Phosphates are in many products we use everyday. Most people don’t realize phosphates are used to enhance the flavor and tartness of cola drinks, as a buffering agent to control pH in antifreeze, and to delay the darkening of cut potatoes used for french fries. Phosphates are also used in detergents and cleaning fluids for their ability to soften water and remove soil deposits.
Phosphates are an important fertilizer used in agriculture to enhance the growth and development of plant roots. However, high concentrations of phosphates in agricultural runoff can cause environmental pollution and are a primary cause of eutrophication. Local laws govern the use of phosphates and the discharge levels into streams.
The HI97717 uses an adaptation of the amino acid method to measure phosphate concentrations of up to 30.0 mg/L (ppm). When the reagent is added to samples containing phosphate, the sample will turn a blue hue; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law. This principle states that light is absorbed by a complementary color, and the emitted radiation is dependent upon concentration. For high levels of phosphate, a narrow band interference filter at 525 nm allows only blue-green light to be detected by the silicon photodetector and omits all other visible light emitted from the LED lamp. As the change in color of the reacted sample increases, absorbance of the specific wavelength of light also increases, while transmittance decreases.
Phosphate HR
Range 0.0 to 30.0 mg/L (as PO43-)
Resolution 0.1 mg/L
Accuracy ±1.0 mg/L ±4% of reading at 25 °C
Method Adaptation of Standard Methods for the Examination of Water and Wastewater, 18th Edition, Amino Acid Method
Measurement System
Light source Light Emitting Diode
Bandpass filter 525 nm
Bandpass filter bandwidth 8 nm
Bandpass filter wavelength accuracy ±1.0 nm
Light detector Silicon photocell
Cuvette type Round 24.6 mm diameter (22 mm inside)
Additional Specifications
Auto logging 50 readings
Display 128×64 pixel B/W LCD with backlight
Auto-off After 15 minutes of inactivity (30 minutes before a READ measurement)
Battery type 1.5 V AA Alkaline (3 pcs.)
Battery life >800 measurements (without backlight)
Environment 0 to 50 °C (32 to 122 °F); 0 to 100% RH, non-serviceable
Dimensions 142.5×102.5×50.5 mm (5.6×4.0×2.0″)
Weight (with batteries) 380 g (13.4 oz.)
Case ingress protection rating IP67, floating case
