User manual

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Principle of nitrat-tester operation
Nitrat-tester Soeks is intended for a primary express assessment
of the nitrate ion content of fresh fruit and vegetables.
The principle of nitrat-tester Soeks operation is based on measur-
ing the electric conductivity of fruit and vegetable medium. Each fruit and
vegetable contains potassium, magnesium, iron, copper and chlorine ions
required for their vital functions as well as many organic acids and other
substances in certain concentrations required for their normal development.
The content of each concrete substance (in the form of ions or molecules) is
determined by biochemistry of the concrete plant (there exists a base level of
ion content) and composition of water and soil, on which it grows. Fertilizer
is very often used to secure an effective plant growth – for example, fertilizer
in the form of salts (nitrate, phosphate, and other fertilizer). Nitrates or
phosphates are dissolved in water, and reach the plant, which willingly
absorbs them in the form of salt ions. The salt ions (nitrates, phosphates, etc.)
spread across the plant, and are accumulated in various parts of the plant,
including fruit, which increases electrolyte content and, accordingly, electric
conductivity of the fruit/vegetable medium. Thus, we can use nitrat-tester
Soeks to measure the electric conductivity of fruit and vegetables, to
compare this value with electric conductivity due to the base level of ion
content, and to say that that the product under test contains an increased
amount of ions with a certain probability. Since nitrate fertilizer is widely
spread in Russia and CIS countries, one may expect with a high degree of
probability that excessive electric conductivity is due to the presence of
nitrate ions.
Nitrat-tester Soeks is calibrated by nitrate ion content. Their
concentration in fruit and vegetables is determined using an independent test
method (potentiometric determination of nitrate ions per GOST 29270-95
(Fruit and Vegetable Processing Products. Nitrate Determination Methods).
The results obtained have been used to download a number of dependences
of the measured electric conductivity on nitrate ion concentration determined
for various fruit and vegetables with due regard to their base electric conduc-
tivities in nitrat-tester Soeks.
Nitrat-tester Soeks delivers the result of express test in the form
of nitrate ion concentration and compares is with the maximum permissible
concentration for the measured product.