AMI. Chem. 7900, 52, 2033-2036
LITERATURE CITED Shimlzo, T. Anal. Chim. Acta 1967, 37, 75. Korklsch, J. “Modern Methods for the Separation of Rare Metal Ions”; Pergamon Press: London, 1969. Stary. J. “The Solvent Extraction of Metal Chelates”; Pergamon Press: London, 1964. Marcus, Y.; Kertes, A. S. “Ion Exchange and Sdvent €*action of Metal Complexes”; Wiley: New Yo&, 1968. De, A. K.; Khopkar, S. M.; Chalmers. R . A. “Solvent Extraction of Metals”; Van Nostrand: London, 1970. Sekene, T.; Hasegawa, Y. “Solvent Extraction Chemistry”; Marcel Dekker: New York. 1977.
1958;p 175. (8) Gawali, S. B.; Shinde, V. M. Anal. Chem. 1976, 48, 62.
2033
(9) Samodelov. A. P. Zh. Neorg. Khim. 1985, 10, 2180. (IO) Alcdc, K.; Bedfwd, B. C.: Hardwlck, W. H.: Mckay. H. A. C. J . Inorg. N w l . Chem. 1957, 4 . 100. (11) Siddall, T. H. J. J. Inorg. Nucl. Chem. 1964, 26, 1919. (12) Kalyanaraman, S.;Khopkar, S. M. Anal. Chem. 1977, 49, 1192. (13) Sandell, E. 8. “Cokrlmetric Determlnetion of Traces of Metals”, 3rd ed.; Interscience: New York. 1965;pp 338,397. 534, 649,874. (14) Gagliardi, E.; Iimair, B. Mikrochim. Acta 1967, 1 , 180. (15) Fritz, J. S.;Johnson, M. Anal. Chem. 1955, 27, 1653. (16) Fritz, J. J.; Ford, J. J. Anal. Chem. 1953, 25, 1640. (17) Shibata, S.; Takevshi, F.; Matsumae, 1.Anal. Chlm. Acta 1959, 21. 177.
RECEIVEDfor review May 23,1980. Accepted August 1,1980.
Sorption Capacities of Graphitized Carbon Black in Determination of Chlorinate Pesticide Traces in Water Alessandro Bacaioni, Giancarlo Goretti, Aldo Lagan&
Bianca Marla Petronio, and Mauro Rotatori
Istituto di Chimica Analitica, Universita di Rorna, 00 185 Rorna, Italy
The appllcatlon of graphltlred carbon black (GCB) to the extractlon of trace organlc pollutants from water is studled. I t Is observed that many classes of organic substances are adsorbed and, In particular, that GCB is a good materlal for the recovery of chlorinated pesticides. Atthough the adsorbent effklencles depend on the nature of other substances that are present In the water samples, GCB has proven to be more advantageous than Tenax for pestlclde determlnatlons.
The determination of organic pollutants in water is essential for the solution of many diverse environmental problems (1). Methods involving direct analysis can be used only with relatively high concentrations of organic pollutants (2). The analysis of lower concentrations of compounds requires an enrichment procedure before the determination. This procedure is often based on the utilization of adsorbent materials such as carbon ( 3 , 4 )or resins (5-7). Chriswell e t al. (8) compare activated carbon with XAD resins and show that the latter are more efficient except for the case of simple a n d chlorinated alkanes; unfortunately none of these two adsorbents is able to retain acids. Van Rossum e t al. (9) use consecutive resin and carbon columns in tap water analysis. Till now graphitized carbon black (GCB) has been used in gas chromatography for t h e preparation of capillary (IO), micropacked ( I I ) , and packed columns (12) and only seldom has i t been employed in high-performance liquid chromatography (HPLC) (13). I n this paper utilization of GCB for the recovery of pollutants from water is examined. Since this material is able to adsorb chlorinated pesticides with good efficiency, the authors have particularly studied t h e use of GCB for the recovery of this class of pollutants which, in the past, have been recovered from water with adsorbents such as XAD resins ( 1 4 , 1 5 ) , porous polyurethane foam (16),and Tenax (27). A comparison of sorption recoveries using GCB with those obtained by using Tenax as adsorbent material is shown in this work. T h e study of t h e recovery of the other adsorbed substances (see Table I) will be the subject of a following paper.
