Lab component:

- 3- Make up your stock solutions of 100 mg/L NO3 -N and PO4 .

Make up your calibrations standards by making dilutions of your stock solution.

For the testing of the calibration standards and the samples you will not do each sample individually as the kit instructions suggest. You will keep a sample of the water used to make the standards (deionized) to blank the instrument when all the calibration standards are ready, and a sample of the water to blank the instrument when testing each sample.

Perform the nitrogen analysis first. To each of the calibration standards and water samples take the required amount for the analysis and add to tubes provided. Add the chemicals required and shake for the required time. Once ready use one of the colorimeters provided and select the testing menu for nitrate and analyse the samples using the colorimeter bottles provided. Make sure the bottles are wiped clean of fingerprints before you place them in the colorimeter and you use the correct blank for the sample you are analysing.

Rinse all bottles and perform the phosphate test as above and per the kit instructions.

Questions

1. You will be making a stock solution of 100mg/L of nitrate as nitrogen(NO3--N)

   and of phosphate (PO43-). You will be provided with sodium nitrate and potassium dihydrogen phosphate. Determine how much of these you need to weigh out to make your stock solution given that you will use a 100 mL volumetric.

2. The linear range of the instruments is 0-3 ppm nitrate-nitrogen and 0-3 ppm orthophosphate. You will need to make up calibration standards within this range as per instructions on colorimetric analysis. Determine how you will make up your calibration standards using the instructions provided or from first principles if you prefer.