in ion - pair extractive separation of metal cations using a neutral chelation reagent and a counter anion , selection of the chelation reagent is one of most important factors to realize preferable separation . especially , investigation of effect of steric structure around electron donor atoms in the reagent on the separation ability is very important for the development of novel reagents having high separation performance . schiff bases derived from the reaction of salicylaldehyde with primary amines ( salen type schiff base ) represent a versatile series of ligand . in attention to importance of these compounds symmetric and asymmetric transition metal complexes of these bases have been developed and used as ligands / catalysts in many reactions such as epoxidation , asymmetric synthesis , asymmetric sulfoxidation , asymmetric silylcyanation   and many other applications . schiff bases and the relevant transition metal complexes are still found to be of great interest in inorganic chemistry , although this subject has been studies extensively . schiff bases play a central role as chelating ligands in main group and transition metal coordination chemistry . the determination of ion - pair formation constants of organic ligands - metal ion complexes in water can be examined with different methods by following the extraction of metals to the varied organic solvents with organic ligands [ 11 - 14 ] . the solvent extraction of metal cations which contains dye ligands is preferred to use for its easy determination by spectrophotometric methods [ 15 - 17 ] . this paper describes extractive - spectrophotometric determination of sodium and potassium ions as ion - pairs and describes extractive - spectroscopic determination of ca , mg , cr , fe , zn , cd , ni , mn , co ions using some chiral schiff bases as complexing agents . an anionic color compounds of 4-(2-pyridylazo)-resorcinol mono sodium monohydrate ( napar ) , sodium picrat ( napic ) and potassium picrat ( kpic ) salts which showed in figure 2 , were used to follow the cation transport process using uv - vis spectrometry [ 11a,18 - 20 ] . the large and strong chromophore anion of the guest metal , na was readily mobilized by the organic ligands   in ch2cl2/water membranes . the selection of the optimum counter anion and chiral schiff bases were made with regard to phase separation efficiency , determination sensitivity and accuracy of complexation constants ( kext ) . the results of ion - pair extractions obtained in our experimental conditions of identical cation / ligand concentrations of monovalent napar , napic and kpic salts are summarised in table 1 . solvent media effects , and the anion in a salt - ligand system , play a fundamental role on both the stability of the ion - pair complexes , their solubilization and the resulting charge separation in solution . since in real extraction systems some amount of dye salts is soluble in organic solvent without schiff base , the values of the solubility in organic solvents are also given in the first lines of table 1 . when the used napar , napic and kpic anionic dyes are extracted as 1:1 complexes with chiral schiff bases , the cation - complexing ability of the schiff bases under experimental conditions show that , selectivity was observed only napar . it is interesting to note that , all of the ligands display higher extracting ability toward napar than do both napic and kpic . we suggest that the presence of the par as the counter ion was increased extraction avidity toward alkali metal salt according to the alkali picrat salts . the organic anion of par is well hydrogen bonded to the schiff base by the o - h hydrogen on the anionic dye counter ion . from the discussion above it was found that napar is much more associated with schiff base and the best extracted organic sodium dye as the ion pair complexes ( 49 - 83% ) than other dyes . the logkext values of i , ii and iii for the transition metal cations in dichloromethane have been decreased in order zn > ni > co > fe > cr cd ; > zn > ni > fe > co > cr and zn > ni > co > fe > cr respectively . zn is found to be the best extracted metal cation for the studied chiral schiff bases and shown to form more stable complex than other divalent cations . chiral schiff bases which studied in this paper , were synthesized according our early study . sodium dye , 4-(2-pyridylazo)-resorcinol monosodium salt monohydrate ( napar ) was commercial product from aldrich dried over p2o5 for 48 hours at 0.1 torr . sodium and potassium picrates ( napic and kpic ) were prepared by adding an alkali metal hydroxyde solution to an aqueous solution of picric acid ; the resulting precipitate of sodium picrate mono hydrate and potassium picrate were recrystallized from water - ethanol ( 1:3 ) mixture and water , respectively . cacl2 , mgcl2.6h2o , crcl3.6h2o , fecl3.6h2o , zncl2 , cdcl2 , nicl2 , mncl2 , cocl2 are analytical grade reagents from fluka dried over p2o5 for 48 h at 0.1 torr . the concentrations of napar , napic and kpic in the aqueous phases were determined by uvvisible spectroscopy ( varian cary model 1e uv - visible spectrophotometer ) at 407.0 , 356.6 and 356.0 nm , respectively , with appropriate quartz cells 2 - 50 mm in length . the concentrations of ca , mg , cr , fe , zn , cd , ni , mn , co metal ions in the aqueous phases have been determined spectroscopically : icp - aes ( inductively coupled plasma - atomic emission spectroscopy : perkin elmer optima 3100 xl ) . the extraction measurements were done in a 100 ml