Colorimetric detectors indicate the presence of a target chemical through a chemical reaction that results in a color change to a reagent. Colorimetric detection covers a wide variety of products, from simple M8 paper for CWA to the SPX 300 for trace explosives detection. All of the products in the colorimetric detection category are generally simple to operate and have well-documented product test results to support vendor claims. The main disadvantages to the colorimetric systems are:
- They are analyte specific and are not typically suited for determination of unknowns;
- They typically require one-time use consumables such as cartridges, reagents, papers or swabs for each target chemical;
- Detection limits are typically in the part-per-million to part-per-thousand range (ppm-ppth);
- Interpretation of results may be subjective;
- Results cannot typically be stored for review at a later time.
A few vendors offer electronic readers that provide more objective results than visual comparison and can store the results of a test. Advantages of colorimetric detection include small size, little or no power requirement, low cost, and minimal operator training.