ORIGINAL PAPER

Karlheinz Ballschmiter Æ Diana Klingler

Stefan Ellinger Æ Rudolf Hackenberg

High-resolution gas chromatography retention data as a basisfor estimation of the octanol–water distribution coefficients (Kow)of PCB: the effect of experimental conditions

Received: 7 March 2005 / Revised: 12 May 2005 / Accepted: 13 May 2005 / Published online: 18 June 2005

� Springer-Verlag 2005

Abstract The semi-experimental approach to approxi-mating physicochemical data relevant to environmentaldistribution (vapor pressure and gas–octanol distribu-tion) by correlation with gas chromatography (GC)retention data has been extended to the determination ofKow values. We estimated Kow values >104 for poly-chlorinated biphenyls (PCB), which are often derived byliquid chromatography, by correlation with gas chro-matographic retention data. Selecting a set of referencecompounds with known Kow values for relative reten-tion time (RRT) correlation enables easy and accuratesemi-empirical calculation of further Kow values for agiven group of congeners. The RRT/log Kow correla-tion is validated in this paper with regard to the fol-lowing gas chromatographic conditions: (1) isothermalversus temperature-programmed elution, (2) the possibleeffect of the polarity of the stationary phase, and (3) theeffect of the format of the standardized GC retentiondata. The advantages of our Kow(GC) method can besummarized as follows: complex mixtures can be ana-lyzed, only amounts in the nanogram-range or less arerequired, Kow values of isomers can be determined andthe exact structure of compounds need not be known.Normalized GC retention data of persistent organicpollutants are readily available. The quality of the Kow

values obtained by the GC method compares well withthat for other Kow estimation methods. It dependsmainly on the accuracy of the Kow data of the struc-turally correlated compounds used as standards for thecorrelation cohort. The Kow(GC) data for all 209 PCBcongeners are given.

Keywords Kow values Æ Relative retention time Æ Totalsurface area Æ Polychlorinated biphenyls

Introduction

Correlation with reversed-phase liquid chromatography(RP-HPLC) data is a classical and widely used methodfor the determination of water solubility (SW) andlog Kow values of single components in complex mix-tures [1–9]. The vapor pressure of subcooled liquids (p0L)can be derived from gas chromatographic retention databy correlation with data from known standards and hasalso been successfully applied in the past, for manygroups of persistent organic pollutants (POP) [10–15].The same has been done for halogenated phenyl methylether (anisols) [16, 17] and alkyl dinitrates [18, 19].

We recently extended the approach by using stan-dardized gas chromatography (GC) data for determi-nation of log Kow values >104 for POP such aspolychlorinated biphenyls (PCB), PCN, PCDE, andPBDE [20]. In this paper, we report in detail that ourapproach of correlating relative retention times (RRT)with Kow values, if correctly applied, is a valuable andexperimentally solidly founded procedure for the deter-mination of Kow values for the hundreds of non-polaror semipolar persistent compounds (POP) found in theenvironment.

As early as 1984, Miller et al. showed that the log -Kow values of PCB determined by using the generatorcolumn method are linearly related to the RRTs inpacked-column GC analysis with the non-polar C-87

Dedicated to the memory of Wilhelm Fresenius

K. Ballschmiter (&) Æ D. Klingler Æ S. Ellinger Æ R. HackenbergDepartment of Analytical and Environmental Chemistry,University of Ulm, Albert-Einstein-Allee 11,89069 Ulm, GermanyE-mail: karlheinz.ballschmiter@uni-ulm.deTel.: +49-0731-5022751Fax: +49-0731-5022763

Present address: S. EllingerDepartment of Polymer Science, University of Ulm,Albert-Einstein-Allee 11, 89081 Ulm, Germany

Present address: R. HackenbergFederal Office of Consumer Protection and Food Safety,Diedersdorfer Weg 1, 12277 Berlin-Marienfelde, Germany

Anal Bioanal Chem (2005) 382: 1859–1870DOI 10.1007/s00216-005-3307-0

stationary phase [21]. The relationship was also con-firmed with a further 13 PCB congeners by Hawker andConnell [22]. They also reported that the total surfaceareas (TSA) of PCB were highly correlated with log -Kow. We tested the Kow(GC) approach for correlationof Kow values of PCB obtained by RP-HPLC [5] withtemperature programmed capillary GC retention data.A solid correlation was found [20, 23].

The Kow(GC) method is validated in this paper withregard to the following gas chromatographic conditions:(1) isothermal versus temperature-programmed elution,(2) the possible effect of the polarity of the stationaryphase, and (3) the effect of the format of the standard-ized GC retention data (RI values compared with rela-tive retention data).

Determination of log Kow from temperature-programmedcapillary gas chromatography data

The octanol–water distribution constant (Kow) coversmore than ten orders of magnitude. On the lipophilicside favoring octanol the molar volume and solutepolarizability are the dominating properties whereasdipolar solute–solvent interactions up to direct hydrogenbonding in the hydration sphere of the solute favor thewater environment. The latter can also be viewed as theshedding of the Lewis electron-donor basicity and elec-tron-acceptor acidity of a solute. Many attempts havebeen made to predict Kow values from structuralmolecular descriptors. A widely used approach is tocalculate the Kow value from the known value of astructurally similar substance by adding the fragmentconstants published by Hansch and Leo [24].

