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Anal. Chem. 1990, 62, 1490-1494
(10) Lacy, N.; Christlen, 0.D.; Ruzicka, J. Ouim. Anal. 1989,8 , 201-209. (11) Ruzicka, J.; Hansen, E. H. Flow lnjectlon Analysis; 2nd ed.; Wiley-Interscience: New York, 1988;pp 303-309. (12) Hlrai. Y.; Yoza, N.; Osashi, S. Anal. Ch/m. Acta 1980, 715, 269-277. (13) Motomlzu, S.; Wakimoto, T.; Toel, K. Talanta 1983. 30, 333-338. (14)Hansen, E. H.; Ruzicka, J. Anal. Chim. Acta 1978,8 7 , 353-363. (15) Linares. P.; Luque de Castro, M. D.;Valcarcel, M. Anal. Chem. 1986, 58, 120-124. (16)Johnson, K. S.;Petty, R. L. Anal. Chem. 1982,5 4 , 1185-1187. (17) Llnares, P.: Luque de Castro, M. D.; Valcarcel, M. Talanta 1986. 33, 889-893. (18) Hart, E. A. personal communication, 1989. (19)Kolthoff, I. M.:Eking, P. J. Treatise on Ana/yt/cal chemistry; Interscience Publishers: New York, 1961;pp 317-394.
(20)Snell F. D.; Snell, C. T. ColormetricMs#mds of Analysk, 3rd ed.;Van Nostrand: New Yo&, 1949;Vol. 2,pp 660-671. (21) Kircher, C. C.; Crouch, S. R. Anal. Chem. 1983,55, 248-253. (22) Clark, G. D.;Christian, G. D.; Ruzicka, J.; Anderson, G. F.; VanZee, J. A. Anal. Instrum. 1989, 78, 1-21. (23)Sandell, E. B.; Onishi, H. PhotomeMc Determination of Traces of N e ments; 4th ed.; Wiley Interscience: New York, 1978;Chemical Analysis Series, Vol. 3,pp 249-256. (24)Sentell, K. B.; Dorsey, J. G. Anal. Chem. 1989, 67, 930-934. (25) Stone, M. J . R . Statist. SOC.6 . 1974,36,111-133. RECEIVED
for review January 17, 1990. Accepted April 17,
1990.
Determination of Chloroaniline Traces in Environmental Waters by Selective Extraction with Two Traps in Tandem and Liquid Chromatography Antonio Di Corcia* and Roberto Samperi
Dipartimento di Chimica, Universitci L a Sapienza di Roma, Piazzale Aldo Mor0 5, 00185 Roma, Italy
Selectlve llquld-solld extraction from environmental waters of 14 chloroanlllnes was achieved by uslng a two-trap tandem system, one contalnhg a nonspeclc adsorMng material, such as graphttlzed carbon black (Carbopack B), and the other one fllled with a resin-based strong catlon exchanger. After percolatlon through the Carbopack column (extractlon cartrldge) of water samples, the two traps were connected In serles, acetadtrHe ack#fted wlth HCI, 10 mmaUL, was allowed to flow along them, and chloroanlllnes displaced from the extractlon cartrldge were selectively readsorbed via hydrogen bondlng on the strong acld exchanger column (Isolation cartridge). After thls column was washed, the analytes were eluted from the lsolatlon cartrldge wlth 1 mL of aqueous acetonitrile basified with KOH, 0.1 mol/L. After sultable neutralzatlon, 0.2 mL of thls solution was dlrectty InJected Into the llquld chromatographlc apparatus, whlch was operated lsocratkally In the reverse-phasemode with UV detectlon at 240 nm. The analytlcal recoveries of the 14 chloroanlllnes were hlgher than 88%. The llmlts of detectability of the analytes consldered were well below 0.1 pg/L. The effectlveness In terms of recovery and selectlvity of the two traps In serles was compared wlth three other cartridges, which contalned a chemlcally bonded siliceous material (C,& Carbopack, and a catlon exchanger. These latter two cartrldges were the very same we used In tandem, but in thls case they were operated lndlvldually.
