Printer Friendly

Determination of the Mineral Compositions of in Six Beans by Microwave Digestion with Inductively Coupled Plasma Atomic Emission Spectrometry.

Byline: QINGHUA YAN, LI YANG, SHUYANG CHEN, XI LIU AND XIAOQIN MA

Summary

In the study, microwave digestion procedure optimized was applied for digesting beans. Nineteen mineral element concentrations were determined by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The result indicated detection limits for the 19 elements were less than 0.0998, and relative standard deviations were 1.01% 5.02% for all the elements, and recoveries were 90.89% 104.55% by adding standard recovery experiment. The study showed the beans selected were abundant in mineral element contents in human nutrition, determination mineral element contents by ICP-AES with microwave digestion technology were a lot of merits of small environmental pollution, fast and accurate determination result, which could satisfy the examination request of bean samples. The results provided evidence that the six beans were a good source of K, P, Mg and Ca.

This study is to give important reference value to people due to individual differences by adjusting the dietary to complement the different mineral elements.

Keywords: Beans; Mineral elements; Microwave digestion; ICP-AES

Introduction

Mineral elements are of critical importance in the diet, even though they comprise only 4-6% of the human body. Throughout the world, there is increasing interest in the importance of dietary mineral elements in the prevention of several diseases. The major mineral elements serve as structural components of tissues and function in cellular and basal metabolism and water and acid- base balance [1-3]. Human, as well as animal, studies originally showed that optimal intakes of mineral elements such as sodium, potassium, magnesium, calcium, manganese, copper and zinc could reduce individual risk factors, including those related to cardiovascular disease [4, 5]. A number of mineral ions are recognized as essential plant nutrients that are directly incorporated into organic compounds synthesized by the plant. Of these, potassium, phosphorus, calcium, magnesium and sodium are the most important part of quantitative studies and are recommended for composition analysis.

Recently, the importance of beans improved diet in human nutrition is increasing for several reasons. Beans are well above average in protein, mineral ions concentrations, etc. So, the flour made from beans are one of the richest sources of mineral in any food. It is, therefore, highly beneficial to adjust metabolic disorders caused by mineral elements deficiency in the body.

The traditional digestion methods reveal that dry ashing and wet methods have disadvantages during the sample digestion process. The dry ashing method in a muffle furnace and subsequent dissolution of the residue with acid is not widely used in element analysis due to the losses of volatile elements and serious contamination as well as failure to dissolve the ash completely. The wet method with various combinations of strong acids is time- consuming and labour-intensive. Microwave digestion method has become more common international digestion methods in recent years, which has many advantages, such as fast dissolving, good dissolving effect, simple, safe, easy to control, low evaporation losses, multiple samples digestion and good reproducibility. Modern analytical instruments such as atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES) are widely used to determine the elemental contents in samples.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) is the most used technique in the determination of mineral elelments because of the capability for rapid multi-element detection over a wide concentration range with relatively low detection limits [6-8]. Therefore, the aim of this work is to establish a method for simultaneously determining nineteen mineral element contents in the different beans by combining the microwave digestion technology with the ICP-AES, which also is useful for the evaluation of dietary information for the different bean samples examined.

Results and Discussion

Optimization of the Microwave Digestion Conditions

It is very well known that not only the determination of the mineral element concentrations in these beans is very important, but also a reliable analytical procedure is a critical step in the studies on mineral element analysis for preventing heavy metal poisoning. For example, simply employing a closed pressurized digestion system without optimizing the type and amount of reagents or heating temperature and program will not provide accurate and precise results. Therefore, in this study, prior to determination of the elements ICP-AES in the beans, optimization of microwave digestion procedure for dissolution of the beans was also studied.

