Determination of Pentachlorophenol by Ultraviolet Ratio Spectrophotometry James E. Fountaine, Phanibhushan B. Joshipura, and Peter N. Keliher‘ Chemistry Department, Villanova University, Villanova, Pa. 19085
John D. Johnson Spectrogram Corporation, 385 State Street, North Haven, Conn. 06473
Pentachlorophenol (PCP) is widely used as a herbicide, fungicide, and insecticide, mainly for the preservation of wood and wood products, and for slime control. According to Rappe and Nilsson ( 1 ), the annual world production of P C P is more than 20,000 tons. Sodium and copper pentachlorophenates are used as molluscacides for the destruction of snail intermediate hosts of human schistosomes (2, 3 ) . Bechhold and Ehrlich as early as 1906 ( 4 ) pointed out the toxic effects of PCP. Extensive studies were carried out by Kehoe and coworkers in 1939 ( 5 ) and Boyd and coworkers in 1940 (6) and 1941 ( 7 ) regarding the toxicity of PCP. Recently, Bergner et al. (8) confirmed the toxic effects of PCP. Stark in 1969 ( 9 ) and Rudling in 1970 ( 1 0 ) reported that P C P is found in streams and accumulated in fish tissues following industrial discharge. The colorimetric procedures used so far for the determination of PCP (11-16) are not specific for PCP but include many other phenolic compounds. Even the colorimetric method most often used ( 1 5 ) is not specific for PCP. In this method, phenazone-PCP dye is prepared. All of the chlorinated derivatives of phenol and phenol itself form colored dyes with phenazone. Presence of bathochromic or hypsochromic substituents on the phenol ring would shift the color of the dyes causing a serious interference. Moreover, these methods use some form of pretreatment and preconcentration techniques. Pretreatment takes time, can adversely affect the accuracy of the determination by contamination from reagents and glassware, and can degrade the precision of the measurement through unavoidable manipulative errors. Recently, Buhler et al. (17) suggested the use of gas chromatography coupled with a mass spectrometer for the determination of P C P in river water. Sensitivity is extremely good (below 1 ppb) but the pretreatment techniques are extremely time-consuming and tedious. A fivegallon sample is required and 600 ml of chloroform is needed for every determination. The current procedures for determining trace quantities of P C P cannot be easily employed when a large number of samples are to be analyzed routinely. We have recently reported on a new instrumental system ( 1 8 ) for the determination of sub-microgram amounts of phenolic compounds. In contrast to the aforementioned procedures, our system was fast, sensitive, accurate, and relatively simple to operate. Our interest in PCP was aroused as a result of reading a report in a local newspaper ( 1 9 ) which indicated that in Haverford Township (suburban Philadelphia area) P C P was entering a stream from an uncertain source. This is, of course, of great concern to the township authorities since the stream (Naylor’s Run Creek) is in a relatively built-up area and discharge into well water might be possible. Accordingly, a specific system To whom correspondence should be addressed.
for the analysis of P C P was devised based upon the principle reported earlier ( I t ? ) and , this system was used for some analyses from the stream.
EXPERIMENTAL Instrumentation. The instrumental system described previously (28) was used with one significant change. For some of the studies reported below, the original platinum hollow cathode lamp was replaced by a copper hollow cathode lamp (Atomic Spectral Lamps, Pty., Melbourne, Australia). Reasons for this change are given below. A Model 202 UV-Visible Spectrophotometer (Perkin-Elmer Corporation, Norwalk, Conn.) was used to record phenolic spectra a t relatively high concentrations, ea. 20 ppm. Reagents. Reagent grade chemicals were used throughout. PCP was obtained from Fisher Scientific and was purified before using. Distilled water was passed through a four-foot activated charcoal column to remove trace quantities of phenolic compounds. l h i s purified distilled water was used to make up all solutions including the 4M NaOH solution. All stock phenolic solutions were kept in a refrigerator a t below 10 “Cand were checked periodically for deterioration. Procedure. P C P has a very low solubility in water. A saturated solution of PCP in distilled water was prepared by heating at 60 OC and cooling to room temperature, followed by a filtration through glass wool. UV spectra in acidic and basic media are obtained as shown in Figure 1. P C P does not show a conventional phenolic bathochromic shift but it does show an enhancement in absorbance upon being made basic. The absorbance maxima is a t approximately 320 nm. The identical experimental procedure as described previously ( 1 8 ) is used. The sample is placed in a quartz windowed 10-cm cell in the acid condition, 2-3 drops of 4M NaOH is added to the cell, and the percent absorption (relative signal) is read as a function of concentration. As PCP has a very low solubility in water, standard solutions were prepared in about 0.2M NaOH. All dilutions were done with the purified distilled water. These diluted standard solutions were then made acidic with hydrochloric acid.
