Whilst the Hanna Instruments Marine Line of colourimeters are about as simple as you can get when it comes to process, making sure you use them correctly does require some thought and care. Not following the correct procedure or taking shortcuts will always have a negative impact on your test results.
Here are some simple ‘best practices’ that you can follow which will ensure that you get the most accurate result every time.
Always Use Clean Cuvettes
All Hanna Checkers are colourimeters. This means that they use an internal light source, usually in the form of an LED with a filter and a light sensing detector to determine absorbance and ion concentration. Since the Checkers are an optical-based measurement, it’s important that the light is not impeded by any fingerprints, scratches, dirt, or air bubbles on your cuvettes.
Use a microfiber cloth to clean the outside of the cuvette. This will remove any fingerprints or dirt that may be on the glass and will obstruct light within the colourimeter. If you need to remove air bubbles, simply tap the cuvette gently before placing it inside the Checker to take a reading.
Use Separate Pipettes & Syringes
Always use separate pipettes & syringes for freshwater and saltwater samples. Not doing so will lead to dramatic inaccuracies due to traces of the last sample being left behind. As we are testing very small sample sizes, even a tiny amount of residual can make a very large difference.
To prevent cross-contamination with syringes and pipettes, it is always best to label each one with its intended use.
Position Cuvettes The Same Way Each Time
As the colourimeter is an optical device, it is crucial that the optical path is always the same length. The best way to ascertain this is the place the cuvette into the check the same way each time. This will ensure consistent test results.
The simplest way to do this is to take note of the ’10ml’ position, marked on each of the cuvettes. Always have this mark facing forwards as you place the cuvette into the checker for testing.
Never Leave Completed Tests in the Cuvette
Allowing a developed test to sit inside a cuvette can cause the glass to become stained. Even the most minute discolouration or staining of the glass can cause major inaccuracies as this will affect the absorbance as light passes through the glass.
This can easily be avoided by simply rinsing the developed sample out of the cuvette immediately after you have completed testing.
Use RO/DI Water to Rinse Your Cuvettes
Your cuvettes need to be contaminant free to ensure the accuracy of each and every test. The smallest amount of residual salt remaining inside a cuvette can result in a very inaccurate test result. Even tap water can leave behind contaminants that will throw results. For this reason, only good quality RO/DO with a 0 TDS reading should be used.
To ensure that your cuvettes are always in excellent condition, always rinse them with RO/DI (deionised) water after testing and dry them with a soft paper towel. Making sure they have been fully dry will ensure that your next sample is not diluted by any remaining RO/DI water.
Make Sure Your Reagents Have Not Expired
All reagents expire and when they do, the results they provide can be false and inaccurate readings.
All Hanna reagents are clearly marked with their expiration dates, so please make sure that you are always using a set of reagents that have not passed their expiration date. It is also important to make sure that you store your reagents in a cool, dry place, away from extreme temperature fluctuations. This will ensure that they remain effective in their full shelf life.
Place on a Stable Surface, With the Hood Fully Closed
During testing, it is best to place the Checker on a stable surface. This will ensure that there are no bubbles being formed during the testing process, which will affect your results. It is also imperative that you fully close the hood to ensure that no ambient light enters the checker. This will cause false and inaccurate readings. Any unexpected or additional light will feedback to the checker’s sensor, giving an incorrect reading.
After positioning the cuvette and fully closing the hood, set it down and continue the testing procedure.
Be Careful When Opening Reagent Packets
The reagent packets used with most of the checkers have a dotted line, intended for you to cut along when opening. If you do not use this guide and cut further in, there is a chance that you could be discarding some of the reagents.
To prevent this from occurring, you should always tap of flick the packet to ensure that the reagent has not settled into the corner that you will be cutting away. Once you have done this, be sure to cut along the dotted line and fold the packet into a small funnel to allow you to pour the reagent into the cuvette as needed. This will also help to prevent spillage which will also result in much more accurate testing.
Hanna Checkers are very simple to use and are amongst some of the most accurate test kit options available to the reef aquarium industry today. Their testing procedures are incredibly simple to follow, however, like all test kits, if the simple steps are not followed, then the results cannot be expected to be accurate. Take the time to do things right and reap the rewards. Following these simple best practices will make sure that you are getting the absolute best out of your Hanna Checkers for years to come.