EXPERIMENTAL SECTION The graphitized carbon black (Carbopack B, Supelco Inc. Bellefonte, PA) is characterized by a surface area of 100 m2/g, 80-100 mesh, and pH 10.25 after suspension in water. This material has basic active centers; Tenax 80-100 mesh (2,6-diphenyl-p-phenylene oxide) was obtained from ENKA Amsterdam, Netherlands. All chemicals were analytical grade products. The chlorinated pesticides were purchased from Riedel de Haen, the organophosphorus pesticides from Supelco, the polychlorobiphenyl 1232 from DANI, and the other substances from Merck. Standard solutions (0.1 mg/mL) were prepared by weighing the pure substances listed in Table I and dissolving them in an organic solvent. The solvent was chosen according to the solubility of the single compounds. Alcohols, acids, phenols, ketones, and aldehydes were dissolved in acetone, PAHs in acetonitrile, organophosphorus pesticides in methanol, chlorinated pesticides in benzene, hydrocarbons in hexane, and ethers and esters in diethyl ether. These solutions were used to make standard mixtures (5pg/mL) containing compounds of the same class. The solventa used for the preparation of the standard solutions were also used for their dilution. Portions of these standard mixtures were then diluted in water to give the test samples. Glass columns (0.5 cm i.d.) were packed with graphitized carbon black (200 or 100 mg). The adsorbent was held in place with small plugs of silanized glass wool. DuF’ont Model 840 liquid chromatograph with spectrophotometric detector at 254 nm was used. The analytical column was ODS Lichrosorb RP 18 Merck 10, mobile phase 100%methanol, flow 1.7 mL/min, pressure 70 atm. A Dani Model 3900 gas chromatograph with 63Nielectron capture detector (ECD) and flame ionization detector (FID) was used. The gas chromatographic columns used were as follows: (1)PEG 20M, 0.06 pg/m precoated with Carbopack A, 70 m X 0.25 mm i.d., n = 160000 for 7-BHC (~-1,2,3,4,5,6-hexachlorocyclohexane or Lindane) at 160 “C, k’ = 3.5. This column was used for the detection of chlorinated pesticides, organophosphorus pesticides, and PCBs. (2) PEG 20M 0.6 mg/m precoated with Carbopack A, 15 m X 0.25 mm i.d., n = 35000 for 2,4-dichlorophenol as 160 OC,k ’ = 11.2. This column was used for alcohols, aldehydes, esters, acids, phenols, and hydrocarbons. The test samples obtained from the dilution of the standard mixtures in distilled water (and in river water or in seawater in the case of chlorinated pesticides) were shaken for 10 min and left at rest for 30 min. Then they were put in a glass tank
0003-2700/80/0352-2033$01.00/00 1980 American Chemical Society
2034
ANALYTICAL CHEMISTRY, VOL. 52, NO. 13, NOVEMBER 1980
TnLle I. Adsorption of Model Organic Compounds from Aqueous Solution (500 m L ) on 200 mg of GCB compoundsa
adsorption, %
alcohols 1-hexanol 1-heptanol 1-octanol benzyl alcohol nonanol (i.s.)b polynuclear aromatic fluoranthene indeno[ 1,2,3-ccl]pyrene benzo[a] pyrene benzo [ b ] fluoranthene benzo[k] fluoranthene 4-methylpyrene ( i s . ) hydrocarbons pentadecane hexadecane octadecane heptadecane ( i s . ) acids caproic acid heptanoic acid octanoic acid (caprylic) decanoic acid (capric) nonanoic acid (i.s.) phenols o-nitrophenol 2,4-dichlorophenol 2,4,6-trichlorophenol p-chloro-rn-cresol p-chlorophenol ( i s . ) ethers anisole p-nitroanisole diphenvl ether p-methilanisole ( i s . ) PCBs arochlor 1 2 3 2 o,p'-DDE ( i.s.)"
0
32 100 0 100
100 100
100 100 0 0 0
100
100 100
100 100
100 100 100
100 100 100
100
compoundsa
adsorption, %
aldehydes and ketones acetophenone 2-undecanone benzaldehyde 2-decanone ( i s . ) esters methyl hexanoate methyl heptanoate methyl octanoate methyl decanoate heptanol (is.) aromatic hydrocarbons hexachlorobenzene 2,4-dinitrotoluene 2,B-dinitrotoluene 1,3-dinitrotoluene
87
100 43 0 0 0 0
100 100
100 100
1,2,4,5-tetrachlorobenzene (is.)
organophosphorus pesticides Di-syston Malathion Parathion Ronnel Aldrin ( i s . ) chlorinated pesticides a -Endosulfan p,p'-DDD a-BHC Heptachlor Aldrin y-BHC 0-Endosulfan Heptachlor Epoxide Rielclrin p,p'-DDE o,p'-DDD o,p'-DDE (is.)"
