Jul 2, 1997 - sorption of a coloured 1 -naphthol azoderivative, which was formed by ... where b'(R) is the Kubeka-Munk function, H is difhse reflectance, E is molar ... dispersing elements are three photodiodes (dark blue, green, and red).
ANALYTICAL LETTERS, 30(14), 2527-2540 (1997)
SORPTION-PHOTOMETRIC DETERMINATION of 1-NAPHTHOL with POLYURETHANE FOAMS
Keywords
1 -Naphthol, Polyurethane Foams, Sorption, Diffuse reflectance
spectroscopy
S.G. Dmitrienko, E.N. Myshak, A.V. Zhigulyev, V.K. Runov, Yu.A. Zolotov Analyhcal Chemistry Division, Chemistry Department, Lomonosov Moscow State University, Vorob’evy Goly, Moscow 119899, GSP, V-234, Russia
ABSTRACT Two approachesto sorption-photometricdetermination of 1-naphthol in waters with application of polyurethane foams are offered. The first approach was based on sorption of a coloured 1-naphthol azoderivative, which was formed by the reaction with 4-nitrophenyldiazonium tetrafluoroborate (NFD). In the second variant, 1-naphthol is first sorbed by a polyurethane foam, and it is then transformed into a coloured
azoderivative by sorbent treatment of a NFD solution. A coloured 1-naphthol azoderivative was determined immediately in the polyurethane foam using diffuse reflectance spectroscopy. Calibration graphs are linear in the interval of concentrations
2521 Copyright Q 1997 by Marcel Dekker, Inc.
DMITRIENKO ET AL.
2528
of 0.01
-
1 pglml. The analytical results indicated that a selective and sensitive
analytical procedure could be easily applied to determination of 1-naphthol concentration in waters.
INTRODUCTION Aromatic hydroxy compounds and in particular, 1-naphthol, are industrial toxicants and are contained in waste waters from technological processes of dyes, polymers, lacquers, and pharmaceutical preparations. Beside several natural compounds, physiologically active substances, and chemical toxins contain phenol and/or naphthol fragments and are degraded up to them. For example, the 1-naphthol
is a major metabolite of carbaryl, widely used pesticide. For this reason, its determination in the environmental materials is topical.
For determination of 1-naphthol, mainly in waters, spectrophotometric 14, fl~orimetric~.~, kinetic7, and
methods are used. Semi-quantitative
determination of carbaryl and 1-naphthol in waters is implemented by testpapers'
'.
This study is devoted to development of a sorption-photometric technique for determination of 1-naphtholwith application of polyurethane foams (PUF) as sorbents. PUF differ from other sorbents by a low cost and availability (they are widely applied as filling and packing materials in various industries and in daily living needs). Moreover, these polymers have good sorption characteristics, which result from the presence of open and closed pores in their membrane structure. The sorption of compounds by polyurethane foams involves not only adsorption. but also absorption mechanisms12. In the case PUF we used quantitative measurements of a diffuse reflectance of sorbatespermitting precise and reproducible results to be ~ b t a i n e d ' ~ , ' ~ . EXPEFUMENTAL
Reagents 1-Naphthol (chemically pure) was further purified by crystallization according
to reference 15. 4-Nitrophenyldiazoniumtetrafluoroborate (NFD) was synthesized and
1-NAPHTHOL
2529
purified as described in reference 4. Commercially available substances of sodium carbonate (high purity grade) and tetrabutylammonium hydroxide (chemically pure) were used with no extra purification. Polyurethane foams on the basis of ethers (5-30 and M-40 trade marks), esters (2200 and MZ trade marks) and their copolymers (VP trade mark), produced by "Polimersintez", Vladimir, Russia and "Radikal", Kiev, Ukraine were used throughout.
Preparation of sorbents PUF tablets (16 mm in diameter) were cut from a commercially available
polymer sheet with a thickness of 5 mm. For purification, tablets were treated with 0.1 M HCI for 30 min, then they were washed with water up to pH 5-6 followed with acetone, and then air-dried. The mass of PUF tablets vaned from 0.03 up to 0.05 g depending on the trade mark of the polymers.
