12. Calculation
12.1 Regress the natural log (ln) of readings A1, A2, and A3 against the number of injections one, two, and three. A linear correlation (correlation coefficient R2 > 0.95) must exist to insure the correctness of the multiple extraction procedure. If R2 is not greater than 0.95, then repeat the procedure with a new sample from a different container.
12.2 Calculate the concentration of H2S as outlined below.
12.3 Calculate the total area difference (or total height difference) using Eq 1.
12.4 Calculate the concentration of H2S in the sample (µg/g) by multiplying the total area difference obtained for the residual fuel sample times the H2S response factor and dividing by the weight of the residual fuel oil sample in (g), Eq 4:
where:
RFH2S = response factor from Eq 3,
C(H2S)F = concentration of H2S in the residual fuel oil, µg/g,
ATF = total area or peak height difference from H2S residual fuel oil analysis, and
WF = weight of residual fuel oil sample, g.
12.5 See Appendix X1 for an example calculation.
13. Precision and Bias
13.1 Precision - Based on limited information from one laboratory, the 95 % repeatability limits when using a lead acetate paper detector are:
NOTE 7 - These repeatability numbers were obtained by Beatriz A. Silva, Intevep, SA, Apdo 76343, Caracas 1070A Venezuela.
13.2 It is not possible to specify the precision of the procedure in this test method beyond what appears in 13.1, since generating the reproducibility data is not practical.
13.3 Bias - Bias cannot be determined because there is no reference material suitable for determining the bias of the procedure in this test method.
14. Keywords
14.1 heavy distillates; heavy distillate/residual fuel blends; hydrogen sulfide; multiple headspace extraction; residual fuels; sulfur specific detection