100 100 100
100 100 100 100 100 100 100 100 100 100 100 100
a Concentration of each compound: polynuclear aromatics and chlorinated pesticides, 5 pg/L; organophosphorus pesticides, 50 pg/L; aromatic hydrocarbons, PCBs, ethers, phenols, and hydrocarbons, 100 pg/L; esters, aldehydes, ketones, acids, and alcohols 200 pg/L. Internal standard. 1-(2-Chlorophenyl)-l-(4-chlorophenyl)-2,2-dichloroethylene.
connected to the adsorption column by a glass joint. The flow rate (4 mL/min) was regulated by a water pump. Aliquots of water solutions, before and after the passage through the adsorption column, were extracted with three equal volumes (20 mL each) of the solvent in a separatory funnel. The combined organic layers were dried with granular anhydrous sodium sulfate and, after an internal standard was added (selected according to the substances to be analyzed), were concentrated in a rotary evaporator and analyzed by either gas chromatography or HPLC. Chlorinated pesticides adsorbed by the GCB columns were desorbed by passing through the column aliquots of various solvents or solvent mixtures at the flow rate of a 1 mL/min. Residual water had been removed from the column by letting air pass through it for 5 min. The eluate, after adding the internal standard l-(2-chlorophenyl)-l-(4-chlorophenyl)-2,2-dichloroethylene ( o , p'-DDE) was evaporated and analyzed. Each experiment was performed three times and the quoted results are an average of the three experiments. In no case did values differ more than =t6% from the mean value.
RESULTS AND DISCUSSION Fifty-one different compounds including alcohols, acids, phenols, ethers, aldehydes, ketones, esters, hydrocarbons, pesticides, and PCBs were added to the water samples at concentrations ranging from 5 to 200 p p b depending on the class (see footnote a in Table I). These were used to obtain the adsorption data reported in Tables I-IV and Figures 1-3. Table I gives the percentage of the model organic compounds adsorbed out of 500 m L of the test solutions for each class when they were passed through fresh sorption columns (200 mg). T h e results obtained show that the amount of
Table 11. Breakthrough Volumes and Specific Retention Volumes for a-BHC in Different Samples
samples river water" seawatera drinking watera drinking waterb a Adsorbent GCB (100 mg). mg).
breakthrough volume, L 1
2 2.5 0.35
specific retention volume, L/g 15 26 30 6
Adsorbent Tenax (100
compounds adsorbed is neither t h e same for all classes nor for all substances in a single class. It is of interest to note that the chlorinated pesticides are among the compounds which are entirely adsorbed. In separate experiments i t was determined t h a t a-BHC shows 50% breakthrough from a 100-mg column after the passage of 3 L of distilled water while -y-BHC is present in the effluent only in traces after this volume has been passed. A large variation in retention of the chlorinated pesticides is observed when the source of the water is changed. Figure l a shows the gas chromatogram obtained for the benzene extract of a water solution containing 5 Ng/L of each of the chlorinated pesticides. Figure lb-d shows the chromatograms obtained on benzene extracts of the effluent after the passage, through 100-mg columns, of 3 L of similar solutions made up
ANALYTICAL CHEMISTRY, VOL. 52, NO. 13, NOVEMBER 1980
2035
Table 111. Recovery (%) of Chlorinated Pesticides Added t o Drinking Water Using Different Eluants pesticides
A
B
C
D
E
Q-BHC Heptachlor Aldrin r-BHC a-Endosulfan Heptachlor Epoxide Dieldrin Endrin p,p'-DDE o,p'-DDD 0-Endosulfan p,p'-DDD
69 53 53 84 83 85 96 97 82 58 60 52
73 65 58 86
69 48 67 83 95 86 85 75 73 56 70 43
95 65 99 83 95 95 91 83 82 58 77 60
80 70 85 88 87 88 70 69 67 50 59 49
100 87
98 103 87
65 101 71
recovery," % F G 105 90 102
79 39 67 74 82 80 81 75 73 87 96 78
100
98 97 89 87 78 66 72 67
H
I
L
M
N
82 46 68 78 86 84 78 63 76 66 87 75
110 74 92 101 94 95 87 75 75 66 81 74
107 58 103 99 105 100 80 62 78 53 45 38
94 90 82 89 90 94 95 86 80 80 87 75
101 93 102 102 98 99 103 104 93 95 100 92
a Key: A = 25 mL of pentane, B = 50 mL of pentane, C = 25 mL of benzene, D = 50 mL of benzene, E = 25 mL of hexane, F = 50 mL of hexane, G = 50 mL of benzene-diethyl ether ( l : l ) , H = 50 mL of benzene-acetone (2:1), I = 50 mL of hexane-acetone (2:1), L = 25 mL of benzene-hexane ( l : l )M , = 25 mL of hexane-diethyl ether ( l : l ) , N = 50 mL of hexane-diethvl ether (1:1). 3 I
I
a
1 ,
I 0
-1
4
+v
1
67
58
49
40
2
31
49
40
d
67
22
31
49
40
31
22
1
2
3
4
I
5 VOLUM E(lit e r s )
Flgure 2. Breakthrough curves of a-BHC on GCB column (100 rng):
1 13-10
Figure 2 shows the breakthrough curves ( C / C o ) of a-BHC.
