3.6 Tube current

Although element peak areas are not exactly linearly related to tube current, they can be approximated to a linear relationship (see Jarvis, Croudace, and Rothwell (2015)). The Q-Spec software can report either peak areas (n) or intensities (n/mA), and it is easy to tell which you are using: peak areas are always integers, but intensities are always fractions. It is easy to adjust from one to the other:

current <- as.numeric(CD166_19_S1$metadata[18, 2])
  CD166_19_S1$xrf %>%
  mutate(intensity_Fe = round(Fe/current, 3)) %>%        # convert to intensity
  mutate(peakarea_Fe  = round(intensity_Fe*current)) %>% # convert to peak area
  select(Fe, intensity_Fe, peakarea_Fe) %>%
  head()

## # A tibble: 6 × 3
##      Fe intensity_Fe peakarea_Fe
##   <dbl>        <dbl>       <dbl>
## 1 19786         660.       19786
## 2 35168        1172.       35168
## 3 36494        1216.       36494
## 4 35952        1198.       35952
## 5 35512        1184.       35512
## 6 44303        1477.       44303

References

Jarvis, S., I. W. Croudace, and R. G. Rothwell. 2015. “Parameter Optimisation for the ITRAX Core Scanner.” In Micro-XRF Studies of Sediment Cores, Developments in Paleoenvironmental Research 17, edited by I. W. Croudace and R. G. Rothwell, 535–62. Dordrecht: Springer.