RESULTS AND DISCUSSION Initially, light from the platinum hollow cathode lamp was adjusted, by control of the small 0.2-meter monochromator, so that a strong platinum line a t 306.5 nm was passed through the cell. This line then becomes the “pH dependent” wavelength ( 1 8 ) .Under these conditions, a linear calibration slope from 50 ppb to over 1ppm is obtained and this is shown in Figure 2A. Although the response is linear, consideration of bathochromic shift wavelengths of other phenolic compounds shows that many phenolic conipounds apt to be present in real samples would be interferents. To improve sensitivity A N D selectivity, the platinum hollow cathode lamp was removed from the instrumentation and replaced by a copper hollow cathode lamp. Copper happens to be a particularly intense hollow cathode lamp and the major resonance line a t 324.7 nm coincides rather well with the P C P ultraviolet absorbance curve. When the copper lamp was inserted, the monochromator adjustment was moved to longer wavelength until the intense 324.7-nm
A N A L Y T I C A L CHEMISTRY, VOL. 47, N O . 1, J A N U A R Y 1975
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Table I. Precision Measurement at Different Concentration Levels PCP in ppb
\vdteI,
320nm.
50 100 250
5 uo
Sid d e l
Re1 std dev, %
47.6
6.4
99.6
254.1
6.1 6.3
499.5
6.35
13.4 6.1 2.47 1.27
Mean o i 15
Abr
I 2
I
-nm
.
r
350
Figure 1. Ultraviolet absorbance spectra of pentachlorophenol under ( A ) acidic (pH 2) and ( B )basic (pH 10) conditions
100
lDD0
Conc Pub
Figure 3. Log-log plots for pentachlorophenol at ( A ) Pt 306.5 nm and ( 8 )Cu 324.7 nm, and (C)relative standard deviation vs. concentration
Concentntlon (PPb)
Flgure 2. Relative response curves for pentachlorophenol at ( A ) Pi 306.5 nm, (€3) Cu 324.7 nm
Cu line was observed. This line was not absorbed by a concentrated solution of 0 - cresoi when made basic, but PCP was strongly absorbed under the same conditions. A response curve for PCP under the new wavelength conditions was obtained and is shown in Figure 2B. As can be seen, sensitivity is improved about fourfold by moving to the longer wavelength. Response was found to be linear to approximately 500 ppb with a slight sloping off a t higher concentrations. The detection limit, with no preconcentration treatment, is about 10 ppb. All of the subsequent measurements were done using the Cu 324.7-nm line as the “pH dependent” wavelength with the chromium lines a t ca. 360 nm serving, as before ( I B ) , as the “pH independent” wavelength. Precision data for PCP a t different concentration levels are shown in Table I. This shows the results of fifteen determinations a t each of the four concentration levels. Fig158
ure 3 shows log-log plots for the Pt 306.5-nm and Cu 324.7-nm wavelengths and also shows relative standard deviation us. concentration for PCP. As we had noted previously ( l a ) ,the “weak link” in the system will be the stability of the hollow cathode lamps. In this case, the copper lamp used was over four years old and had had an extensive life in conventional atomic absorption equipment. Nevertheless, the precision data would seem quite adequate. Table I1 shows different phenolic compounds including chlorinated phenolic compounds which were studied for their interference effects a t a constant concentration of 100 ppb PCP. This table also shows A,, under acidic (pH 2) and basic (pH 10) conditions for the phenolic compounds studied. No interference was observed from o -, m -, or p chlorophenol a t concentrations up to 10 ppm. The presence of 2,4,6-trichlorophenol does show an interfering effect a t higher concentrations. This interference could be somewhat reduced by using the 327.4-nm line from the copper lamp but the sensitivity would be somewhat reduced. We are presently using the ultraviolet ratio spectrophotometric system for the analysis of selected samples taken from various points in Haverford Township. Where samples are relatively dirty, a preliminary extraction is used. Two-hundred-fifty ml of sample (under acidic conditions) is extracted into 25 ml of chloroform and the PCP is subsequently extracted back into 60 ml of 0.2M NaOH. This is then made acidic with HC1 (pH 2) and then measured in the normal way with the ultraviolet ratio spectrophotometer. Standards are, of course, brought through the same
ANALYTICAL CHEMISTRY, VOL. 47, NO. 1, JANUARY 1975
Table 11. Interference Studies on Pentachlorophenol Phenolic compound a
Amas (acidic), nm
'max (basic), nm
Concentration*
Phenol 269 286 10 o- Cresol 270 290 10 p-Cresol 278 298 5 iii-Cresol 271 291 10 Resorcinol 273 290 10 Thy mol 274 294 10 Tyrosine 275 293 10 / I [ -hlethoxyphenol 272 286 10 o -Chlorophenol 261 290 10 p-Chlorophenol 279 297 10 P I / - Chlorophenol 278 297 10 2,4Dichlorophenol 282 3 04 0.5 -Bromophenol 272 291 10 o-Bromophenol 271 292 10 4 -C hloro-2 methyl phenol 279 297 10 4-Chloro-3,5dimethyl phenol 278 296 10 p-C hlorothio phe no 1' 269 269 10 2-Chloro-4phenvl phenol 261 290 0.5 2 , 4 . 6-Trichlorophenol 292 310 0.05 p-Methoxyphenol 288 305 0.2 p - P henylphenol 258 290 0.2 Salicylic acidc 298 298 0.5 100 p p h pentachlorophenol constant. Concentration (in ppm) at which no interference was observed; 10 p p m was maximum concentration studied. No hathochromic shift.
