Spectrophotometric detection of pentachlorophenol (PCP) in water using immobilized and water-soluble porphyrins

Biosensors and Bioelectronics 20 (2005) 1595–1601

Spectrophotometric detection of pentachlorophenol (PCP) in water using immobilized and water-soluble porphyrins A. Mufeed Awawdeh, H. James Harmon∗ Department of Physics, Oklahoma State University, Stillwater, OK 74078, USA Received 20 May 2004; received in revised form 21 July 2004; accepted 22 July 2004 Available online 2 December 2004

Abstract The spectrophotometric properties of porphyrins are altered upon interaction with chlorophenols and other organochlorine pollutants. Mesotetra(4-sulfonatophenyl)porphyrin (TPPS), zinc meso-tetra(4-sulfonato phenyl)porphyrin (Zn-TPPS), monosulfonate-tetraphenylporphyrin (TPPS1 ), meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl)porphyrin (C1 TPP), meso-tetra(4-carboxyphenyl)porphyrin (C4 TPP), and copper meso-tetra(4-carboxyphenyl)porphyrin (Cu-C4 TPP) in solution exhibit a broad absorbance in the range 400–450 nm Soret region. The interaction of the above mentioned porphyrins in solution with pentachlorophenol (PCP) induces a red shift in the Soret spectrum with absorbance losses at 413, 418, 403, 405, 407, and 404 nm, respectively, and the appearance of new peaks at 421, 427, 431, 416, 417, and 416 nm, respectively. The intensity of the Soret spectral change is proportional to the pentachlorophenol concentration with a detection limit of 1, 0.5, 1.16, 1, 0.5, and 0.5 ppb, respectively. The interaction of (C4 TPP) and (Cu-C4 TPP) in solution with PCP shows to concentration dependent for concentrations less than 4 ppb the dependence was log-linear. However, for concentrations greater than 4 ppb the relation was linear. Monosulfonate-tetraphenylporphyrin immobilized as a monolayer on a Kimwipe® tissue exhibits an absorbance peak in the Soret region at 422 nm. The interaction of the porphyrin with PCP induces a red shift in the Soret spectrum with absorbance loss at 419 nm and the appearance of new peaks at 446 nm. The intensity of the Soret spectral change is proportional to the log of PCP concentration. The detection limit with immobilized TPPS1 for PCP is 0.5 ppb. These results suggest the potential for development of spectrophotometric chemosensor for PCP residues in water with detection limits less than US EPA maximum contaminate level (MCL) of 1 ppb. The immobilized TPPS1 on the Kimwipe® will make it possible to develop a wiping sensors to monitor the PCP or other pesticides residues on the vegetables or wood products. © 2004 Elsevier B.V. All rights reserved. Keywords: Porphyrin; Immobilized; Pentachlorophenol (PCP); Spectrophotometric; Detection

1. Introduction Pentachlorophenol (PCP) has many applications in the industrial, agricultural, and domestic fields as a wood preservative to control mold and insects. The lipophilicity of chlorophenols (CP) contributes to their bioaccumulation in the food chain. The United State Environmental Protection Agency (US EPA) has classified PCP as B2 (a probable human carcinogenic) based upon evidence from animal toxicity studies and human clinical data (Abbas et al., 2001; ∗

Corresponding author. Tel.: +1 405 744 9692; fax: +1 405 744 7421. E-mail address: [email protected] (H.J. Harmon).

0956-5663/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2004.07.028

Saby and Luong, 1999; Veningerova et al., 1997). The (US EPA) has regulated the maximum contaminate level (MCL) of PCP in drinking water at 1 ppb (Oubin et al., 1997), while European Union (EU) legislation requires the maximum admissible concentration of phenols in drinking water to be 0.5 ppb (Jauregui and Galceran, 1997). The environmental persistence of PCP, the acute toxicity, and its potential health threat combined with strict regulations of (US EPA) and (EU) require highly selective and sensitive sensors to accomplish effective environmental monitoring. Currently, pesticide concentrations in surface water are quantified by the use of liquid chromatography/mass spectroscopy or gas chromatography/mass spectroscopy

