Mysteries of the Solid Secondary Standard Revealed
A Solid Secondary Standard is available for most Turner Designs fluorometers. Solid Secondary Standards provide a quick and easy way to validate instrument performance. Questions related to the Solid Secondary Standards are very common. I don’t think a day has gone by when I did not receive a phone call or email asking about our Solid Secondary Standards. So I hope to dispel some of the mystery and confusion surrounding them.
What are they made of? The outer black casing of the Solid Secondary Standard is made of delrin plastic and is very durable. The core of the Solid Secondary Standard is one of several stable fluorescent plastic materials. It holds up to the rigors of photo-decay and as long as it is stored under ambient conditions free from dust and humidity, it will provide you with stable consistent readings for many years.
What is the best way to use it? I usually recommend that you use the Solid Secondary Standard as a stable reference check of the instrument and not as a calibration tool. It is stable and unless adjusted, it should give stable readings. If you notice a drift in readings greater than +/-2.5% from the initial value recorded, then we suggest recalibrating or contacting technical support.
But can I use it to calibrate my instrument? Given the nature of the Solid Secondary Standard and the fact that it is a plastic material and not the fluorophore of interest, we do not advise using it as the primary standard for calibrating your instrument. For applications such as dyes and turbidity there are known and tested primary calibration standards that can be used for calibrating the instrument. However, for in vivo applications - there is no calibration standard. These samples are raw water samples and are qualitative (relative) measurements. It is important though to make sure that the instrument’s sensitivity is appropriately set for reading samples and the Solid Secondary Standard can be used as a tool to accomplish this. We have a great video demonstrating this for the AquaFluor, see below, and you can contact Technical Support if you have questions about our other instruments.