It seems that, for a number of elements, the microwave digestion provides higher recoveries. However, the selection of digestion solution for samples was also very important. At first, the digestion solution of HNO3 and HClO4 (12:2) were used in the study, with the reagents used, it was impossible to dissolve such material completely. All digestion solutions of the beans contained a slight precipitate even under optimized experimental conditions. H2O2 were used instead of HClO4 in the experiments, when the value of HNO3: H2O2 (V:V) was 12:2, the digestion was provided completely. In addition, the running power, the temperature rising time, the running temperature, the running time of the microwave digestion were also optimized. Optimum conditions of the microwave digestion were summarized in Table-1.

Table-1: The operational parameters of the microwave digestion

Stage###Power###Temperature rise time###temperature###Running time

###(W)###(min)###(degC)###(min)

1###800###4###130###5

2###800###3###160###7

3###800###5###210###20

Detecting Wavelength, Linearity and Detection Limit

Selecting the spectral lines for detecting, which must have little spectral interference and high precision. The linearity, the limit of detection for all the analysis elements by ICP-AES method were investigated under the above optimum analysis conditions. Calibration curves were obtained for analysis elements using a series of multi-element calibration standard solutions, detection limit were calculated using 3 SD/b (SD is the standard deviation of the curve and b is the slope of the curve). A good linear relationship between the corresponding sensitivities and the concentrations of the analysis elements was achieved. The calculated regression equation, correlation coefficients (r), detection limit by ICP-AES method were showed in Table-2.

Table-2: Wavelengths, calibrations and detection limits of the elements by ICP-AES

###Correlation###Detection

###Regression###coefficient###limits###Wavelength

Element###equationa###(r)###(ug/mL)###(nm)

Na###Y=2099814X-19368###0.999274###0.0953###589.62

K###Y=756801X-74418.5###0.999392###0.0804###766.514

As###Y=778.1X+6.7###0.999724###0.0950###193.69

Se###Y=1191X+81.1###0.999476###0.0999###196.02

P###Y=6439X+3221.7###0.999812###0.0998###213.63

Zn###Y=156356X+301.6###0.999899###0.0090###213.85

Pb###Y=4829X+81.7###0.999901###0.0850###220.35

Cd###Y=61897X+30.2###0.999912###0.0185###226.50

Ni###Y=27588X+333.1###0.999976###0.0225###231.60

B###Y=92891X+2.9###0.999924###0.0195###249.69

Mn###Y=184265X+5122.4###0.999891###0.0050###257.61

Fe###Y=170673X+1587.8###0.999991###0.0095###259.93

Cr###Y=27148X+240.9###0.999898###0.0145###267.71

Mg###Y=2782X+230.1###0.999967###0.0555###279.07

Be###Y=3408678X+35899.9###0.999486###0.0084###313.06

Ca###Y=20548X+9857.2###0.999332###0.0529###317.93

Cu###Y=47612X+1698.1###0.999995###0.0082###324.75

Al###Y=23575X+478.9###0.999987###0.0783###396.18

###Y=218185328X-

Ba###0.999991###0.0062###455.42

###119801.1

a Y= sensitivity (cps), X= concentration of compound (ug/mL)

Precision and Recovery Test

To ensure the precision and accuracy of the experiment, Green bean was selected to detect the precision and recovery with five parallel samples. The relative standard deviations (RSDs) ranged from 1.01% to 5.02%, and the recoveries range from 90.89% to 104.55% (Table-3), which proved this method was accurate and precise.

Table-3: Accuracy and recovery of determination method (ug/mL). n=5

Element###Base###RSD (%)###Quantity###Quantity Recovery (%)