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(Clement et al., 1997). The detection of chlorophenols in the environment using chromatographic techniques has been adequately reported (Sarrion et al., 2002; Rogers et al., 1999; Nakamura et al., 2001; Polese and Riberio, 1998; Becker et al., 2002; Muir and Eduljee, 1999; Gurka et al., 1997; Castillo et al., 1997; Sarrion et al., 2002; Guidotti and Ravaioli, 1999) at very low detection levels; however, these techniques are time consuming, expensive, and require trained technicians. Since pesticides are known to inhibit enzymes in the living organisms, they can be used to design biosensors and immunoassays for several types of pesticides including phenols and chlorophenols (Barzen et al., 2002; Ristori et al., 1996; Frohner et al., 2002; Cowel et al., 1995; Repetto et al., 2001; Young et al., 2001; Rosatto et al., 2001; Evtugyn et al., 1997; Denesison and Turner, 1995; Rogers et al., 1998; Freire et al., 2001) and organophosphates (Mulchandani et al., 1998; Chough et al., 2002). The use of inhibitionbased enzyme biosensors has been reviewed (Alberly et al., 1990a,b,c) and shows that enzyme-inhibitor interaction depends on activity of the enzyme and the inhibitor concentration. Using an optical multiple-analyte immunosensor, PCP in water was detected at 4.32 ppb (Barzen et al., 2002). The ability of chloroperoxidase to oxidize CP was used to design an amperometric electrode that reacts with many species of CP but is unreactive to PCP (Saby and Luong, 1999), while electrochemical biosensor arrays based on the inhibition of lactate dehydrogenase by PCP were able to detect 26.6 ppb PCP (Young et al., 2001). Spectrophotometric techniques are also reported; 4-aminopyrazolone (Fiamegose et al., 2000) and cobalt phthalocyanine (Mafatel and Nyokong, 1997) showed reactivity with both chlorophenols and organohalides. Porphyrins and metalloporphyrins can provide recognition sites through their cationic central metal ion and various functional groups at the four meso- and eight ␤positions of the pyrolles (Peng et al., 2000). Immobilized metallo-protoporphyrins (Xiao and Meyerhoff, 1996) and metallophenyl-porphyrins (Mikros et al., 1988) provide two avenues of interaction via the metallic center of porphyrin and/or the π-electrons of the porphyrin macrocycle resulting in a spectral change. Cobalt tetraphenylporphyrin was used to detect three classes of organohalide pollutants in aqueous medium: haloalkanes (DDT) to 1 ␮M, haloalkenes (HCC) to 10 ␮M, and haloarenes (PCP) to 20 ␮M (Dobson and Saini, 1997). In another study a cyclodextrin–porphyrin assembly changed its spectrum when exposed to organohalides or PCP (Zhao and Loung, 1995; detection limits were not given). Porphyrins have been successfully immobilized onto different surfaces to yield a solid-state chemosensor of different ligands in solution (White and Harmon, 2004; Legako et al., 2003; Awawdeh et al., 2003). In this study, we present a spectrophotometric detection method using mesotetra(4-sulfonatophenyl)porphyrin (TPPS), zinc meso-tetra (4-sulfonatophenyl)porphyrin (Zn-TPPS), meso-tri(4-sulf-

onatophenyl)mono(4-carboxy-phenyl)porphyrin (C1 TPP), meso-tetra(4-carboxyphenyl)porphyrin (C4 TPP), and copper meso-tetra(4-carboxyphenyl)porphyrin (Cu-C4 TPP) in solution, and monosulfonate-tetraphenylporphyrin (TPPS1 ) in solution and immobilized on Kimwipe® to detect PCP in water down to the MCL limits.

