J Sci Food Agric 1998, 77, 456�8 Mineral Element Composition of Spinach Santanu Bhattacharjee,* Pranab Dasgupta, Adhir R Paul, Sunanda Ghosal, Karuna K Padhi and Lallan P Pandey Analytical Chemistry Division, National Metallurgical Laboratory, Jamshedpur 831007, India (Received 27 August 1996 ; revised version received 24 October 1997 ; accepted 20 November 1997) Abstract : An extensive study has been made on the mineral element compositions of spinach leaves and stems. Twenty two locally grown di?erent spinach samples have been analysed for 16 elements using ICP and atomic absorption spectrophotometric techniques. Both spinach leaves and stems were analysed separately. A detailed elucidation of the inorganic matrix in spinach leaves and stems has been provided. ( 1998 SCI. J Sci Food Agric 77, 456�8 (1998) Key words : spinach ; leaf ; stem ; mineral elements ; ICP ; AAS INTRODUCTION In the second category, an established method was used for the determination of one or more elements in spinach for the purpose of monitoring. Presently, a project is being carried out at National Metallurgical Laboratory, Jamshedpur on the ?Appraisal of Metal Concentrations in Indian Vegetable Crops�. The study of mineral elements in spinach constitutes a part of this study. In this communication, an extensive report on the mineral element compositions of spinach leaves and stems has been provided. Twenty two local spinach samples collected at di?erent times and from di?erent places were analysed for 16 elements using 補me atomic absorption spectrometry (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The objective of the present communication is to provide a comprehensive account of the mineral element values in spinach and 衝d out their pattern of occurrence in spinach leaves and stems. To the best of the authors� knowledge no such study on spinach has been reported before. Spinacia Linn, family : Chenopodiaceae, a small genus of annual herbs may be found from the eastern Mediterranean to central Asia and Afghanistan. One species, S oleracea, native to south-west Asia is extensively cultivated in India and is well known for its nutritious leaves. This species is also known as garden spinach. Spinach is a mineral-rich vegetable. An earlier study on the edible portion (87%) of spinach records (%) : moisture, 92�; protein, 2�; fat, 0�; 衎re, 0�; mineral matter, 1�; carbohydrate, 2�; and oxalic acid, 658 (mg per 100 g). Mineral composition includes (mg per 100 g) : calcium, 73 ; magnesium, 84 ; potassium, 206 ; iron, 10�; phosphorus, 21 ; sodium, 58�; copper, 0� ; sulphur, 30 ; nickel, 0� ; manganese, 9� ; molybdenum, 0� ; zinc, 13� ; and strontium, 0�7. Spinach is a good source of the vitamin B complex, ascorbic acid, vitamin A and carotin. It is also a natural source of vitamin K (CSIR 1976). Mineral elements in spinach have been studied by several workers employing a large number of techniques (Lin and Julshamn 1984 ; Stephen et al 1985 ; Salinas et al 1987 ; Alegria et al 1988 ; Yan and Schwedt 1990 ; Mittal et al 1993). The available literature may be broadly classi衑d into two categories. In the 衦st category, a newly developed reagent or a technique was tested for a particular element with reference to spinach. EXPERIMENTAL Preparation of spinach leaf and stem samples Spinach samples were procured from within an area of 64 km2 around Jamshedpur. Each sample was cleanly separated into its leaf and stem sections. Each section was thoroughly washed and cut into very small pieces * To whom correspondence should be addressed. 456 ( 1998 SCI. J Sci Food Agric 0022�42/98/$17.50. Printed in Great Britain Mineral element composition of spinach 457 and dried in an oven at 110 for 4 h. Dried samples were powdered and again dried for 1 h at 110. A total of 22 spinach samples were processed which gave 22 leaf sections and 22 stem sections. Dissolution of spinach samples Standard wet digestion procedure was used in the present work for dissolving the spinach leaf and stem samples. Approximately 1 g of the dried sample was weighed accurately and digested with 10 ml of concentrated HCl and 5 ml of concentrated HNO for about 3 2 h. HClO (5 ml) was added to the solution and heated 4 till dense white fumes came out and the solution became clear. Distilled water (20 ml) was added to it and digested for D 30 min. The resulting solution was cooled and the volume was made upto 50 ml. For every batch of samples a representative blank was prepared. Reagents HCl, HNO , HClO and other reagents used were of 3 4 AR grade. 