Taft et al. [25] developed a linear solvation energyrelationship (LSER) with four molecular descriptors forprediction of Kow values. The four descriptors are:solute dipolarity/polarizability, solute hydrogen-bondacidity, solute hydrogen-bond basicity, and its intrinsicvolume in cm3 mol�1. This approach has been modifiedand extended by many other authors [26, 27]. Abrahamand colleagues developed a LSER equation that can beapplied to processes in which the condensed phase in GCis a liquid phase, an adsorbent, a polymer or simply anorganic solvent (Eq. 1). This equation can also be usedin a modified form to calculate the Kow value (Eq. 2).

The first more general LSER equation is:

log SP ¼ cþ rR2 þ spH2 þ aaH2 þ bbH

2 þ l log L16; ð1Þ

where SP is a property of a series of solutes in a fixedsystem, R2 the excess molar refraction of solutes that canbe obtained from refractive index measurements, p2

H thesolute dipolarity/polarizability that can be determinedby gas chromatographic measurements, a2

H the effectivehydrogen-bond acidity, b2

H the effective hydrogen-bondbasicity, and L16 the gas–hexadecane partition coeffi-cient at 25�C. Replacing the term l log L16 in Eq. (1) bya descriptor Vx, which is an estimate of the van derWaals volume of the solute (cm3 mol�1), leads to Eq. (2)

that can be directly used to calculate the log Kow ofsolutes

log SP ¼ cþ rR2 þ spH2 þ aaH2 þ bbH

2 þ vVx: ð2Þ

Abraham et al. [26] compared calculated and mea-sured values of log Kow for a broad spectrum of com-pounds. Equation (2) can be simplified significantly ifpart of descriptors, e.g. descriptors a a2

H and bb2H are

very small or even zero for a series of solutes.We were interested in determination of log Kow

values that exceed 104, because the value Kow=105 is animportant value for definition of the bioaccumulationproperties of POP. For this large group of non-polarcompounds solute size and the solute polarizability arethe dominant factors favoring the octanol environment,thus increasing the values of Kow.

The solute size and polarizability of a compound arealso dominant in the separation of solutes by GC. Ad-justed GC retention data summarize the molecularinteractions of the compound considered in all its com-plexity, with the molecules of the stationary phaseforming cavities and solute–solvent interaction at theoutside of the cavity. In more formal terms, the retentionof a molecule in GC is the sum of its polarizabilityvolume a, its ionization energy I, its electron affinity F,and the square of its dipole moment l [28]. A measure ofthe complex interactions in the stationary phase is givenin simple time units. GC retention data thus reflect themolecular interaction in solution seen as Coulomb-typeforces, ranging in a very general sense from van derWaals to dipole–dipole and Lewis acid/base-type inter-actions. It is, therefore, not surprising that suitablecorrelation of gas chromatographic retention data canlead directly to estimates of log Kow values in the range>104. Fenner et al. [29] have objected that GC datacorrelation to determine Kow values has its limitationsfor polar compounds. Our results reported here startwith log Kow values >4.0.

One can formalize the correlation of GC retentiondata to calculate the Kow values by applying the Col-lander equation (Eq. 3) [30, 31]:

log KdðAÞ ¼ a logKdðBÞ þ b: ð3Þ

Equation (3) enables derivation of the distributioncoefficient Kd, in a solvent system A, from the constantsmeasured in a different system B, if the experimentallydetermined values (constants a and b) are available. TheCollander equation is based on constant temperature.

An equation for the determination of log Kow valuesby GC as suggested by Miller et al. [21] and Hawker andConnell [22] is:

logKow ¼ a logtRtM� 1

� �þ C ð4Þ

where tR is the retention time of the compound and tMthe dead time in the chromatographic system. Theexpression (tR/tM�1) is the retention factor k often

1860

applied in chromatography. Equation (4) is derivedbelow.

The retention factor k is defined by:

k ¼ ns

nM¼ csVs

cMVM¼ tR � tM

tMð5Þ

In this equation nS and nM are the numbers of mol-ecules, cS and cM the concentrations of the solutes in thetwo phases, and VS and VM the volumes of the sta-tionary and mobile phases, respectively. Because cS/cM=Kgc and VS/VM=q, q represents the inverse of thephase ratio b, which can be obtained for capillary col-umns from the linear diameter and the film thickness(b=ID/d f). If ID�d f, the retention factor k can beexpressed as:

k ¼ Kgc� q ¼ tR � tMtM

ð6Þ

Rearrangement leads to an expression for the distri-bution coefficient (Kgc) in the gas–liquid system, whichcan be substituted in the Collander equation (Eq. 3) togive:

logKow ¼ a logtRtM� 1

� �þ a log

1

qþ b

� �ð7Þ

Combining the term (a log 1/q+b) into a new constantC, an equation of the type y=mx+t is obtained [log -Kow=a log (tR/tM�1)+C, which is Eq. (4)].

Equation (4) is derived for isothermal conditions.Multi-component mixtures with a wide spread of boilingpoints are analyzed, for practical reasons, by tempera-ture programmed GC. In this case, the GC data arestandardized using RRT or temperature-programmedretention indices (RITP values). We can prove experi-mentally that if the retention factor k is replaced byRRT data obtained by linearly temperature pro-grammed GC, the basic correlation with log Kow is stillvalid (Eq. 8).

log Kow ¼ aTPRRTþ CTP ð8Þ

Structurally correlated reference compounds withknown log Kow values, e.g. specific PCB congeners,have to be used for the group of PCB. The relativeretention data have to be obtained under the sameconditions for the compounds under investigation andfor the correlation standards to derive the constantsaTP and CTP of Eq. (8) needed for the linear correla-tion.