2. Methods Pentachlorophenol was obtained from Chemical Service in West Chester, PA at 99% purity. The following porphyrins: meso-tetra(4-sulfonatophenyl)porphyrin, zinc meso-tetra (4-sulfonatophenyl)porphyrin, monosulfonate-tetraphenylporphyrin, meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl)porphyrin, meso-tetra(4-carboxyphenyl)porphyrin, and copper meso-tetra(4-carboxyphenyl)porphyrin were obtained from Frontier Scientific (Logan, UT) and used without further purification. Tetra-chloro-1,4-benzo quinone (TCBQ) and 2,5-dichloro-1,4-benzoquinone (DCBQ) were obtained from Sigma Aldrich and used without purification. To make a saturated solution (14 ppm), 2 mg of PCP was put in 142.8 ml of de-ionized water and stirred until the PCP was completely dissolved. The stock solution was stored refrigerated wrapped in foil to block light. The stock solutions of meso-tetra(4-sulfonatophenyl)porphyrin, zinc meso-tetra(4-sulfonatophenyl)porphyrin, and meso-tri(4-sulfonatophenyl)mono(4-carboxy phenyl) porphyrin were prepared at 1 mM concentrations in de-ionized water. However, meso-tetra (4-carboxyphenyl)porphyrin and copper meso-tetra(4-carboxyphenyl)porphyrin required base titration in order to dissolve. Monosulfonatetetraphenylporphyrin was dissolved in 75% ethanol/water. Stock solutions were stored refrigerated in foil. The immobilization of TPPS1 on the Kimwipe® paper tissue was done using the protocol described in the literature (White and Harmon, 2004). To study the interaction of PCP with the porphyrins in solution, 5 ␮l of required porphyrin (1 mg/ml) was added to 3 ml of 50 mM pH7 sodium phosphate (Sorensen) buffer. The tissues of immobilized TPPS1 (approximately 0.9 cm × 2 cm) were held flat against the internal wall of the cuvette with a plastic holder open in the center to pass light. Absorbance spectra in the presence and absence of PCP were collected using a Cary 4E UV-visible spectrophotometer at 0.05 nm resolution. To quantify the changes in the spectra, difference spectra were obtained by subtraction of absolute spectra using Grams/32 (Galactic Industries, Salem, NH). The location of the peaks in the difference spectra was determined from the second derivative of the spectra using GRAMS/32. PSI-Plot was used to plot the net absorbance versus the concentration of PCP in the cuvette; the data was fitted to a straight line at a 99% confidence interval. All of the figures that displayed the  absorbance dependence on the PCP concentration represent an average of at least three sets of collected data.

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Fig. 1. The absorbance spectrum of meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) in the absence/presence of PCP at pH 7. The subtraction of the absolute spectrum of TPPS trace 1 from the absolute spectrum of TPPS + 1 ppb of PCP trace 2 gives the difference spectrum TPPS + 1 ppb of PCP minus TPPS trace 3. In the inset, trace 1 shows the dependence of the change in the absorbance (421–413 nm) on PCP concentration in the difference spectrum TPPS + PCP minus TPPS. The net change in the absorbance is found to be linearly dependent on the PCP concentration and follows the relation given in Table 1. Trace 2 shows the dependence of the absorbance peak intensity at 427 nm on PCP concentration in the difference spectrum Zn-TPPS + PCP minus Zn-TPPS. The net change in the absorbance is linearly dependent on the PCP concentration and follows the relation in Table 1.

Fig. 2. The absorbance spectrum of copper meso-tetra(4-carboxyphenyl)porphyrin (Cu-C4 TPP) in the absence/presence of PCP at pH7. The subtraction of the absolute spectrum of Cu-C4 TPP trace 1 from the absolute spectrum of Cu-C4 TPP + 0.5 ppb of PCP trace 2 gives the difference spectrum Cu-C4 TPP + 0.5 ppb of PCP minus Cu-C4 TPP trace 3. In the inset, trace 1 shows the dependence of the new peak at 416 nm of the (Cu-C4 TPP)–PCP complex; the peak shows a log-linear dependence given in Table 1 for concentrations <4 ppb where the ratio of PCP:Cu-C4 TPP is <1. However, for higher concentrations of PCP it shows a linear dependence and follows the relation given in Table 1. Trace 2 in the inset the dependence of the new peak at 417 nm of the C4 TPP–PCP complex; the peak shows a log-linear dependence for concentrations <4 ppb, and follows a linear relation given in Table 1 for concentrations >4 ppb.

3. Results

from 0.5 to10 ppb as shown in the inset of Fig. 1 (trace 2), and the linearity of the relation ship is given in Table 1. The results of this part show that metalloporphyrin Zn-TPPS shows higher sensitivity to PCP than non-metallated porphyrin. Upon addition of 0.5 ppb (1.88 nM) of PCP to the carboxylporphyrins C4 TPP and Cu-C4TPP the spectra show a slight shift to a longer wavelength (Fig. 2, trace 2 for CuC4 TPP). This shift is more clearly observed in the difference spectrum Cu-C4 TPP + PCP minus Cu-C4 TPP in (Fig. 2, trace 3), which shows a trough located at 404 nm that indicates a decrease in the spectrum of the uncomplexed Cu-C4 TPP and a new absorbance peak at 416/417 nm representing the interaction of PCP with the Cu-C4 TPP and C4 TPP, respectively. The net change in the absorbance of the new peak depends on the log of PCP concentration from 1 to 4 ppb where the ratio of PCP:C4 TPP/Cu-C4 TPP is less than one (unity) as shown in the inset of Fig. 2 (traces 1 and 2, respectively). However, when the ratio of PCP:C4 TPP/Cu-C4 TPP is greater than one (unity) the absorbance change linearly decreases with further additions of PCP, indicating that the interaction between the PCP molecules and the C4 TPP and Cu-C4 TPP molecules is concentration dependent and the relations are given in Table 1. The absorbance spectrum of monosulfonate-tetraphenylporphyrin in solution in the absence of PCP shows a broad peak in the Soret; in the presence of 1.16 ppb of PCP the spectrum shifts to a longer wavelength. The difference spectrum in the presence of 1.16 ppb PCP shows a trough at 403 nm