glass thermostated cell compartment with a mechanical stirrer where a 25 ml solution of an any aqueous salt ( 410 m ) and chiral schiff bases in ch2cl2 organic solvent in appropriate concentration were placed and stirred for 120 minutes at 25  0.1 c and subsequently allowed to stand for 30 min . to complete the phase separation . the optimum concentration of chiral schiff bases were determined by extracting the alkali salts with 10 ml of various concentrations of schiff bases ( 410 m ) . all the extractions were carried out at the natural ph of the aqueous organic salt solution which were about 6.1 - 6.7 . after extraction , napar , napic and kpic concentrations in the aqueous phase were determined using uv - visible spectrophotometer and the ca , mg , cr , fe , zn , cd , ni , mn , co concentrations in the aqueous phase were determined using icp - aes ( inductively coupled plasma - atomic emission spectroscopy ) . complexation and distribution constants are summarized in table 1 . and table 2 . in the present work we made use of a common formalism of equations ( 1 - 15 ) . the equilibrium processes taking place during the extraction between an aqueous solution containing the alkali metal cation , m(w ) , and organic anion , a(w ) , and an organic solution containing schiff base l(org ) , can be written as : for the extraction process of an acid , ha , with the organic anion in the equations above , [ m]w , [ a]w and [ mlna]org denote the concentrations of uncomplexed cation and anion in aqueous phase and the complex ion - pair extracted in the organic phase , respectively . mass balances for these processes are expressed as : where the subscript ( 0 ) designates the initial concentrations . as can be seen from the results of blank experiments without the schiff base in table 1 therefore , for the overall extraction process , the following equation can be written by adding the eq.(1 ) to the reverse of eq.(2 ) , the equilibrium constant of the extraction process can be written as : at n = 1 , where refers to a stoichiometric coefficient for the reaction . here kd , l denotes a distribution constant of a schiff base between water and organic solvent and is defined as , hence the eq.(12 ) at n = 1 is rewritten as , according to the eq.(15 ) , kext values were obtained by determining [ a]w spectrophotometrically . the results obtained for chiral schiff bases are shown in table 1 and table 2 . the extraction measurements were done in a 100 ml glass thermostated cell compartment with a mechanical stirrer where a 25 ml solution of an any aqueous salt ( 410 m ) and chiral schiff bases in ch2cl2 organic solvent in appropriate concentration were placed and stirred for 120 minutes at 25  0.1 c and subsequently allowed to stand for 30 min . to complete the phase separation . the optimum concentration of chiral schiff bases were determined by extracting the alkali salts with 10 ml of various concentrations of schiff bases ( 410 m ) . all the extractions were carried out at the natural ph of the aqueous organic salt solution which were about 6.1 - 6.7 . after extraction , napar , napic and kpic concentrations in the aqueous phase were determined using uv - visible spectrophotometer and the ca , mg , cr , fe , zn , cd , ni , mn , co concentrations in the aqueous phase were determined using icp - aes ( inductively coupled plasma - atomic emission spectroscopy ) . in the present work we made use of a common formalism of equations ( 1 - 15 ) . the equilibrium processes taking place during the extraction between an aqueous solution containing the alkali metal cation , m(w ) , and organic anion , a(w ) , and an organic solution containing schiff base l(org ) , can be written as : for the extraction process of an acid , ha , with the organic anion in the equations above , [ m]w , [ a]w and [ mlna]org denote the concentrations of uncomplexed cation and anion in aqueous phase and the complex ion - pair extracted in the organic phase , respectively . mass balances for these processes are expressed as : where the subscript ( 0 ) designates the initial concentrations . as can be seen from the results of blank experiments without the schiff base in table 1 therefore , for the overall extraction process , the following equation can be written by adding the eq.(1 ) to the reverse of eq.(2 ) , the equilibrium constant of the extraction process can be written as : at n = 1 , where refers to a stoichiometric coefficient for the reaction . here kd , l denotes a distribution constant of a schiff base between water and organic solvent and is defined as , hence the eq.(12 ) at n = 1 is rewritten as , according to the eq.(15 ) , kext values were obtained by determining [ a]w spectrophotometrically . the results obtained for chiral schiff bases are shown in table 1 and table 2 .
the constants of the extraction equilibrium and the distribution for dichloromethane as an organic solvent having low dielectric constant of metal cations with chiral schiff bases , benzaldehydene-(s)-2-amino-3-phenylpropanol ( i ) , ohydroxybenzaldehydene- ( s)-2-amino-3-phenyl - propanol ( ii ) , benzaldehydene-(s)-2- amino-3-methylbutanol ( iii ) with anionic dyes [ 4-(2-pyridylazo)-resorcinol mono sodium monohydrate ( napar ) , sodium picrat ( napic ) and potassium picrat ( kpic ) ] and some heavy metal chlorides were determined at 25 c . 
 all the ligands have given strongest complexation for napar . 
 in contrast , similar behaviour for both alkali metal picrates is not apparent in the complexation of corresponding ligands .