Experimental

The standard reference material (SRM) 2262 used forcalculation of the constants aTP and CTP of Eq. (8) is asolution of 29 polychlorinated biphenyl congeners(PCB 1, 8, 18, 28, 29, 44, 50, 52, 66, 77, 87, 101, 104,105, 118, 126, 128, 138, 153, 154, 170, 180, 187, 188,

194, 195, 201, 206, and 209) in 2,2,4-trimethylpentane(isooctane).

Gas chromatographic separations with electron-cap-ture detection (ECD) were performed on a Varian 3800GC with H2 as carrier gas. Sample injection was doneusing the cold on-column technique.

Capillary column and temperature program

Varian CP Sil-8 (60 m·0.32 mm; 0.25-lm film thickness;2-m retention gap): 80�C (2-min hold); 5� min�1

fi 290�C (20-min hold); 5� min�1 fi 310�C (10-minhold); re-equilibration to 80�C.

Results and discussion

The RRT/log Kow correlation presented here waschecked to determine the extent to which the differentGC data used to calculate log Kow(GC) affect the re-sults and their accuracy. We first performed the corre-lation shown in Eq. (8) for a set of PCB standards(correlation cohort) with known Kow values to obtainthe constants aTP and CTP and the respective correlationcoefficient. We then calculated the Kow partition coef-ficients for all further PCB congeners using their mea-sured retention factor k or their RRT and the previouslycalculated constants aTP and CTP. To indicate whichdata were used to obtain the log Kow values, we addedthe suffix (GC) when RRT were used as moleculardescriptors. We compared these calculated Kow(GC)data with HPLC-based Kow values and with PCB Kowvalues obtained from the literature.

Kow data of PCB as reference values

A set of Kow values evaluated for 16 polychlorinatedbiphenyls (PCB 3, 8, 15, 28, 29, 31, 52, 61, 101, 105, 118,138, 153, 155, 180, and 194) was derived by Li et al. [32]on the basis of all the experimentally obtained valuesreported for these congeners in the literature. The se-lected log Kow value for congener 138 deviates signifi-cantly from the other reference values (Table 2). The setof evaluated Kow values [Kow(EVA)] was also used forcorrelation with RRT measured on a C18 (50%) capil-lary. The results are given for the congeners of NIST SM2262 as Kow(GC-EVA), to indicate their origin(Table 5).

We used three further sets of Kow values of PCB tocheck our RRT/log Kow correlation. The first set ofKow values was determined by correlation of RP-HPLCretention data of PCB. We used the data reported byBrodsky and Ballschmiter [5]. The values are reportedhere as Kow(HPLC). A second set of Kow values of PCBwas obtained by correlation of the TSA of PCB withexperimentally determined Kow values, as reported byHawker and Connell [22]. The values are reported here

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as Kow(TSA). A further set of Kow values, reportedhere as Kow(HQSAR), was calculated by a molecularhologram-derived quantitative structure–property rela-tionship (HQSAR), as reported by Wang et al. [33].

Kow values of PCB obtained by reversed phase HPLC

Although reversed phase HPLC is a method of highreliability for determination of Kow values, the resultsshow some deviation depending on the experimentalset-up, e.g. the use of different stationary phases andeluents. We previously studied these effects for threedifferent stationary phases and three sets of eluents [5].Six sets of Kow(HPLC) values of PCB [5] were assessedon the basis of how well they correlated with therespective RRT values of the PCB (Eq. 8). For practicalreasons PCB and all the other POP are nearly alwaysseparated by temperature-programmed GC. Retentiondata of PCB are often reported as relative retention(RRT) based on the sum of the retention times of PCB52 and 180, RRT(52+180) [38]. We also used thisstandardization for retention data.

We used for our experiments the NIST standardsolution of PCB SRM 2262 that contains 29 congenerswith different degrees of chlorination from 1 to 10 toobtain the constants a(TP) and C(TP) required by Eq. (8)in order to calculate log Kow(GC) values by a RRTcorrelation. We used between 16 and 26 congeners forthe RRT/Kow correlation to calculate the constantsaTP and CTP of Eq. (8). We included the later-eluting

PCB 206 and 209 to extend the calibration range. Thestructure-correlated numbering of the PCB congenershas been taken from Ref. [34] and is used throughoutthis paper.

The constants aTP and CTP and the coefficients ofcorrelation for the log Kow(GC) values of PCB refer-ence mixture (SRM 2262) are listed in Table 1. Thehighest correlation coefficients were obtained withlog Kow (HPLC) values measured with the stationaryphase Nucleosil 5 CN using either water–methanol(R2=0.98) (system Bro5) or water–acetonitrile(R2=0.97) (system Bro6) as eluent. The correlationcoefficient is lower (R2=0.93) for the widely used C18,water–methanol system (system Bro1). Most log Kowvalues were determined using this HPLC system,how-ever. We used the log Kow(HPLC) values of systemBro2 (Nucleosil 5 C18/water+acetonitrile) and Bro4(Sepralite diphenyl/water+acetonitril), respectively, forour log Kow(GC) determinations. These two sets ofdata combine high correlation coefficients (0.95 and0.97, respectively) with a large set of Kow valuesreported in [5].

The correlation between the RRT(52+180) and thelog Kow(HPLC) Bro4 values for the PCB is depicted inFig. 1.