3.1. Interaction of porphyrins in solution with PCP The absorbance spectrum of TPPS in the absence of PCP exhibits an absorbance peak in the 400–450 nm Soret region as shown in (Fig. 1, trace 1). Upon addition of 1 ppb (3.75 nM final concentration) of PCP, the spectrum shows a shift to a longer wavelength (Fig. 1, trace 2) which is more clearly observed in the difference spectrum TPPS + PCP minus TPPS in (Fig. 1, trace 3); the trough located at 413 nm indicates a decrease in the spectrum of the uncomplexed TPPS and a new absorbance peak at 421 nm is a result of the formation a PCP–porphyrin complex. The net peak minus trough absorbance difference in the difference spectrum is linear from 1 to 10 ppb PCP as shown in the inset of Fig. 1 (trace1), and the linearity of the relationship is given in Table 1. The absorbance spectrum of Zn-TPPS in the absence of PCP exhibits an absorbance peak at 421 nm in the Soret region. Upon addition of 0.5 ppb (1.88 nM) of PCP, the spectrum shifts to a longer wavelength similar to that seen with TPPS (data not shown). This shift can be seen clearly in the difference spectrum Zn-TPPS + PCP minus Zn-TPPS, which shows a trough located at 418 nm that indicates a loss of the uncomplexed Zn-TPPS and a new absorbance peak at 427 nm resulting from the interaction of PCP with the Zn-TPPS (data not shown). The net peak minus trough absorbance difference in the difference spectrum depends on the PCP concentration

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Table 1 The peak/trough wavelengths of difference spectra and the detection limit of PCP for each porphyrin based on the lowest absorbance value measurable at a 3:1 signal-to-noise ratio Porphyrin type

Trough at (nm)

Peak at (nm)

λ (nm)

Absorbance dependence

TPPS Zn-TPPS TPPS1 C1 TPP

413 418 403 405

421 427 431 416

8 9 28 11

A = 0.00096 × (x) × 0.001714 A = 0.001676 × (x) + 0.003756 A = 0.0056 × ln(x) + 0.0094 A= 0.0009 × ln(x) + 0.0053

C4 TPP

407

417

10

P = 0.0014 × ln(x) + 0.0054 P = −0.0008 × (x) + 0.0105

Cu-C4 TPP

404

416

12

P = 0.0016 × ln(x) + 0.0039 P= −0.000422 × (x) + 0.0076

Immobilized TPPS1

446

419

27

A = 0.0033 × ln(x) + 0.0075

λ is the difference between the position of the peak/trough.

and an apparent peak at 431 nm (data are not shown). The net peak minus trough absorbance in the difference spectra for the 431/403 nm wavelength pair shows a linear dependence on the log of PCP concentration as shown in the inset of Fig. 3 (trace 1). Upon addition of 1 ppb (3.75 nM) of PCP, the spectrum of C1 TPP shows a shift to a longer wavelength. This shift is more clearly observed in the difference spectrum C1 TPP + PCP minus C1 TPP, which shows a trough located at 405 nm that indicates a decrease in the spectrum of the uncomplexed C1 TPP and a new absorbance peak at 416 nm representing the interaction of PCP with the C1 TPP. The plot of the net

Fig. 3. The absorbance spectrum of immobilized monosulfonatetetraphenylporphyrin (TPPS1 ) in the absence/presence of PCP at pH 7. The subtraction of the absolute spectrum of TPPS1 trace 1 from the absolute spectrum of TPPS1 + 1 ppb of PCP trace 2 gives the difference spectrum TPPS1 + 1 ppb of PCP minus TPPS1 trace 3. In the inset, trace 1 shows the dependence of the change in the absorbance peak at 446 nm on PCP concentration in the difference spectrum TPPS1 + PCP minus TPPS1 . This dependence is log-linear and follows the relation given in Table 1. Trace 2 the dependence of the absorbance peak at 431 nm of TPPS1 in solution on PCP concentration in the difference spectrum TPPS1 + PCP minus TPPS1 . The net change in the absorbance is log-linear and follows the relation given in Table 1. Trace 3 the dependence of the absorbance peak at 416 nm in the difference spectrum C1 TPP + PCP minus C1 TPP on PCP concentration. The net change in the absorbance follows the log-linear relation given in Table 1.

