No.
Theoretically, the color associated with a certain ppm color block will develop when the sample or standard is that exact ppm. If the sample is between two ppm color blocks, the color developed by the strip will be between the colors of those two blocks.
The color is not “fixed” for a certain range or for a given step. The color scale is a gradient that is “fixed” along the way at certain points. It is normal to select points that are at least double the previous ppm value. This allows for variation in paper, reagents, process, etc.
Keep in mind that variation in label print runs, test strips, test methods, etc. can contribute to the colors not being an exact match. We do our best to minimize this but some variation is inevitable.
Test strips should be stored in closed vials/bags,in a cool, dry place out of direct sunlight.
The ideal condition is 25C (77F). A range of 20C (68F) – 30C (86F) is acceptable. Test strips should not be stored in a refrigerator or freezer. Test Strips should not be stored where they can be exposed to heat (for example, inside a vehicle or shed).
In some cases, our test strips are packaged in a flip-top vial which has a desiccant liner included to prevent moisture from reacting with the test strips prior to use. This desiccant liner provides a very dry environment inside when closed. The capacity of the liner is sufficient to last over 5 years of opening and closing, as long as it is closed promptly when not in use. Leaving the vial open will shorten the shelf-life of the desiccant liner. Be careful not to introduce moisture into the vial with wet fingers.
Many of our test strips have a minimum shelf-life of 2 years when stored and handled correctly. In reality, the strips are stable for much longer. We have experienced test strips over 3 years old that still perform to specification.
We suggest the test strips be used within one year from the date of opening, given proper storage and handling.
Unless otherwise stated, Precision Laboratories test strips have a shelf-life of two years from the date of purchase when stored properly.
If you are preparing glucose standards in a lab to use with our Glucose Test Strips, in order for it to work properly, you must wait about 3 hours to allow mutarotation to occur.
Solid glucose is dissolved in water and over time (3 hours) undergoes mutarotation to the cyclic forms a-d-Glucose and b-d-glucose (equilibrates in a ratio of 36:64). These cyclic forms are what the glucose enzyme interacts with on the test paper.
We have several different packaging options, including:
- Clear resealable bags
- Amber resealable bags (light protection)
- Foil bags (light and humidity protection)
- Clear vials
- White flip-top vials (light and moisture protection)
- Amber bottles (light protection)
Some of our test strips are light sensitive or humidity sensitive and must be stored in more protective packaging than other strips. Our goal is to aim for at least 2 years stability from the date of manufacture, and this goal helps us determine the most appropriate packaging for each test strip.
Development time for test strips is dependent upon many factors. The kinetics of the color development are manipulated by altering the formula employed on the test pad, along with adjusting the conditions of the test (dip time, swirl versus dip, shake excess water off versus no shake, etc.) to offer the best color separation in the shortest time possible.
In the case of the different chlorine test strips, while the color developing indicator is the same, the formulas have been adjusted to slow the development of the color allowing the range of the test strip to be expanded to accommodate the higher chlorine values.
Specifying a specific development time is normally very important. The nature of these test strips is that the color continues to change over time. It is not like a titration with a definite endpoint. Reading the result before or after the specified development time will result in inaccurate results, just like under or over-titrating a sample would.
Our goal is to provide the best color separation at the values requested in the shortest time possible. We try to standardize this whenever we can, however, user requirements often require specific and unique instructions.