Analytica Chimica Acta 475 (2003) 137–150 Quantifying catecholamines using multi-way kinetic modelling Rikke P.H. Nikolajsen a,b,∗ , Karl S. Booksh c , Åse M. Hansen a , Rasmus Bro b a National Institute of Occupational Health, Copenhagen, Denmark b Chemometrics Group, Food Technology, The Royal Veterinary and Agricultural University, Copenhagen, Denmark c Department of Chemistry and Biochemistry, Arizona State University, Arizona, AZ, USA Received 21 December 2001; received in revised form 24 September 2002; accepted 8 October 2002 Abstract A new method for quantifying adrenaline and noradrenaline concentrations from mixtures of catecholamine standards is described. The method derives selectivity from the different rates, at which the fluorescing 3,5,6-trihydroxyindole derivatives (lutines) of the catecholamines are formed and degraded for adrenaline and noradrenaline. The standards used had the concentration ranges 50–1200 nmol/l for adrenaline and 30–1400 nmol/l for noradrenaline. Fluorescence landscapes were measured at consecutive time points for every sample hereby creating a four-way data array. It is shown that the raw dataset can be dramatically reduced in size without loosing significant information hereby making calculations much faster and lessening instrumental performance requirements. The data follow a two-component four-way parallel factor analysis model (PARAFAC), from which quantitative information is also obtained. Two-component multilinear partial least squares regression (N-PLSR) was also employed for the quantification of the catecholamines. The results for PARAFAC and N-PLSR were very similar with root mean squared errors of cross-validation (RMSECV) being in the range 24–30 nmol/l. Several improvements of the method are suggested, and it is expected that the method will be suitable for determination of catecholamines in urine from healthy subjects. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Catecholamines; PARAFAC; Kinetics; Trihydroxyindole; Urine; Stress 1. Introduction Urinary catecholamine excretion is a measure of acute stress, and has been used as such in several oc- cupational health investigations, for review see [1]. At present, high performance liquid chromatography (HPLC) methods are typically used for separation of adrenaline (A) and noradrenaline (NA) followed by quantification using fluorescence or electrochemical detection (see e.g. [2–4] and for review see [5]). A ∗ Corresponding author. Present address: Mikroelektronik Cen- tret (MIC), Technical University of Denmark, Ørsteds Plads, Build- ing 345 Ø, Lyngby DK-2800, Denmark. E-mail address: rpn@mic.dtu.dk (R.P.H. Nikolajsen). representative HPLC method using the lutine reac- tion as post-column derivatisation reaction [4] has a limit of detection (LOD) of 3.1 nmol/l for adrenaline and 5.2 nmol/l for noradrenaline. Development of a faster and cheaper method for determining adrenaline and noradrenaline in urine would facilitate that these biomarkers are used more often in the investigation and prevention of stress in the working environment. An analytical method for the determination of the cat- echolamines should firstly be able to distinguish the two analytes, and secondly be able to accurately de- termine small concentration changes in the urine from healthy subjects. The urinary concentrations in healthy subjects are in the ranges 0–100 nmol/l for adrenaline and 50–500 nmol/l for noradrenaline. 0003-2670/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0003-2670(02)01256-4