for these ratios are reported at https://www-s.nist.gov/srmors/certificates/view_certPDF.cfm?certificate=981. The function will evaluate data from the first to the last SRM and samples outside these range will be ignored.

The standard bracketing techniques uses the average mass bias factor measured in standard solutions with known isotope ratio values to correct the isotope ratios measured in samples. As mass bias factor is influenced by temporal random fluctuations, standard solutions must be analysed just before and after the samples for which the correction will be applied.

A data.table containing the Pb isotope ratios corrected for the mass bias using the standard bracketing technique. Extended uncertainty (U = k u, k = 2) is also provided for each ratio and it is stored in Pb20x20y.U columns. Uncertainty budget take into account the relative standard errors for the sample, the mass bias factor and the certified values for NIST SRM 981.

extract_data calc_ratios

file.long <- system.file("extdata", "spmnya_2012.csv", package = "pbratios")
spmnya.2012 <- extract_data(file.long, report = "long")
spmnya.2012avg <- calc_ratios(spmnya.2012)
spmnya.2012cor <- corr_mbf(spmnya.2012avg)