Investigation of the electrochemical conversion of brighteners during nickel electrodeposition, Part 1: chemical analysis by mass spectrometry

Results of an investigation of the action of various pyridinic and acetylenic brighteners during the electrodeposition of nickel are reported here. The focus was on the qualitative and quantitative analysis of the individual compounds 1-(3-sulphopropyl)-pyridinium betaine (PPS) and sulphopropylated 2-butyne-1,4-diol (HBOPS) and their reaction products. High performance liquid chromatography (HPLC) with a mass spectrometric detector (HPLC-MS) and a diode array detector in the UV range (HPLC-UV) were used to examine the various additives and the cathodic reaction products. PPS is almost completely hydrogenated to the piperidine compound (3-piperidin-1-yl-propane-1-sulphonate, PIPS) at the catalytically active nickel electrode; as intermediate products, only tetrahydrogenated pyridine (THPPS) compounds occur in the solution, in low concentrations. The entire hydrogenation chain takes place on the surface; partially hydrogenated products are either not desorbed at all or only desorbed in small quantities. Further by-products are dimers and after ring cleavage a pentylamine derivative {3-(pentylamino)-1-propanesulphonic acid, PAPS}. Via the olefinic intermediate stage, the butynediol compound (HBOPS) reacts to become sulphopropylated butanediol. After elimination of water, this forms butanoxy-propanesulphonate in a further hydrogenation step.