Science Buddies: "Ask an Expert"

Posted: **Tue Sep 09, 2014 7:24 pm**

I want to measure Nitrogen level in water as part of my science fair. Is there kit to use or easy way to do this at home ?

Thanks!

Posted: **Wed Sep 10, 2014 5:40 am**

The most common forms of nitrogen that are found in water are nitrate and nitrate ions, which have the chemical formulas NO3^- and No2^-, respectively. These ions are relatively easy to test for with kits that you can easily acquire online--one example is http://www.hach.com/nitrate-and-nitrite ... 7640211606 . These strips can measure up to 50 mg/L of nitrate and 3 mg/L of nitrite; if that doesn't meet the range that you're expecting to test, you can easily Google to find more options.

Posted: **Thu Sep 11, 2014 8:10 pm**

Thank you for the feedback and link.

Posted: **Fri Sep 12, 2014 7:20 am**

Is there a better way to measure glucose/sugar content other than using Benedict solution ? Using Benedict solution we need to observe color and will totally based on user color judgement. For my science experiment, I would like to quantify the sugar quantity in a given solution. Please suggest.

Posted: **Sat Sep 13, 2014 10:44 am**

Although color perception is subjective, the color change you get with Benedict's test is such a wide range that, as long as the same person is making the color judgements, I don't think it will have too much of an impact on your final results.

The principle of Benedict's test is that when reducing sugars are heated in the presence of an alkali, they get converted to powerful reducing compounds known as enediols. Enediols reduce the cupric ions (Cu2+) present in the Benedict's reagent to cuprous ions (Cu+) which get precipitated as insoluble red copper(I) oxide. The color of the obtained precipitate gives an idea about the quantity of sugar present in the solution, hence the test is semi-quantitative. A greenish precipitate indicates about 0.5 g% concentration; yellow precipitate indicates 1 g% concentration; orange indicates 1.5 g% and red indicates 2 g% or higher concentration.

If you are interested in a more quantitative way to test glucose concentration:

You could perform a quantitative Benedict's test where you time how long it takes for a certain volume of glucose to change color when heated with a certain volume of Benedict's solution.
In this practical you will test the glucose concentration in a variety of solutions of known value and you will draw a graph to show your results. This type of graph is known as a Standard Curve. You will then use this graph to estimate the glucose concentration in some unknown solutions. This is the method which was used in hospital labs to measure the glucose level in blood samples. You will be measuring the time taken for a pink color (potassium permanganate) to disappear.

(http://www.saps.org.uk/attachments/arti ... ighers.pdf)

Science Buddies: "Ask an Expert"

Measuring nitrogen levels in water

Measuring nitrogen levels in water

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