ASTM D7621 Standard Test Method for Determination of Hydrogen Sulfide in Fuel Oils by Rapid Liquid Phase Extraction
11. Procedure
11.1 Initial Conditions:
11.1.1 Procedure A:
11.1.1.1 Confirm that the temperature of the heater jacket is 60.0 °C +/- 1.0 °C and the vapor phase processor is -20.0 °C +/- 2.0 °C.
11.1.1.2 Insert a new filter cartridge (7.4) into the vapor phase processor, and screw on the cap.
11.1.2 Procedure B:
11.1.2.1 Confirm that the temperature of the heater jacket is 60.0 °C +/- 1.0 °C.
11.2 Remove the screw cap from the cleaned test vessel (see 9.5) and introduce 20.0 mL +/- 0.5 mL of diluent oil (see 7.1) using the syringe (see 6.3) and then replace the screw cap. Place the test vessel in the temperature controlled heating jacket and fit the input/output tubing.
11.3 Air is pumped through the diluent in the test vessel and to the detector for 5 min. This allows the diluent oil to warm up, and the system to be purged.
11.4 Air is then pumped directly to the detector, bypassing the test vessel, to allow the test specimen to be introduced without purge air affecting the concentration of the H2S. Ensure that the instrument is operating in bypass mode before introducing the test specimen. Introducing the test specimen before this condition is met will likely result in premature loss of H2S and an erroneously low result. Ifthis is suspected or the instrument indicates that an incorrect procedure has been followed, abandon the test and repeat using a fresh test specimen.
11.5 Depending on the expected H2S concentration, draw the appropriate volume of the sample from at least 3 cm below the sample surface, avoiding the bottom of the container, into the disposable syringe or positive displacement pipette (6.7 and 6.6) and weigh to the nearest 0.001 g (see 6.2). Avoid applying a strong vacuum to the sample when using the syringe or pipette and ensure that the integrity of the material is maintained so that the possible loss of H2S is kept to a minimum. Do not expel air from the syringe or pipette into the sample. Using the keypad, enter the total mass, which includes the syringe/pipette and sample, into the apparatus. The appropriate volume shall be determined by reference to Table 1.
NOTE 8 - A single mass can be entered rather than entering the mass before and after sample introduction if the balance is tared.
11.6 Introduce the test specimen into the test vessel, ensuring that the syringe or pipette is held vertically to avoid sample adhering to the test vessel walls. Ensure that the syringe or pipette does not touch the surface of the diluent liquid. Any pickup of diluent oil onto or into the syringe or pipette will result in the mass of the oil being included in the mass of the empty syringe or pipette leading to an erroneously high result. If this is suspected, abandon the test and repeat it.
11.7 Immediately, after removing the syringe or pipette, screw the cap tightly onto the top of the test vessel.
11.8 Weigh the emptied syringe or pipette to the nearest 0.001 g (see 6.2) and using the keypad enter the mass into the apparatus.
11.9 Immediately start the test, which proceeds automatically.
11.10 The detector reading is normalized to zero.
11.11 Air Path:
11.11.1 Procedure A:
11.11.1.1 Air is pumped directly through the filter cartridge for 3 min. After these 3 min the air is diverted through the diluted test specimen in the test vessel and to the detector.
11.11.2 Procedure B:
11.11.2.1 Air is pumped through the test specimen and diluent in the test vessel and to the detector.
11.12 The millivolt readings (mV) from the detector are recorded at least every 4 s throughout the test until 15 min have elapsed. The result is automatically calculated and displayed in mg/kg.
11.13 Air is pumped to purge the detector.
11.14 Remove the test vessel and check that the test specimen and diluent oil have properly mixed. If two distinct phases exist, check the air connections and repeat the test.
11.15 Clean the test vessel.
11.16 For Procedure A, remove and dispose of the cartridge from the vapor phase processor.
12. Calculation
12.1 Report the H2S content to the nearest 0.01 mg/kg for <10 mg/kg, and 0.1 mg/kg for ≥10 mg/kg.
H2S = (A x C)/m mg/kg
where:
A = integrated area of cell output over the test time (mV.s),
C = calibration constant of the detector (µg)/(mV.s), and
m = mass of the test specimen to be tested (g).