Total surface area-derived Kow values of PCB

A further independent set of Kow data for PCB isobtained by correlation of the calculated TSA values of

Table 1 Constants a(TP) and C(TP) of Eq. (8) and correlation coefficients obtained for correlation of RRT(52+180) of PCB congenerspresent in reference mixture NIST SRM 2262 with six sets of log Kow(HPLC) values [5]

Set numberof log Kow(HPLC)

Stationary phasein RP-HPLC

Eluent inRP-HPLC

aTP CTP Correlationcoefficient

Bro(1) Nucleosil 5 C18 CH3OH–H2O 9.158 1.877 0.93Bro(2) Nucleosil 5 C18 CH3CN–H2O 9.020 2.070 0.95Bro(3) Sepralyte Diphenyl CH3OH–H2O 9.394 1.855 0.95Bro(4) Sepralyte Diphenyl CH3CN–H2O 8.992 2.052 0.97Bro(5) Nucleosil 5 CN CH3OH–H2O 9.621 1.788 0.98Bro(6) Nucleosil 5 CN CH3CN–H2O 9.357 1.950 0.97

Fig. 1 Correlation ofRRT(52+180) for the PCBcongeners of SRM 2262 withlog Kow(HPLC)(Bro4) for thecongeners in Table 3. Thecorrelation coefficient isR2=0.97

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PCB with experimentally determined Kow values of acalibration set of PCB congeners [22]. This correlation ishighly significant. TSA values can be calculated using thecomputer program Spartan 5.1.3. The Kow(TSA) valuesof the PCB congeners of SRM 2262 are listed in Table 2.The Kow(TSA) values compare well with the Kow(HPLC) values. Correlation of RRT(52+180) withlog Kow(TSA) (Table 2) leads to the linear regressionequation y=9.587x+1.767 and an R2 value of 0.97(Fig. 2).

Kow values of PCB derived by a hologram quantitativestructure–property relationship (HQSAR)

We chose as a third reference set of Kow values ofPCB the values calculated by a molecular hologram-derived quantitative structure–property relationship(HQSAR) (Table 2) [33]. HQSR is a new QSARmethod. It converts the molecules of a selected groupinto counts of their constituent fragments. Thesefragment counts are then related to physicochemical

Table 2 Kow values of PCB congeners present in NIST SRM 2262 that are obtained by different independent approaches

PCB congener no. PCB structure log Kow(HPLC)Bro2 [5]

log Kow(HPLC) Bro4 [5]

log Kow(TSA) [22]

log Kow(HQSAR) [33]

log Kow(EVA) [32]

1 2 4.39 4.43 4.46 4.70 –8 2,4¢ 5.05 5.15 5.07 5.12 5.1218 2,2¢,5 5.37 5.37 5.24 5.33 –28 2,4,4¢ 5.77 5.74 5.67 5.60 5.6629 2,4,5 5.82 5.76 5.60 5.76 5.6044 2,2¢,3,5 5.78 5.79 5.75 5.80 –50 2,2¢,4,6 5.84 5.74 5.63 5.66 –52 2,2¢,5,5¢ 5.87 5.81 5.84 5.88 6.166 2,3¢,4,4¢ – – 6.20 6.07 5.9177 3,3¢,4,4¢ – 6.37 6.36 6.29 –87 2,2¢,3,4,5¢ 6.27 6.27 6.29 6.27 –101 2,2¢,4,5,5¢ 6.39 6.27 6.38 6.32 6.33104 2,2¢,4,6,6¢ – – 5.81 6.00 –105 2,3,3¢,4,4¢ 6.68 6.93 6.65 6.60 6.82118 2,3¢,4,4¢,5 – – 6.74 6.63 –126 3,3¢,4,4¢,5 – – 6.89 6.93 –128 2,2¢,3,3¢,4,4¢ 6.67 6.73 6.74 6.74 –138 2,2¢,3,4,4¢,5¢ 6.77 6.74 6.83 6.75 7.21153 2,2¢,4,4¢,5,5¢ 6.90 6.74 6.92 6.76 6.87154 2,2¢,4,4¢,5,6¢ 6.81 6.64 6.76 6.63 –170 2,2¢,3,3¢,4,4¢,5 – – 7.27 7.27 –180 2,2¢,3,4,4¢,5,5¢ – – 7.36 7.28 7.16187 2,2¢,3,4¢,5,5¢,6 – – 7.17 6.93 –188 2,2¢,3,4¢,5,6,6¢ – – 6.82 6.87194 2,2¢,3,3¢,4,4¢,5,5¢ – – 7.80 7.82 7.76195 2,2¢,3,3¢,4,4¢,5,6 – – 7.56 7.38 –201 2,2¢,3,3¢,4,5¢,6,6¢ – – 7.62 7.26 –206 2,2¢,3,3¢,4,4¢,5,5¢,6 7.91 7.94 8.09 7.84 –209 2,2¢,3,3¢,4,4¢,5,5¢,6,6¢ 8.37 8.28 8.18 8.18 –

The data sets are used as reference data to monitor the quality of the RRT/log Kow correlation according Eq. (8) to calculate theKow(GC) values. The numbering of the PCB congeners follows Ref. [34]–, not given

Fig. 2 Correlation ofRRT(52+180) of PCBcongeners of SRM 2262 withlog Kow(TSA) values for thesecongeners [22] (Table 2). Thecorrelation coefficient is 0.97

1863

data using partial least-square (PSL) regression anal-ysis [35, 36].

Kow values of PCB taken from Brodsky and Ballsch-miter [5] have been used to derive the HQSR set of Kowvalues for all 209 congeners [33]. The log Kow(HQSAR)values of the congeners of SRM2262 are listed in Table 2.The Kow(HQSAR) values correlate well withKow(HPLC) values and with Kow(TSA) values.

