Carissa

Since I have no idea how to link to an old thread I copied this. I recently used this to validate my test kits as well.

It was a Tom Barr Re-Post of a Thread by LeftC

How to Make NO3 and PO4 Reference Solutions

Here's a way to make 10, 20, 30 and 40 ppm NO3 reference solutions:

Add 1.631 g of KNO3 to 1 L DI/RO water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 100 ppm NO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of DI/RO water. This makes 30 mL of a 50 ppm NO3 solution.

To make a 10 ppm NO3 solution:

Add 2 mL of the 50 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 10 ppm NO3 solution.

To make a 20 ppm NO3 solution:

Add 4 mL of the 50 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 20 ppm NO3 solution.

To make a 30 ppm NO3 solution:

Add 6 mL of the 50 ppm solution to 4 mL of DI/RO water. This makes 10 mL of a 30 ppm NO3 solution.

To make a 40 ppm NO3 solution:

Add 8 mL of the 50 ppm solution to 2 mL of DI/RO water. This makes 10 mL of a 40 ppm NO3 solution.

Here's a way to make 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

Add 1.433 g of KH2PO4 to 1 L DI/RO water. This makes a 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 10 ppm PO4 solution.

To make a 1.0 ppm PO4 solution:

Add 1 mL of the 10 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 1.0 ppm PO4 solution.

To make a 2.0 ppm PO4 solution:

Add 2 mL of the 10 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 2.0 ppm PO4 solution.

To make a 3.0 ppm PO4 solution:

Add 3 mL of the 10 ppm solution to 7 mL of DI/RO water. This makes 10 mL of a 3.0 ppm PO4 solution.

To make a 4.0 ppm PO4 solution:

Add 4 mL of the 10 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 4.0 ppm PO4 solution.

To make a 5.0 ppm PO4 solution:

Add 5 mL of the 10 ppm solution to 5 mL of DI/RO water. This makes 10 mL of a 5.0 ppm PO4 solution.

Left C