Recognizing a Compromised Reagent
Tuesday, April 20, 2021
A reagent's suitability for testing is suspect if it is over one year old. Considering the active ingredients need to be just that, active, then any reduction in a reagent’s concentration or effectiveness will compromise test results. How can you tell if the concentration or effectiveness is not what it should be? If the reagent is not the color you are used to seeing (or has changed color over time), if you see floating particles in it that do not dissolve when shaken, if it has begun to stain its container, or if it has crusted around the tip of the dropper bottle. These items indicate the active ingredient has been affected.
Here are some clues that indicate these specific reagents should be discarded:
Any liquid that has frozen: A liquid reagent still may be effective after freezing. Allow it to thaw at room temperature—do not microwave or heat in a warm bath. If the bottle cracks, if you see a crusty buildup around the dropper tip, or if there are floating particles that do not dissolve when the bottle is shaken, replace the reagent.
R-0002 DPD Reagent #2: This solution should be colorless to be effective. As it reacts with oxidizers, the color will vary, ranging from colorless to pink then darkening to a final brown.
R-0003 DPD Reagent #3:This solution should be colorless. As it degrades, the color will become increasingly yellow.
R-0004 pH Indicator (Phenol Red): As it degrades, the solution changes from its original red color to a yellow or purple.
R-0008 Total Alkalinity Indicator: This solution should be a dark green color. When it begins to stain the milky-colored plastic bottle, differences in initial test and endpoint colors also will be observed.
R-0011L Calcium Hardness Indicator: This solution should be a deep blue color. If any other color, replace.
R-0718 Silver Nitrate Reagent: This solution should be colorless. There are no easily observable indications. We recommend you discard and replace on an annual basis. Note: R-0718 will stain skin.
R-0871/R-8072 FAS-DPD Titrating Reagent (for chlorine/bromine): This solution should be colorless. As it degrades, the color will become increasingly yellow.
Our consultants can assist you in determining whether a reagent should be replaced.
Taylor formulates its reagents to remain effective for at least one year, with only very few exceptions. As a general precaution, replace all reagents more than one year old, or at the beginning of a new testing season.