Sorption techniques Sorption was carried out under batch conditions. Procedure 1. A test solution, containing from 2.5 up to 25 pg of I-naphthol. 5 ml of a 0.9 M Na2C03 solution, 0.6 ml of a 0.02 M fresh solution of 4-nitrophenyldiazonium tetrafluoroborate and water up to a volume of 25 ml were sequentially added to vessels with ground stoppers. In each vessel, a single PUF tablet was placed. Air bubbles were removed using a glass rod, and the vessels were shaken mechanically for 40 min. Tablets were removed and dried between sheets of filter paper, and a diffuse reflectance was measured. Procedure 2. A 25 ml portion of the test solution containing 2.5 to 25 pg of 1-naphthol was placed in a vessel with a ground stopper. In each vessel one PUF tablet was put. Air bubbles were removed using a glass rod, and vessels were shaken mechanically for 40 min. Tablets were removed, dried between sheets of filter paper, were placed in vessels with ground stoppers, and treated by 3 ml of a 0.3 M Na,C03 followed by 2 ml of a 0.001 M fiesh solution of NFD. Vessels were shaken
DMITRIENKO ET AL.
2530
mechanically for 30 min. PUF tablets were removed, dned between sheets of filter paper. and diffuse reflectance was measured.
Measurements
The basis for quantitative measurements of diffuse reflectance spectroscopy of coloured samples is the equation of Kubelka and Munk''
where b'(R) is the Kubeka-Munk function, H is difhse reflectance,
E
is molar
absorptivity of sorbate, c is its concentration, .s is the light scattering coefficient. The procedure for measurement of a diffuse reflectance spectrum is reduced to measurement of a dependence of the diffuse reflectance coefficient R for a wavelength and to calculate I;(R)=function at each wavelength Ai; then a calibration graph of F(R) vs. concentration of the compound in water phase is constructed. Diffuse reflectances were measured on a Spectroton colorimeter (Chirchik OKBA, NPO Khimavtomatika), and an "Multiekotest" portable reflectometercolorimeter ("Kostip" corporation, Russia). Operation of tlus instrument is based on simultaneous measurment of diffuse reflectances at 24 fixed wavelengths (in the visible spectral range) under illumination of a solid sample with an ISK-25 pulsed xenon lamp, followed by subsequent data processing. Radiation from the lamp, which is mounted inside a photometric sphere, produces diffuse illumination of the sample through the aperture ( 15 mm in diameter) in the sphere. The design of the photometric sphere provides the measurement
geometry of the difl8" type, which makes it possible either to eliminate the mirrorreflectance component using a diaphragm inside the sphere, or to take it into account. The light reflected by the sample is directed to the end face of the light-conducting bundle by a lens, and is thereby transmitted to a transducer. In the transducer, the light is broken into 26 channels by a light-conducting collector. The light-conducting
1-NAPHTHOL
2531
bundles of the 46-channel are attached to the blocks of light filters where lenses, interferencelight filters, and photodiodes are placed. The light filters separate narrow bands from the radiation spectnun in the range 380 - 720 nm with a step of 10 nm. The access time is 1 x 10" s; the time of data processing is no longer than 5 s, and the time interval between two consecutive measurements is no longer than 10 s.
In a "Mulbekotest" potable reflectometer-calorimeter (overall size of the device: the console - 185x85~35mm, sensor - 9 0 x 6 5 ~ 3 5mm, the device weight - 600 g) dispersing elements are three photodiodes (dark blue, green, and red). The order of measurement of diffuse reflectance on this device includes the following operations. An initial (not painted) tablet of a polyurethane foam is placed in the photometric Sensor cell its reflectance (L) is measured by a pre-selected photodiode (in the case of 1-naphthol
-
dark blue). Then, PUF tablets with sorbed coloured 1-naphthol
azoderivatives are placed in the cell, one by one and their reflectances (Pi) are measured. The analytical signal that is linearly connected with the concentration is L P i (relative diffusion factor).
Calculations The values of recoveries (R, %) were determined by a spectroscopy measurement and calculated according to the following equation:
where ('o is the concentration of the tested compound in solution before sorption and ('
is the concentration in solution after sorption. The value of the distribution factor ( D ) was calculated as follows:
where V is a volume of test-solution (ml), m - mass of polyurethane foams table (g). The logarithm value of the distribution factor (lo@) was employed.
