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524 CHEMICAL PROBLEMS 2018 no. 4 (16) ISSN 2221-8688
UDC 543.4:542.61:546.812
SPECTROPHOTOMETRY METHOD FOR THE DETERMINATION OF SILVER USING 2,2',3,4-TETRAHIDROKSY-3'-SULFO-5'-NITROAZOBENZENE
A.R. Guliyeva, P.R. Mammadov, F.M. Chiragov, R.A. Abdullayev G.R. Mugalova
Baku State University 23, Academic Zahid Khalilov street, AZ1148 Baku, Azerbaijan e-mail: ayten.rehmanli.90@mail.ru
Received 26.09.2018
A fairly simple, selective and non-extractive spectrophotometric method for the determination of trace amounts of silver (I) was developed and 2,2,3,4-tetrahidroksy-3-sulfo-5-nitroazobenzene(TSNAB) suggested as a new analytical reagent for the direct non-extractive spectrophotometric determination of silver (I). In the aqueous medium TSNAB reacts with silver to give a highly orange absorbent chelate with a molar ratio of 1:2 (Ag: TSNAB). Note that the reaction is instantaneous and the maximum absorption was obtained at 490 nm that remains stable for 24 h. The average molar absorptivity and Sandell's sensitivity were found to be 1.37*104 l mol-1 cm-1 and 8.0 mkg cm'2 of silver(I) respectively. Linear calibration graphs were obtained for 0.864-5.184mkgmlof silver(I). A large excess of over 30 cations, anions and complexing agents impedes no determination. The non-extractive method is rather selective for silver(I) to have been successfully applied to synthetic mixtures.
Keywords: spectrophotometry, silver, 2,2',3,4-tetrahidroksy-3'-sulfo-5'-nitroazobenzene, determination, synthetic mixtures.
DOI: https://doi.org/10.32737/2221-8688-2018-4-524-529
INTRODUCTION
Silver is a useful element in many respects. Silver is used in solar panels, water filtration, electrical contacts and conductors; specialized mirrors; catalysis of chemical reactions; a colorant in stained glass. Its compounds are used in photographic and X-ray film. Silver is both vital and toxic for many biological systems and its content in drink and tap water samples grows together with increased use of silver compounds and silver-containing products in industry and medicine. Of growing interest is the separation, pre-concentration and sensitive determination of silver ion.
1,5-Diphenylthiocarbazone is one of the most widely used photometric reagents to form colored water-insoluble complexes with silver ions. Silver-dithizone complexes are water insoluble and thus their determination requires a prior solvent extraction step into
CHCl3 or CCl4, followed by spectrophotometric determinations [1]. In considering that these methods involve solvent, the extraction is lengthy, time-consuming and lacking selectivity due to excessive interference, CHCl3 and CCl4 have been listed as toxic. The problem has recently been resolved by suggesting a new analytical reagent for the direct non-extractive spectrophotometric determination of silver (I). The azocompounds on the basis of pyroghallol had widely been applied for the determination of noble metal ions, for this type of reagent has higher sensitivity and higher selectivity [2]. In the search for more sensitive azocompounds on the basis of pyroghallol reagent, the paper thoroughly analyzed a reagent 2,2',3,4-tetrahidroksy-3' -sulfo-5' -nitrorazobenzene (TSNAB) which was synthesized under the
method of [3] and a color reaction of TSNAB with Ag(I) in aqueous media.
Although many sophisticated techniques, such as electro-thermal AAS [3], flame AAS [4], graphite furnace AAS [5], liquid chromatography [6] and electrophoresis [7] are used for the determination of silver at trace levels in numerous complex materials, factors such as the low cost of the instrument, easy handling, portable, lack of any requirement for consumables and practically no maintenance, have caused spectrophotometry to remain a popular
technique, particularly in laboratories of eveloping countries with limited budgets.
The aim of the present study is to develop a simpler direct spectrophotometric method for trace determination of silver (I) with TSNAB in aqueous solutions. This method is far more selective, non-extractive, simple and rapid than all of existing spectrophotometry methods [9-12-8-11]. This method is very reliable and a concentration in the mkg ml-1 range in an aqueous medium at room temperature can be measured in a very simple and rapid way.
EXPERIMENTAL PART
Instrumentation
The absorbance of solutions was measured with a Perkin Elmer (United States) (Model: Lambda-40) double-beam UV/VIS spectrophotometer and with a KFK-2 photoelectrocolorimeter (Russia), with 1 cm matched quartz cells. The pH values of solutions were controlled on the ionomer i-121 with a glass electrode customized by standart bufer solutions. Chemicals and Reagents 2,2',3,4-tetrahidroksy-3'-sulfo-5-nitrorazobenzene (2*10-3 M) The reagent was synthesized according to the method of [2]. The solution was prepared by dissolving the requisite amount of bis-(2,3,4-
trihidroksifenilazo) benzidine in a known volume of absolute ethanol. More dilute solutions of the reagent were prepared as required.
