Nitrates are present in nature as a result of decomposition of organic microorganisms or due to their use as fertilizers. Nitrates reduce to nitrites, which in turn easily combine to form substances dangerous to man. A maximum level of 45 milligrams per liter (ppm) is established as a worldwide guideline for nitrate concentration in water. In Europe, the maximum consented level of nitrates in potable water is 50.0 milligrams per liter (ppm), while in the USA the EPA has established a guideline for the maximum level of nitrate (nitrogen) of 10 milligrams per liter (NO-3-N), which corresponds to 45.0 milligrams per liter of nitrates. The HI96728 meter measures the nitrate content in water and wastewater. This meter uses an exclusive positive-locking system to ensure that the cuvette is in the same place every time it is placed into the measurement cell. HI96728 is supplied with 2 sample cuvettes with caps, 9V battery and instruction manual. 0.0 - 30.0 milligrams per liter pH range. 0.1 milligrams per liter pH resolution. +/-0.5 milligrams per liter +/-10 percent of reading at 25 degree C accuracy. Tungsten lamp. Silicon photocell with narrow band interference filter at 525nm light detector. 0 - 50 degree C (32 - 122 degree F); RH maximum 95 percent non-condensing environment. Auto-off: after 10 minutes of non-use in measurement mode, after 1 hour of non-use in calibration mode with last reading reminder. Measures 7.6" length by 4.1" width by 2.7" height. Adaptation of the photometric method.