Aromatic amines may be present in the aquatic environment as a result of industrial discharges from factories using anilines as intermediates for the synthesis of special chemicals or as result of the degradation of some commonly used herbicides, such as phenylureas. Toxicological data are known for several aromatic amines and some are suspected to induce cancer (1,2). In this vein, the European Economic Community (EEC) has included many anilines in the list of priority pollutants which should be monitored in environmental *To whom correspondence should be addressed.
waters. Although several analytical schemes for the extraction, concentration, and detection of various basic compounds in water have appeared in the literature (3-6), several aniline derivatives, such as monochloro-, dichloro-, and methylchloroanilines are still included in that particular class of pollutants for which a reliable analytical procedure able to detect them a t 0.1 pg/L in water is unavailable. Various, additional reasons contribute to make conventional analytical schemes inadequate to the trace determination of aromatic bases. Firstly, the hydrophilic nature of these compounds results in partial extraction from relatively large water volumes by using either solvent or solid-phase extraction (7). Secondly, severe losses of the more volatile anilines may take place during the solvent removal step performed to increase the enrichment factor. Thirdly, the adoption of nonselective extraction procedures is ultimately reflected in great complexity of the final chromatogram when the simultaneous analysis of variously substituted anilines is performed. To enhance selectivity, extraction procedures of aromatic bases from water by cation exchangers have been proposed (8-11). However, these methods generally have detection limits higher than 1pg/L. Nielen et al. (12)reported a high-performance liquid chromatography (LC) procedure for determining traces of aromatic bases that involves on-line preconcentration on a short precolumn filled with a strong acid exchanger. This method, however, requires a sample pretreatment to eliminate calcium ions and it seems unsuitable for preconcentrating very weak bases, such as halogen ortho substituted anilines. The combination of on-line preconcentration by means of a nonselective adsorbent and LC subfractionation with electrochemical detection was found effective for determining four aromatic amines spiked in seawater samples (13). Because of a severe baseline deflection resulting from the sample back flushing onto the analytical column, this method appears to be uneffective for assaying aromatic amines at the level of 0.1 E/L. Recently, the isolation of triazine herbicides, which are weak bases, from an acetone extract of soil has been accomplished by exploiting the hydrogen bond formation between triazines and the acidic sites of a strong cation exchanger (14). More recently, a double trap tandem system, consisting of a cartridge
0003-2700/90/0362-1490$02.50/00 1990 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 62, NO. 14, JULY 15, 1990
filled with a nonspecific adsorbent, that is graphitized carbon Black (Carbopack B), connected in series with another containing a silica-based cation exchanger, succeeded in extracting and isolating triazines from large volumes of actual water samples (15). The object of this work was that of extending the use of the double trap assembly to the extraction and purification of traces of organic bases in environmental waters. In particular, we paid attention to chloroanilines, as their determination at the parts-per-trillion level is a challenging problem. EXPERIMENTAL SECTION Reagents. Authentic chloroanilines were of more than 90% purity and supplied by Fluka, Merck, and Aldrich. They were used as supplied for the preparation of 1g/L and 10 mg/L stock solutions in methanol. Working standards were prepared daily by adding aliquots of the stock standards to water samples. Hydrazine sulfate was of analytical-reagent grade (Carlo Erba, Milan, Italy). A 200-mg portion of hydrazine sulfate was dissolved in 200 mL of water and this solution was neutralized by adding 160 mg of sodium carbonate. For LC, deionized water was purified by passing through a Norganic cartridge (Millipore, Bedford, MA). Working phosphate buffer (10 mmol/L, pH 7) was prepared from analytical grade reagents (Carlo Erba). Before use, the buffer solution was filtered (0.45 pm pore size). LC grade acetonitrile (Carlo Erba) was used as supplied as organic modifier to the mobile phase. Before use, all phases were thoroughly mixed and degassed by sonication. The mobile phase was recycled by connecting directly the outlet of the analytical column to the mobile-phase-containing reservoir. This mobile-phase batch was discarded after 3 weeks of continuous use. Apparatus. A 150-mgportion of Carbopack B (120-400 mesh) was packed in polypropylene tubes 6 cm X 1 cm i.d. A 200-mg portion of the resin-based cation exchanger, Amberlite CG-120-11 (200-400 mesh), was packed in a plastic tube 6 cm X 0.5 cm i.d. Polyethylene frits (20 pm pore size) were located above and below each sorbent bed. The connection between the two traps was realized by a plastic adapter. Except for the exchanger material, which was from Fluka AG, Buchs, Switzerland, all other materials cited above were kindly supplied by Supelco, Bellefonte, PA. Before use, the cation exchanger material was converted from the Na form to the H form by washing with 10 mL of HCl(1 mol/L), 3 mL of water, and 3 mL of acetonitrile. The two cartridges were fitted into side-arm filtering flasks and liquids were forced through the cartridges by vacuum from a water pump. Procedure. Artificially polluted water samples were prepared by adding known volumes of the working standard solution and agitating the water for 1 min to ensure complete solution of the chloroanilines. The organics from the water samples were then adsorbed onto the Carbopack surface by passing the sample through the trap at a flow rate of about 30 mL/min. Then, the sample reservoir was disconnected and 3 mL of distilled water was percolated through the cartridge in order to remove water sample drops stuck on the plastic walls of the cartridge. The major part of water was removed from the cartridge by drawing room air through it by vacuum for 1min. The content of water, which can affect readsorption of the least basic chloroaniline, that is 2,6-dichloroaniline, was further decreased on the Carbopack surface by passing slowly 0.3 mL of acetonitrile/water (5050, by volume). Air was again forced through the trap by vacuum for 1 min. After this, the Carbopack cartridge was connected to the cation exchanger, and chloroanilines were moved from the Carbopack surface to the exchanger surface by passing 2.8 mL of acetonitrileacidified with HCl, 10 mmol/L, at a flow rate of about 2 mL/min. The two cartridges were then disconnected and the strong acid exchanger was washed with 0.5 mL of acetonitrile, whose residue was removed by drawing air for 1 min. A second washing of the exchanger cartridge was carried out by passing through it 1.3 mL of KOH, 1 mol/L. Chloroanilines were then eluted by percolating through the cartridge acetonitrile/water (6040, by volume) basified with KOH, 0.1 mol/L, at a flow rate of 0.5 mL/min. The 1-mL extract collected was neutralized with 1.2 mL of H3P04 (50 mmol/L), and 0.2 mL of the resulting
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Table I. Accuracy and Precision of the Method with High, Medium, and Low Chloroaniline Contents in 200-mL Distilled Water Samples % recovery f standard deviation"
0.2 rg/L p-chloroaniline rn-chloroaniline o-chloroaniline 4-chloro-2-methylaniline 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2-chloro-4-methylaniline 2-chloro-6-methylaniline 3,4-dichloroaniline 2,3-dichloroaniline 2,4-dichloroaniline 2,5-dichloroaniline 2,6-dichloroaniline 3,5-dichloroaniline a
93.1 f 4.11 101.6 f 4.18 102.1 f 3.62 96.5 f 2.65
2 rg/L
20 r g l L
97.5 f 1.89 96.3 f 2.13 98.5 f 1.71 96.8 k 1.34
86.6 f 3.47 87.2 f 2.95 87.6 f 2.57 92.3 k 2.65
99.2 f 3.43 100.8 f 1.67
99.9 i 1.99
100.8 f 2.82 100.2 f 1.07
98.3 f 2.27
105.4 f 4.84 101.5 f 2.01
95.2 f 2.41
97.4 f 3.05
99.5 f 1.11 100.2 i 1.37
96.0 f 2.12 99.3 f 1.60 97.7 f 1.25 98.8 f 1.79 98.8 f 1.07 99.0 f 1.71 97.5 f 3.53 100.2 f 1.42 98.5 f 1.61 101.0 f 3.03 97.2 f 2.03 96.5 f 2.31 88.6 f 5.08 89.9 f 4.64 72.1 f 7.12 105.9 f 2.84 102.0 f 1.15 100.5 f 1.54
Standard deviations calculted from six determinations.
