Determination of nanomolar concentrations of nitrite and nitrate in natural waters using long path length absorbance spectroscopy

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es9709583· OSTI ID:655408

Yao, W; Byrne, R H; Waterbury, R D ^[1]

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1. Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science

The concentrations of nitrite and nitrate in many natural waters are below the detection limits of conventional colorimetric analysis. A liquid core waveguide (LCW) has been used to extend the sensitivity of conventional colorimetric nitrite and nitrate determinations by more than an order of magnitude. Long path length absorbance spectroscopy (LPAS) with a 4.5 m path length LCW made of Teflon AF-2400 provides detection limits for NO{sub 2}{sup {minus}} and NO{sub 3}{sup {minus}} equal to 0.5 and 1.5 nM, respectively. The absorbance response of the LPAS system varies linearly with concentration. Calculations of azo dye molar absorbance using LPAS observations at nanomolar concentrations are in excellent agreement with molar absorbance results obtained with conventional measurement systems at much higher concentrations. For 1 nM NO{sub 2}{sup {minus}} and NO{sub 3}{sup {minus}} concentration differences, the 4.5 m path length LCW used in this work produces absorbance differences on the order of 0.02. No significant changes in the behavior of the LPAS system have been observed for periods of 6 month and more. The system is simple, rugged, and amenable to field studies.

• OSTI ID: 655408
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 17 Vol. 32; ISSN 0013-936X; ISSN ESTHAG
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION SPECTROSCOPY
ECOLOGICAL CONCENTRATION
MONITORING
NITRATES
NITRITES
WATER POLLUTION