18 M) ASTM Grade 1 water was used for preparing the solutions. Instrumental Mg, Ti, Cr, Mn, Al, Fe, Cu, Co, Ni and Zn were analysed by a Shimadzu GVM1014P Simultaneous ICP-OES. Na, K, Ba and Sr were analysed by a Shi- madzu ICPS-1000III Sequential ICP-OES. Ca was analysed by GBC 908-AA 補me atomic absorption spectrometer. For the determination of Ca the sample solution was diluted 10 times followed by addition of 1000 ppm of K and La to suppress the interference due to ionisation and presence of P, respectively. The blank was also diluted accordingly. Results obtained from ICP-OES were occasionally cross checked by 補me AAS. Barnstead nanopure system water was used for making 18 M) water. RESULTS AND DISCUSSION Table 1 gives the average concentrations of 16 elements on a dry basis in spinach leaves and stems obtained from 22 di?erent spinach samples. Also, given in Table 1 are the standard deviations and range of occurrence for these elements. Some general inferences may be derived from Table 1. Except for Na, K and Co, the remaining elements have a higher trend of occurrence in spinach leaves. The inorganic matrix in both leaves and stems are primarily comprised of Na, K, Mg and Ca. Mg is generally appreciable in all green vegetables because of its association with chlorophyll but the abundance of Na, K and Ca show the mineral-rich nature of spinach. P comes next in terms of signi衏ance. It may be noted that both leaves and stems contain appreciable amount of Al. Spinach leaves and stems also contain signi衏ant amount of Fe. However, it is interesting to note that the occurrence of Fe is usually associated with trace TABLE 1 Compositions (dry wt%) of 16 elements in spinach leaves and stems obtained from 22 di?erent spinach samples (n \ 22) Elements Na K Sr ] 10~3 Ba ] 10~3 Mg Al P Ca Cr ] 10~3 Ti ] 10~3 Mn ] 10~3 Fe ] 10~3 Cu ] 10~3 Co ] 10~3 Ni ] 10~3 Zn ] 10~3 a n \ 20. L eaf Stem Range Average SD Range Average SD 1�1 1�8 21�1�1�1 0�3 0�8 0�2 0�0�37�2267 1�0�0�37� 2� 3� 4� 4� 1� 0� 0� 0� 1� 15 16�52�1� 0� 0�7� 1� 1� 1� 1� 0� 0� 0� 0� 0� 1� 19� 49� 0� 0� 0� 3� 1�1 2��� 2�0 1�0�8 0�8 0�1 0�6 0�0�21�700 0�0�� 26� 4� 5� 3� 3� 1� 0� 0� 0� 0� 1� 6� 41� 1� 0� � 6� 2� 1� 1� 1� 0� 0� 0� 0� 0� 0� 6� 40� 0� 0� � 3� S Bhattacharjee et al 458 occurrence of Mn and Zn. Other remaining elements occur only at ultratrace level. To derive more information about the inorganic matrix in di?erent spinach samples, all the elements in each sample were sorted in the descending order of their concentration. For both leaves and stems, the inorganic matrix may be classi衑d into four categories : major, submajor, trace and ultratrace. Na, K and Mg constitute the major matrix for both leaves and stems. Their relative positions, however, change from sample to sample. Only on one stem sample, P replaced Mg as the third element. P, Ca and Al constitute the submajor matrix in both leaves and stems. Once again their relative positions change from sample to sample. In the trace category, Fe, Zn and Mn are the mostly occurring elements with Sr and Ba occasionally changing places with Mn and/or Zn. In at least one sample, Fe was obtained in appreciable amount. Sr, Ba, Ti, Cr, Cu, Co and Ni are generally present in ultratrace amounts in both leaves and stems with no apparent order of occurrence. It may be seen in Table 1 that for most of the elements the width of the concentration range is considerably large. This may be due to several factors that include soil condition, fertiliser, humidity, irrigation water quality etc. The distributions have also been found to be severely skewed. All these together result into high SD values. However, this may be noted with caution that a probable outlier does not necessarily mean an erroneous measurement. Especially, in biological samples, it may also indicate a phenomenon, probably caused by some extreme environmental parameters. CONCLUSION The present study concludes the following. Na, K and Mg constitute the major inorganic matrix of spinach leaves and stems followed by Ca, Al and P which are present in appreciable quantity. Both spinach leaves and stems contain signi衏ant amount of Fe which normally cooccurs with Mn and Zn. Other remaining elements usually occur at ultratrace level with occasional crossover by Sr and Ba from ultratrace to trace. Of the 16 elements studied, except for Na, K and Co, the remaining elements have a higher trend of occurrence in spinach leaves. ACKNOWLEDGEMENT The authors wish to thank the Director, NML for his permission to publish this work. REFERENCES Alegria A, Barbera R, Farre R 1988 Atomic absorption spectrophotometric determination of Ni in foods. J Micronutr Anal 4 229�9. CSIR 1976 T he W ealth of India. A Dictionary of Indian Raw Materials & Industrial Products. Raw Materials (Vol X : Sp-W). Publications & Information Directorate, CSIR, New Delhi, India, pp 12�. Lin S W, Julshamn K 1984 Comparative study of the determination of phosphorus by electrothermal AAS and solution spectrophotometry. Anal Chim Acta 158 199�6. Mittal R, Allawadhi K L, Sood B S, Singh N, Kumar A, Kumar P 1993 Determination of potassium and calcium in vegetables by X-ray 製orescence spectrometry. X-Ray Spectrometr 22 413�7. 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