separated by HPLC on an octadecyl C?s bonded phase. The eluent (aka. mobile phas

Question

separated by HPLC on an octadecyl C?s bonded phase. The eluent (aka. mobile phase) was 65vol % methanol in water with a total analysis time of4 min. The detine marker Bghthalene Anthracene Abenzee 10500 7000 naphthalene anthracene 3500 timin eluted at 0.5 min (shown at the point of arrow with no visible peak). a)Calculate an increase or decrease in capacity factor (k) and retention of the last compound anthracene if 90 vol % of methanol were used instead? b)Would you expect the resolution between benzene-naphhalene pair to increase or decrease with increasing vol% of methanol. c)What chemical compound would you use as a dead time marker to calculate the capacity factor (k0? Note that the dead time marker peak is not shown but it elutes at a point marked with arrow d) Name the HPLC detector will be best suited if picogram (10ig) levels of the three PAHs needs to be detected in gasoline engine smoke?

Explanation / Answer

a).methanol is polar so increasing the mobile phase would leads to be more polar, making retention time more because anthracene is nonpolar ,so they will be more attracted to the column,

b).at high levels of methanol pH will increase, benzene-napthalene pair sample begins to resolve, but baseline resolution is never achieved, resolution is independnet of mobile phase pH.

c)nitrate compound usedas a dead time marker to caliculate K.

d)HPLC-FLD was developed for the determination of 13 polycyclic aromatic hydrocarbon(PAHs)

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