DMITRIENKO ET AL.
2532
RESULTS AND DISCUSSION The general approach The
widely
used
azocoupling
reaction
of
1-naphthol
with
4-nitrophenyldiazonium tetafluoroborate was applied as a basis for the development of sorption-photometric method for determination of 1-naphthol4:
Two procedures of a sorption-photometricdetermination of I-naphthol using PUF are offered. The intensively coloured compound (11) formed in the course of the reaction is efficiently sorbed by polyurethane foams (procedure 1). Such factors as pH, 4-nitrophenyldiazonium tetrafluoroborate concentration. time of a phase contact. structure of the PUF polymeric link affect the sorption of I-naphthol azoderivative. The maximum sorption of the 1-naphtholazoderivative is reached by separation from a 0.20.8 M Na2C0, solution (PH
- 11). in the presence of a 2.6-5.5 x 10"M
4-nitrophenyl-
diazonium tetrafluoroborate solution. The sorption equilibrium is esteblished in 40 min
(fig. 1). The PUF chemical composition essentially affects the sorption of the test compound. The values of recoveries (R, %) and distribution factors (logD) of the 1-naphthol azoderivative on PUF of test trade marks are shown below:
PUF R, %
IogD
140
95 4.07
5-30 94 4.00
M-40 86 3.56
w 91 3.76
2200 75 3.28
MZ 80 3.41
As shown the ether-based polyurethane foams (5-30 and M-40) are more effective in comparison with ester-based (2200, M Z ) . The VP polyurethane foam on the basis of copolymer of ethers and esters is in the middle. The development of sorptionphotometric procedure for 1-naphthol determination was made using PUF 5-30.
1-NAPHTHOL
-
R,% 100
2533
-+ 2
0
1
.~
i0
0
80
90c-
60 -
40
10
50
I
I
I
40
SO
00
7
i
10
t,mln
0
a c,,, mvo'
n
DMITRIENKO ET AL.
2534
In the case of procedure 2, I-naphthol was first sorbed on PUF 5-30, than the coloured product 1 -naphthol azoderivative was formed by treating the sorbate with 4-nitrophenyldiazonium tetrafluoroborate. It was shown that 1-naphthol is sorbed by polyurethane foams in pH range of 1-8, where it exists in the molecular form. The same picture was observed for all the test PUF based on ethers, esters, and their copolymers. Sorption equilibrium is established in 40 min (fig. I ) .
Spectra of diffuse reflectance The spectra of d f i s e reflectance of the I-naphthol azoderivative are shown in fig. 2. The spectrum is shfted batochromically compared to an absorption spectrum of a water solution by 50 nm. It is necessary to stress that the changes in the spectra of diffuse reflectance of PUF tablets with sorbed I-naphthol azoderivative are observed when they are stored in air. The effect was observed as a decrease in band with h,, = 620 nm
and appearance of a band at 460 nm. After treatment of polyurethane foam
tablets by vapours of HCI the band at 620 nm disappears and that at 460 nm increases in amplitude. Such changes are accounted for by the transformation of
4-nitophenylazonaphtholateinto its cumulative acid, 4-nitrophenylazonaphthol, by interaction with acids that are present in laboratory air, resulting in a decrease in the regularity of analytical results. To stabilize the colour we suggest treating a tablet with sorbed 1-naphthol azoderivative with a tetrabutylammonium hydroxide solution. The diffuse reflectance of a PUF tablet after such treatment does not change for days following the moment of sample preparation. The absorption spectra of the sorbate are shown in fig. 3.
1-Naphthol determination Sorption-photometric determination of 1-naphthol was perfomed using both procedures (see above) with a Spektroton colorimeter. Calibration graphs are linear in the range of 1-naphthol concentration of 0.01-1 &ml
(procedure 1 or 2),
corresponding to initial linear segments on sorption isotherms of I-naphthol and
1-NAPHTHOL
2535
A
0.1 5
0.1 0
0.05
I
I
I
I
1
I
I
I
I
400 440 480 520 560 600 640 680 72%,,, Fig. 2.
