ASTM D7319 Standard Test Method for Determination of Existent and Potential Sulfate and Inorganic Chloride in Fuel Ethanol by Direct Injection Suppressed Ion Chromatography
7. Apparatus
7.1 Analytical Balance, capable of weighing up to 100 g accurately to 0.0001 g.

7.2 Drying Oven, controlled at 110 +/- 5°C for drying sodium sulfate and sodium chloride.

7.3 Desiccator, containing freshly activated silica gel (or equivalent desiccant) with moisture content indicator.

7.4 Pipets or Volumetric Transferring Devices, appropriately sized Class A glass pipets or their equivalent or variable volume automatic pipets fitted with disposable polypropylene tips.

7.5 Volumetric Flasks (with Glass Stoppers), Class A of 10, 25, 50, 100, 1000, 2000-cc capacity.
7.5.1 Container, equipped with a closure to prevent ethanol evaporation, 1 L (for sample collection). See 6.3 for additional information.

7.6 Ion Chromatograph, analytical system with all required accessories including syringes, columns, suppressor, and detector.
7.6.1 Injection System, capable of delivering 20 µL with a precision better than 1 %, or as recommended for this determination by the manufacturer.

7.6.2 Pumping System, capable of delivering mobile phase flows between 0.2 and 2.5 mL/min with a precision better than 2%, or as recommended for this determination by the manufacturer.

7.6.3 Guard Column, for protection of the analytical column from strongly retained constituents. Better separations are obtained with additional theoretical plates.

7.6.4 Anion Separator Column, 100 % solvent compatible and capable of producing satisfactory analyte (sulfate and chloride) separation (Fig. 1).

7.6.5 Anion Suppressor Device, vendor specific and capable of using acid suppression technology.
7.6.5.1 Tri-Chamber Approach, 100 % solvent compatible tri-chamber micro packed bed with cation exchange resin (or equivalent). Suppressor device should simultaneously be online continuously chemically regenerated to its hydrogen form using any mineral acid providing H+ ion.

7.6.5.2 Continuous Approach, Continuous suppressor membrane regeneration.

7.6.6 Conductivity Detector, (low volume), temperature controlled to 0.01°C, capable of at least 0 to 1000 µS/cm on a linear scale.

7.6.7 Integrator or Chromatography Data System Software, capable of measuring peak areas and retention times, and correcting the data in accordance with the baseline of the chromatogram.

7.7 Gloves, powder-free examination type.

8. Reagents
8.1 Purity of Reagents - Reagent grade or higher purity chemicals shall be used for the preparation of all samples, standards, eluent, and regenerator solutions. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.

8.2 Purity of Water - Unless otherwise indicated, reference to water shall be understood to mean reagent water as defined by Type II or better in Specification D1193. For eluent preparation and handling, comply with all ion chromatograph instrument and column vendor requirements (for example, filtering, degassing, and the like).

8.3 Eluent Buffer Stock Solution - Sodium bicarbonate (NaHCO3) 1.0 mM and sodium carbonate (Na2CO3) 3.2 mM. Dissolve 8.4 +/- 0.0005 g of NaHCO3 and 33.92 +/- 0.0005 g of Na2CO3 in reagent water in a 1-L Type A volumetric flask and dilute to volume. Dilute 10.0 mL of this stock solution to 1 L in a 1-L Type A volumetric flask with degassed reagent water. The eluent solution used may be different if other system or analytical columns are used.

NOTE 1 - Other volumes of stock solution can be prepared using appropriate ratios of reagents. Follow the specific guidelines for this solution from the vendor of the column being used. Alternatively, this solution can be purchased from a qualified vendor.

8.4 Suppressor Regenerant Solution for Suppressor - 0.1 M sulfuric acid. Carefully add 334 mL of reagent grade sulfuric acid (relative density 1.84) to approximately 500 mL reagent water in a 1-L volumetric flask. (Warning - This will generate a very hot solution. Allow it to cool before diluting to 1000 mL volume. Never add water to concentrated acid.) Dilute to 1000 mL with reagent water, and label this solution as 10.0 M sulfuric acid. Dilute 10.0 mL of this concentrate to 1000 mL with reagent water for the final 0.1 M working suppressor solution.

NOTE 2 - Other volumes of this solution can be prepared using appropriate ratios of reagents. Follow the specific guidelines for this solution from the vendor of the suppressor being used.

8.5 Sodium Sulfate - anhydrous, reagent grade, 99 % minimum purity. (Warning - Do not ingest. Avoid unnecessary exposure.)

8.6 Sodium Chloride - ACS or reagent grade, 99 % minimum purity.

8.7 Ethanol - denatured with methanol, formula 3A or histological grade ethanol, anhydrous, denatured with ethyl acetate, methylisobutyl ketone and hydrocarbon naphtha. (Warning - Flammable, toxic, and may be harmful or fatal if ingested or inhaled. Avoid skin contact.)

8.8 Hydrogen Peroxide - ACS reagent grade, 30 wt % in water.

8.9 Hydrogen Peroxide Solution, 30 % - commercially available 30 % hydrogen peroxide solution.