342 Journal homepage: www.fia.usv.ro/fiajournal Journal of Faculty of Food Engineering, Ştefan cel Mare University of Suceava, Romania Volume XIII, Issue 4- 2014, pag. 342 - 348 AN I NV ES T IGAT ION O N T HE EX TRACTI ON C ONCE NT RA T ION OF MI CROE LE M EN TS FROM AQUE OUS S OLU T ION FOR ATOM - ABSO RBT IO N AN ALYS IS *Igor KOBASA1, Vasyl BILOGOLOVKA1, Mariya VOROBETS1, Oxana PANIMARCHUK2 1 Yury Fedkovych National University of Chernivtsi, Ukraine, i.kobasa@chnu.edu.ua 2 Bukovynian State Medical University, Ukraine, imk-11@hotmail.com *Corresponding author Received November 27th 2014, accepted December 29th 2014 Abstract: Some sodium diethyldithiocarbamate and 8-oxyquinoline based mixtures were tested as potential extractant to concentrate solutions containing ions of Cu2+, Co2+, Pb2+, Ni2+, Zn2+, Fe3+, Cd2+ while preparing the samples for atom-absorption analysis. The mixture of butylacetate/sodium diethyldithiocarbamate has shown the best performance. The method of the metal ions determination that combines the sample concentration using this extractant followed by the flame atom-absorption spectroscopy provides high sensitivity and selectivity outperforming characteristics as compared to the classical method of evaporation the concentration of samples. Keywords: extraction, heavy metal ions, atom-absorption analysis, natural waters 1. Introduction The atom-absorption spectroscopy method (AAS) is a powerful analytical tool used widely in investigations of various envi- ronmental objects: soils, natural waters and wastewaters, air, biomaterials, foodstuff and raw materials. A number of macro- and microelements can be successfully identified using this method along with proper chemical pre- processing of the samples. Since regular contents of some microele- ments in the natural water samples and some other probes can be under the AAS sensitivity threshold, the preliminary con- centrating of the probes is required prior to AAS measurements. In case of heavy metals, such concentrating can be performed through extraction by dithiocarbamates, 8-oxyquinoline, dithi- zone and some other [1, 2] while chloro- form, carbon tetrachloride, a mixture of the polar oxygen-containing (spirits, ketones) or non-polar oxygen-free (benzene) com- pounds can be used as the organic solvents [3]. However, these organic compounds are hardly combustible and can produce side colorization of the flame hindering accu- rate AAS determination of the ingredients. Besides, some of them release toxic prod- ucts of incomplete combustion [4]. This paper reports the results of investiga- tion of performance of new extraction mix- tures based on the butyl and amyl esters of acetic acid as extractants used for the AAS preconcentrating of the heavy metals com- pounds from the probes taken from natural waters. Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 343 2. Materials and methods The following mixtures were used as extractants for the heavy metals ions: bu- tylacetate/sodium diethyldithiocarbamate; amylacetate/sodium diethyldithiocarba- mate; butylacetate/8-oxyquinoline; amy- lacetate/8-oxyquinoline. The 10 % solution of sodium diethyldithiocarbamate prepared on deionized water and 0.01 M solution of 8-oxyquinoline prepared on the heavy met- als-free butylacetate or amilacetate [5] were used throughout all experiments as components for the working mixtures. Ac- cording to [6], all extractants were used in excessive amounts (this does not effect the extraction degree), then the volatile organ- ic compounds were distilled off and the heavy metals contents were analyzed in the distillation residue by AAS method. Aque- ous solutions of some heavy metals (Cu2+, Co2+, Pb2+, Ni2+, Zn2+, Fe3+, Cd2+) with concentrations close to the usual values occurring in natural water objects were used as model samples. All solutions were prepared using deion- ized water with specific resistance 15 MOhm or above. pH levels were adjusted by adding some amounts of metals-free HCl or NH4OH. All pH measurements were performed by pH-meter pH-150 equipped with the glass electrode ECL-47- 07 and silver-chlorine reference electrode EVL-1M. All extraction processes were carried out according to the method [7] and the flame atom absorption spectrometer KAS-120-M1 was involved in the direct determination of metal ions concentrations. 