C/C, is defined as the concentration of chlorinated pesticides
5
rnin
0
I
7
58
0
I
I1
I
58
rnin
I
(0) river water; (0)seawater; (A) drinking or distilled water.
1 67
5
13 10
7
C
I
05
7 b
13 10
5
min
0
Flgure 1. Chromatograms of chlorinated pesticides: 1, a-BHC; 2, Heptachlor; 3, Aldrin; 4, y-BHC; 5, a-Endosulfan; 6, Heptachlor Epoxide; 7, o.p'-DDE (internal standard); 8, Dieldrin; 9, Endrin; 10, p,p'-DDE; 11, o,p'-DDD; 12, @-Endosulfan; 13, p,p'-DDD; (a) before passage through the adsorbent column (100 mg GCB); (b) after the passage of drinking or distilled water (3 L); (c) after passage of seawater (3 L); (d) after the passage of river water (3 L).
in distilled water (Figure l b ) , seawater (Figure IC),and river water (Figure Id).
in the effluent divided by the chlorinated pesticides in the influent. T h e column was packed with 100 mg of GCB and three different kinds of water (drinking, river, and seawater) were used. T h e values of the specific retention volume and of the breakthrough volumes, shown in Table 11,were obtained from this plot. It can be seen t h a t the differences observed in the chromatograms are better evidenced in Table 11. These differences are ascribed to the effect of the composition of the examined solutions. In river water with methyleneblue anionic surfactants ( M B A S ) = 0.8 mg/L, oxygen consumption during oxidation with KMn04 (Kubel) = 4 mg/L, biochemical oxygen demand (BOD,) = 16 mg/L, and pH 6.5, and a decrease in the specific retention volume and in the breakthrough volume is observed. In this case the presence of surfactants improves the solubility of pesticides in water ( I 7)and consequently the recovery efficiencies decrease. A smaller effect can be seen in the recovery from seawater ( ( M B A S ) = 0.05 mg/L, (BOD5) = 16 mg/L). T h e NaCl present in the water sample causes a decrease of the solubility of the examined compounds which
ANALYTICAL CHEMISTRY, VOL. 52, NO. 13, NOVEMBER 1980
2036
Table IV. Recovery ( % ) of Model Organic Compounds from 100 mg of GCB with 50 mL of a n-Hexane-Diethyl Ether (1:1) Mixture compounds
recovery, %
alcohols 1-hexanol 2-heptanol 1-octanol benzyl alcohol acids caproic acid heptanoic acid octanoic acid decanoic acid phenols o-nitrophenol 2,4-dichlorophenol 2,4,6-trichlorophenol p-chloro-m -cresol aldehydes and ketones 2-undecanone acetophenone benzaldehyde ethers anisole p-nitroanisole diphenyl ether
100 100 100 100
67 78 80 82 90 67 43 42 90
95
36 99 100 101 5 0 0 0 0
95 97 100
90 30-40
95 100
50 on a Celite column before Tenax may be used successfully. The results shown in Table I11 give the recoveries obtained by using different eluants or solvent mixtures for the desorption of pesticides, after the passage of a 500-mL volume of water, containing 2.5 pg of each pesticide, through the column. The best mixture for the recovery of chlorinated pesticides is hexanediethyl ether (50:50);the recovery is generally 100% with 50 mL of eluant. The recoveries of the other substances using the same mixture (50 mL) are reported in Table IV. It must be pointed out t h a t the utilization of GCB is advantageous when there are PCBs in the water sample. In fact, the recovery of the PCBs from GCB using hexane-diethyl ether is very poor (40% for the boiling components) although their adsorption on GCB appears excellent. Interferences from PCBs in pesticide analysis are hence decreased.
