8. Sampling
8.1 Sampling is defined as all steps required to obtain an aliquot of the contents of any pipe, tank, or other system and to place the sample into the laboratory test container. Only representative samples obtained as specified in Practices D4057 (API MPMS Chapter 8.1) and D4177 (API MPMS Chapter 8.2) shall be used for this test method.
8.2 The size of the test portion should be based on the expected water content of the sample, such that the water yield does not exceed the capacity of the trap (unless a trap with a stopcock is used permitting excess water to be withdrawn into a graduated cylinder).
8.3 Practice D5854 (API MPMS Chapter 8.3) contains information on sampling and homogenization efficiency of unknown mixers. This test method should not be followed without strict adherence to Practice D5854 (API MPMS Chapter 8.3).
9. Verification
9.1 The accuracy of the graduation marks on the trap shall be certified or verified, using only national or international standards, such as National Institute of Standards and Technology (NIST) traceable equipment. Verification shall be with a traceable 5mL Micro Burette or Micro Pipette, readable to the nearest 0.01mL.
9.1.1 In styles A, B, C, and D, as specified in Table 2 (Table 1 in Specification E123), each subdivision (that is, 0.1mL through 1.0mL) in the conical portion of the tube shall be verified. Thereafter, each major subdivision (that is, 2.0 mL, 3.0mL, 4.0mL, and up to the total volume of the trap) shall be verified.
9.1.2 In styles E and F, as specified in Table 2, each major subdivision (0.1mL, 1.0mL, 2.0mL, 4.0mL, and 5.0mL in the case of Style E; 0.05mL, 0.5mL, 1.0mL, 1.5mL, and 2.0mL in the case of Style F) shall be verified.
9.2 The entire glassware assembly shall be verified prior to first use and at a regular frequency thereafter as follows.
9.2.1 Put 400mL of dry (0.02% water maximum) xylene or the solvent to be utilized in the analysis of unknown samples into the apparatus and test in accordance with Section 10. When complete, discard the contents of the trap and add the volume of water as specified as first test in Table 3 directly to the distillation flask and test in accordance with Section 10.
9.2.2 Repeat the test in 9.2.1, and add the volume specified as second test in Table 3 directly to the flask. The assembly of the apparatus is satisfactory only if the trap readings are within the tolerances specified in Table 3.
9.3 A reading outside the permissible limits suggests a malfunction resulting from vapor leaks, too rapid boiling, inaccuracies in calibration of the trap, or ingress of extraneous moisture. Eliminate these factors before repeating the verification.