###value###added###found

Na###517.25###2.09###100.00###615.71###98.46

K###18508.33###1.37###200.00###18708.87###99.87

As###ND###2.99###0.50###0.47###93.27

Se###7.75###2.01###5.00###12.29###90.89

P###5656.66###1.57###200.00###5865.76###104.55

Zn###45.08###1.01###10.00###55.25###101.69

Pb###24.66###5.02###10.00###35.14###104.78

Cd###ND###1.97###0.50###0.49###98.12

Ni###12.58###1.88###10.00###22.28###97.03

B###151.00###2.12###50.00###202.60###103.21

Mn###24.58###1.67###10.00###34.44###98.61

Fe###112.83###1.49###50.00###162.59###99.52

Cr###2.83###2.96###2.00###4.88###102.67

Mg###2541.66###1.79###200.00###2738.14###98.24

Be###4.50###1.48###2.00###6.56###102.97

Ca###1988.33###2.52###200.00###2185.71###98.69

Cu###20.33###3.59###10.00###30.01###96.82

Al###171.83###3.76###50.00###220.70###97.75

Ba###3.33###1.87###2.00###5.41###103.79

ND:Non Detected

The beans not only need nutrients for normal plant growth, but also can selectively uptake and accumulate some mineral elements which are good for human health and the important basic substance to prevent and control disease[9].The mineral contents of the different beans were presented in Table-4. The result indicated that the six beans analyzed were abundant in mineral elements. K, P, Ca, Mg, Na, Al, Fe, Mn, Zn, Cu, B were major minerals of all beans. Ba, Be, Cr, Ni, Se and Pb contents of beans were found to be low. Cd was not established in all beans. In addition, the As was not determined in black bean, green bean and soybean.

Major mineral elements were of interest due to their pro-oxidant activity and health benefits [10-12].The potassium content was high in most cases and ranged from 12183.33 ug/g (mung bean) to 18508.33 ug/g (green bean). The phosphorus content ranged from 3535.83 ug/g (black bean) to 6480.83 ug/g (soybean). Ca was found to be high, ranging from 365.41 ug/g (mung bean) to 2670.00 ug/g (soybean). The magnesium content varied from 1290.83 ug/g (mung bean) to 2541.66 ug/g (green bean). Na and Al content varied similarly, ranging from 259.00 ug/g and 48.16 ug/g (soybean) to 629.19 ug/g and 159.24 ug/g (cowpea), respectively. Fe content ranged from 53.91 ug/g (red bean) to 159.16 ug/g (cowpea). Mn content ranged from 9.91 ug/g (mung bean) to 36.83 ug/g (soybean). Zn content ranged from 28.33 ug/g (red bean) to 52.75 ug/g (soybean). Cu content ranged from 14.41 ug/g (mung bean) to 29.62 ug/g (cowpea). B content ranged from 35.91 ug/g (red bean) to 151.00 ug/g (green bean).

It is noteworthy that trace mineral elements were important not only for human nutrition, but for plant nutrition as well, such as Be, Cr, Se and Ni. Be contents were found in similarly small percentages in all the beans analyzed, ranging from 4.28 ug/g (cowpea) to 4.50 ug/g (green bean). Cr content was also present in similarly in the six beans but red bean presented the lowest mean concentration of Cr 1.5 ug/g. Se and Ni contents displayed a wide variability among the six beans. Might be due to growth conditions and geographical variations, some heavy metal elements were detected in some beans, such as Pb, Ba, As. But Cd was not established in all beans. Ozcan determined the Al, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P and Zn contents of soybean and K, P, Ca, Mg, Na contents were found higher than those of other elements. Na and Cr concentrations found in this work were lower than those published for soybean.

P, Zn, B, Mn, Ni, Mg, Ca, Cu contents found in this work were higher than those published for soybean, whereas the levels of Al, Fe and K were similar to those determined in soybean [13-16].

Experimental

Equipment and Working Conditions

Optima2100 DV inductively coupled plasma atomic emission spectrometer (ICP-AES, PerkinElmer Corporation of USA), MAS microwave digestion system (CEM Corporation of USA).

Working conditions of ICP-AES: RF Power: 1.3 KW. Auxilary gas flow rate (Ar): 0.2 L/min. Cooling gas flow (Ar): 15.0 L/min. Carrier gas flow (Ar): 0.6 L/min.

Working conditions of microwave digestion were showed in Table-1.