Effect of temperature and format of GC retentiondata; isothermal versus temperature-programmedGC retention data

The literature contains many sets of retention data forPCB. An extended set of isothermal retention index(RI) values (stationary phase Apiezon L; elution tem-perature 180�C) of PCB is given in [37]. We used theisothermal RI values of congeners present in the NISTSRM 2262 and their respective log Kow(HPLC)Bro4values (Table 2) to obtain the constants a and C ofEq. (4) (correlation cohort). This set of constants wasused to calculate, with the reported RI values [37], thecorresponding Kow(GC) values of the other PCB

congeners. The correlation is highly significant. Weobtained values of a=2.555 and C=0.797 and a cor-relation coefficient of 0.97. The Kow(GC-RI) values ofthe congeners of SRM 2262 obtained this way aregiven in Table 3.

We also measured the relative retention (log k) of aset of PCB present in NIST SRM 2262 under threedifferent isothermal conditions (stationary phase Sil-8;elution temperatures 140, 160, and 180�C). We usedthese isothermal retention values and the Kow(HPLC)-Bro4 set (Table 3) to obtain the constants a and C ofEq. (4) and used this set to calculate the Kow(GC) val-ues of further PCB congeners. The results are summa-rized in Table 3. On average the log Kow(GC) valuesdeviate from the set of reference values by ±0.2 units.This is well within the range of direct measurements ofKow values.

The quality of the correlation of temperature-pro-grammed RRT data with log Kow(HPLC) data is givenin Table 1. The results in Table 3 clearly indicate thatthe GC elution temperature has no significant effect oncalculated Kow(GC) values. RRT based log Kow(GC)values of PCB are given in Table 5. The Kow(GC) val-ues, based on retention data obtained by linearly tem-

Table 3 Kow(GC) values of PCB (NIST SRM 2262) obtained by correlation of standardized GC retention data measured underisothermal conditions and the Kow(HPLC)Bro4 set (Table 2)

PCBcongenerno.

log Kow(GC) 140�C (1)

log Kow(GC) 160�C (2)

log Kow(GC)180�C (3)

log Kow(GC-iso) meanvalue (1)–(3)

log Kow(GC-RI)

log Kow(HPLC)Bro4 [5]

log Kow(TSA) [22]

8 5.21 5.18 5.25 5.21 5.24 5.15 5.0718 5.44 5.49 5.45 5.46 5.38 5.37 5.2428 5.58 5.59 5.68 5.58 5.70 5.74 5.6729 5.61 5.63 5.60 5.61 5.63 5.76 5.6044 5.79 5.83 5.93 5.85 5.85 5.79 5.7550 5.90 5.96 5.66 5.84 – 5.74 5.6352 5.91 5.96 5.84 5.90 5.79 5.81 5.8466 6.02 6.11 6.13 6.09 – – 6.2077 – 6.14 6.42 6.28 6.49 6.73 6.3687 – 6.24 6.38 6.31 6.32 6.27 6.29101 6.19 6.45 6.25 6.30 6.25 6.27 6.38104 5.59 5.46 5.90 5.65 – – 5.81105 – 6.53 6.80 6.67 6.68 6.93 6.65118 – 6.66 6.56 6.61 – – 6.74126 – 6.72 6.84 6.78 – – 6.89128 – – 6.91 6.91 6.86 6.73 6.74138 – 6.76 6.79 6.78 6.78 6.74 6.83153 – 6.79 6.67 6.73 6.71 6.74 6.92154 – 6.79 6.42 6.61 – 6.64 6.76170 – – 7.27 7.27 – – 7.27180 – – 7.14 7.14 – – 7.36187 – – 6.87 6.87 – – 7.17188 – 6.60 6.61 6.61 – – 6.82194 – – – – – – 7.80195 – – – – – – 7.56201 – – 7.07 7.07 – – 7.62206 – – – – – 7.94 8.09209 – – – – – 8.28 8.18

Kow(GC-RI) values were calculated using the RI values of [37]. Kow(HPLC)Bro4 and Kow(TSA) values are given for comparison. Thestructures of the PCB congeners are given in Table 2–, not determined

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perature-programmed elution, correspond well with thedifferent sets of reference data.

Effect of the polarity of the stationary phase usedfor GC separation

GC retention data of PCB given as RRT(52+180) val-ues obtained from 20 different capillary columns with awide range of polarity are found in the literature [38].We used part of these data to check the possible effect ofthe polarity of the stationary phase on the correlationexpressed by Eq. (8).

The correlation of the RRT(52+180) values of thePCB congeners of reference mixture NIST 2262 oncapillaries of different polarity with the Kow(HPLC)values of set Brodsky4 and the TSA-derived Kow(TSA)values, respectively, are summarized in Table 4. Weobserved no relevant influence of the polarity of thestationary phases on the values of Kow(GC) valuescalculated by use of Eq. (8). The correlation coefficientfor the very polar phase 8 (78% cyanopropylphenyl,22% methyl silicone) is the only one markedly differentfrom the generally high values, R2=0.96–0.97, obtainedfor all the other stationary phases.