/c,
A
aromatic hydrocarbons hexachloro benzene 2,4-dinitrotoluene 2,6-dinitrotoluene 1,3-dinitrobenzene polynuclear aromatics fluoranthene indeno[1,2,3-cd] pyrene benzo[a]pyrene benzo[ b ] fluoranthene benzo[h] fluoranthene organophosphorus pesticides Di-syston Malathion Parathion Ronnel PCBs Arochlor 1232
recovery, %
100
C
I t
compounds
A
LITERATURE CITED
1
2
3
4
5 VOLUME ( I i t e r s )
Flgure 3. Breakthrough curves of chlorinated pesticides on a Tenax column (100 mg): (0)a-BHC, y-BHC; ( * ) Endosulfan, Endrin, &Endosulfan, Dieldrin; (‘I Heptachlor ) Epoxide; (0)o,p’-DDD, p,p’DDE; (+) Aldrin; (A)Heptachlor.
partly compensates for the increase caused by the surfactants. The values t h a t give a measure of the efficiency of the adsorbent are less different from those obtained in drinking water. A comparison of the adsorption efficiencies of GCB and Tenax was carried out. Figure 3 shows the breakthrough curves obtained when distilled water containing chlorinated pesticides was passed through a column packed with 100 mg of Tenax. The specific retention volume for a-BHC on Tenax was much smaller than the one obtained with GCB. GCB is therefore a more effective adsorbent than Tenax, especially in nondrinking water treatment. In fact, in this case Leoni et al. (17) have shown that one must resort to a pretreatment
Dressler, M. J . Chromafogr. 1979, 165, 167. Fujll, T. J . Chromafogr. 1977, 139, 297. Rosen, A. A.; Mlddleton, E. M. Anal. Chem. 1959, 31, 1729. Buclow. R. W.; Carswell, J. K.; Symons, J. M. J.-Am. Wafer Works Assoc. 1973, 65. 195. (5) Chmil’, V. D. Zh. Anal. Khim. 1975, 30, 2444. (6) Mc Nel, E. E.; Otson, R.; MUes, W. F.; Rajabalee, F. J. M. J. cluomsfoq. 1978. 132, 277. (7) Junk, G. A.; Rlchard, J. J.; Grieser. M. D.; Wltiak, D.; Wltlak, J. L.; Arguello, M. D.; Vlck, R.; Svec, H. J.; Fritz, J. S.; Calder, G. V. J. Chromatogr. 1974, 99, 745. ( 8 ) Chriiwell, C. D.; Erlcson, R. L.; Junk, G. A.; Lee, K. W.: Fritr, J. S.; Svec, H. J. J.-Am. Wafer Works Assoc. 1977. 69, 669. (9) Van Rossum, C.; Webb, R. G. J . Chromafogr. 1978, 159, 381. (10) Gorettl, G.; Llberti, A,; Pill, G. HRC & CC, J. H@hResolut. Chromafogr. Chromafogr. Commun. 1078, 1 , 143. (11) DI Corcia, A.; Llbertl, A.; Samperl. R. J . Chromafogr. 1978, 167, 243. (12) Di Corcia, A.; Llberti, A. A&. Chromatogr. ( N . Y . ) 1976, 14, 305. (13) Colin, H.; Eon, C.; Guiochon, 0. J . Chromafogr. 1976, 122, 223. (14) Musty, P. R.; Nickiecs, G. J. Chromafogr. 1974, 89, 185. (15) Rees. G. A. V.; Au, L. Bull. Envlron. Confam. Toxlcol. 1979, 21, 561. (16) Musty, P. R.; Nickless, G. J. Chromatogr. 1974, 100. 83. (17) Leonl, V.; Puccetti, G.; Colombo, R. I.; D’Ovldb, A. M. J . Chromafogr. 1976, 125, 399. (1) (2) (3) (4)
RECEIVED for review February 4, 1980. Accepted J u n e 16, 1980. Work carried out with contributions from the National Council of Research (Italy).
