How to split get utf string.

if (cmd == "card_request") {

         Debug.Log("FOund cards");
         ISFSObject responseParams = (SFSObject)evt.Params["params"];
         Debug.Log(responseParams.GetClass("cards").ToString());
         SFSArray data = (SFSArray)responseParams.GetSFSArray("cards");
         Debug.Log(data.GetUtfString(0));

         //for (int i = 0; i < data.GetUtfString(0).IndexOf("value"); i++) {
             firstSplit = data.GetUtfString(0).Split(';');
             Debug.Log(firstSplit);
         //}
         for (int i = 0; i < firstSplit[0].IndexOf("value"); i++) {
             secondSplit = firstSplit[0].Split(':');
             Debug.Log(secondSplit);
         }
         for (int i = 0; i < secondSplit[0].IndexOf("value"); i++) {
             thirdSplit = secondSplit[0].Split(',');
             Debug.Log(thirdSplit);
         }
     }

the data is coming fine at this line Debug.Log(data.GetUtfString(0)); But when I try to split it it gives errors. Somebody can please suggest me the effective way to split UTF string. Null exceptions occurs at secondSplit and thirdSplit