The Kow(GC) values for the stationary phases 50%octadecyl, 50% methyl silicone (stationary phase 2), and35% phenyl 65%methyl silicone (stationary phase 6) are given for thePCB congeners of NST SRM 2262 in Table 5. They arecompared with the Kow(HPLC), Kow(TSA), and Ko-w(EVA) reference values. The calculated Kow(GC)values compare well with the three independent sets ofKow values. The RRT data given in [38] have also beenused to calculate the Kow(GC) values of all 209 PCBcongeners (Table 6). A detailed analysis of the structure-correlated deviations of single Kow values as a result ofa possible coplanarity for PCB congeners will be pub-lished elsewhere.

Conclusions

The experiments reported here prove that the RRT/log Kow correlation presented for calculation of Kowvalues from standardized GC RRT data, as exempli-fied for the PCB congeners, has its own standing.Using a set of structurally correlated reference com-pounds with known Kow values for a RRT correlationenables easy and accurate semi-empirical calculation offurther Kow values for a given group of congeners.The RRT/log Kow correlation can be extended toincorporate structural aspects of the PCB, e.g. takinginto account the various degrees of coplanarity as aselection principle for a correlation. The RRT/log Kowcorrelation can be applied to non-polar compounds ofthe POP type with log Kow values stretching from 5 to8 and beyond. It clearly supplements the TSA/log Kowcorrelation and is another simple means of obtainingT

able

4Effectofstationary

phase

polarity

onthelogKow(G

C)values

calculatedforthePCBcongenersofreference

mixture

NIST2262usingthelogKow(H

PLC)Bro4setandthe

logKow(TSA)setofTable

2ascorrelationcohorts

GC

system

12

34

56

78

(a)Correlation:logKow(H

PLC)Bro4setversusRRTPCB

(52+180)

Stationary

phase

ApiezonL

50%

C850%

methylsilicone

50%

C1850%

methylsilicone

5%

Phenyl95%

methylsilicone

13%

Phenyl87%

methylsilicone

35%

Phenyl65%

methylsilicone

DBXLB(extra

low

bleed)

78%

Cyanopropylphenyl22%

methylsilicone

aTP

4.2445

4.4805

4.5516

5.0098

4.8819

5.4993

6.9803

4.8500

CTP

4.3951

4.3252

4.2563

4.0134

4.0670

3.7615

2.8212

4.0681

Correlation

coeffi

cient

0.96

0.96

0.97

0.97

0.96

0.96

0.97

0.89

(b)Correlation:logKow(TSA)versusRRTPCB(52+

180)

Stationary

phase

ApiezonL

50%

C850%

methylsilicone

50%

C1850%

methylsilicone

5%

Phenyl95%

methylsilicone

13%

Phenyl87%

methylsilicone

35%

Phenyl65

methylsilicone

DBXLB

(extralow

bleed)

78%

Cyanopropylphenyl22%

methylsilicone

aTP

4.3582

4.5494

4.6681

5.1850

5.0379

5.6897

7.3154

4.7617

CTP

4.3575

4.2889

4.2094

3.9414

4.0055

3.6796

2.6590

4.1516

Correlation

coeffi

cient

0.96

0.96

0.97

0.97

0.96

0.96

0.97

0.84

1865

Table 5 Kow(GC) values calculated using the RRT (PCB 52+180) of congeners of SRM 2262 given for the stationary phases C18 (50%)and phenyl (35%), as reported in Ref. [38]

PCB-congenerno.

Structure log Kow(HPLC)Bro4 [5]

log Kow(EVA) [32]

log Kow(TSA) [22]

log Kow(GC) (C18+EVA)

log Kow(GC) (C18+Bro4)

log Kow (GC)(Phenyl+Bro4)

1 2 4.43 4.46 4.95 4.83 4.698 2,4¢ 5.15 5.12 5.07 5.27 5.17 5.1518 2,2¢,5 5.37 5.24 5.41 5.31 5.3828 2,4,4¢ 5.74 5.66 5.67 5.68 5.59 5.5929 2,4,5 5.76 5.60 5.60 5.62 5.53 5.4944 2,2¢,3,5 5.79 – 5.75 5.88 5.80 5.9450 2,2¢,4,6 5.74 – 5.63 5.68 5.60 5.5952 2,2¢,5,5¢ 5.81 5.91 5.84 5.81 5.73 5.7866 2,3¢,4,4¢ – – 6.20 6.18 6.12 6.1577 3,3¢,4,4¢ 6.37 – 6.36 6.53 6.48 –87 2,2¢,3,4,5¢ 6.27 – 6.29 6.40 6.37 6.46101 2,2¢,4,5,5¢ 6.27 6.33 6.38 6.31 6.25 6.24104 2,2¢,4,6,6¢ – – 5.81 5.86 5.78 5.91105 2,3,3¢,4,4¢ 6.93 6.82 6.65 6.78 6.74 6.82118 2,3¢,4,4¢,5 – 6.69 6.74 6.69 6.65 6.61126 3,3¢,4,4¢,5 – – 6.89 7.04 7.01 6.95128 2,2¢,3,3¢,4,4¢ 6.73 – 6.74 7.01 6.98 7.14138 2,2¢,3,4,4¢,5¢ 6.74 7.21 6.83 6.92 6.88 6.90153 2,2¢,4,4¢,5,5¢ 6.74 6.87 6.92 6.82 6.78 6.70154 2,2¢,4,4¢,5,6¢ 6.64 – 6.76 6.53 6.48 6.43170 2,2¢,3,3¢,4,4¢,5 – – 7.27 7.45 7.44 7.48180 2,2¢,3,4,4¢,5,5¢ – 7.16 7.36 7.35 7.34 7.24187 2,2¢,3,4¢,5,5¢,6 – – 7.17 7.02 6.99 6.96188 2,2¢,3,4¢,5,6,6¢ – – 6.82 6.71 6.66 6.68194 2,2¢,3,3¢,4,4¢,5,5¢ – 7.76 7.80 7.86 7.86 7.75195 2,2¢,3,3¢,4,4¢,5,6 – – 7.56 7.66 7.66 7.71201 2,2¢,3,3¢,4,5¢,6,6¢ – – 7.62 7.19 7.17 7.19206 2,2¢,3,3¢,4,4¢,5,5¢,6 7.94 – 8.09 8.03 8.04 7.94209 2,2¢,3,3¢,4,4¢,5,5¢,6,6¢ 8.28 – 8.18 8.15 8.16 8.10

