2988
Anal. Chem. 1984, 56,2988-2990
Table I. TOCl in Sludgea
total chlorideb extractable chloride' TOCl
n
X
9
5 3
2340 360 1980
160 80 180
Milligrams per kilogram (oven dry weight). sludge. In 0.1 M NaN03.
In combusted
combusted under 30 atm of oxygen in a Paar stainless steel bomb containing 5.0 mL of 5% (w/v) sodium carbonate. The residue was rinsed into a volumetric flask with distilled deionized water and diluted to 100 mL. To extract the inorganic chloride the moisture content of an aliquot of the wet sludge was adjusted to 900% with distilled deionized water. Sufficient sodium nitrate was added so that its concentration in water was 0.1 M. The mixture was then blended for 10 min in a Waring Deluxe Model blender operated at its highest speed. The extracting solution was separated from the solids by centrifugation at 8000g and decanted for chloride analysis. The chloride was measured in the combustate and in the 0.1 M NaN03 extract with an Orion Model 9417B chloride electrode by using the method of standard addition. An aliquot of the sludge was also spiked with pentafluorophenol, phenol-d6, and naphthalene-d8 at the rate of 100 wg/g, blended with acidified anhydrous sodium sulfate, and Soxhlet extracted with methylene chloride for 16 h. The extract was concentrated and analyzed by HRGC/MS using a Hewlett-Packard Model 5992 equipped with an Ultra No. 1 (Hewlett-Packard) fused silica column (25 m X 0.33 mm i.d.). The column was temperature programmed from 40 to 270 "C at 8 OC/min with initial and final hold times of 2 and 20 min, respectively. The helium carrier gas flow rate was set at 5 mL/min. A "splitless" injection technique was used. The Soxhlet apparatus and the volumetric glassware were thoroughly rinsed with methanol and methylene chloride prior to use. All other glassware and the sodium sulfate were heated at 400 O C for 2 h prior to use. The methylene chloride used was Baker pesticide residue analysis grade. The spiking compounds were obtained from Aldrich. Reagent blanks were tested in each set of analyses.
RESULTS AND DISCUSSION The results of the TOCl analysis of replicate subsamples of the sludge are reported in Table I. TOCl was determined as the difference between the total chloride after combustion and the extractable chloride.
Notably no halogenated hydrocarbons were detected in the HRGC/MS analysis at an estimated method detection limit of 10 mg/kg (oven dry weight) for pentachlorophenol. The recovery of the spiking compounds was 115%, 19%, and 25% for the naphthalene-da, phenol-d,, and pentafluorophenol, respectively. The chlorinated organic compounds in this waste were not detectable using gas chromatographic conditions similar to those described by Nulton et al. for HRGC/MS analysis of benzene extrack of solid waste (2). Similar HRGC conditions have also been described for the analysis of the semivolatile organic priority pollutants ( 3 ) . The identity of the chlorinated organics is unknown; however, it is likely that they are relatively high molecular weight products of lignin chlorination. Lindstrom et al. have found, for example, that 95% of the TOCl in the effluent of the "E" stage in a pulp mill bleachery was in a molecular weight range greater than lo00 (4). Fifty-five percent was in a range greater than 25000. The molecular weight range was assigned by ultrafiltration and TOCl measured by oxygen bomb combustion. They also found that chemical degradation of the chlorinated organic compounds with potassium permanganate and sodium periodate in an alkaline medium yielded chlorinated guaiacols, catechols, phenols, and related compounds.
ACKNOWLEDGMENT I thank Stanley Johnson for performing the TOCl analyses. This work was performed while I was employed by the State of Maine, Department of Environmental Protection. Registry No. Chlorine, 7782-50-5.
LITERATURE CITED (1) Fed. R8gkt. 1979, 44, 179. (2) Nulton, C. P.; Haile, C. L.; Redford, D. P. Anal. Chem. 1984, 56, 598-599. .._ ...
(3) Sauter, A. D.; Betowski, L. D.;Smith, T. R.; Strlckler, V. A.; Belmer, R. G.; Colby, 8. N.; Wliklnson, J. E. HRC CC, J . H@h Resolut. Chromatogr. Chromatogr. Commun. 1981, 4 , 366-384. (4) Llndstrom, K.; Nordin, J.; Osterburg, F. I n "Advances in the Identification and Analysis of Organlc Pollutants in Water"; Keith, L. H., Ed.; Ann Arbor Science: Ann Arbor, MI, 1981; Vol. 2, pp 1039-1056.
Thomas L. Potter State of Maine Department of Environmental Protection Augusta, Maine 04333 RECEIVEDfor review May 25,1984. Accepted August 3,1984.
T * -Dipolarity
Numbers and a-Scale Acidities of Some Strong Hydrogen Bond Donor Solvents
Sir: An important analytical dimension to the separation and the determination of ionic species using equilibria in a nonaqueous medium is the choice of suitable parameters for the quantitative specification of the characteristics of the solvent itself. Of the several phenomenological scales measuring solvent properties, the Kamlet-Taft "linear solvation energy relationship" (the linear free-energy function in eq 1) has been more successful in correlating solvent effects among a wide range of chromatographic and kinetic equilibria as well as resolving the influences on the more fundamental thermodynamic and spectral quantitites for solutes in nonaqueous media (1). In this system the magnitude of the observable P = Po s(a* d6) aa + bp (1)
+
+
+
P is determined by these major properties of the solvent: the
hydrogen bond donor acidity (a), the hydrogen bond acceptor basicity (B), and the dipolarity of the solvent molecule ( r * ) . The d6 term is a solvent polarizability correction having a nonzero value for polyhalogenated alkanes and aromatics ( I ) . The preceding segments in this series of investigations have dealt with the analytical validity of the Kamlet-Taft parameters when applied to the electrochemical and solvatochromic behavior of organometallic species in differing nonaqueous solvents (2,3) as well as with the development of new probes for the measurement of solvent dipolarities (4-6). Among the latter, it was demonstrated that the nitrogen-15 NMR shifts for benzonitrile could be used effectively to evaluate both the a* and a parameters for moderate-to-weak hydrogen bonding solvents (6). The objectives of the present communication are twofold to report the extension of the previous techniques
0003-2700/84/0356-2988$01.50/00 1984 Amerlcan Chemical Soclety
ANALYTICAL CHEMISTRY, VOL. 56, NO. 14, DECEMBER 1984
Table I. Values for Kamlet-Taft Parameters at 25 O C 7r*-
(expt1)O r*(litJb r*(calcd)c a(exptl)d a(litJb Aprotic and Weak HBD Solvents 0.50 0.39 0.58
n-butyl chloride sec-butyl chloride tert-butyl chloride n-propyl chloride isopropyl chloride acetaldehyde acetone 2-butanone 3-pentanone
0.54
0.56
0.60
0.61
0.55
0.55
0.58
0.59
0.59 0.70 0.69 0.70
formic acid acetic acid propionic acid n-butyric acid 2-chloroethanol 2-fluoroethanol 2,2-difluoroethanol 2,2,2-trifluoroethanol
0.71 0.67 0.72
0.58 0.65 0.69 0.71
Strong HBD Solvents 0.78 0.67 0.64 0.62 0.60 0.83 0.76
0.08
0.05 1.88
1.14 1.06 1.04 1.04
1.12
0.97
0.72
1.40
0.78 0.75
0.00
0.10 0.07
1.53
0.73
1.51
"Overall uncertainty in these results is k0.014.02 (SD)for non-hydrogen-bonding solvents and f0.03 for HBD liquids. Most recent values reported by Kamlet, et al. (1). cComputed values using eq 2. duncertainties are 10.02 for weak HBD and f0.044.07 (SD)for strong HBD solvents. and probes to a series of additional strong hydrogen bond donor solvents and to further test a predictive equation for T* developed by Bekarek (7) and in this case using the continuously tunable polarity of a cosolvent system. Since no new experimental methods were used for this study, readers should consult the earlier published work for the procedural details. All of the reagent grade solvents used were purified by standard methods (8).
RESULTS AND DISCUSSION In the earlier portions of this series (4-6) the selected solvents were a random mix of differing types of non-hydrogen-bonding liquids representing a wide variety of hydrocarbons and functional groups. Thus, the first test in the present investigation was to reexamine the validity of the earlier probes and their regression functions by determining a* values for a set of closely related solvents; the lower monochloroalkanes and ketones were chosen for that purpose (with the assumed zero for the d6 term). The new and amended a* numbers for these nine solvents are included in Table I. Here, the composite precision for the set is based upon results from the three structurally dissimilar probes (i.e., phenol blue, 1-methyl-4-acetylpyridinyl radical, and benzonitrile) and is slightly greater than that reported previously, as would be expected for more restricted solvent species having functional groups in common. As an added check upon the experimental a* values for the aprotic and very weak HBD solvents, calculated a* numbers are listed in Table I which were obtained from the most reliable of the theoretical Bekarek functions ( 7 ) T*(calcd) = 14.65
(r
- l)(n2 - 1)
(2r + 1)(2n2
+ 1)
1
- 0.573 (2)
2989
In eq 2 t is the dielectric constant and n is the index of refraction for the alkane or alkyl derivative. The agreement between the a*(exptl) and a*(calcd) for the non-hydrogenbonding solvents in Table I is similar in magnitude to that reported by Kamlet et al. ( I ) as well as by Bekarek (7). For the strong hydrogen bond donors listed in Table I, only the NMR probe (benzonitrile) was applied. As has been noted before (6),the increased sensitivity of the ISN chemical shift to hydrogen bonding effects is reflected by the condition of a > s in eq 1 whereas the opposite (a < s) is usually the case for simple solvatochromic indicators. Comparisons among the four carboxylic acids listed in Table I indicate that the substantial dipolarities of these HBD molecules are consistently overshadowed by their HBD acidities as the major solvent influences. As would be expected from structural considerations, the a-acidity value drops sharply from formic acid to the successive n-alkanoic acids. Likewise, polyfluoro substitution on the a carbon in the ethanol molecule causes a marked increase in the HBD acidity of the hydroxyl group as would be anticipated. For ethanol itself, the a-scale number of 0.83 is somewhat less than the measured values of the haloethanols. On the other hand, even though the dipolarities of the carboxylic acids and the corresponding alcohols are similar in magnitude ( I ) , the n-alkanoic acids are far stronger hydrogen bond donors with a values greater than unity on the Kamlet-Taft scale. Since the primary relationships derived by Bekarek (7) have been evaluated statistically for only pure solvents (i.e., discrete points), it is important to extend these critical tests to cosolvent systems where the dipolarity can be varied continuously by changing the composition of the mixture. The particular binary solvent chosen for this purpose was CC14benzene, and the rationale for its selection includes the following: (a) the pure components are nearly isodielectric (2.27 for benzene and 2.23 for CC14);(b) although n vs. X (mole fraction) is ideal for this solvent pair, r vs. X departs slightly from linearity in mixtures approaching pure benzene; and (c) the system provides a sizeable A* range (0.28-0.59)as a fully non-hydrogen-bonding pair. One minor limitation on the CC14-benzene system is that each component requires a 6polarizability correction term in the Kamlet-Taft model (9). Bekarek proposed separate though parallel f(r, n2)regression functions for computing a* values for alkane and aromatic solvents; however, one may use eq 2 as the basic function and then incorporate the d6 correction as a perturbation term by analogy to the approach used in the usual LFE equations (I). (Equation 2 is also supported by the largest data set and best correlation coefficient (7).) Thus, it can be easily shown that eq 2 can be modified to eq 3 which should fit an ideal cosolvent mixture, m.
For CC14-benzene mixtures, the specific function given in eq 4 applies over the complete mole fraction range. A,*
= 14.65
(E,
(2r,
- N n m 2- 1)
1
+ 1)(2nm2+ 1) + 0.286,X1+ 0.4062x2- 0.573 (4)
Here, the solvent components 1and 2 are CC14and benzene, respectively, and 61 = 0.50 and 62 = 1.00 (I). Dielectric constants and indexes of refraction for the CC1,-benzene mixtures are listed in Table 11. Because literature data (IO) on the system are somewhat incomplete, it was necessary to redetermine these parameters for the total
29PO
Anal. Chem. 1984, 56.2990-2992
Table 11. Summary of Solvent Properties (at 25 “C)for the Test System CC14-Benzene mole fraction CCll
ea
nD
r*(exptl)b
r*(eq 4)
2.273 2.269 2.266 2.258 2.254 2.246
1.4982 0.588 (0.59)‘ 0.589 1.4927 0.550 0.546 1.4885 0.513 0.512 1.4812 0.461 0.459 1.4777 0.430 0.432 1.4714 0.386 0.383 2.242 1.4675 0.352 0.353 2.235 1.4623 0.311 0.312 2.228 1.4578 0.275 (0.28)c 0.280 ‘Combined experimental data and published dielectric constants of Perez, Block, and Knobler (10). bValuesdetermined with phenol blue as the solvatochromic indicator; overall uncertainty in these results is rt0.003 (SD).CAcceptedliterature values (1). 0.000
