Seawater CO2 System

The National Insitute of Standards and Technology (NIST) Chemical Sciences Division (CSD) provides the measurement science, standards, technology, data and chemical informatics required to support the nation’s needs in the determination of chemical composition and chemical structure of gases, organic, and inorganic species. CSD is involved in developing measurement services to support ocean carbon metrology and enhancing NIST’s existing capabilities for greenhouse gas metrology. To determine the amount fraction of carbon dioxide (CO2) in air samples and dissolved inorganic carbon in seawater, the division seeks to procure a custom designed borosilicate vacuum extraction line which will enable researchers to acidify a sample of seawater with a known mass and then quantitatively extract and purify the carbon dioxide in the seawater sample. The vacuum extraction line will be modeled after the system developed and currently used at Scripps Institution of Oceanography in the Andrew Dickson seawater carbon dioxide reference material laboratory.

Objectives

The Contractor shall provide scientific glass blowing services to fabricate a custom borosilicate vacuum extraction line designed according to the specifications outlined by the CSD laboratory. The vacuum line construction is designed to minimize the adsorption of carbon dioxide onto the glass and valve surfaces and consists of four modular units on the frontside with a mirrored but nonmodular rear vacuum line. The first section of the frontside will consist of an acidification module/sample introduction system which allows for the delivery of phosphoric acid from a 3 L reservoir into an acid chamber and then to a Wong pipette designed to deliver a gravimetric sample of seawater. Following the acidification module, along the second and third sections, the liberated gases from the seawater sample must be purified through a series of low temperature traps – an ethanol slush flask, a liquid nitrogen flask, and two ethanol/liquid nitrogen traps. These sections require connections to Pirani pressure gauges (3) and a diffusion pump (1). The final section, the sample collection module will consist of a series of ports to flame seal the purified gas samples. This section must also be connected to a Pirani pressure gauge (1) and a diffusion pump (1). Preliminary schematics of the vacuum line and the required/suggested valves and joints are provided in Appendix 1 and Appendix 2. Note, design changes and substitutions may be warranted in cases where adapters are no longer available (e.g., Pirani gauge adaptors) or if Contractor recommends a more suitable substitute or design change.