Kow(HPLC)Bro4 and Kow(EVA) values were taken for the RRT/log Kow correlation. The Kow(HPLC), Kow(EVA), and Kow(TSA)reference values are given for comparison. The numbering of the PCB congeners follows Ref. [34].–, not given

Table 6 Kow(GC) values of all 209 PCB congeners based on the correlation of RRT(52+180) on the stationary phases C18 (50%) andphenyl (35%), respectively, as reported by G. Frame [38] and the log Kow(HPLC)Bro4 values [5]

PCB-congenerno.

Structure log Kow(HPLC) Bro4 [5]

log Kow(TSA) [22]

log Kow(HQSAR) [36]

log Kow (GC)(C18- 50%+EVA)

log Kow (GC)(C18- 50%+Bro4)

log Kow (GC)(Phenyl- 35%+Bro4)

1 2 4.43 4.46 4.70 4.95 4.83 4.692 3 4.62 4.69 4.67 5.08 4.96 4.823 4 4.59 4.69 4.64 5.09 4.97 4.844 2,2¢ 4.94 4.65 4.76 5.10 4.99 4.985 2,3 5.05 4.97 5.08 5.26 5.16 5.176 2,3¢ – 5.06 5.09 5.23 5.13 5.127 2,4 5.12 5.07 5.18 5.23 5.12 5.048 2,4¢ 5.15 5.07 5.12 5.27 5.17 5.159 2,5 5.10 5.06 5.30 5.22 5.11 5.0410 2,6 5.01 4.84 4.98 5.11 5.00 4.9711 3,3¢ 5.18 5.28 5.11 5.44 5.34 5.2912 3,4 5.11 5.22 5.28 5.46 5.37 5.3313 3,4¢ – 5.29 5.05 5.46 5.36 5.3814 3,5 5.16 5.28 5.28 5.38 5.28 5.1515 4,4¢ 5.28 5.30 5.05 5.48 5.39 5.3816 2,2¢,3 – 5.16 5.15 5.47 5.37 5.5217 2,2¢,4 – 5.25 5.34 5.44 5.34 5.3818 2,2¢,5 5.37 5.24 5.33 5.41 5.31 5.3819 2,2¢,6 5.19 5.02 4.93 5.29 5.19 5.31

Table 6 (Contd.)

1866

PCB-congenerno.

Structure log Kow(HPLC) Bro4 [5]

log Kow(TSA) [22]

log Kow(HQSAR) [36]

log Kow (GC)(C18- 50%+EVA)

log Kow (GC)(C18- 50%+Bro4)

log Kow (GC)(Phenyl- 35%+Bro4)