peak minus trough absorbance difference in the difference spectrum versus the log of PCP concentration from 1 to 8 ppb is shown in the inset of (Fig. 3, trace 3) and the relation is given in Table 1. All the spectra were corrected for the dilution effect for all volumes added to the starting volume of 3 ml. 3.2. Interaction of immobilized porphyrin with PCP The absorbance spectrum of immobilized TPPS1 in the absence and in the presence of 1 ppb of PCP is shown in (Fig. 3, traces 1 and 2, respectively). Immobilized TPPS1 gives an absorbance peak of 422 nm. In the presence of 3.75 nM PCP, the difference spectrum TPPS1 + PCP minus TPPS1 (Fig. 3, trace 3) shows a trough located at 420 nm that indicates a decrease in number of uncomplexed porphyrin and a peak at 446 nm resulting from the interaction of the PCP with the immobilized porphyrin. The net peak minus trough absorbance difference in the difference spectrum depends on the log of PCP concentration from 0.5 to145 ppb as shown in the inset of (Fig. 3, trace 1).

Fig. 4. A comparison of the change in the absorbance peak/trough for TPPS1 upon interacting with PCP, TCBQ, and DCBQ. The log-linear dependence of the change in the absorbance on the analyte PCP, TCBQ, and DCBQ concentrations [x] is found to be A = 0.0074 × ln(x) + 0.0411, A = 0.0052 × ln(x) + 0.0286, A = 0.004 × ln(x) + 0.0165, respectively in the range 0.03–0.95 nM.

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In order to investigate the specificity of the immobilized TPPS1 to PCP, we studied the interaction of TPPS1 with some of the byproducts of PCP such as 2,5-dichloro-1,4benzoquinone and tetra-chhloro-1,4-benzoquinone. The interaction of TPPS1 with both of them shows a red shift to the spectrum with a peak/trough located at 444/420 nm and 445/419 nm, respectively. The net change in the absorbance of the immobilized TPPS1 upon interacting with PCP, DCBQ, and TCBQ shows a log-linear dependent on the concentrations of the analytes as shown in Fig. 4. As seen in Fig. 4, upon adding equal amounts of these analytes, the net change in the absorbance for PCP > TCBQ > DCBQ suggesting that TPPS1 has a stronger affinity for PCP.

4. Discussion The optically based immunosensor, electrochemicalbased biosensor, and cobalt tetraphenyl porphyrin electrodes as biomimetic sensor were able to detect PCP to the limits of 4.23, 26.6, and 20 ppb, respectively (Barzen et al., 2002; Young et al., 2001; Dobson and Saini, 1997). An enzyme-less biosensor was able to detect phenol at 2.4 ppm (Sotomayor et al., 2002). However, none of the previous sensors could detect PCP at the EPA maximum admissible contaminating level of 1 ppb. The interaction of PCP molecules with the following water-soluble porphyrins meso-tetra(4-sulfonatophenyl)porphxyrin, zinc meso-tetra(4-sulfonatophenyl)porphyrin, monosulfonate-tetraphenylporphyrin, meso-tri(4-sulfonatophenyl)mono(4-carboxyphenyl)porphyrin, meso-tetra(4-carboxyphenyl)porphyrin, and copper meso-tetra(4-carboxyphenyl)porphyrin causes a shift in the Soret spectrum to a longer wavelength; as a result, the difference spectrum shows a peak/trough located at different positions depending on the type of porphyrin used as shown in Table 1. PCP molecules are electron-rich and aromatic; consequently it is expected that π–π interaction is the dominant interaction between the PCP molecules and the porphyrin molecules; as a result, the charge density of the porphyrin system will increase and cause a red shift to the Soret band (Shelnutt, 1983) as shown in all the difference spectra. It is also expected that PCP molecules may interact with the porphyrin via hydrogen bonding with the nitrogen atoms in the center of the porphyrin ring of TPPS, TPPS1 , C1 TPP, and C4 TPP. The net absorbance in the difference spectra for TPPS and Zn-TPPS shows to be linearly dependence on the PCP concentration as shown the insets of Fig. 2 (traces 1 and 2, respectively). However, the net absorbance in the difference spectra for TPPS1 , C1 TPP, C4 TPP, and Cu-C4 TPP shows a log-linear dependent on the PCP concentration as shown in the insets of Figs. 2 and 3. For TPPS1 at 2.32 ppb PCP where the molecular ratio of PCP: TPPS1 is 1:47, a small peak is located at 431 nm and may result from co-facial parallel stack-