11. Procedure
11.1 Initial Conditions:
11.1.1 Procedure A:
11.1.1.1 Confirm that the temperature of the heater jacket is 60.0 °C +/- 1.0 °C and the vapor phase processor is -20.0 °C +/- 2.0 °C.
11.1.1.2 Insert a new filter cartridge (7.4) into the vapor phase processor, and screw on the cap.
11.1.2 Procedure B:
11.1.2.1 Confirm that the temperature of the heater jacket is 60.0 °C +/- 1.0 °C.
11.2 Remove the screw cap from the cleaned test vessel (see 9.5) and introduce 20.0 mL +/- 0.5 mL of diluent oil (see 7.1) using the syringe (see 6.3) and then replace the screw cap. Place the test vessel in the temperature controlled heating jacket and fit the input/output tubing.
11.3 Air is pumped through the diluent in the test vessel and to the detector for 5 min. This allows the diluent oil to warm up, and the system to be purged.
11.4 Air is then pumped directly to the detector, bypassing the test vessel, to allow the test specimen to be introduced without purge air affecting the concentration of the H2S. Ensure that the instrument is operating in bypass mode before introducing the test specimen. Introducing the test specimen before this condition is met will likely result in premature loss of H2S and an erroneously low result. Ifthis is suspected or the instrument indicates that an incorrect procedure has been followed, abandon the test and repeat using a fresh test specimen.
11.5 Depending on the expected H2S concentration, draw the appropriate volume of the sample from at least 3 cm below the sample surface, avoiding the bottom of the container, into the disposable syringe or positive displacement pipette (6.7 and 6.6) and weigh to the nearest 0.001 g (see 6.2). Avoid applying a strong vacuum to the sample when using the syringe or pipette and ensure that the integrity of the material is maintained so that the possible loss of H2S is kept to a minimum. Do not expel air from the syringe or pipette into the sample. Using the keypad, enter the total mass, which includes the syringe/pipette and sample, into the apparatus. The appropriate volume shall be determined by reference to Table 1.
NOTE 8 - A single mass can be entered rather than entering the mass before and after sample introduction if the balance is tared.
11.6 Introduce the test specimen into the test vessel, ensuring that the syringe or pipette is held vertically to avoid sample adhering to the test vessel walls. Ensure that the syringe or pipette does not touch the surface of the diluent liquid. Any pickup of diluent oil onto or into the syringe or pipette will result in the mass of the oil being included in the mass of the empty syringe or pipette leading to an erroneously high result. If this is suspected, abandon the test and repeat it.
11.7 Immediately, after removing the syringe or pipette, screw the cap tightly onto the top of the test vessel.
11.8 Weigh the emptied syringe or pipette to the nearest 0.001 g (see 6.2) and using the keypad enter the mass into the apparatus.
11.9 Immediately start the test, which proceeds automatically.
11.10 The detector reading is normalized to zero.
11.11 Air Path:
11.11.1 Procedure A:
11.11.1.1 Air is pumped directly through the filter cartridge for 3 min. After these 3 min the air is diverted through the diluted test specimen in the test vessel and to the detector.
11.11.2 Procedure B:
11.11.2.1 Air is pumped through the test specimen and diluent in the test vessel and to the detector.
11.12 The millivolt readings (mV) from the detector are recorded at least every 4 s throughout the test until 15 min have elapsed. The result is automatically calculated and displayed in mg/kg.
11.13 Air is pumped to purge the detector.
11.14 Remove the test vessel and check that the test specimen and diluent oil have properly mixed. If two distinct phases exist, check the air connections and repeat the test.
11.15 Clean the test vessel.
11.16 For Procedure A, remove and dispose of the cartridge from the vapor phase processor.
12. Calculation
12.1 Report the H2S content to the nearest 0.01 mg/kg for <10 mg/kg, and 0.1 mg/kg for ≥10 mg/kg.
H2S = (A x C)/m mg/kg
where:
A = integrated area of cell output over the test time (mV.s),
C = calibration constant of the detector (µg)/(mV.s), and
m = mass of the test specimen to be tested (g).