Absorption ( 1 ) and diffuse reflectance spectra (2) of the I-naphthol azoderivative
CN,,,
=
1.4 x lo4 M, CNa2C03 = 0.2 M, CN,
= 5.1 x
lo4 M, I = 1 cm
1 -naphthol azoderivative, respectively. Performance characteristics and data on
selectivity of the developed procedures are summarized in Table 1. Selectivity of sorption photometric methods was characterized by a selectivity factor, i.e. ultimate weight ratio: interference compound - 1-naphthol with the determination error (RSD) no more than 10 %. Selectivity of the methods is higher in the procedure 2. For instance, at least 100-fold amounts of S2--ion, 20-fold amounts of phenol, 5-fold amounts of 2-naphthol were not interfere in the determination of I-naphthol by procedure 2. But in the case of procedure 1 the interference influence of these compounds appears with the weight ratio approximately equal to unity.
DMITRIENKO ET AL.
2536
6 5 4
3
2 1 I
I
I
I
0 ' 380 420 460 500 540 580 620 660 700 h,nm I
Fig. 3.
I
I
I
Diffuse reflectance spectra of I-naphthol azoderivative: 1 - immediately after sorption; 2 - after treatment of a PUF tablet with
HCl vapours; 3 - after treatment of a PUF tablet with NH, vapours, 4 after treatment of a PUF tablet with tetrabutylammonium hydroxide Cnaphh= 1.4 x
M, CNazCOj = 0.2 M, CNFD= 5.1 x l o 4 ,
-
mpUF 0.03 I?. V = 25 ml
The tablets of polyurethane foams after sorption of 1-naphthol azocompound have a dark blue colour of various intensities depending on the naphthol content in the test sample. This allows a semi-quantitative test of 1-naphthol. Such a determination was made by visual comparison of colour saturation of polyurethane foam tablets with a colour scale obtained for a series of standard solutions. It was very interesting to use portable devices measuring di&se reflectance for rapid determination of 1-naphthol. A "Multiekotest" portable reflectometer-colonmeter, designed for rapid determination
2537
1-NAPHTHOL
Table 1
Characteristics of the technique for determination of 1-naphthol
(n=5 Procedure variant
I*
Calibration range,
-E&!!!L
cmin.
!&!I
0.01 - 1
2*
0.01 - 1
1 **
0.02 - 0.4
0.003
0.004
0.005
* S ktroton colo: neter
* ‘Multiekotest” reflectometer- colorimeter
= 0.9!
RSD,%
Tolerable excess amount
6
H 2 P 0 i - 3500; Ca, Mg, Co(I1) 2000; Li, Na, K, Ba, Fe(III), Ni, Cd, Cu(lI), Cr(VI), F-, Cl-, B i , 1NO,-, CH,COO-, citrate, tartrate - 1000; Zn, NH,+, aniline, Al (in the presence of 0,OIM H,POi) - 500; Mn, Cr(III), Pb (in the presence 0,OIM HZPO,) - 300; Hg(I1) 10; phenol and 2-naphthol stoichiometricamount Ca, Mg, Co(I1) - 2000; Li, Na, K, Ba, Fe(III), Ni, Cd, Cu(II), Cr(III,VI), Mn, F-, Ct , Bi , - I NO,-, CH~COO-,citrate, tartrate - 1000; ; Zn, NH,+ 700; aniline, Al (in the presence of 0,OlM H2P04-)- 500; Pb (in the presence of 0,OlM H,PO,-) 300; S2- - 100, phenol - 20; 2-naphthol - 5 H,PO, - 3500; Ca, Mg, Co(I1) 2000; Li, Na, K, Ba, Fe(III), Ni, Cd, Cu(II), Cr(VI), F-, Cl-, B i , 1NO,-, SO:-, CH~COO-,citrate, tartrate - 1000; Zn, NH,+, aniline, Al (in the presence of 0,OIM H2P0,) - 500; Mn, Cr(III), Pb (in the presence 0,OIM H,PO,-) - 300; Hg(I1) 10; phenol and 2-naphthol stoichiometric amount
5
7
DMITRIENKO ET AL.
2538
Table 2 Analysis of model solutions of I-naphthol
Added 1-naphthol.