procedure and percent recovery for P C P is about 98%. The detection limit for PCP, using this simple extraction procedure, is about 2 ppb. Samples taken from Naylor's Run Creek contain up to 12 ppm PCP. Concentration levels appear t o be very dependent upon climatic conditions. Specific details of these analyses may be obtained by writing to one of the authors (PNK). In order to verify that the measured signal is entirely due to PCP, conventional acidic and basic spectra have been run on those samples for which high results have been obtained, and these spectra are identical to the standard (Figure 1) P C P spectra. Presence of other phenolic compounds, a t these concentration levels, would, of course, shift the A,, under acidic and basic conditions. i.e. the spectra would not be identical to the P C P spectra. L I T E R A T U R E CITED (1) C. Rappe and C.-A. Nilsson, J. Chromatogr., 67, 247 (1972). (2) E. G. Berry, M. 0. Nolan, and J. 0. Gonzales, Pub. Health Rept., 65, 939 (1950). (3) M. 0. Nolan and E. G. Berry, Pub. Health Rept., 64, 942 (1949). (4) H. Bechhold and P. L. Ehrlich. Physiol. Chem., 47, 173 (1906). (5) R. A. Kehoe, W. Diechmann, and K. V. Kitzmiller, J. lnd. Hyg. Toxicol., 21, 160 (1939). (6) L. J. Boyd, T. H. McGavack, R. Terranova, and F. V. Piccione, N. Y. Med. Coll. Flower Hosp. Bull., 3, 323 (1940). (7) T. H. McGavack, L. J. Boyd, F. V. Piccione, and R. Terranova, J. hd. Hyg. Toxicol., 23, 239 (1941). (8) H. Bergner, P. Constantinidis, and J. H. Martin, Can. Med. Ass. J., 92, 488 (1965). (9) A. Stark, J. Agr. FoodChem., 17, 871 (1969). (10) L. Rudiing, Water Res., 4, 533 (1970). (11) A. Steigmann. J. SOC.Chem. lnd., 61, 180(1942). (12) W. Diechmann and L. J. Schafer, lnd. Eng. Chem., Anal. Ed., 14, 310 (1942). (13) S. Gottlieband P. B. Marsh, lnd. Eng. Chem., Anal. Ed., 18, 16 (1946). (14) G. R. Wallin, Anal. Chem., 22, 1208 (1950). (15) K. Bcncze, Analyst, 88, 622 (1963). (16) W. T. Haskins, Anal. Chem., 23, 1672 (1951). (17) D. R. Buhler, M.E. Rasmusson, and H. S. Nakaue, Environ. Sci. Techno/., 7, 929 (1973). (18) J. E. Fountaine, P. B. Joshipura, P. N. Keliher, and J. D. Johnson, Anal. Chem., 46, 62 (1974). (19) News ofDelaware County, January 24, 1974, p 5
RECEIVED for review June 3, 1974. Accepted September 19, 1974. Paper presented a t the First Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) Meeting, Atlantic City, N. J., November 21, 1974
Determination of Hydrogen in Metals by a Combination of the So-called Carrier Gas Method and the Technique of Frontal Chromatography Vlastimil Rezl, Boiena Kaplanova, and Jaroslav Janak lnstitute of Analytical Chemistry, Czechoslovak Academy of Sciences, Brno, Czechoslovakia 66228
The determination of hydrogen in metals, particularly in steels, belongs to the basic metallurgical analyses ( I , 2 ) . Most of the methods are based on the extraction of hydrogen in vacuum a t higher temperatures (600-1200 "C) and its separation and determination, frequently with the use of gas chromatography ( 2 - 5 ) . The finding that the extraction of hydrogen is feasible practically under about atmospheric pressure by the so-called carrier gas method (6) can markedly simplify the instrumental arrangement. The sample of the metal is passed about by a stream of argon
(or nitrogen, etc.) which continuously upsets the equilibrium between the concentrations of hydrogen inside the sample and a t its surface as long as the hydrogen is completely extracted out of the metal. After the mixture becomes homogeneous, only a small portion of'this highly diluted mixture of hydrogen in the inert gas is introduced into the gas chromatograph for analysis (e.g. 7 ) .The evaluation is carried out from the heights of the chromatographic peaks (less precise, cheaper) or from the peak areas determined with an integrator (more precise, costlier). The
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