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ing of the PCP molecules to the porphyrin molecule via π–π interaction. The interaction of PCP molecules with C4 TPP and metalloporphyrins Cu-C4 TPP in solution here seems to be concentration-dependent such that for concentrations <4 ppb where the molecular ratio of PCP: C4 TPP or Cu-C4 TPP is less than one (unity); the absorbance of the peak and trough shows a log-linear dependence. However, for concentrations >4 ppb where the molecular ratio of PCP: C4 TPP or CuC4 TPP is greater than one (unity), the absorbance of the peak and trough shows a linear dependence as shown in the insets of (Fig. 2). These results indicate that C4 TPP and CuC4 TPP interact with PCP in a way that may be concentrationdependent. For the immobilized TPPS1 on a Kimwipe® tissue paper, the interaction with DCBQ, TCBQ, and PCP molecules causes a red shift with a new peak at 444, 445, and 446 nm; the difference between the peak and the trough position is 24, 25, and 27 nm, respectively suggesting a stronger interaction between the PCP molecules and the immobilized porphyrin in comparison with DCBQ, and TCBQ. The change in the wavelength of the Soret band is proportional to the association energy between the porphyrin and the aromatic ligands (Schneider and Wang, 1994) further suggesting that π–π stacking interaction between the PCP and immobilized porphyrin molecules is a predominant. The interaction of TPPS1 with different analytes that vary in the number of chlorine atoms shows that the shift in the Soret peak depends on number of chlorine atoms; chlorine atoms have large electronegativity that in turn increases the charge density of the porphyrin upon the interacting and causes a larger red shift to the spectrum.

5. Conclusions The interactions of PCP molecules with the following porphyrins: meso-tetra(4-sulfonato phenyl)porphyrin, zinc meso-tetra(4-sulfonatophenyl)porphyrin, monosulfonatetetraphenylporphyrin, meso-tri(4-sulfonatophenyl)mono(4carboxy phenyl)porphyrin, meso-tetra(4-carboxyphenyl) porphyrin, and copper meso-tetra(4-carboxyphenyl)porphyrin in solution and immobilized (TPPS1 ) cause a red shift in the Soret band that enables us to spectrophotometrically quantify the PCP in water as low as 1, 0.5, 1.16, 1, 0.5, 0.5, and 0.5 ppb, respectively. Comparing the slopes of the straight lines and the net changes in the absorbance for equal additions of PCP concentrations indicates that C4 TPP has larger affinity to PCP than TPPS and C1 TPP; on the other hand, metallated porphyrins Zn-TPPS and Cu-C4 TPP are more reactive with PCP than non-metallated porphyrins in solutions. Immobilized TPPS1 on Kimwipe® tissue shows a strong reactivity to PCP in water suggests the possibility to develop a wiping sensor modified to monitor the pesticides residues on the vegetables.

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The ability to detect PCP in water using spectrophotometric chemosensors with detection limit less than the US EPA maximum contaminate level of 1 ppb will make it possible to accomplish efficient surface and ground water environmental monitoring programs and to enhance the food safety industry to allow the quality of the food products to match requirements of the health and safety departments.

