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D7328_11 (17) 10-2017

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Obtain samples in accordance with practice D4057 or practice D4177. Samples should be well mixed to ensure homogeneity. A representative portion shall be taken from each sample for analysis. Samples should be collected in preferably glass or polyethylene containers with closures that seal well to prevent evaporation. Sample containers shall not contain any residual or extractable sulfate or chloride. If containers have been cleaned and rinsed with water, they shall be thoroughly rinsed with type II reagent water and dried prior to use. Thoroughly mix the samples in their containers immediately prior to withdrawal of the test specimen. Samples may be analyzed for either or both existence and potential inorganic sulfate, as well as total chloride. Set up the ion chromatograph in accordance with the manufacturer's instructions. Equilibrate the system by pumping eluant for 15 minutes to 30 minutes until a stable baseline is obtained. Start the chromatographic run in accordance with the manufacturer's instructions. Carefully add 2.00 milliliters of the ethanol test specimen into a clean, dry, tared 15-milliliters glass vial without its screw cap closure. See note 5 of the written standard. Note 5-- larger amounts of test specimen may be prepared as needed for auto-sampler use, as long as the preparation maintains the prescribed ratio of components. Preparation of larger test specimen might increase drying time. Precision was determined with 2.00-milliliter aliquots. Place the vial with sample in a hot block at 65 degrees Celsius and blow a steady stream of nitrogen gas over the sample at 2 milliliter per minute to 3 milliliter per minutes. Allow the sample to dry completely. This may take 5 minutes to 10 minutes. When all of the liquid is gone, remove the vial from the hot block and allow it to cool to room temperature, 60 degrees Fahrenheit to 80 degrees Fahrenheit. It is possible that a slight oily residue from the ethanol denaturant could remain. Do not worry about this residue if it is a thin film, as any sulfide or chloride in it will be extracted into the water phase. Various commercial apparatus are used to evaporate the sample. Depending on the apparatus used, the flow can be adjusted to optimize the evaporation. The purpose of the nitrogen is to sweep the ethanol vapors away from the sample tube so they do not condense back into the sample. There should be enough flow to sweep the ethanol vapors without creating turbulence in the sample and possible loss of analyte. When the flow gets too high, the cooling effect from the nitrogen gas can work against the intent. If the temperature in the sample block does not reach 65 degrees Celsius, this can also extend the time to evaporate. Typical nitrogen flow are 2 to 3 millimeters per minute. The flow may be varied to accommodate available laboratory apparatus. Carefully add 2.00 milliliters of type II water to the dried sample. Seal the vial with a screw cap, and shake the vial vigorously to dissolve all of the solid salts. Inject the resulting solution into the ion chromatograph as in 11.6 of the written standard. Carefully add 2.00 milliliters of the ethanol test specimen into a clean, dry, tared 15-milliliter glass vial without its screw cap closure. See note 5 of the written standard. Place the vial with sample in a hot block at 65 degrees Celsius, and blow a steady stream of nitrogen over the sample. Allow the sample to dry completely. This may take 5 to 10 minutes. When all of the liquid is gone, remove the vial from the hot block and allow it to cool to room temperature, 60 to 80 degrees Fahrenheit. See note 6 of the written standard. Carefully add 2.00 milliliters of 0.90% hydrogen peroxide solution, 9.3 of the written standard, to the dried sample. Seal the vial with a screw cap, and shake the vial vigorously to dissolve all of the solid salts. Inject the resulting solution into the ion chromatograph as in 11.6 of the written standard. Inject 25 microliters of sample solution from 11.4 or 11.5 of the written standard into the ion chromatograph, and measure the areas of the peaks corresponding to chloride and sulfide ions. If the concentration of the anion of interest exceeds that of the highest calibration solution, dilute the sample solution with type I water containing no measurable sulfate or chloride as appropriate, and repeat the sample measurement. Take into account the dilution factor in the calculation of sulfate content in the ethanol sample, and calculate the dilution factor as shown in equation 4 of the written standard, where F equals dilution factor, Vi equals volume of the initial sample diluted, milliliters, and Vf equals volume of the final solution, milliliters.

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Posted by: abuckmaster on Sep 14, 2018

D7328_11 (17) 10-2017

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