Sea-Bird Scientific SUNA V2, User Manual

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2.4 Analytical
This sensor is designed to measure the concentration of nitrate ions in water.
Measurements are in units of micro molar (µM). This is converted into mg/L. Note that
1 µM nitrogen = 0.014007 mg/L nitrogen.
2.4.1 Nitrate measurement accuracy
Table 1 10 mm pathlength
Concentration range Class-based fresh water Fresh water Seawater
Best 0.035 mgN/L (2.5 µM) 0.028 mgN/L (2 µM) 0.028 mgN/L (2 µM)
up to 1000 µM (14 mgN/L) 20% 10% 10%
up to 2000 µM (28 mgN/L) 25% 15% 15%
up to 3000 µM (42 mgN/L) 30% 20% 20%
up to 4000 µM (56 mgN/L) N/A N/A N/A
The specified accuracy is best accuracy or a percentage, whichever is more.
• A sensor-specific calibration uses extinction coefficients from the sensor itself.
• A class-based calibration uses extinction coefficients that are the average of many
sensors.
2.4.2 Nitrate measurement precision
Processing configuration Seawater or fresh water with T-S
correction
Seawater (0–40 psu)
Short-term precision (3 sigma) and limit of detection 0.3 µM (0.004 mgN/L) 2.4 µM (0.034 mgN/L)
Change ("drift") per hour of lamp time < 0.3 µM (< 0.004 mgN/L) < 1.0 µM (< 0.014 mgN/L)
Limit of quantification 1.0 µM (0.014 mgN/L) 8.0 µM (0.112 mgN/L)
Specifications
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