References Abbas, M.N., Mostafa, G.A.E., Homoda, A.M.A., 2001. PVC membrane ion selective electrode for determination of pentachlorophenol in water, wood and soil using teterazolium pentachlorophenolate. Talanta 55, 647–656. Alberly, W.J., Cass, A.E.G., Shu, Z.X., 1990a. Inhibition enzyme electrodes. Part 1: Theoretical model. Biosens. Bioelectron. 5, 367– 378. Alberly, W.J., Cass, A.E.G., Shu, Z.X., 1990b. Inhibition enzyme electrodes. Part 2: The kinetics of the cytochrome oxidase system. Biosens. Bioelectron. 5, 379–395. Alberly, W.J., Cass, A.E.G., Mongland, B.P., Shu, Z.X., 1990c. Inhibition enzyme electrodes. Part 3: A sensor for low levels of H2S and HCN. Biosens. Bioelectron. 5, 397–413. Awawdeh, M.A., Legako, J.A., Harmon, H.J., 2003. Solid-state optical detection of amino acids. Sens. Actuators B 91, 227–230. Barzen, C., Bretch, A., Gauglita, G., 2002. Optical multiple-analyte immunosensor of water pollution control. Biosens. Bioelectron. 17, 289–295. Becker, R., Buge, H.G., Win, T., 2002. Determination of pentachlorophenol (PCP) in water wood-method comparison by a collaborative trial. Chemosphere 472, 1001–1006. Castillo, M., Puig, D., Barcelo, D., 1997. Determination of priority phenolic compounds in water and industrial effluents by polymeric liquid–solid extraction cartridges using automated sample preparation with extraction columns and liquid chromatography use of liquid-solid extraction cartridge for stabilization of phenols. J. Chromatogr. A 778, 301–311. Chough, S.H., Milchandani, A., Mulchandani, P., Chen, W., Wang, J., Rogers, K.R., 2002. Organophosphorus hydrolase-based amperometric sensor: modulation for sensitivity and substrate selectivity. Electroanalysis 14 (4), 273–276. Clement, R.Y., Yang, P.W., Koester, C.J., 1997. Environmental analysis. Anal. Chem. 69 (12), 251R–287R. Cowel, D.C., Dowman, A.A., Ashcroft, T., Caffoor, I., 1995. The detection and identification of metal and organic pollutants in potable water using enzyme assays suitable for sensor development. Biosens. Bioelectron. 10, 509–516. Denesison, M.J., Turner, A.P.F., 1995. Biosensors for environmental monitoring. Biotech. Adv. 13, 1–12. Dobson, D.J., Saini, S., 1997. Porphyrin-modified electrodes as biomimetic sensors for the determination of organohalides pollutants in aqueous samples. Anal. Chem. 69 (17), 3532–3538. Evtugyn, G.A., Bundikov, H.C., Nikolskaya, E.B., 1997. Sensitivity and selectivity of electrochemical enzyme sensors for inhibitor determination. Talanta 46, 465–484. Fiamegose, Y.C., Stalikase, C.D., Pilidis, G.A., Karayannis, M.I., 2000. Synthesis and analytical applications of 4-aminopyrozolone derivatives as chromatographic agents for the spectrophotometric determination of phenols. Anal. Chim. Acta 403, 315–352. Freire, R.S., Duran, N., Kubota, L.T., 2001. Effect of fungal laccase immobilization procedures for the development of biosensors for phenol compounds. Talanta 4, 681–686.

