Attenuated total reflectance infrared determination of sodium nitrilotriacetate in alkaline liquid detergents

An attenuated total reflectance infrared (ATR–FTIR) method has been developed for the direct determination of the chelating agent sodium nitrilotriacetate (NTA) in high pH cleaning formulations. Aqueous samples and standards were placed directly on the diamond ATR cell without any pre-treatment and FTIR spectra were recorded between 4000 and 600 cm−1. Measurement conditions were evaluated. Results obtained for five different commercial formulations containing from 6.22 to 9.25% (w/w) of NTA were in good agreement with the manufacturerʹs declared content (differences between 3.2 and −3.7%). Recovery studies evidenced the accuracy of the developed method, having found values between 98.4 and 102.4%. The developed procedure provides an excellent throughput of 50 independent determinations per hour, and each measurement required only less than 0.2 ml of sample or standard.