A comparator is a set of sealed ampoules that contains color standards made of dye mixtures. CHEMetrics offers two kinds of comparators: FLAT comparators with a white background intended for high range measurements, and ROUND, cylindrical comparators for low range measurements. We’ll tell you more about how each of those comparator styles are read in a minute.
First, some background: CHEMetrics comparators are specially manufactured to match the color (or hue) as well as the intensity of CHEMetrics test ampoules that have been snapped in various samples – that is, in solutions of corresponding analyte concentrations. By sealing our dyes in ampoules, we’re able to closely recreate the color generated in the test ampoules.
To obtain the most accurate readings using a comparator, we must first consider how various light sources affect a test ampoule’s perceived color. When using CHEMetrics comparators, LED and natural outdoor light are adequate light sources, though full sunlight can be too intense.
Fluorescent indoor lighting allows for optimal color matching.
Regardless, when taking multiple readings, be sure to use a consistent light source.
When reading a round or low range comparator, insert the ampoule, flat end first, into the comparator, point the comparator toward the light source, and view from the bottom. Align the test ampoule directly above the color standard with the lowest concentration, then slowly turn the comparator counterclockwise until the intensity of the test ampoule’s color matches a color standard, or appears to be in between those of two color standards. Look to the bottom of the comparator to determine your result.
When reading a high range comparator, It’s very important to hold it in a manner that eliminates glare or reflections from the light source. This can be accomplished by angling the comparator relative to the light source until the reflection disappears. Some analysts prefer to hold the comparator so the bubble is at the top of the ampoule. Others prefer to angle the top of the comparator down to make the bubble disappear into the body of the comparator, thus displaying longer stretches of continuous colors against which the test ampoule can be matched. Next, the test ampoule should be placed between the first and second color standards at the left or lower concentration end of the comparator. Progressively move the ampoule to the right until the intensity of the test ampoule appears to be in between two nearly matching standards. Alternately move the test ampoule to the right and left as subtle changes in the viewing angle can make the test ampoule look more or less intense than an adjacent standard. Again, once the analyst identifies a match, the result may be determined.
Thank you for relying on CHEMetrics by AquaPhoenix Scientific for simplicity in water analysis.
