There are some interferences to consider:
The nitrate/nitrite test strip employs the well-known Griess reaction. Any nitrate present is first reduced to nitrite which then will turn pink due to the Griess reagents present. Both the nitrate and nitrite test pads contain the Griess reagents. Only the nitrate test pad contains the reducing agent. For these reasons, if only nitrate is present in the sample being tested, only the nitrate test pad will turn pink because the reducing agent will reduce the nitrate to nitrite which then reacts to turn pink. The nitrite test pad will remain colorless because there is no nitrite in the sample being tested. If the sample being tested contains nitrite both the nitrate and nitrite test pads will turn pink since the chemicals needed to detect nitrite are present on both test pads.
The nitrate/nitrite test strips are useful in determining if the test solution contains nitrate but not nitrite. They are also useful in testing solutions that contain nitrite only (disregard the nitrate test pad). They are not as useful on solutions that contain both nitrate and nitrite.
No. The Phosphate test strip uses the Molybdenum Blue method and detects only orthophosphates.
Tripolyphosphates must be converted to orthophosphate first to be detected. This can be accomplished by treating the sample with acid first, and then neutralizing the solution before using the test strip.
Remember that the Phosphate test strip gives ppm as Phosphate, not phosphate ion. The result should be corrected for any dilutions/additions and multiplied by 3 to arrive at the phosphate ion ppm.
The reaction of the Fluoride test strip is very dependent upon the acidity level of the solution to be tested. Before testing, the solution has to be acidified to a pH ≤ 0.5. For acidification, we recommend hydrochloric acid (muriatic acid), preferably concentrated (1-2-3 M) depending on the rough presumption of the fluoride concentration in the test sample because in the process of acidification, the solution is always more or less diluted with added HCl (dilution has to be noted and the result is then multiplied with the dilution factor).
For example, 1M HCl has pH about 0.1
0.1M HCl has pH about 1.09
If a high concentration of fluoride is predicted in the sample to be tested, then 1M HCl can be used for acidification, added to the sample in the ratio, 2 parts of 1M HCl and 1 part sample, meaning the sample is 3 times diluted and the result must be multiplied by 3. For example, if the result is read by comparing the test pad with the color chart at about 10ppm, then the actual result is 10 x 3 = 30ppm.
If a lower concentration of fluoride is predicted in the sample to be tested, then more concentrated HCl should be used to avoid a higher dilution than necessary. The final pH of the sample before testing should be between 0 and 0.5. After acidifying the solution, the test strips are easy to use. Simply dip the strip into the pH adjusted solution for one second, remove, and compare the strip to the included color chart after 10 seconds.
Hydrochloric Acid (muriatic acid) should be available at a local hardware or pool/spa store, as well as at any chemical supply distributors, such as Fisher Scientific or VWR.
The solution to be tested must be at a pH of 0.5 in order for this test to be accurate. This pH measure can be accomplished using concentrated Hydrochloric acid (muriatic acid) to acidify the test solution, and measured with the pH 0-1.5 test strip.
Hydrochloric acid should be available at a local hardware store or pool/spa store, as well as at any chemical supply distributors, such as Fisher Scientific or VWR.
The Phosphate test strip is measuring phosphate (as phosphorous) in ppm. We do not offer a strip that can read as low as ppb.
Precision Labs Nitrate and Nitrite test strips measure results as nitrite and nitrate ions, not as nitrogen content (commonly referred to as nitrite-nitrogen and nitrate-nitrogen).
It is important to know which result to report. Agricultural applications typically report results as nitrate while drinking water limits for nitrite and nitrate are expressed as nitrogen.
To convert from nitrite to nitrogen content (nitrite-nitrogen) divide the nitrite result by 3.3.
To convert from nitrate to nitrogen content (nitrate-nitrogen) divide the nitrate result by 4.4.
For example, a drinking water limit of 1 ppm nitrite (as nitrogen) is the same as a result of 3.3 ppm nitrite. Likewise, a 10 ppm nitrate limit (as nitrogen) is the same as a result of 44 ppm nitrate.
The pad for reading the results is the one at the bottom of the channel or well. When laid on a table with the “bump” facing up, it is the pad you can see. This is going to be the darker pad.
The other pad is flush with the “back” of the strip. When constructed, the first pad (the one to read) is laid in the channel and the second pad placed on top of the first pad. The two pads are then secured in place by taping the back of the card.