Materials

The beans used in the experiment including samples of black bean, red bean, soybean, green bean, mung bean and cowpea were bought from the agricultural product market in Xinxiang, China and authenticated by Doc. Benguo Liu (School of Food Science, Henan Institute of Science and Technology, Xinxiang, China).

Reagents and Standard Solutions

HNO3 (superior grade of pure, Zhengzhou Piney ChemicalReagent Factory), H2O2 (analysis grade of pure, Shenzhen Yongsheng Chemical Co., Ltd.), mixed standard stock solution: concentration of Na, K, Cu, Fe, Zn, Mn, Ca, Mg, Al, Se, B, Be and Ba were all 1000 ug/mL, Cr, Pb, Ni, As and Cd were all 100 ug/mL (Merck of Germany).

50 ug/mL P standard stock solution: 0.2195 g of KH2PO4 baked at 105 degC for 2 h was accurately weighed into deionized water of 400 mL and 5.0 mL concentrated H2SO4 was added (prevent mould growing). At last the mixture solution was transferred to 1000 mL volumetric flasks and made up to 1000 mL with deionized water.

Preparation of Standard Solution

The standard stock solution was diluted with 2% nitric acid step by step. Mixed standard solutions of Na, K, Cu, Fe, Zn, Mn, Ca, Mg, Al, Se, B, Be and Ba were prepared by the gradient of 0.00, 0.5, 1.00, 2.00, 4.00 and 8.00 ug/mL. Mixed standard solutions of Cr, Pb, Ni, As and Cd were prepared by the gradient of 0.00, 0.25, 0.5, 1.00, 2.00 and 4.00 ug/mL. Standard solution of P was prepared by the gradient of 0.00, 5.00, 10.00, 15.00 and 25.00 ug/mL.

Table-4: Mineral contents in different beans (ug/g).

Element###Black beans###Red bean###Soybean###Green bean###Mung bean###Cowpea

Na###299.91###319.50###259.00###517.25###348.91###629.19

K###13725.00###12208.33###18097.82###18508.34###12183.33###12731.16

As###ND###1.83###ND###ND###2.25###3.33

Se###6.33###2.83###4.66###7.75###3.25###1.71

P###3535.83###4022.50###6480.83###5656.66###3763.33###3895.54

Zn###30.08###28.33###52.75###45.08###34.75###36.81

Pb###6.91###7.75###5.75###24.66###5.66###6.16

Cd###ND###ND###ND###ND###ND###ND###ND

Ni###15.16###6.16###14.08###12.58###1.83###3.42

B###74.75###35.91###56.75###151.00###70.58###123.80

Mn###23.83###11.75###36.83###24.58###9.91###16.35

Fe###81.33###53.91###75.83###112.83###74.83###159.16

Cr###2.16###1.5###2.16###2.83###2.58###2.14

Mg###1865.00###1336.66###2410.83###2541.66###1290.83###1434.07

Be###4.41###4.33###4.33###4.50###4.33###4.28

Ca###2553.33###1075.83###2670.00###1988.33###365.41###609.50

Cu###14.75###19.08###21.41###20.33###14.41###29.62

Al###115.41###50.00###48.16###171.83###94.75###159.24

Ba###9.41###4.16###7.75###3.33###1.83###2.56

ND:Non Detected

Sample Handling and Determination

The different beans were baked in oven after washed with deionized water. At last, all samples were smashed using high speed universal grinder, respectively and the powder was standby. Three replicate samples (0.50 g) of powder of the different beans were accurately weighed into the decomposition vessels and a mixture of 10.0 mL concentrated HNO3 and 2.0 mL concentrated H2O2 was added. After samples were digested, the digestion solution was transferred to different beakers and acid was removed on a heating plate at 180 degC, at last the samples digested were transferred to 25 mL volumetric flasks, major volume with 2% HNO3. Concentrations of mineral element were determined with ICP-AES.