Standard silver solution (1x10-2 M)
A stock solution 1x10-2 M, 100 ml of silver(I) was prepared by dissolving 0.1575 g of silver nitratein 100 ml of distilled deionized water and added 0.1 ml con. HNO3. The working standard of silver solution was prepared by suitable dilutions of this stock solution. Other solutions
Solutions of a large number of inorganic ions and complexing agents were prepared from their analytical or equivalent grades and water soluble salts.
RESULTS AND
Absorption spectra
The absorption spectra of orangecolor of the silver - TSNAB system in the presence of pH 9 solution were recorded using a spectrophotometer. The absorption spectra of the silver - TSNAB is a symmetric curve with maximum absorbance at 490 nm and an average molar absorptivity of 1.37 x 104 l mol-1 cm-1 and the reagent blank having maximum absorbance wave length at 380 nm. In all instances, measurements were made at 490 nm against a corresponding reagent blank. Effect of acidity
Of the various pH 0-10of the solution studied, pH 9 was found to be the optimal for the silver - TSNAB system. The maximum and constant
DISCUSSIONS
absorbance of the silver - TSNAB system was obtained in the presence of pH 9 at room temperature (25±5)0C. The absorbance of the reagent solution and the silver - TSNAB system depends on the medium pH; therefore, the absorption spectra are studied relative to a blank experiment (TSNAB). Effect of time
The reaction is fast. Constant maximum absorbance was obtained just after 5 min of the dilution to volume at room temperature (25 ±5oC), and remained strictly unaltered for 24 h.
Effect of temperature
The absorbance at different temperatures, 0-80oC, of a 25 ml solution of silver - TSNAB
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SPECTROPHOTOMETRY METHOD FOR THE
was measured according to the standard procedure. The absorbance was found to be strictly unaltered throughout the temperature range of 10-40oC. Therefore, all measurements were performed at room temperature (25 ±5oC).
Stoichiometry.The component ratio in the complexes was found using the isomolar series method, the relative yield method by Starik and Barbanel', and the equilibrium shift method. All the methods showed that the component ratio was 1 : 2 in the the silver -TSNAB system. The number of protons displaced upon complexation was determined by the Astakhov method, and the indicated
Table 1. Selected analytical parameters obt<
component ratio in the complexes was confirmed [12].
Analytical performance of the method Calibration curve
The effect of silver (I) concentration was studied over 0.01-10mkg l-1, distributed in four different sets (0.1-10mkg l-1) for convenience of the measurement. The absorbance was linear for 0.864 - 5.184mkg l-1 of silver (I) in aqueous media. From the slope of the calibration graph, the average molar absorption coefficient was found to be 1.37*104 l mol-1 cm-1 in aqueous media. The selected analytical parameters obtained with the optimization experiments are summarized in Table 1.
ied by optimization experiments.
Parameters Studied range Selected value
Wave length A.max (nm) 200-800 490
pH 0 - 11 9
Time / h 1 - 24h 5 - 10 min
Temperature /oC 0 -80oC 25±5oC
Me:R - 1:2
Molar absorption coefficient / l mol-1 cm-1 0.5x104-1.8x104 1.37* 104
Linearrange/mkg l-1 0.1-10 0.864-5.184
Detectionlimit /mkgl-1 - 1
Sandell'ssensitivity /mkgcm-2 - 8
Relative Standard 0 -2 0 -2
RegressionCo-efficient 0.998-0.9999 0.999
Effect of foreign ions
The effect of over 30 cations, anions and complexing agents on the determination of only 1 mkgml-1 of silver was studied. The criterion for interference was an absorbance value varying by more than 5% from the expected value for silver (I) alone. During
interference studies, if a precipitate was formed, it was removed by centrifugation. The quantities of these diverse ions mentioned were the actual amounts studied but not the tolerance limit. However, for those ions whose tolerance limit has been studied, their tolerance ratios are mentioned in Table 2.