solution was injected into the HPLC apparatus. LC Apparatus. A liquid chromatograph, Model 5000 (Varian, Walnut Creek, CA), equipped with a Rheodyne Model 7125 having a 0.2-mL loop and a 2550 UV detector (Varian) was used. A 25 cm X 4.6 mm i.d. column filled with 5-11 LC-18-DB reversed-phase packing (Supelco) was used. The mobile phase was a premixed phosphate buffer/acetonitrile (64:36, by volume) and the flow rate was 1.5 mL/min. Chloroanilines were monitored with the UV detector set at 240 nm. RESULTS AND DISCUSSION Initially, following a recently reported extraction procedure for analyzing triazine herbicides in water (15),a Carbopack cartridge was used in tandem with one containing a silicabased sulfonic acid type cation exchanger for the extraction from water and purification of chloroanilines. By this device, however, a low recovery of the ortho-substituted dichloroanilines was obtained, as the low-capacity (0.27 mequiv/g) acidic exchanger was unable to reextract such very weak basic compounds from the eluant system flowing down from the Carbopack cartridge. This obstacle was removed by replacing the silica-based acidic exchanger with a resin-based exchanger, that is Amberlite CG-120-11, which has a much higher capacity, namely 3.9 mequiv/g. Accuracy and Precision. The analytical recovery and the precision of this method a t high, medium, and low concentrations of chloroanilines in water were assessed. Two hundred milliliter aliquots of distilled water were spiked with different volumes of the stock solutions to obtain individual concentrations of the analytes considered, 0.2, 2.0, and 20 pg/L, respectively. Each water sample was then analyzed 6 times. Typical quantitative results, reported in Table I, show that the extraction efficiency of the double trap tandem system was independent upon the chloroaniline concentrations, thus demonstrating the absence of any adverse effect of irreversible adsorption by the materials composing the two cartridges. The slight loss of 2,6-dichloroaniline occurring on analyzing the water sample containing chloroanilines a t the highest concentrations considered was likely due to partial displacement of the least basic of the chloroanilines from the adsorption sites of the exchanger material by the other analytes. Matrix Effect. Although solid-phase extraction procedures by small cartridges have become popular during the last decade, this technique suffers mainly from the disadvantage that, when sampling large volumes of contaminated aqueous
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ANALYTICAL CHEMISTRY, VOL. 62, NO. 14, JULY 15, 1990
Table 11. Recovery of Chloroanilines at Different Ground-, River, and Seawater Volumes SampledD ground river water seawater water -~~
p-chloroaniline m-chloroaniline o-chloroaniline 4-chloro-2-methylaniline 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2-chloro-4-methylaniline 2-chloro-6-methylaniline 3,4-dichloroaniline 2,3-dichloroaniline 2,4-dichloroaniline 2,5-dichloroaniline 2,6-dichloroaniline 3,5-dichloroaniline
200
500
200
500
mL
mL
mL
200 mL
500
mL 99 99 97 102 101 101 98 99 98
80 85 82 96 97 100 101 100 101 100 101 100 75
98 96 95 100 97 98 97 100 102 97 98 97 88 103
47 52 51 97 99 100 101 102 95 96 98 102 70 100
96 100 97 98 97 97 96 98 101 99 99 95 85 102
37 38 36 96 97 97 100 99 103 100 100 99 48 102
100
99 98 90 100
100
mL
Water samples were spiked with 1gg/L of each compound. *Mean values obtained from triplicate measurements.
environmental samples, saturation effects by organics present in water may provoke abrupt and unpredictable decreases of the breakthrough volumes of the analytes of interest, as measured by extracting them from pure water. The matrix effect on the recovery of chloroanilines was assessed by adding them to actual water samples supposed to have different total organic carbon (TOC) levels, that is river, sea-, and groundwaters, and analyzing. Seawater was sampled very near the outlet of the river considered (Tevere). The pH of the river, sea-, and groundwater specimens were 8.1, 7.8, and 7.1, respectively. TOC levels of 6.5, 1.7, and 0.9 mg/L were measured for the river, sea-, and groundwater samples. Results are reported in Table 11. Among the chloroanilines, monochloroanilines have the highest mobilities on Carbopack, whereas 2,6-dichloroaniline has the highest mobility on the cation exchanger material. Therefore, recovery data show that, when extracting 500 mL of an aqueous sample having a high degree of organic contamination, both the Carbopack and the cation exchanger cartridges may be saturated by organics present in the real water sample. In any case, an accurate determination by this method of chloroanilines can be performed by extracting no more than 200 mL of an aqueous environmental sample, whatever its origin may be. Limits of Detection. By extraction of 200 mL of water, the limits of detection of this method (signal-to-noise ratio equal to 3) were estimated to be within the range between 9 and 50 ng/L, the minimum and maximum figures referring to the first and latter chloroanilines eluted from the LC column. Method Comparison. The extraction efficiency of the two-trap assembly was compared with those obtained by using both a 0.5-g octadecyl-bonded silica (CIS)disposable cartridge (Supelco) and a cation-exchanger-containing cartridge. This latter was the very same we used in association with the Carbopack cartridge. The exchanger material was converted to the H form prior to use. For these experiments, 200-mL aliquots of a groundwater sample were supplemented with chloroanilines at the individual concentrations of 5 wg/L. The analytes adsorbed on the chemically bonded silica surface were completely eluted with two 1-mL aliquots of methanol which were diluted with an equal volume of water before LC quantitation. After water removal by drawing room air through the cartridge, desorption of chloroanilines from the exchanger surface was carried out in the same way as described under the Experimental Section. Recovery data reported in Table I11 show that the CI8 cartridge failed to retain quantitatively the most hydrophilic chloroanilines, such as the
9
I I
-1 L 5
0
15 20 t i m e (min)
10
G
A
2+D
'I
4
1
0
5
I 10
7
I I 15 20 t i m e (min)
Figure 1. Chromatograms obtained on sampling 200 mL of groundwater spiked with 0.5 pg/L concentrations of the chloranilines and some interfering compounds by this method (A) and by the Carbopack cartridge alone coupled with EC detection (B): 1, p-chloroanlline; 2, m-chloroaniline; 3, o-chloroaniline; 4, 4-chloro-2-metylaniline; 5, 3chloro-2-methylaniline; 6, 5-chloro-2-methylaniline; 7, 2-chloro-4methylaniline; 8, 2-chloro-6-methylanillne; 9, 3,4dichloroaniline; 10, 2,3-chloroaniline; 11, 2,4dichloroaniline; 12, 2,5dichloroaniline; 13, 2,6dichloraniline; 14, 3,5dichloroaniline;A, metribuzin; B, o-chlorophenol; C,p-chlorophenol; D, N-methylaniline; E, atrazine; F, chlortoluron; G, 2-naphthylamine; H,diuron; I , monolinuron; J, p-chloro-mcresol; K, propazine; U, unknown compounds from the plastic cartridges.
ANALYTICAL CHEMISTRY, VOL. 62, NO. 14, JULY 15, 1990
Table 111. Recovery of Chloroanilines from 200-mL Groundwater Samples by the Proposed Method Compared with Those from Two Other Extraction Methods % recovery’ this method cation exchanger C18
p-chloroaniline m-chloroaniline o-chloroaniline
4-chloro-2-methylaniline 3-chloro-2-methylaniline 5-chloro-2-methylaniline 2-chloro-4-methylaniline 2-chloro-6-methylaniline 3,4-dichloroaniline 2,3-dichloroaniline 2,4-dichloroaniline 2,5-dichloroaniline 2,6-dichloroaniline 3,5-dichloroaniline
25 18 5 34 28 27 30 34 27 15 22 12 ndb 16
54 36 35 89 92 92 90 85 87 85 93 90 72
95 97 96 96 96 97 94 99 101 99 96 97 87 103
88
Mean values obtained from triplicate measurements. detected.
nd, not
Table IV. Retention Times (min) of Chloroanilines and Potentially Interfering Compounds compound metribuzine o-chlorophenol p-chloroaniline p-chlorophenol carbofuran rn-chloroaniline N-methylaniline o-chloroaniline atrazine chlortoluron fluormeturon carbaryl 2-naphthylamine 4-chloro-2-methylaniline diuron monolinuron diazinon 3-chloro-2-methylani1ine
retention time, min 6.6 6.6 7.2 7.5 7.9 7.9 8.0 8.4 9.0 9.1 9.4 9.4 10.0 10.9 11.3 11.3 11.4 11.6
compound
retention time, min
5-chloro-Z-methylaniline 3,3’-dichlorobenzidine paraoxon p-chloro-n-cresol 2-chloro-4-methylaniline metobromuron 2-chloro-6-methylaniline propachlor 3,4-dichloroaniline propham propazine 2,3-dichloroaniline propanil 2,4-dichloroaniline 2,5-dichloroaniline 2,6-dichloroaniline dichlobenil 3,5-dichloroaniline
12.5 12.6 12.8 12.8 13.1 13.1 13.7 14.0 14.2 14.4 15.1 16.3 17.9 18.2 19.2 19.6 19.8 20.2
monochloroanilines. The cation exchanger trap was unsuitable for extracting chloroanilines from relatively large volumes of untreated real water samples. The elimination of calcium by precipitation with oxalic acid improved significantly the performance of the exchanger cartridge, but results comparable with those obtained by the two-trap tandem system were attained only by extracting chloroanilines from 200 mL of deionized water. It appears that the role played by Carbopack, when associated to an exchanger material, is mainly that of eliminating any inorganic ion so that the unique feature of the latter material, that is selectively, can be fully exploited.