Conclusions

ICP-AES is simple and precise method to determine mineral elements in bean samples simultaneously.

From nutritional point of view, green bean was rich in mineral elements such as K, Mg, Al, B, Pb and Be. Soybean contained relatively large amounts of P, Zn, Mn and Ca. Black bean was rich in Ni and cowpea was rich in Na, Fe, Cu.

References

1. M. M. Saleh-e-in, A. Sultana, M. A. Hossain, M. Ahsan and S. K. Roy, Bangladesh Journal of Scientific and Industrial Research, 43, 483 (2008).

2. J. C. Fleet, R. Replogle and D. E. Salt, Journal of Nutrition, 141, 512 (2011).

3. W. Sauer, M. Cervantes, J. Yanez, B. Araiza, G. Murdoch, A. Morales and R. T. Zijlstra, Livestock Science, 122, 162 (2009).

4. F. M. Gemma, N. A. Ana, P. B. Roberto and G. Eliseo, American Journal of Clinical Nutrition, 84, 762 (2006).

5. C. P. Sanchez-Castillo, P. J. S. Dewey, A. Aguirre, J. J. Lara, R. Vaca, P. L. Barra, M. Ortiz, I. Escamilla and W. P. T. James, Journal of Food Composition and Analysis, 11, 340 (1998).

6. L. Aleksieva, N. Daskalova and S. Velichkov, Spectrochimica Acta Part B-Atomic Spectroscopy, 57, 1339 (2002).

7. N. Bahramifar and Y. Yamini, Analytica Chimica Acta, 540, 325(2005).

8. P. Liang, B. Hu, Z. C. Jiang, Y.C. Qin and T. Y. Peng, Journal of Analytical Atomic Spectrometry, 16, 863 (2001).

9. Q. H.Yan, L. Yang, Q.Wang and X. Q. Ma, Journal of Saudi Chemical Society, (In press).

10. L. M. Gaetke and C. K. Chow, Tolicology, 189, 147 (2003).

11. J. Kovacik, B. Klejdus, J. Hedbavny, R. Stork and M. Backor, Plant Soil, 320, 231 (2009).

12. S. Bastida, M. P. Vaquero, M. Veldhuizen and F. J. Sanchez-Muniz, Acta Paediatr, 89, 1201 (2000).

13. M. Ozcan, Grasas Y Aceites, 57, 211 (2006).

14. I. Hussain, M. U. R. Khattak, F. A. Khan, I. U. Rehman, F. U. Khan and F. U. Khan, Journal of the Chemical Society of Pakistan, 33, 495 (2011).

15. R. Perween, M. Mumtaz, Qamarul-Haque and T. Mehmood, Journal of the Chemical Society of Pakistan, 33, 313 (2011)

16. T. Mahmud, R. Rehman, S. Ali, J. Anwar, A. Abbas, M. Farooq and A. Ali, Journal of the Chemical Society of Pakistan, 33, 339 (2011).

1Department of Life Science and Technology, Xinxiang Medical University, Xinxiang Henan 453003, P.R. China., 2Department of Experimental Center, Henan Institute of Science and Technology, Xinxiang Henan 453003, P.R. China., 3School of Chemistry and Pharmaceutical Engineering, Nanyang Normal University, Nanyang Henan 473061, P.R. China. yqh3499@yahoo.com.cn
COPYRIGHT 2012 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2012 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Qinghua Yan; Li Yang; Shuyang Chen; Xi Liu; Xiaoqin Ma
Publication:Journal of the Chemical Society of Pakistan
Article Type:Report
Geographic Code:9PAKI
Date:Jun 30, 2012
Words:3199
Previous Article:Effects of Whole Flower and Fractions of Ixora coccinea Linn. on Cardiovascular System: A Preliminary Report.
Next Article:Characterization and In-Vitro Release Study of Celecoxib Microspheres Synthesized from Polymethacrylate and Polyvinyl Pyrolidone.
Topics:

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters