var
SL: TStringList;
S: string;
I: Integer;
begin
S := '123,32,123,456';SL.Delimiter := ',';
SL.StrictDelimiter := True;
SL.DelimitedText := S;
for I := 0 to SL.Count - 1 do
SL[I] := '"' + SL[I] + '"';
S := String.Join(',', SL.ToStringArray);
end;