Apparatus and method for in situ pH measurement of aqueous medium
US5925572A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 6, 1997 |
| Grant date | Jul 20, 1999 |
| Priority date | — |
| Expiry date | Aug 6, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/272
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A pH sensor based upon spectrophotometric techniques has been developed for in situ analysis of an aqueous medium, e.g., surface seawater. This sensor utilizes a spectrophotometric pH indicator (Thymol Blue), which has been calibrated for use in seawater as a function of temperature and salinity. Shipboard spectrophotometric pH analyses routinely demonstrate a precision on the order of .+-.0.0004 pH units. In situ analysis of seawater pH has demonstrated a precision on the order of .+-.0.001 and an accuracy, using shipboard measurements as a standard, on the order of .+-.0.01. The sensor is a self-contained system that pumps seawater, meters in indicator, and spectrophotometrically determines indicator absorbance cells, each with three wavelength channels, to obtain the spectrophotometric absorbance. The sensor system, rated for depths up to 500 m, provides pH, conductivity, and temperature and can be operated via computer or in a standalone mode with internal data storage. The sensor utilizes less than 12 watts of power and is packaged in an aluminum housing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.