Doing it this way would get you proper query.
foreach (string item in sc)
{
string insertsql = "INSERT INTO Items(Description,ItemNo,Qty)VALUES (";
sb.AppendFormat("{0}", insertsql);
if (item.Contains(","))
{
splitItems = item.Split(",".ToCharArray());
sb.AppendFormat("'{0}','{1}','{2}');", splitItems[0], splitItems[1], splitItems[2]);
}
}