Fresenius J Anal Chem (1996) 356: 49-51 © Springer-Verlag 1996 ORIGINAL PAPER J.M. Lopez Fernandez • A. Rios • M. Valcarcel Automatic determination of total aliphatic amines by on-line photometric liquid-liquid microextraction Received: 27 June 1995/Revised: 25 September 1995/Accepted: October 1995 Abstract An automatic flow method for the determina- tion of total aliphatic amines has been developed. Using an integrated micro extraction unit at the detec- tion point that allows continuous on-line monitoring of small organic plug from which amines are extracted. It is based on the formation of ion-pairs between aliphatic amines and sodium 1,2-naphthoquinone-5-sulphonate that are subsequently extracted into chloroform. The gradual enrichment of the organic phase with the ion- pair is continuously monitored at 460 nm. Absorbance readings at a fixed time and the slopes of absorbance- time recordings are the measured parameters used for determination purposes. The proposed method has been applied to the determination of total aliphatic amines in both synthetic and real (food) samples. Introduction The determination of amines is of great importance in different areas, one of which is food analysis [1, 2]. In fact, monitoring amine levels in malting and brewing processes allows to draw up a balance of amines from malt to the finished beer [3]. Wine is another beverage frequently analysed for amines on account of their toxic effects [4]. A wide variety of separation, derivatization and detection methods for amines in beverages of sam- ples have been reported [5], of which the chromato- graphic alternatives are the most useful. This paper reports a new method for the fast, automated deter- mination of total aliphatic amines in beer and wine using a recent approach to continuous liquid-liquid extraction methodology [6, 9], advantageous in com- parison to the classical procedure [7, 8]. J. M. Lopez Fernandez • A. Rios - M. Valcarcel (® ) Department of Analytical Chemistry, ETSIAM, Faculty of Sciences, University of Cordoba, E-14004 Cordoba, Spain Experimental Reagents. All chemicals used were of analytical-reagent grade and solutions were prepared in ultrapure water (bidistilled water from a Millipore water purification system). A 3.0 g1 1 sodium 1,2-naph- thoquinone-4-sulphonate (NQS) solution was prepared daily and stored in the dark. A 1.000g1 - ' ethylamine hydrochloride stock solution was also prepared. Chloroform and methanol were ob- tained from Merck and used without further purification. Apparatus. A Unicam 8625 single-beam spectrophotometer fur- nished with a Hellma QS cuvette (10 mm light path) and connected to a Knauer x-t recorder was used. Two Gilson Minipuls-3 peristal- tic pumps, a Rheodyne 5301 injection valve and three switching valves were also employed. Manifold and procedure. The assembly used is already described in detail in [6, 9] and is shown with its four steps used in Fig. 1. Results and discussion Aqueous sodium 1,2-naphtoquinone-4-sulphonate (NQS) was used as reagent for the formation of ion- pairs with amines in alkaline medium subsequently continuously extracted and monitored at 460 nm. The reaction was favoured by heating the reactor coil. The fast kinetics of both the ion-pair formation and the extraction process allowed a high overall flow-rate and hence a high analyte extraction yield, sensitivity and sampling frequency to be achieved. Optimization experiments carried out with the manifold depicted in Fig. 1 showed a flow-rate of 1.4 ml min - t to be suitable for the NQS, NaOH and sample channels, and 3.0 ml min - i for the auxiliary channels used to flush the cuvette and load the injec- tion valve. The length of the reaction coil was fixed at 50 cm because longer coils did not further increase the extraction efficiency. A concentration of NQS between 0.5 and 5.0 mg ml -1 favoured ion-pair formation. Since excess reagent was not extracted into the organic phase,