Substring in Informix

I need to split a field(Name) into Two (First Name and Last Name) based on a comma in Informix.

Example: "Mark, Wheeler J" has to be split as Mark and Wheeler. I have tried using SQL syntax but it gives me a syntax error in Informix. Please help me.

SELECT
  SUBSTRING(name, 1, CHARINDEX(',', name ) - 1) AS FirstName,
  SUBSTRING(name, CHARINDEX(',', name) + 1, 8000) AS LastName
FROM
 employee