We report on a measurement of the ratio of the strong coupling constants es(Mzo) for various data samples with different quark flavour compositions obtained f rom e + e annihilation at LEP. We select events with muons, electrons, and D *• mesons f rom charm and bot tom decays, events with highly energetic K ~ mesons originating predominantly f rom strange quarks, and events with highly energetic stable charged particles f rom a combination of up, down and strange quarks. F rom the jet production rates in these events we obtain f rom these samples the relative value of c% for the individual quark flavours as b c ~s -1.017__+0.036, es 0 . 9 1 8 • u d s c O~ s O~ u d s b s u d s 0% -1 .158• 0% --1.038__+0.221, with quadratically combined statistical and systematic errors. We also compare the 0% values for quarks of different weak isospin, charge and generation. No evidence for a dependence of as on any of these quark properties is observed. Finally, combining all samples and deter~ s /~s ratio for each flavour, we do not find mining the f incl any dependence of the strong coupling constant on flavour.