Attachment 04 - NIH Chloride.1714658465661.docx

Attachment 04: NIH Chloride (Titrimetric, Mercuric Nitrate)

Summary An acidified sample is titrated with mercuric nitrate in the presence of mixed diphenylcarbazone-bromophenol blue indicator. The end point of the titration is the formation of the blue-violet mercury diphenylcarbazone complex. For more information, please see EPA Method 9252A, Chloride (Titrimetric, Mercuric Nitrate), Revision 1, September 1994.

Since this method involves mercury salts, appropriate disposal procedure needs to be followed.

Sample Collection NIH shall collect samples, and the Contractor shall pick up the samples from NIH Bethesda, Building 11.

The Contractor’s personnel assigned to pick up the samples shall be trained in sampling procedures, such as wearing gloves and eye protection when collecting samples.

In the event that the Contractor also collects the sample, they shall follow the following procedure:

Rinse the bottle and cap three times with sample water and fill the bottle to within one to two inches from the top. The Contractor shall adhere to the correct procedures for sample collection, sample preservation, sample handling, sample identification, and prompt transfer of the sample to the laboratory. Remove any attachment from the tap such as hoses, filters, screens, or aerators. Flush the water for 2-3 minutes or until the water temperature reaches a constant temperature.

Sample Preservation and Storage There are no special requirements for preservation and storage.

Method of Shipping and Duration Place the sample into a cooler with ice for immediate delivery or shipment to the laboratory. The sample shall be received with a chain of custody (COC). The COC shall have the name of the sample collector, date and time of sample collection, signature or initial of the sample collector, location of the sample and type of sample to be analyzed.

Lab Procedure for Analysis The contractor shall follow the procedures included in EPA Method 9252A, Chloride (Titrimetric, Mercuric Nitrate), Revision 1, September 1994

Maintenance Plan for the Instrument The Contractor shall perform the daily maintenance on their equipment as outlined per the manufacturer’s instructions.

Calibration Procedure The Contractor shall provide the calibration protocol used on associated equipment.

Analysis Method and Protocol The Contractor shall follow EPA method 9252A. The method is suitable for all concentration ranges of chloride content; however, to avoid large titration volume, a sample aliquot containing not more than 10 to 20 mg Cl per 50 mL shall be used.

Interferences Anions and cations at concentrations normally found in surface waters do not interfere. However, at the higher concentration often found in certain wastes, problems may occur.

Sulfite interference can be eliminated by oxidizing the 50 mL of sample solution with 0.5-1 mL of H2O2.

Bromide and iodide are also titrated with mercuric nitrate in the same manner as chloride.

Ferric and chromate ions interfere when present in excess of 10 mg/L.

Data Acquisition The Contractor shall provide the procedure for data acquisition, if requested by NIH.

References EPA Method 9252A, Chloride (Titrimetric, Mercuric Nitrate), Revision 1, September 1994 U.S. Environmental Protection Agency, Methods for Chemical Analysis of Water and Wastes, EPA 600/4-79-020 (1983), Method 325.3.

Standard Methods for the Examination of Water and Wastewater, 15th ed., (1980).