Procedure
Found 1-naphthol,
RSD,
Pdml
variant
vdml
YO
0.1 0.1
1
2
0.10 0.01 0.10 i 0.02 0.019 0.004
0.02
I
1
* *
4 6 1
9
of the pollutants by indicator papers was tested. It was shown that the device is suitable for measuring reflectance of a porous polyurethane sample without any change in design. Calibration (LPi - L/Pbld) via I-naphthol concentration. (in pg/ml) is linear in the range of I-naphthol in the test solution from 0.02 to 0.4 pg. The characteristics of the developed procedure are shown in table 1. Selectivity of test determination is analogous to the case of the procedure 1 with a Spektroton colorimeter. Humus and fulvoacids in amounts corresponding to their real concentrations in natural waters (20 pg/ml) do not interfere in the determination of 1-naphthol. The method is used for determinationof 1-naphthol in model mixtures (table 2). The data obtained allow a conclusion that there is a good agreement between two proposed procedures in determination of 1-naphthol. In comparison to the known methods for 1-naphthol determination, the procedure developed is more sensitive than one with the same reagent in solution, and permits determination of I-naphthol in a wide range of concentrations. The proposed methods are sensitive, accurate, reliable, time saving and applicable to routine analysis. The sensitivity of the developed procedures meet the requirements existing in Russia for the determination of 1-naphthol in natural waters (maximum permissible concentration of 0.1 mg/l).
1-NAPHTHOL
2539
ACKNOWLEDGEMENTS
The authors gratefully acknowledge financial support from the Russian Foundation of Fundamental Research (Project No. 96-03-33578a) and Scientific Program of Fundamental Natural Sciences, St.Petersburg State University (Project No. 95-0-9.5-272).
REFERENCES 1. K.M. Appaiah, R. Ramakrkhna, R.R. Subbarao, 0. Kapur. J. Assoc. OffA d . Chem. 65, 32 (1982) 2. K.M. Appaiah, U.C. Nag, O.P. Kapur, K.V. Nagaraja. J.Food Sci. Technol. 20, 252 (1983). 3. Ya.1. Korenman, S.P. Kalinkina, P.O. Sukhanov, S.I. Niftaliev, N . N . Sel’manschuk, E.A. Podolina, N.Yu. Strashilina. Zhurn. Analit. Khimii. 49, 1189 (1994). [Russ. J. of Analytical Chemistry (Engl. Transl.) 49. 1069 (1994).]. 1. .M. Korenman. Photomhcheskyl an&. Metody opredeleniya organicheskih 4. coedineniy (Photometric analysis. Methods of determination of organic compounds). M.: Khimiya. 1970. 339 p.(in Russian) F. Gareia Sanchez, C. Cruces Blanco. Tulunru. 37. 573 (1990). 5. J. Sansenon, J.L.Canion, M. la Guardia. Fresenius J.Anu1.Chem. 336. 389 6. ( 1990) 7. M.C. Quintero, M. Silva, D. Perez-Bendito. Tuluntu. 36. 717 (1989). A.M. Hensen, O.M. Poulsen, T. Sigsgaard, J.M. Christensen. Anul.Chim.Actu. 8. 291.341 (1994). C.M. Sparacino, J.W.Hines, J.Chromutogr.Science. 14. 549 (1976). 9. 10. M.De Berardinis, J.W.A. Wargin. J.Chromutog. 246. 89 (1982). H.S. Rathore, S.K. Saxena. Anuf.Let?.23,93 (1990) 11. 12. T. Braun, J.D. Navratil, A.B. Farag. Polyurethane Foam Sorbents in Separation Science. CRC Press. Boca Raton, F1. 1985. 208 p. 13. V.K. Runov, V.V. Tropina. Zhurn. Analit. Khimii. 51,71 (1996) [Russ. J. of Analytical Chemistry (Engl. Transl.) 51. 64 (1996).]. 14. S.G. Dmitrienko, E.V. Loginova, O.A. Kosyreva, E.Ya. Gurary,
DMlTRlENKO ET AL.
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I.L. Kolyadkina, V.K. Runov. Vestnik. hskovskogo universiteta.. 37. 367 ( 1996).
15.
D.D. Penin, W.L.F. h o r e g o , Dawn R. Perrin. Purification of Laboratory Chemicals. Pergaman Press. 1980. 569 p. Received: April 7, 1997 Accepted: July 2, 1997
