indicator paper for determining the nitrate content in fruits and vegetables. Today there are two known methods for determining nitrates and nitrites. The first is considered strictly specific. It is based on the diazo coupling reaction, but it uses quite rare and, moreover, very carcinogenic substances (there is a high probability of cancer). The second is considered non-specific, but in the case of food analysis, strict specificity is guaranteed! The method is well known to most from school, but we were not taught to use the knowledge... It is called the “iodine-starch reaction”.
To make indicator paper you will need:
- strips of white filter paper.
- liter saucepan.
-tablespoon
-shallow bowl
- the necessary and sufficient number of clothespins.
from reagents:
- half a liter of water
-starch (any starch, you can even use “fruit and berry jelly”)
- potassium iodide (in the pharmacy - 200 ml of 3% solution - eye drops)
Let's get started. In a saucepan, bring 0.5 liters of water to a boil and pour in the starch suspension in a thin stream while stirring. Boil for another five minutes. When the liquid clears, stop heating. Dissolve 1-3g of potassium iodide in a hot liquid or simply pour in a bottle of eye drops while stirring. After the liquid has cooled, saturate the paper with it. If the saucepan is not deep, you can do without a bowl. Remove excess solution from the soaked strip using a subsequent strip. Dry using a clothespin. The specified amount of reagent is quite enough to produce hundreds of 250*100 mm strips.
Paper can be stored in the absence of light for decades without changing its properties, but if it does darken, you should not despair. It can deteriorate for a trivial reason: pipes with cold water are leaking, and the water is chlorinated. In this case, it is necessary to invite the san. equipment, eliminate the malfunction, and treat the indicator paper with gaseous sulfur dioxide. In a few seconds the display will be restored.
In conclusion, and to complete the picture, I will provide a little more information. Type "World" where they draw, find all shades of blue.
So (with 10% error):
BLACK - nitrate concentration is higher than 1000 mg/kg of product.
this is very dangerous (unfortunately, I observed this) - severe poisoning is guaranteed
BLACK-BLUE - 1000 mg/kg - severe poisoning.
BLUE 750 mg/kg -........
LIGHT BLUE - 500 mg/kg - nausea, chills... ("hangover")
AZURNY - 250 mg/kg - malaise, weakness.
BLUE - 100 mg/kg - acceptable
ST.BLUE - 50 mg/kg - safe.
WHITE absent - ideal.
Perhaps that's all. The method is not ideal (there are spots on the Sun too); colored juices will have to be compared with a control (simple) piece of paper.
Good health and bon appetit to everyone!