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Interferences. Under the chromatographic conditions selected, 70 organic pollutants (herbicides, insecticides, fungicides, intermediates, and final industrial products) which may be present in the aquatic environment were tested for possible interferences with the analysis of chloroanilines. Many of the compounds tested are considered as priority pollutants in Europe and/or in the United States. Table IV lists the chromatographic retention times of those compounds having mobilities in the LC column similar to those of the chloroanilines. As observed by dissolving these pollutants in water and analyzing, the double cartridge tandem assembly effectively eliminates acidic and neutral organic compounds, except metribuzin, atrazine, propazine, N-methylaniline and 2-naphthylamine, which are weakly basic in nature. Of these, only N-methylaniline interferes with the analysis of mchloroaniline, as they produce overlapping peaks. Although basic in nature, 3,3’-dichlorobenzidine does not interfere with the analysis of 5-chloro-2methylaniline, as the eluant system selected for eluting chloroanilines from the Carbopack cartridge was uneffective for desorbing the benzidine derivative. As compared to UV detection, electrochemical (EC) detection has been reporeted to have a higher sensitivity and better selectivity for aniline (12). On the other hand, the former detector offers the advantages over the latter of being of prompt use, and its performance is virtually unaffected by a prolonged use. For the purpose of comparison, groundwater samples were spiked with both chloroanilines and those organic compounds we considered as potential interferences at the individual concentrations of 0.5 pg/L. Two hundred milliliter aliquots of this water specimen were then analyzed by the method under discussion, which involves the use of UV detection, and by a conventional three-step analytical procedure, that is extraction of the analytes by the use of a Carbopack cartridge alone, elution of the analytes by acidified acetonitrile and concentration by partial solvent removal of the extract, and quantification by LC with EC detection. The EC detector was a dual porous electrode system (Coulochem Model 5010, ESA Associates, Bedford, MA) which was operated by setting the first and second electrodes at potentials of +0.1 and +0.8 V, respectively. To avoid severe evaporative sample loss during the solvent concentration step, the acetonitrile extract was further acidified before solvent removal under a nitrogen stream and then neutralized before HPLC quantitation. Figure 1shows typical chromatograms obtained by the two analytical methods. As can be seen, the analytical procedure we propose appears even less prone to positive bias than that involving the use of a single extraction cartridge and selective detection. This is because some phenols and phenylurea herbicides, which are washed out by the two traps in series, coelute with chloroanilines by the use of a single trap and are monitored by the EC detector. Finally, it was observed that the difference in sensitivity for anilines between the two detectors was in practice largely attenuated by the fact that, when using the EC detector, the maximum volume of the final extract injectable into the HPLC apparatus
Table V. Recovery of Some Selected Chloroanilines Extracted from Groundwater Samplesa with Carbopack Cartridges after Storage under Different Conditions
p-chloroaniline rn-chloroaniline o-chloroaniline 4-chloro-2-methylaniline 2,5-dichloroaniline
hvdrazine-treated water l h 24 h 170 h
% recoveryb hydrazine washing l h 24 h 170 h
98 100 102 97 97
96 99 98 95 102
95 98 99 95 101
92 98 96 94 98
Groundwater samples spiked with 0.5 U K / L of each chloroaniline.
97 98 100 97 100
93 98 101 95 101
l h 78 88 97 93 104
no hydrazine 24 h 170 h 36 55 75 47 96
Mean values obtained from triplicate measurements.
15 33 56 22 86
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ANALYTICAL CHEMISTRY, VOL. 62, NO. 14, JULY 15, 1990
without provoking a prolonged base-line instability was about 5 times less than that injectable into the HPLC apparatus equipped with the UV detector. Sample Storage. Compared to the classical solvent extraction technique, that based upon liquid-solid extraction by small cartridges offers the advantage of being adaptable to field use. After extraction, the light-weight cartridge can be shipped to the laboratory for analyte desorption. Recently we found (16) that benzidine extracted from water by a Carbopack cartridge and stored on the adsorbent was uncompletely desorbed by organic solvents, unless hydrazine was added to the water sample before extraction. With this in mind, storage experiments were accomplished by spiking a groundwater sample with some selected chloroanilines at the individual concentrations of 0.2 Fg/L. This sample was then divided in two parts, and to one of the two, hydrazine sulfate and Na2C03, 1 and 0.8 g/L respectively, were added. Thereafter, 200-mL aliquots of the two water samples were extracted by Carbopack cartridges. Just after extraction, an aliquot of the Carbopack cartridges used for extracting chloroanilines from hydrazine-unspiked water was treated with hydrazine. This operation was carried out by passing through the cartridges 3 mL of the hydrazine solution prepared as reported in the Experimental Section, allowing the cartridges to remain wet during stroage by stopping the flow when the level of the solution was a few millimeters above the head of the Carbopack bed. All cartridges were then sealed and stored in the laboratory at room temperature, by analyzing them periodically over 2 weeks of storage. Before the organic solvent desorption, each cartridge was washed with 3 mL of deionized water, which was removed by drawing room air for 1min. This operation is particularly important for cartridges containing hydrazine, as it competes with chloroanilines for subsequent readsorption on the exchanger surface. Results reported in Table V show that chloroanilines extracted from the groundwater sample without added hydrazine and stored in hydrazine-unwashed Carbopack cartridges were increasingly lost during storage. Vice versa, no sample degradation took place during storage on the adsorbent having hydrazine adsorbed on its surface.
