Prebum time

Define the prebum time. Why is it used Would you expect that (a) galhum and (b) tungsten could be satisfactorily determined in steel using the same prebum time Explain your answer. 

The uranium oxide data in Table 7.8 were collected on a Teledyne Leeman Labs Prodigy DC Arc. The uranium oxide was mixed with a small amount of gallium oxide/cobalt oxide buffer and 125 mg of the buffered sample were analyzed. The prebum time was 4 s, and the elements were determined in a 4-45 s integration time. The details are available in an application note available from Teledyne Leeman Labs, along with other examples of the use of DC arc emission for materials analysis. 

In spark ablation, a spark at constant density is obtained in a matter of seconds, and thus, particularly in the case of small spark chambers, prebum times are accordingly low. In plasma emission as well as in plasma mass spectrometry a linear dynamic range of more than 4 orders of magnitude can be obtained and RSDs are a few percent in the case of absolute measurements. However, as shown by the results in Table 6, they can easily fall to below 1%, when using an internal standard element (Fe in the case of steel samples). The matrix effects from the sampling... 

The time scale in the flame is obtained from the linear flow rate, which in turn is calculated from the area of cross section of the flame, and its volume flow rate. The volume flow rate is calculated from the prebumed flow rate, the composition of the burnt gases and their temperature. The... 

---