Simultaneous spectrophotometric flow-through measurements of pH, carbon dioxide fugacity, and total inorganic carbon in seawater.

An autonomous multi-parameter flow-through CO2 system has been developed to simultaneously measure surface seawater pH, carbon dioxide fugacity (fCO2), and total dissolved inorganic carbon (DIC). All three measurements are based on spectrophotometric determinations of solution pH at multiple wavelengths using sulfonephthalein indicators. The pH optical cell is machined from a PEEK polymer rod bearing a bore-hole with an optical pathlength of approximately 15 cm.

High-resolution in situ analysis of nitrate and phosphate in the oligotrophic ocean.

Accurate, high-resolution profiles of nitrate and phosphate distributions in the open ocean are difficult to obtain using conventional techniques. Concentrations typically range from low nanomolar levels in the stratified euphotic zone to micromolar levels below the nutricline. With multiple pumps, a heating cartridge, a long-path-length cell, and a multiwavelength spectrometer, the reconfigured Spectrophotometric Elemental Analysis System (SEAS) provides the capability to fully ascertain the distributions of nitrate and phosphate in the upper 200 m of the oligotrophic ocean.

Spectrophotometric measurements of pH in-situ: laboratory and field evaluations of instrumental performance.

Automated in-situ instrumentation has been developed for precise and accurate measurements of a variety of analytes in natural waters. In this work we describe the use of 'SEAS' (spectrophotometric elemental analysis system) instrumentation for measurements of solution pH. SEAS-pH incorporates a CCD-based spectrophotometer, an incandescent light source, and dual pumps for mixing natural water samples with a sulfonephthalein indicator.

In-situ measurements of Cu in an estuarine environment using a portable spectrophotometric analysis system.

Application of a portable in-situ spectrophotometric analysis system for the measurement of Cu in estuarine environments is described in this work. Our spectrophotometric elemental analysis system (SEAS) used for in-situ observations of Cu concentrations is capable of fully autonomous or user-controlled operations. The optical cells used in SEAS systems are flexible liquid core waveguides (LCWs) with optical path lengths as long as 5 m.