0.139 0.247 0.420 0.505 0.658 0.754 0.886 1.000
mole fraction interval (0.0-1.0). Experimental a* values for the binary solvent were measured as well, using a single but reliable solvatochromic indicator. The d coefficients in eq 4 were evaluated algebraically by comparison of the function for alkane solvents with that using six pure aprotics and polychloroalkanes. When the computed results from f(t, n2) are compared to a*(exptl), the overall statistical uncertainty is f0.003 (SD) and the correlation coefficient is 0.992 for nine points. As a further confirmation of the suitability of eq 4 for the solvent pair, graphic correlations of both a*(exptl) and a*(calcd) vs. mole fraction (XI)were observed to be definitely linear. This conclusion was also verified by the randomness of the residuals in Aa*(calcd). Other theoretically based a* regressions have been critically examined by Brady and Carr (11);their major equations using the reaction field function, e,, were applied to the CC14benzene system. Although regression equations in f(e,)and f(e,, n2) predict reasonable a* values for pure CC14 (ranging from 0.23 to 0.31), the errors in a*(calcd) numbers for benzene and benzene-rich solvent mixtures are very large. The latter
results are not fully unexpected in light of the known limitations of various model 8, functions when applied to polyfunctional and aromatic solvents separately (11). Therefore, the results of this study indicate that the previous methods and probes for the measurement of a*-and a-scale numbers can be extended to strong HBD solvents with sufficient reliability that structural variables influencing trends in the Kamlet-Taft parameters can be discerned. Likewise, the Bekarek modified reaction field f(t, n2) can be used to verify the a* values for select non-hydrogen-bonding cosolvents as well as for the estimation of unknown a* numbers of pure nonpolar and polar aprotic solvents. Registry No. n-Butyl chloride, 109-69-3;sec-butyl chloride, 78-86-4; tert-butyl chloride, 507-20-0;n-propyl chloride, 540-54-5; isopropyl chloride, 75-29-6;acetaldehyde, 75-07-0; acetone,67-64-1; 2-butanone, 78-93-3; 3-pentanone, 96-22-0; formic acid, 64-18-6; acetic acid, 64-19-7; propionic acid, 79-09-4; n-butyric acid, 10792-6; 2-chloroethanol, 107-07-3;2-fluoroethanol, 371-62-0; 2,2difluoroethanol, 359-13-7; 2,2,2-trifluoroethanol, 75-89-8.
LITERATURE CITED (1) Kamlet, M.; Abboud, J.; Abraham, M.; Taft, R. J . Org. Chem. 1883, 48,2877. (2) Kolling, 0. W. Anal. Chem. 1980, 52. 987. (3) Kolllng, 0. W. Anal. Chem. 1882, 54,260. (4) Kolling, 0. W. Anal. Chem. 1881, 53,54. (5) Kolllng, 0. W. Anal. Chem. 1983, 55, 143. (6) Kolling, 0. W. Anal. Chem. 1884, 56,430. (7) Bekarek, V. J . Phys. Chem. 1981, 85, 722. (8) Riddick, J.; Bunger, W. “Organic Solvents”, 3rd ed.; Wlley-Interscience: New York, 1970; Chapter 5. (9) Taft, R.; Abboud, J.; Kamlet, M. J . Am. Chem. SOC. 1881, 103, 1080. (10) Perez, P.; Block, T.; Knobler, C. J . Chem. Eng. Data 1871, 16, 333. (11) Brady, J.; Carr, P. Anal. Chem. 1882, 54, 1751.
Orland W. Kolling Chemistry Department Southwestern College Winfield, Kansas 67156
RECEIVED for review July 9, 1984. Accepted September 24, 1984.
AIDS FOR ANALYTICAL CHEMISTS Dead-Volume Free Termlnation for Packed Columns In Microcapillary Liquid Chromatography Dennis C. Shelly, Jennifer C. Gluckman, and Milos V. Novotny* Department of Chemistry, Indiana University, Bloomington, Indiana 47405 The use of slurry-packed capillary columns in high-performance liquid chromatography (HPLC) (1-6)has allowed separation efficiencies exceeding 250 000 theoretical plates to be achieved within a few hours. The nanoliter volumes and high resolving powers of these microcolumns require, however, that all contributions to extra column volume be kept to an absolute minimum. One rather irreproducible source of such volume can be found in the small quartz wool filter which has typically been used to terminate the column and retain the packing material (2). This paper describes the production and use of a porous Teflon end-frit which may be directly inserted and subsequently cemented into the end of the column blank prior to packing. This frit then forms a highly reproducible, low-volume column termination which facilitates either the
placement of the detection cell immediately adjacent to the end of the column or, alternatively, detection directly on the column packing itself (7, 8).
EXPERIMENTAL SECTION To manufacture the Teflon frits, porous Teflon (obtained from conventional Teflon end-frits, part no. 77725, Hamilton Co., Reno, NV) was carefully cut into 300 pm thick slices, which were then further compressed in a micrometer to a thickness of 150 pm. Frits were subsequently cut from the compressed Teflon using fusedsilica tubing identical in diameter with the proposed column blank. To accomplish this, a small (1-2 cm) segment of the tubing, with the end cut to be as flat as possible, was firmly held in the jaws of a pin vise and then pressed against the Teflon slice, while being held exactly perpendicular to its surface. The pin vise was
0003-2700/84/0356-2990$01.50/00 1984 American Chemical Soclety