Table 2. Tolerance limits of foreign ions, tolerance ratio [Species(x)]/Ag (w/w)
Species x Tolerance ratio [Species (x) /Ag (w/w)] Reference[13] Species (x) Tolerance ratio, [Species (x) /Ag (w/w)] Reference[13]
Na(I) 150 100 Au(III) 50 25
K(I) 150 10 Ga(III) 140 100
Mg(II) 180 100 La(III) 130 100
Ca(II) 160 20 Ta(IV) 140 100
Cr(III) 140 200 Ni(II) 165 100
Fe(III) 50 25 Pb(II) 130 100
Cu(II) 60 50 Cl- 100 20
Cd(II) 80 50 HCO3- 180 100
Hg(II) 80 50 C2°4" 300 100
Mo(II) 145 100 EDTA 1500 1000
Co(III) 150 100 tartarat 1500 1000
Zn(II) 50 10 CH3COO- 1400 1000
Be(III) 140 50 Sr(II) 100 20
Sn(IV) 40 10 phosphate 150 100
Mn(II) 120 100 cyanide 120 50
V(V) 40 10 Al(III) 50 10
Precision and accuracy
The precision of the present method was evaluated by determining different concentrations of silver (I) (each analyzed at least five times). The relative standard deviation (n = 5) was 2%-0%, for 0.864-5.184mkg of Ag (I), indicating that this method is highly precise and reproducible. The detection limit (3 s of the blank) and Sandell's sensitivity (concentration for 0.001 absorbance unit) for Ag (I) were found to be 0.8mkg ml-1. The reliability of our Ag-chelate procedure was tested by recovery studies. Regression analysis of Beer's law plots at 490 nm revealed a good correlation (R2 = 0.999). The method was also tested by analyzing several synthetic mixtures containing silver and diverse ions (Table 3). The results for silver
recovery were in good agreement with added
values.
Applications
The present method was successfully applied for determination of silver in a series of synthetic mixtures of various compositions. Determination of silver in synthetic mixtures
Several synthetic mixtures of varying compositions containing silver (I) and diverse ions of known concentrations were determined by the present method using EDTA as a masking agent and the results were found to be highly reproducible. The results are shown in Table 3. The accurate recoveries were achieved in all solutions.
Composition of mixture (mkq/ml) Siver(I) (mkq/ml) Recovery ± s(%)
Added Found
A Ag+ 1.5 2.0 1.48 1.98 97±0.3 98±0.2
B As in A + Cr3+ (25)+Fe3+(25) 1.5 2.0 1.52 2.04 102±0.3 104±0.2
C As in B +Mg2+ (25)+Hg22+ (25) 1.5 2.0 1.51 2.02 101±0.2 102±0.2
D As in C + Co 2+(25)+ Ca2+ (25) 1.5 2.0 0.52 1.03 102±0.4 103±0.2
E As in D +Cu2+(25)+Ni2+ (25) 1.5 2.0 1.49 1.02 98±0.2 102±0.1
Table 3. Determination of silver (I) in synthetic mixtures
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SPECTROPHOTOMETRIC METHOD FOR THE
CONCLUSION
It is a new approach and alternative for the standard silver method (I). The present work provides that a simple, selective non-extractive and inexpensive method with silver
- TSNAB system was developed for determination of silver (I) in samples for continuous monitoring to establish trace level of silver (I) in difficult sample matrices.
REFERENCES
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2. Gambarov D.G. New class of photometric reagents of azo compounds on the basis of pyrogallol. doctoral dissertation. Moscow: MSU, 1984, 380p.
3. Manzoori J.L., Abdolmohammad-Zadeh H. and Amjadi M. Ultra-trace determination of silver in water samples by electrothermal atomic absorption spectrometry after preconcentration with a ligand-less cloud point extraction methodology. Journal of Hazardous Materials. 2007, vol.144, no.2, pp.458-463.
4. Chakrapani P.L., Mahanta D.S.R., Murty B. Gomathy. Preconcentration of traces of gold, silver and palladium on activated carbon and its determination in geological samples by flame AAS after wet ashing. Talanta. 2001,vol. 53, pp. 1139-1147.
5. Resano M., Aramend'ya M., Garcya-Ruiz E., Crespo C. and Belarra M.A. Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silver at trace and ultratrace levels. AnalyticaChimicaActa. 2006, vol. 571, no. 1, pp. 142- 149.
6. Wang L., Hu Q., Yang G., Yin J., Yuan Z. Online solid phase extraction reverse phase liquid chromatographic determination of lead, cadmium, silver and mercury in water. Fenxi Huaxue. 2004, vol. 32, pp. 421-427. (In Chinese).
7. Aguilar M., Farran A., Martinez M. Determination of gold (I) and silver (I) cyanide in ores by capillary zone
electrophoresis. J. Chromatogr. 1993, vol. 635, pp. 127-131.
8. Shui-Chieh Hung, Chang-Ling Qu, Shui-Sheng Wu. Spectrophotometry determination of silver with 2-(3,5-dibromo-2-pyridylazo)-5-diethyl-aminophenol in the presence of anionic surfactant. Talanta. 1982, vol. 29(2), pp. 85-88.
9. Ivanova C., Popova S. Spectrophotometry determination of silver with brom pyrogallol red (BPR) and 1,10-phenantroline in the presence of gelatin. J. Univ. Chem.Tech. Met. 2002, vol. 37, pp. 33-38.
10. Gao H.W., Wang L., Tao M. Primary-secondary wave length spectrophotometric determination of trace amounts of silver in waste water with 2,4-dibromo-6-carboxy-benzendiazoaminoazobenzene (DBCBAAB), Paks. J. Chem. Soc. 2000, vol. 22, pp.275-280.