3. Results and discussion The atom absorption spectra of the pure extractants combustion products were in- vestigated preliminary using the deionized water as the reference. The results of this investigation are shown in Fig. 1. Fig. 1. Light absorbance for combustion prod- ucts of amylacetate (1) and butylacetate (2). As seen from Fig. 1, light absorbance of the butylacetate and amylacetate combus- tion products within the range 200-240 nm is lower than that of water. Then both light absorbance values remain close within 240-320 nm. The former light absorbance becomes positive only after 320 nm. This unfavorable situation impedes accurate de- termination of AAS using water as the ref- erence. However, pure extractants still can be used as reference solutions in case of the heavy metals ions contents analysis. There were two experimental series per- formed in the framework of this investiga- tion. Free metals ions were analyzed within one series while their chelate complexes were analyzed within the other. It was found that AAS of both series were quite close and lie within the experimental er- rors. Besides, an influence of pH on the extraction degree of the ions Cu2+, Co2+, Pb2+, Ni2+, Zn2+, Fe3+, Cd2+, Mn2+, Cr3+ has also been investigated (Figs 2-8). As seen from Fig. 2, the highest (almost 100 %) extraction degree can be reached for the ions Pb2+ within quite a wide range of pH (2-9) for the system sodium diethyldithio- carbamate/butylacetate (curve 1) while on- ly about 50 % of Pb2+ ions can be extracted out by the mixture sodium diethyldithio- carbamate/amylacetate within the pH range 2-5 (curve 2). The extraction activity of the mixtures amylacetate/8-oxyquinoline and butylacetate/8-oxyquinoline (curves 4 and 3) within the range of pH 6-8 is lower. Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 344 Fig.2. An influence of pH on the Pb2+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8-oxyquinoline (3); amylacetate/8-oxyquinoline (4). Fig.3. An influence of pH on the Cu2+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8-oxyquinoline (3); amylacetate/8-oxyquinoline. Details of extraction of Cu2+ ions are shown in Fig. 3. It is seen that the pattern of both curves for the sodium diethyldithi- ocarbamate containing system is similar to the previous case while the degree of ex- traction for the 8-oxyquinoline containing systems is significantly higher and reaches 80 % for the system butyl acetate/8- oxyquinoline (see curve 3). The pH range of effective extraction is quite wide (2-6) for all the Cu2+ containing systems. Details of extraction of Ni2+ ions are shown in Fig. 4. The range of effective ex- traction (about 90 %) by the mixture sodi- um diethyldithiocarbamate/butylacetate is also quite wide (see curve 1). The sodium diethyldithiocarbamate/amylacetate mix- ture provides only 55 % efficiency of ex- traction within the same range of pH. Low solubility of the Ni2+/8-oxyquinoline che- lates causes very low efficiency of the cor- responding systems (see curves 3 and 4). Fig.4. An influence of pH on the Ni2+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8-oxyquinoline (3); amylacetate/8-oxyquinoline. Fig.5. An influence of pH on the Cd2+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8-oxyquinoline (3); amylacetate/8-oxyquinoline. The highest extraction degrees for the Cd2+-systems can be reached for the sys- tem sodium diethyldithiocarba- mate/butylacetate (see Fig. 5, curve 1). This extractant remains active within very wide range of pH (1.8-9.0). Similarly to the above case, the amylacetate/sodium diethyldithiocarbamate mixture ensures extraction degree about 50 % within the same pH range (curve 2) while the 8- oxyquinoline based systems are inactive (curves 3 and 4). Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 345 Fig.6. An influence of pH on the Zn2+ extraction degree for the mixture of butylacetate/sodium diethyldithio- carbamate (1); amylacetate/sodium diethyldithiocar- bamate (2); butylacetate/8-oxyquinoline (3); amy- lacetate/8-oxyquinoline. Fig. 7. An influence of pH on the Co2+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8- oxyquinoline (3); amylacetate/8-oxyquinoline. Both sodium diethyldithiocarbamate mix- tures ensure almost complete extraction of Zn2+ under pH 3.5-8.5 (with butylacetate) or 4.5-7.5 (with amylacetate) (see Fig. 7, curves 1 and 2). Both 8-oxyquinoline based systems in this case are also inactive (curves 3 and 4). The extraction degree of ions Co2+ by the mixture sodium diethyldithiocarba- mate/butylacetate within the pH range 1.5- 8.0 is about 80 % (see Fig. 8, curve 1) and by the mixture sodium diethyldithiocarba- mate/amyacetate – about 40 % (same pH range, see curve 2). The extraction degrees by the 8-oxyquinoline systems are also quite fair: 60 % for the system bu- tylacetate/8-oxyquinoline (cobalt oxynate is formed within pH values 6.5-9.5, curve 3) and 30 % for the system amylacetate/8- oxyquinoline, where the oxynate copound is formed within pH values 7.8-9.0 (curve 4). Fig.8. An influence of pH on the Fe3+ extraction de- gree for the mixture of butylacetate/sodium diethyl- dithiocarbamate (1); amylacetate/sodium diethyl- dithiocarbamate (2); butylacetate/8-oxyquinoline (3); amylacetate/8-oxyquinoline. The data related to extraction of Fe3+ ions are shown in Fig. 8. It is seen that about 40 % of the ions can be extracted by sodium diethyldithiocarbamate/butylacetate mix- ture for the range of pH 1.5-5.0 while the mixture sodium diethyldithiocarba- mate/amylacetate ensures extraction of about 40 % of Fe3+ only (pH = 3.0-7.0, see curves 1 and 2). The 8-oxyquinoline based systems exhibit higher extraction degrees: 70 % for the system butylacetate/8- oxyquinoline (pH = 5.0-8.5, see curve 3) and 55 % for the system amylacetate/8- oxyquinoline (weakly acid media, see curve 4). No tangible extraction activity has been determined for all the four mix- tures under investigation and ions Cr3+ and Mn2+. Therefore, the highest extraction de- grees were found for the sodium diethyl- dithiocarbamate based systems. The heavy metals ions chelates are formed in such systems and then dissolve in butylacetate or amylacetate. It should also be noted that the chelates solubility in butylacetate is better than in amylacetate. Besides, bu- tylacetate also facilitates further atomiza- tion and improves light absorbance (1.3- 3.1 times depending on the metal nature). Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 346 The best extraction degrees can be achieved for the weakly acid (pH=4.0-6.0) solutions (see Figs 2-8). The above results were applied at the next stage when a se- ries of experiments was carried out in or- der to build the calibrating lines for all the metal ions. The butylacetate/sodium di- ethyldithiocarbamate was used as the ex- tracting while the same system without any heavy metals was used as the reference solutions. All experimental results were compared with the similar data obtained using the classical method of concentrating by evaporation of the samples. The con- centrating coefficients were similar for the extraction and evaporation methods. The “extraction” calibrating lines are represent- ed in Figs 9 and 10. They all are close to linear meaning that the experimental method was correct and adequate. The higher is the line slope, the better is the sensitivity of determination related to the corresponding metal. In this context we can state the this method exhibits the high- est sensitivity towards ions Zn2+ and Cd2+ while the sensitivity of determination of Pb2+ is the worst. The sensitivities of de- termination of Co2+, Cu2+, Ni2+ and Fe3+ are very close. Fig. 9. Calibrating curves for the ions Fe2+ (1), Ni2+ (2), Co2+ (3), Cu2+ (4) and Pb2+ (5) after their extraction by the mixture butylactate/sodium diethyldithiocarbamate. Fig. 10. Calibrating curves for the ions Zn2+ (1) and Cd2+ (2) after their extraction by the mixture butylac- tate/sodium diethyldithiocarbamate. Then the calibrating lines were applied to determine the ions concentrations in the model solutions and then the results of the “extraction” analyses were compared to the results of evaporation” analyses. All related data and results of their statistical analysis are shown in Table 1. Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 347 Table 1 Results of analysis of the model solutions Metal Tested concen- tration mg/l Found concentration, mg/l Statistical dispersion, S2 Confidence interval limits Evapora- tion Extraction Evapora- tion Extraction Evapora- tion Extraction Co2+ 0.065 0.065 0.064 4.917·10-6 2.425·10-5 0.0625 ± 7.823·10-6 0.066 ± 3.858·10-7 0.063 0.069 0.060 0.063 0.061 0.057 0.125 0.112 0.120 5.00·10-5 1.076·10-4 0.096 ± 7.955·10-5 0.112 ± 1.712·10-4 0.115 0.11 0.054 0.10 0.104 0.12 Fe3+ 0.065 0.048 0.056 1.7·10-4 1.500·10-5 0.061 ± 2.705·10-4 0.060 ± 2.38·10-5 0.053 0.062 0.066 0.065 0.077 0.059 0.125 0.122 0.11 3.933·10-4 1.87·10-4 0.130 ± 6.257·10-4 0.107 ± 2.975·10-4 - 0.09 0.162 0.12 0.123 0.11 Pb2+ 0.125 0.124 0.118 4.090·10-5 1.00·10-5 0.124 ± 6.507·10-5 0.121 ± 1.591·10-5 0.120 0.119 0.134 1.122 0.121 0.125 0.250 0.245 - 1.806·10-4 1.250·10-5 0.0256 ± 2.865·10-4 0.249 ± 1.989·10-5 - 0.250 - 0.249 0.268 0.249 Cu2+ 0.065 0.060 0.059 3.3·10-4 4.56·10-5 0.57 ± 5.25·10-4 0.56 ± 1.453·10-4 0.031 0.055 0.073 0.048 0.064 0.064 0.125 0.146 0.110 1.795·10-4 4.360·10-5 0.127 ± 2.856·10-4 0.117 ± 6.33·10-5 0.142 0.121 - 0.115 0.118 0.125 Ni2+ 0.065 0.061 0.044 8.667·10-6 9.963·10-9 0.060 ± 1.379·10-5 0.057 ± 1.585·10-4 - 0.057 0.064 0.060 0.057 0.068 0.125 0.116 0.125 4.667·10-6 9.667·10-6 0.119 ± 7.425·10-6 0.120 ± 1.538·10-5 0.119 0.123 0.120 0.118 0.121 0.120 Zn2+ 0.013 0.024 0.0125 4.823·10-5 7.507·10-7 0.016 ± 7.673·10-5 0.012 ± 1.194·10-6 0.013 0.011 0.021 0.013 0.02 0.0125 0.025 0.039 0.026 1.805·10-4 2.0·10-6 0.029 ± 2.87·10-4 0.024 ± 3.182·10-6 - 0.023 - 0.025 0.020 0.0265 Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University - Suceava Volume XIII, Issue 4 – 2014 Igor KOBASA, Vasyl BILOGOLOVKA, Mariya VOROBETS, Oxana PANIMARCHUK, An investigation of the extraction concentrating of microelements from aqueous solution for atom-absorbtion analysis ,Volume XIII, Issue 4 – 2014, pag. 342 – 348 348 As seen from Table 1, the extraction meth- od ensured lower deviation and better sen- sitivity for the majority of samples of Cu, Fe, Pb, Zn. Therefore, we can conclude that the extraction method of concentrating the traces of Co, Cu, Fe, Ni, Cd, Zn, Pb using butylacetate/sodium diethyldithio- carbamate extractant and AAS determina- tion can ensure better concentrating de- gree, shorter processing time, higher selec- tivity and sensitivity (up to 1.3-3.1 depend- ing on the metal nature). 4. Conclusion The mixture of butylacetate and sodium diethyldithiocarbamate ensures the highest concentrating degree for the heavy metals ions extraction from aqueous solutions. Almost complete extraction of the metal ions can be reached within the pH range 4- 6. This result is based on rise in the AAS ana- lytical signal intensity (1.3-3.1 times) caused by atomization of the chelate com- plexes formed by the heavy metals ions and butylacetate or amylacetate molecules. The extraction method also ensures less laborious and more sensitive and selective analysis than the classical evaporation method. Besides, lesser number of the treatment stages in the method of extraction lowers chances of unwilled and uncontrollable probes pollution while processing. 5. References [1]. KORENMAN I. Extraction in organic com- pounds analysis. Khimiya. Moscow. 392 p. (1977). [2]. GONCHAROVA N. et al. Atom-absorption determination of metals-microelements in natural and industrial waters. Chem. and Tech. of Water. 6. 152-157. (1984). [3]. GRANZHAN A.. KUNUK G.. CHARYKOV A. Extraction atom-absorption determination of the heavy metals ions. J. Analyt. Chem. 4. 711-717. (1991). [4]. NOVIKOV Yu.. LASTOCHKINA K.. BOLDINA Z. Methods of the natural waters quality investigations. Medicine. Moscow. 181 p. (1990). [5]. STARYI M. Extraction of chelates. Mir. Mos- cow. 392 p. (1966) [6]. NOVIKOV M. Application of atom- absorption method of heavy metals analysis in natu- ral objects. Khimiya. Moscow. 189 p. (1989). [7]. KOBASA I. Atom-absorption method of de- termination of Selenium content in some raw mate- rials and food. J. Food and Environment Safety of the Suceava University. 12. 233-239. (2013).