Talanta 64 (2004) 1189–1195 Sequential injection spectrophotometric determination of iron as Fe(II) in multi-vitamin preparations using 1,10-phenanthroline as complexing agent  Zeriet O. Tesfaldet, Jacobus F. van Staden ∗ , Raluca I. Stefan Department of Chemistry, University of Pretoria, Pretoria. 0002, South Africa Received 16 January 2004; received in revised form 23 February 2004; accepted 23 February 2004 Available online 19 July 2004 Abstract A sequential injection analysis (SIA) system is proposed for the determination of iron (II). Fe(II) was determined by SIA based on the reaction between 1,10-phenanthroline and iron (II), yielding an orange–red colour complex with absorption maximum at 512 nm. The method involved aspiration of 187 l sample/standard zone followed by a zone of a reagent solution containing 140 l of 7.8 × 10 -4 mol l -1 1,10-phenanthroline into a carrier stream to be stacked inside a holding coil and flow reversed through a reaction coil to a detector. The optimum condition was evaluated and the calibration curve is linear over a range of 0.25 to 5.0 mg l -1 of Fe(II) with detection limit of 18 gl -1 . A sample throughput of 40 h -1 was established. This technique is found to be simple, accurate, reproducible and sensitive. The proposed method was successfully applied for the determination of total iron as Fe(II) in pharmaceutical products (multi-vitamin tablets) and is especially useful for the determination of iron (II) in tablets with lower iron (II) contents. The results were found to be in good agreement with the results obtained by manual UV/Vis spectrophotometry and flame atomic absorption spectrometry (FAAS) and with claimed values by the manufacturers. © 2004 Elsevier B.V. All rights reserved. Keywords: Spectrophotometry; 1,10-phenanthroline; Sequential injection 1. Introduction Iron is an essential nutrient in the human diet. In the body, it is complexed with hemoglobin, which carries oxygen from the lungs to the cells of the body, and plays an equally essen- tial role in respiratory enzymes such as cytochromes, which allows us to use oxygen [1]. Iron deficiency is the most com- mon cause of diseases mainly during infancy, pregnancy and adolescence [2]. When the dietary intake is deficient in iron, a condition called anaemia results. In order to avoid such deficiencies, an adequate supply of iron is needed. Some people take dietary supplements, which contain iron, such as multi-vitamins. Thus, it is necessary that an accurate, fast  Presented at the 12th International Conference on Flow Injection Analysis, including related techniques (ICFIA’2003), held in Merida, Venezuela, December 7–13, 2003. ∗ Corresponding author. Tel.: +27-084-480-7263. E-mail address: koosvanstade@telkomsa.net (J.F. van Staden). and a cheap method for the determination of iron in phar- maceuticals and food supplements should be developed. Several methods for the analysis of iron in pharmaceu- ticals and environmental samples have been reported, in- cluding potentiometry [3], chemiluminescence [4], graphite furnace atomic absorption spectrometry [5], flame atomic absorption spectrometry [6], (these two methods are very expensive), fluorometric analysis [7,8], anodic stripping voltammetry [9], volumetric analysis [10] and spectropho- tometry [11,12]. As compared with the other techniques, spectrophotometry is very simple, rapid and less expensive for determination of elements in a variety of samples. Most of these classical detectors are coupled with flow injection analysis (FIA) or sequential injection analysis (SIA) and are used for quantification of elements in a variety of real samples. The application of SIA for the determination of iron (II) using ,-bipyridyl [1] and 1,10-phenanthroline af- ter reduction of iron (III) to iron(II) with a cadmium 0039-9140/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2004.02.044