One screw-top bottle with 50 g of soil to be analyzed for TPH. Use with EPA IR or Gravimetric Methods 8440, 9071B, or other applicable methods. For CRMs, #570 contains no interfering fatty acids and #571 contains interfering fatty acids. #632 (PT) and #572QR may or may not contain interfering fatty acids. Identifying the presence or absence of fatty acids is part of the proficiency test.