String Into Seperate characters problem

Hello people, having problems with getting a string into an array and could do with some help...i have a string of names seperated by comma's which i passed into a split method and the code i used works fine, but then when i try and pass the split name into another split function to get the seperate characters using the same method i get an index out of range message. the code i am using is this : -

 function ConvertTunesChar(splitter : String){          
 Debug.Log(splitter);
 var tuneChar = new Array();
  tuneChar = splitter.Split(""[0]);
  for(i = 0; i < tuneChar.Length; i++){
     print(tuneChar[i]);
                                   
  }
  }

Splitter been the array string i placed the string with seperated with comma's into in another function using the exact same split approach but the split was using (","[0]) instead of (""[0]) and it worked fine..any help please ?.