Characterization and quantification of N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine biocide by NMR, HPLC/MS and titration techniques

The present paper reports the determination of the tri-amine N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine (TA) present in a raw material called LONZABAC used to formulate various, widely used commercial biocides. The active principle, TA, is present in LONZABAC together with other molecules at lower concentration levels. Three independent analytical approaches, namely solution NMR spectroscopy, liquid chromatography coupled to high resolution mass spectrometry (LC/HRMS) and acid-base titration in mixed solvent, were used to overcome the problem of the non-availability of the active principle as high purity standard. NMR analysis of raw material, using a suitable internal standard, evidenced in all analyzed lots the presence of the active principle, the N-dodecyl-1,3-propanediamine (DA) and the n-dodecylamine (MA) and the absence of non-organic, NMR-inactive species. NMR peak integration led to a rough composition of the MA:DA:TA as 1:9:90. The LC/HRMS analysis allowed the accurate determination of DA and MA and confirmed in all samples the presence of the TA, which was estimated by difference: MA = 1.4 ± 0.3%, DA = 11.1 ± 0.7%, TA = 87.5 ± 1.3%. The obtained results were used to setup an easy, rapid and cheap acid-base titration method able to furnish a sufficiently accurate evaluation of the active principle both in the raw material and in diluted commercial products. For the raw material the results were: TA + MA = 91.1 ± 0.8% and DA − MA = 8.9 ± 0.8%, statistically coherent with LC/MS ones. The LC/MS approach demonstrated also its great potentialities to recognize trace of the biocide components both in environmental samples and in the formulated commercial products.