11. Kawatkar S.G., Manol P.S. A simple and sensitive spectrophotometric method for determination of silver (I) with resacetophenon eguanyl hydrazone (RAG). Acta Cie. Ind. 1998, vol. 24, pp. 167-169.
12. Bulatov M.I., Kalinkin I.P. A practical guide to photometric methods of analysis. Leningrad.1986, 432 p. (In Russian).
13. Jamaluddin M. Ahmed and Syeda Rahimon Naher. A rapid spectrophotometric method for the determination of trace level silver using 1,5-diphenylthiocarbazone in aqueous micellar solutions. International research journal of pure and applied chemistry, 2014, vol. 4 (4), pp. 468-485.
SPEKTROFOTOMETRÍKMETODLA 2,2',3,4-TETRAHiDROKSi-3'-SULFO-5'-NÍTROAZOBENZOL (TSNAB) iLd GÜMÜgÜNKÍ0KiZMiQDARJNJNJN TdYiNi
A.R. Quliyeva, P.R. M9mm9dov, F.M. Qtraqov, R.d. Abdullayev, G.R. Mugalova
Baki Dovlat Universiteti AZ 1148, Akademik Zahid Xdlilov kügasi, 23 e-mail: ayten.rehmanli.90@mail.ru
Gümü§ün(I) kigik miqdarlarmi tayin edilmdsi ügün gox sada, yüksdk segiciliyd malik vd ekstraksiyasiz spektrofotometrik üsul hazirlanib. Yeni analitik reagent 2,2',3,4-tetrahidroksi-3'-sulfo-5'-nitroazobenzol (TSNAB) gümü§ün(I) kigik miqdarlarini birba§a ekstraksiyasiz spektrofotometrik tayin edilmasi ügün taklif olunub. Sulu mahlulda TSNAB gümü^la reaksiyaya daxil olaraq 1:2 molar nisbatinda sarimtil-ya§il xelat amala gatirir (Ag : TSNAB). Reaksiya süratlidir, maksimal udma 490 nm-da mü§ahida olunur va 24 saat arzinda sabit qalir. Gümü§ (I) ügün i§iqudmanin orta molyar amsali va Sendel hassasligi 1.37*104 l/mol sm va 8 mkq/sm2 ta§kil edir. Xatti daracali qrafik gümü§ (I) ügün 0.864-5.184 mkq/ml alinib. 30-dan gox kation, anion va kompleks amalagatiran agentlarin artiq miqdari gümü^ün tayin edilmasina mane olmur. Metod gümü§a qar§i kifayat qadar hassasdir va bir sira suni qari§iq nümunalari ügün ugurla tatbiq olunub.
Agar sozlar: spektrofotometriya, gümü§, 2,2',3,4-tetrahidroksi-3'-sulfo-5'-nitroazobenzol, sintetik qari§iqlar.
БЫСТРЫЙ СПЕКТРОФОТОМЕТРИЧЕСКИЙ МЕТОД ДЛЯ ОПРЕДЕЛЕНИЯ СЛЕДОВЫХ КОЛИЧЕСТВ СЕРЕБРА (I) С ИСПОЛЬЗОВАНИЕМ 2,2',3,4-ТЕТРАОКСИ-3'- СУЛЬФО- 5'-НИТРОАЗОБЕНЗОЛА
А.Р. Гулиева, П.Р. Мамедов, Ф.М. Чирагов, Р.А. Абдуллаев, Г.Р. Мугалова
Бакинский государственный университет AZ1148, ул. акйё. З. Халилова, 23; e-mail: ayten.rehmanii.90@maii.ru
Разработан очень простой, высокоселективный и безэкстракционный спектрофотометрический метод определения следовых количеств серебра (I) с помощью нового аналитического реагента 2,2',3,4-тетраокси-3'-сульфо-5'-нитроазобензола (ТСНАБ). В водной среде ТСНАБ, реагируя с серебром, дает желтовато-зеленый хелат с молярным соотношением 1:2(Ag :ТСНАБ). Реакция быстрая и максимальное поглощение наблюдается при 490 нм и остается постоянной в течение 24 ч. Средний молярный коэффициент светопоглощения и чувствительность Сэндела для серебра (I) равны 1.37*104 л/мольсм и 8мкг/см2 соответственно. Линейный градуировочный график получен в интервале 0.864-5.184мкг/мл. Избыток более 30 катионов, анионов и комплексообразующих агентов не мешают определению. Метод достаточно селективен по отношению к серебру и был удачно применен к ряду образцов. Ключевые слова: спектрофотометрия, серебро, 2,2',3,4 -тетраокси -3'- сульфо - 5'-нитроазобензол, определение.
