Attachment 02 - NIH Dissolved Silica.1714658486817.docx

Attachment 02 – NIH Dissolved Silica (Gas Segmented Continuous Flow Colorimetric Analysis) Summary This method provides a procedure for the determination of dissolved silicate concentration in steam and chilled waters. The dissolved silicate is mainly in the form of silicic acid, H4SiO4, in steam and chilled waters. All soluble silicate, including colloidal silicic acid, can be determined by this method. Long chain polymers containing three or more silicic acid units do not react at any appreciable rate, but no significant amount of these large polymers exists in estuarine and coastal waters.

This method is based upon the method of Koroleff, adapted to automated gas segmented continuous flow colorimetric analysis. For more information, please see EPA Method 366.0, Determination of Dissolved Silicate in Estuarine and Coastal Waters by Gas Segmented Continuous Flow Colorimetric Analysis, 1997

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. For collecting surface samples, an acid-cleaned plastic bucket or a large plastic bottle can be used as convenient samplers.

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

The contractor shall rinse the bottle and cap three times with sample water and fill the bottle to within one to two inches from the top, and they shall adhere to the correct procedures for sample collection, sample preservation, sample handling, sample identification, and prompt transfer of the sample to the laboratory. The Contractor shall remove any attachment from the tap such as hoses, filters, screens, or aerators. Samples shall be filtered through 0.45 µm non-glass membrane filters as soon as possible after collection.

Sample Preservation and Storage After collection and filtration, samples shall be analyzed as soon as possible. If samples will be analyzed within 24 hours, then keep refrigerated in a tightly sealed, high density polyethylene bottles in the dark at 4 deg. C until analysis can be performed.

If samples are to be frozen for long-term storage, the Contractor shall ensure that none of the sample bottles are filled more than 3/4 full and that the cap is firmly screwed on. Place the bottles upright on a rack and store in the freezer (-20 C). Before analysis, frozen samples shall be taken out of the freezer and allowed to thaw in a refrigerator at 4 deg. C in the dark. Thawing times depend upon sample conditions. After completely thawing, take samples out of the refrigerator and mix thoroughly. Keep samples in the dark at room temperature overnight before analysis.

Method of Shipping and Duration The Contractor shall 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.

Maintenance Plan for The Instrument Comment by Hughes, Casey (NIH/OD/ORF) [E]: This seems to be what instrumentation to use rather than a maintenance plan.

The Contractor shall perform maintenance on their equipment as outlined per the manufacturer’s instructions.

The maintenance protocol shall be available and be delivered to NIH upon request.

Calibration Procedure At least five calibration standards shall be used to establish an ongoing precision statement prepared daily for system calibration. Place the calibration standards before samples for each run. All the calibration solutions shall be analyzed in duplicate. The calibration curve containing five data points or more shall have a correlation coefficient 0.995.

Analysis Method and Protocol EPA method 366 shall be used to determine the dissolved silicate concentration.

References EPA Method 366.0, Determination of Dissolved Silicate in Estuarine and Coastal Waters