Test Techniques for Colorimetry, Electronic, and Titrimetric Methods

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  1. Tests which determine the concentration of a substance are based on Beer’s Law. Simply stated, this says that the higher the concentration of a substance, the darker the color developed in the test, so more light is absorbed by the sample.
  2. pH tests use an indicator which changes color with changes in the concentration of hydrogen ions, or the acidity of the solution.
Octa-Slide 2 Octa-Slide 2 Comparator The eight color standards in the Octa-Slide 2 are placed in a bar so that they can be compared to the sample individually.
Low Range Comparator Low Range Comparator The Low Range Comparator allows extremely faint colors to be matched to color standards by viewing the reaction down the length of the tube increasing the path length by ten times compared to comparators that view the reaction across the diameter of the tube.
insta-TEST basic icon Test Strips Test strips are either dipped or swirled in test solutions. The resulting color reaction is compared to a color chart provided.
color-chart-comparator Color Chart Comparator Color charts are laminated color standards. The reacted sample is held against the panel and compared to the color standards.

Electronic

Electronic methods generally use a special electrode for measuring a specific test factor. An electrode is immersed into a sample and an amplified current or voltage is produced and translated into a digital readout.

Electronic colorimeters measure the amount of light which travels through the reacted sample, and convert the measurement to a reading as ppm, absorbance or %T. In addition to colorimeters, LaMotte manufactures instruments to test pH, TDS/conductivity, dissolved oxygen, and turbidity.

Titrimetric

Titrimetric tests can be used to determine the concentration of a substance in a sample solution. After the sample is treated with an indicator, a standard titrant is added until a color change indicates a completed reaction. LaMotte offers four separate types of titration methods, allowing a choice of precision and convenience.

Direct Reading Titrator Direct Reading Titrator The Direct Reading Titrator is a 1.0 mL microburet calibrated to allow direct reading of the test result. Each Titrator has a specific range, but may be refilled to test higher concentrations.
Dropper Pipet Dropper Pipet The drop count test uses a pipet to provide fast, reliable measurements in the field. The number of drops used to obtain a color change is multiplied by a given factor to produce the test result.
Automatic Buret Automatic Buret The self-zeroing automatic buret is calibrated from 0 to 10 mL in 0.1 mL increments. It is available with a squeeze valve (pinchcock), glass stopcock, or stopcock.
Dropper Bottle Dropper Bottle The dropper bottle test uses bottle tips which deliver a consistent standard drop size to add titrant to the sample. As with the drop count test, the number of drops used to complete the reaction is multiplied by a given equivalence factor to determine the concentration. Many dropper bottle tests use different sample sizes for different equivalences.