The active ingredient in Roundup Weed and Grass Killer is a chemical called glyphosate. On the Roundup label, glyphosate, N-(phosphonomethyl)glycine, is in the form of its isopropylamine salt. In this form, glyphosate is easier to handle and more effective. Regular Roundup is 2% glyphosate, and when it is ready for use, the Roundup needs to be even more diluted with water.
In this experiment, we tested these low concentrations of glyphosate with a special variable path length dip probe with a narrow tip to measure the chemical’s absorbance. We tested the dip probe with a path length of 10mm and 5mm to also measure the limit of detection for the lower concentrations. As path length is inversely correlated with detection limits in an absorbance measurement, we predicted that the 10mm path length would give more accurate and reliable results. We tested with the 5mm path length to see if the shorter path length still detected the glyphosate and if it provided similar results to the 10mm path length.
*The narrow tip variable path length dip probe is available only from Avantes North America. Avantes HQ offers a complete line of transmission dip probes with fixed or variable path lengths.
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