CSV splitter for lines with escaped delimeters

SplitCSV.fsx

(***
Converts a csv line which contain escaped elements delimited by for example ". The elements inside these delimters
can contain a , so a simple line.Split(',') would be incorrect.

example:
converts
    val line : string = ""22 Dec 2014",BP,"EXPENSES ","1000.00", , "
to
    val toks : string [] = [|"22 Dec 2014"; "BP"; "EXPENSES "; "1000.00"; " "|]
***)  

//parse csv char by char
let SplitCSV (line:string) =
    let rec csv_splitter (line:string) (escape_char:char) (i:int) (is_in_q:bool) (tok:char[]) (toks:string[]) = 
        if i = line.Length then
            toks
        else
            let c = line.[i]
            if c = escape_char then 
                csv_splitter line escape_char (i+1) (not is_in_q) tok toks
            elif c = ',' && (not is_in_q) then // actual delimter
                let stok = tok |> System.String //convert char[] to string
                csv_splitter line escape_char (i+1) (is_in_q) [||] (Array.concat [| toks; [|stok|] |])
            else
                csv_splitter line escape_char (i+1) (is_in_q) (Array.concat [| tok; [|c|] |]) toks
    //execute splitter with escape char "                   
    csv_splitter line '"' 0 false [||] [||]