Frohner, K., Meyer, W., Grimme, L.H., 2002. Time-dependent toxicity in the long-term inhibition assay. Chemosphere 46, 987–997. Guidotti, M., Ravaioli, G., 1999. Total p-chlorophenol determination in urine samples of subjects exposed to chlorobenzene, using SPME and GC-MS. J. High Resolut. Chromatogr. 22 (7), 427–428. Gurka, D.F., Pyle, S., Titus, R., 1997. Environmental applications of gas chromatography/atomic emission detection. Anal. Chem. 69, 2411–2417. Jauregui, O., Galceran, M.T., 1997. Determination of phenols in water by on-line solid-phase disk extraction and liquid chromatography with electrochemical detection. Anal. Chim. Acta 340, 191–199. Legako, J.A., White, B.J., Harmon, H.J., 2003. Detection of cyanide using immobilizes porphyrin and myoglobin surfaces. Sens. Actuators B 91, 128–132. Mafatel, T., Nyokong, T., 1997. Use of cobalt(II) phthalocyanine to improve the sensitivity and stability of glassy carbon electrodes for the detection of cresols, chlorophenols and phenol. Anal. Chem. Acta 354, 307–314. Mikros, E., Gaudemer, A., Pasternack, R., 1988. Interaction of watersoluble zinc porphyrin with amino acids. Inorg. Chem. Acta 153, 199–200. Muir, J., Eduljee, G., 1999. PCP in the freshwater and marine environment of the European union. Sci. Total Environ. 2356, 41–56. Mulchandani, A., Kaneva, I., Chen, W., 1998. Biosensors for direct determination of organophosphate nerve agents using recombinant Escherichia coli. With surface-expressed organophosohoroius hydrolase. 2 Fiber-optic microbial sensor. Anal. Chem. 71 (23), 5042–5046. Nakamura, S., Takino, M., Dashima, S., 2001. Trace level determination of phenols as pentaflourobenzyl derivatives by gas chromatographynegative-ion chemical ionization mass spectroscopy. Analyst 126, 835–839. Oubin, A., Puig, D., Gascon, J., barcelo, D., 1997. Determination of pentachlorophenol in certified waste water, soil samples and industrial effluents using ELISA and liquid solid extraction followed by liquid chromatography. Anal. Chim. Acta 346, 49–59. Peng, X.-b., Huang, J.-w., Li, T., Ji, L.-n., 2000. Molecular recognition of amino acid ester by porphyrinatozinc(II): observation of a new bindidng mode. Inorg. Chem. Acta 305, 111–117. Polese, L., Riberio, M.L., 1998. Methods for determination of Hexachlorobenzene in soil samples. Talanta 46, 915–920. Repetto, G., Jos, A., Hazen, M.J., Molero, M.L., Del Peso, A., Salguero, M., Del Castillo, P., Rodriguez-Vicente, M.C., Repetto, M., 2001. A test battery for the ecotoxicoligical evaluation of pentachlorophenol. Toxicol. In Vitro 15, 503–509. Ristori, C., Del Carlo, C., Martini, M., Barbaro, A., Ancarani, A., 1996. Potentiometer detection of pesticides in water samples. Anal. Chim. Acta 325, 151–160. Rogers, K.R., Becker, J.Y., Wang, J., Lu, F., 1999. Determination of phenols in environmental relevant matrices with the use of liquid chromatography with an enzyme electrode detector. Field Anal. Chem. Technol. 3, 161–169. Rogers, K.R., Mascini, M.M., 1998. Biosensors for field analytical monitoring. Field Anal. Chem. Technol. 2 (6), 317–331. Rosatto, S.S., de Oliveira, N.G., Kubota, L.T., 2001. Effect of DNA on the peroxidase based biosensors for phenol determination in waste waters. Electroanalysis 13 (6), 445–450. Saby, C., Luong, H.T.J., 1999. A biosensor syaytem for chlorophenols using chloroperoxidase and a glucose oxidase based amperometric electrode. Electroanalysis 10 (1), 7–11. Sarrion, M.N., Santos, F.J., Galceran, M.T., 2002. Determination of phenols by solid-phase micro-extraction and liquid chromatography with electrochemical detection. J. Chromatogr. A 947, 155–165. Schneider, H.J., Wang, M., 1994. Ligand–porphyrin complexes: quantitative evaluation of biosensor for the determination of phenolic compounds. J. Org. Chim. 59, 7464–7472. Shelnutt, J.A., 1983. Molecular complexes of copper uroporphyrin with aromatic acceptors. J. Phys. Chem. 87, 605–616.

A.M. Awawdeh, H.J. Harmon / Biosensors and Bioelectronics 20 (2005) 1595–1601 Sotomayor, M.D.-P.T., Tanaka, A.A.T.E., Kubota, L.T., 2002. Development of an enzymeless stacking and ionic contributions. J. Org. Chem. 59, 7464–7472. Veningerova, M., Prachar, V., Kovacicova, J., Uhnak, J., 1997. Analytical method for the detrmination of organochlorine compounds application to environmental samples in the Slovak Republic. J. Chromatogr. A 744, 333–347. White, B.J., Harmon, H.J., 2004. Interaction of dipicolinic acid with water soluble and immobilized porphyrins. Sens. Actuators B, 277– 283. Xiao, J., Meyerhoff, M.E., 1996. Retention behavior of amino acids and peptides on protoporphyrin-silca stationary phases with varying metal ion centers. Anal. Chem. 68, 2815–2818. Young, S.J., Hart, J.P., Downman, A.A., Cowell, D.C., 2001. The nonspecific inhibition of enzymes by environmental pollutants: a study of

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a model system towards the development of electrochemical biosensor arrays. Biosens. Bioelectron. 16, 887–894. Zhao, S., Loung, J.H.T., 1995. A cyclodextrin–porphyrin assembly as chemosensor for pentachlorophenol. J. Chem. Soc. Chem. Commun., 663–664. Mufeed A. Awawdeh received a MS in physics from Yarmouk University, Jordan, in 1992 and is currently a doctoral student in Environmental Science at Oklahoma State University, Stillwater, OK. H. James Harmon is a Full Professor, Department of Physics and is jointly appointed in the Center for Sensors and Sensor Technology at Oklahoma State University, Stillwater, OK. Current research directions involve photocatalytic modification of organic molecules as well as the design of optical solid-state real-time sensors for chemical, biological, and energetic agents. He received his Ph.D. from Purdue University and did post-doctoral research at the University of Pennsylvania.