The preservative effect of hydrazine is, probably that of deactivating particular active centers contaminating the Carbopack surface and able to react slowly with anilines (17). Registry No. p-Chloroaniline, 106-47-8; rn-chloroaniline, 108-42-9;o-chloroaniline,95-51-2;4-chloro-2-methylaniline, 9569-2; 3-chloro-2-methylaniline, 87-60-5; 5-chloro-2-methylaniline, 95-79-4; 2-chloro-4-methylaniline, 615-65-6; 2-chloro-6-methylaniline, 87-63-8; 3,4-dichloroaniline, 95-76-1; 2,&dichloroaniline, 608-27-5; 2,4-dichloroaniline, 554-00-7;2,5-dichloroaniline, 95-82-9; 2,6-dichloroaniline, 608-31-1; 3,5-dichloroaniline,7732-18-5; water, 7732-18-5. LITERATURE CITED (1) Scott, T. S. Carcinogenic and Toxic Hazards of Aromatic Amines; Elsevier Publishing: New York, 1962. (2) Sender. J. H. Occupational Safety and Health Standards. Fed. Resist. 1974, 3 9 , 3756-3797. (3) Riggin, R. M.; Howard, C. C. Anal. Chem. 1979, 57, 210-214. (4) Bowman, M. C.; King, J. R.; Holder, C. L. Int. J . Environ. Anal. Chem. 1978, 4 , 205-211. (5) Coutts, R. G.; Hargesheimer, E. E.; Pasutto, F. M.; Backer, G. B. J . Chromatogr. Sci. 1981, 19. 151-155. (6) Kulikova, G. S.; Kirichenko. V. E.; Pashkevich, K. I . Zh. Anal. Khim. 1919. . 790-793. ... ., 3 .4 ., . . -. (7) Rostad, C. E.; Pereira, W. E.; Ratcliff, S. M. Anal. Chem. 1984, 56, 2856-2860. (8) Kaczvinsky, J. R.; Saitoh, K.; Fritz, J. S. Anal. Chem. 1983. 55, 1210-1 215. (9) Stuber, H. A.; Leenheer, J. A. Anal. Chem. 1983, 55, 111-115. (10) Riggin, R. M.: Cole, F. T.; Billets, S. Anal. Chem. 1983, 55, 1862- 1865. (11) Riggin, R. M.; Howard, C. C. J . Li9. Chromatogr. 1983, 6 , 1897-1903. (12) Nielen, M. W. F.; Frei, R. W.; Brinkman, U. A. T. J . Chromatogr. 1984, 317, 557-567. (13) Varney, M. S.: Preston, M. R. J. Chromatogr. 1985, 348, 265-274. (14) Battista, M.; Di Corcia, A.; Marchetti, M. J . Chromatogr. 1988, 454, 233-242. (15) Battista, M.: Di Corcia, A.; Marchetti, M. Anal. Chem. 1989, 67, 935-939. (16) Di Corcia, A.; Liberatori, A.; Marchetti, M.; Samperi, R. proceedings of the Workshop Organic Micropollutants In the A9uatk Environment, Berlin, Oct 1986; Commission of the European Communities: Bruxelles, 1987; pp 103-116. (17) Campanella, L.; Di Corcia, A,; Samperi, R.; Gambacorta, A. Mater. aChem. 1982, 7 , 429-438.
RECEIVED for review November 27, 1989. Accepted March 2 , 1990.
