enantiomeric separating study of d－and l－carnitinewith capillary zone electrophoresis
lengtao－hua1，guo wei－qiang1，renyi－ping2
（1．dept．of chemistry，zhejiang university，hangzhou 310027 china；2．zhejiang centerfor disease prevention and control，hangzhou 310003，china）
carnitine［β－hydroxy－γ－trimethylaminobutyric acid］is a chiralbiologicalsubstance found in differenttissues ofani－mals，some plants and microorganisms．its enantiomers showdifferent biological activities．l－carnitineisfound to play animportant role in thetransport offatty acids across the mitochondrial membrane bythe transferase and translocase enzymesystem［1，2］．recently，carnitine and its ramifications have been proved to possessinteresting pharmacological and nutri－tional properties［3］；on the other hand，d－carnitine has been shown to have a considerabletoxic influence on biochemi－cal processes［4］．in the past，patients have been treated with d，l－carnitinefor anorexia，dyspepsia and other patholo－gies．however，d－carnitine is an emulative depressorto the l－carnitine acetyltransferase，leading to a depletion of bodyl－carnitine storage［5］，the use ofthe pure l－carnitine and its esteris recommended．an uncoated capillary，sulfated－β－cyclodextrin and（s，s）－1，7－bis（4－benzyl－5－hydroxy－2－oxo－3－azapentyl）－1，7－diaza－12－crown－4 as chiral additive andacetonitrile as electroosmoticflow（eof）modifier were used forthe separation．the optimized method has beencharacter－ized and appropriately validated for the determination ofthese compounds．
1 experiment
1．1 instrumentation
abeckman capillary electrophoresis instrument p／ace2000（beckman instruments，fullerton，ca，usa）e－quipped with a diode array detector operating at260 nmwas used and a 32 karat software station was usedto performthedata collection and controlling the operational variables ofthe system． dow）×75μmi．d．was used．operation voltages were 30 kv．injection was performed in the electrokinetic mode．in－jection time was 10 seconds using a voltage of10 kv．
1．2 operating conditions
apositive powersupply of30 kvwas used with a constantcurrent mode of operation．capillaries of effectivelengthof60cm×75μmi．dwere used and the temperature was 25℃．the capillaries were washed for 5 min with 0．1 mol／lsodiumhydroxide solution，10 min with waterand 5 min with running buffer．the separation buffer was50 mmol／lphos－phoric acid，1．25％（w／v）sulfated－β－cyclodextrin，0．94％（w／v）（s，s）－1，7－bis（4－benzyl－5－hydroxy－2－oxo－3－aza－pentyl）－1，7－diaza－12－crown－4（in acetonitrile）and the detection was carried outat 260 nm．
1．3 derivatization
the derivatization reaction is described as follows．
2 results and discussion
2．1 optimization ofthe ceseparation
2．1．1 influence of ph
pheffects were studied overthe range of3～9．6forthe modelsubstance using phosphate 50 mmol／las backgroundelectrolyte and 1．25％（w／v）sulfated－β－cyclodextrin and 0．94％（w／v）（s，s）－1，7－bis（4－benzyl－5－hydroxy－2－oxo－3－azapentyl）－1，7－diaza－12－crown－4（in acetonitrile）as chiralselector．as a result，allseparations showed enhanced res－olution at ph3～7，the bestseparation was ph＝3．0．
2．1．2 effect of applied voltage
the effect ofthe applied voltage in the range of10～30 kvon the migration time as well as on the separation wasstudied at a phosphate buffer system（50 mmol／l）with 1．25％（w／v）sulfated－β－cyclodextrin and 0．94％（w／v）（s，s）－1，7－bis（4－benzyl－5－hydroxy－2－oxo－3－azapentyl）－1，7－diaza－12－crown－4（in acetonitrile）as chiral selector．goodenantiomeric separations were achieved
