Publisher: Chemical Society of Nigeria

Use of Mixed Ligand Complex As Sensitive Titrant For Trace Analysis of L- Ascorbic Acid In Green Leaf Vegetables.

S. Y. Aboho, E. W. Nsi, D. C. Nzewi, B. M. Wufem, E. O. Ekanem
KEYWORDS: M LC, Sensitive, Titrant, Trace analysis, Ascorbic acid.

ABSTRACT:

A  procedure  is  developed  for  the  trace  analysis  of  l  -  ascorbic  acid  (  Vitamin  C)  in  green  ‘leafy’ vegetables,  Talinium  triangulare  (Water  leaf  );  Amaranthus  hybridus  (  Green  );  Cochorus  olitorum          (  Ewedu  );  using  Hydrogen  tetracyano-mono-1,10-phenanthroline  ferrate(II)dihydrate;  H  [Fe (phen)(CN)].2H2O  (Mixed  Ligand  Complex)  as  a suitable analytical  titrant. Two  existing  methods  were  selected  for  comparative  study  with  the  MLC  method.    Observations  drawn on  the  basis  of  experimental  and  statistical  analyses  showed  the  sensitivity  values  as:  Iodine  (0.95);  N– Bromosuccinimide  [  NBS  ]  (0.98  );  MLC  (1.00  ),  MLC  being  more  sensitive  than  the  selected  methods, and  the  practical  detection  limit  showed  Iodine  (  0.01ppm  );  NBS  (0.01ppm);    MLC  (0.002ppm). Precision  of  results  using  pure  ascorbic  acid  solution  through  standard  error  values  (  S.E  )  was    Iodine (0.55  );  NBS    (0.94  )and  MLC  (1.00),  showing  the  MLC  method  as  most  precise  using  the  green  ‘leafy’ vegetables.  Relative  accuracy  of  methods  showed  Iodine  (1.82);  NBS  (1.06);  MLC  (9.67).    Sixteen probable  interferents  investigated  showed  non-  selectivity,  except  in  the  presence  of  S2−  ions  (500ppm); S2O32−  ions  (100ppm);  PO43−ions(50ppm)  and  Cu2+ions(50ppm),  the  reaction  was  stoichiometric  at  pH 1.8  .  The  percentage  recovery  showed  a  range  (94.20  –  98.22%).    Finally,  the  basic  advantage associated  with  the  proposed  method  is  its  sensitivity,  selectivity,  comparative  rapidity,  simplicity  and applicability  which  may  be  extended  to  some  coloured  food  samples  and  pharmaceuticals.    Therefore,  is recommended for both routine laboratory and research studies.  


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