20 2,3,3¢ – 5.57 5.50 5.69 5.60 5.6921 2,3,4 5.73 5.51 5.67 5.69 5.61 5.6822 2,3,4¢ – 5.58 5.49 5.73 5.64 5.7423 2,3,5 – 5.57 5.80 5.60 5.51 5.4824 2,3,6 5.46 5.35 5.40 5.46 5.37 5.4425 2,3¢,4 – 5.67 5.55 5.64 5.55 5.5526 2,3¢,5 5.68 5.66 5.69 5.62 5.53 5.5327 2,3¢,6 – 5.44 5.35 5.45 5.36 5.4328 2,4,4¢ 5.74 5.67 5.60 5.68 5.59 5.5929 2,4,5 5.76 5.60 5.76 5.62 5.53 5.4930 2,4,6 5.48 5.44 5.65 5.40 5.31 5.2431 2,4¢,5 5.76 5.67 5.69 5.66 5.58 5.5932 2,4¢,6 5.52 5.44 5.36 5.50 5.41 5.4933 2¢,3,4 5.71 5.60 5.62 5.70 5.61 5.6734 2¢,3,5 – 5.66 5.63 5.59 5.50 5.4735 3,3¢,4 – 5.82 5.70 5.95 5.87 5.8936 3,3¢,5 – 5.88 5.72 5.85 5.77 5.6737 3,4,4 5.85 5.83 5.66 5.98 5.91 5.9538 3,4,5 – 5.76 5.93 5.91 5.83 5.8139 3,4¢,5 – 5.89 5.62 5.88 5.80 5.7440 2,2¢,3,3¢ 5.76 5.66 5.59 5.95 5.88 6.1041 2,2¢,3,4 5.78 5.69 5.74 5.94 5.87 6.0342 2,2¢,3,4¢ – 5.76 5.72 5.91 5.84 5.9643 2,2¢,3,5 – 5.75 5.80 5.82 5.74 5.8144 2,2¢,3,5¢ 5.79 5.75 5.70 5.88 5.80 5.9445 2,2¢,3,6 – 5.53 5.34 5.69 5.60 5.7946 2,2¢,3,6¢ – 5.53 5.21 5.71 5.62 5.8547 2,2¢,4,4¢ 5.94 5.85 5.91 5.88 5.80 5.8248 2,2¢,4,5 5.71 5.78 5.79 5.86 5.78 5.8449 2,2¢,4,5¢ 5.86 5.85 5.87 5.84 5.76 5.8150 2,2¢,4,6 5.74 5.63 5.66 5.68 5.60 5.5951 2,2¢,4,6¢ – 5.63 5.52 5.69 5.60 5.7252 2,2¢,5,5¢ 5.81 5.84 5.88 5.81 5.73 5.7853 2,2¢,5,6¢ 5.80 5.62 5.49 5.69 5.60 5.7054 2,2¢,6,6¢ 5.52 5.21 5.27 5.49 5.40 5.6355 2,3,3¢,4 – 6.11 6.06 6.20 6.13 6.2256 2,3,3¢,4¢ – 6.11 6.03 6.23 6.17 6.2957 2,3,3¢,5 – 6.17 6.21 6.13 6.06 5.9958 2,3,3¢,5¢ – 6.17 6.04 6.10 6.03 6.0559 2,3,3¢,6 – 5.95 5.75 5.90 5.82 5.9460 2,3,4,4¢ 6.37 6.11 6.08 6.25 6.18 6.2961 2,3,4,5 6.36 6.04 6.35 6.15 6.08 6.1062 2,3,4,6 – 5.89 6.10 5.89 5.82 5.8563 2,3,4¢,5 – 6.17 6.17 6.14 6.07 6.0764 2,3,4¢,6 – 5.95 5.75 5.97 5.89 6.0265 2,3,5,6 5.85 5.86 6.05 5.88 5.80 5.8466 2,3¢,4,4¢ – 6.20 6.07 6.18 6.12 6.1567 2,3¢,4,5 6.33 6.20 6.13 6.12 6.05 6.0268 2,3¢,4,5¢ – 6.26 6.05 6.06 5.99 5.9269 2,3¢,4,6 5.89 6.04 5.98 5.84 5.76 5.7370 2,3¢,4¢,5 6.29 6.20 6.19 6.16 6.09 6.1271 2,3¢,4¢,6 – 5.98 5.76 5.95 5.87 6.0072 2,3¢,5,5¢ – 6.26 6.22 6.03 5.96 5.8873 2,3¢,5¢,6 – 6.04 5.82 5.82 5.73 5.7674 2,4,4¢,5 – 6.20 6.15 6.17 6.10 6.0875 2,4,4¢,6 5.97 6.05 6.02 5.89 5.82 5.8176 2¢,3,4,5 – 6.13 6.10 6.16 6.09 6.1477 3,3¢,4,4¢ 6.37 6.36 6.29 6.53 6.48 –78 3,3¢,4,5 – 6.35 6.36 6.45 6.40 6.3479 3,3¢,4,5¢ – 6.42 6.28 6.41 6.35 6.2780 3,3¢,5,5¢ 6.41 6.48 6.33 6.29 6.23 6.0281 3,4,4¢,5 – 6.36 6.27 6.49 6.44 6.4382 2,2¢,3,3¢,4 – 6.20 6.16 6.48 6.43 6.6383 2,2¢,3,3¢,5 – 6.26 6.23 6.34 6.28 6.38

Table 6 (Contd.)

1867

PCB-congenerno.

Structure log Kow(HPLC) Bro4 [5]

log Kow(TSA) [22]

log Kow(HQSAR) [36]

log Kow (GC)(C18- 50%+EVA)

log Kow (GC)(C18- 50%+Bro4)

log Kow (GC)(Phenyl- 35%+Bro4)

84 2,2¢,3,3¢,6 – 6.04 5.68 6.17 6.10 6.3485 2,2¢,3,4,4¢ – 6.30 6.31 6.44 6.38 6.4986 2,2¢,3,4,5 6.29 6.23 6.28 6.38 6.33 6.4287 2,2¢,3,4,5¢ 6.27 6.29 6.27 6.40 6.34 6.4688 2,2¢,3,4,6 – 6.07 6.06 6.14 6.07 6.1989 2,2¢,3,4,6¢ – 6.07 5.78 6.20 6.14 6.3590 2,2¢,3,4¢,5 – 6.36 6.35 6.31 6.24 6.2591 2,2¢,3,4¢,6 – 6.13 5.94 6.15 6.08 6.2292 2,2¢,3,5,5¢ – 6.35 6.34 6.27 6.20 6.2193 2,2¢,3,5,6 6.12 6.04 5.95 6.11 6.04 6.1794 2,2¢,3,5,6¢ – 6.13 5.84 6.05 5.98 6.1195 2,2¢,3,6,6 6.05 6.13 5.87 6.09 6.02 6.1896 2,2¢,3,6,6¢ – 5.71 5.60 5.90 5.82 6.0997 2,2¢,3,4¢,5¢ 6.28 6.29 6.19 6.39 6.33 6.4298 2,2¢,3,4¢,6¢ – 6.13 5.97 6.11 6.04 6.1599 2,2¢,4,4¢,5 – 6.39 6.33 6.35 6.29 6.27100 2,2¢,4,4¢,6 – 6.23 6.25 6.09 6.02 6.02101 2,2¢,4,5,5¢ 6.27 6.38 6.32 6.31 6.25 6.24102 2,2¢,4,5,6¢ – 6.16 5.92 6.11 6.04 6.15103 2,2¢,4,5¢,6 6.14 6.22 6.20 6.04 5.96 5.98104 2,2¢,4,6,6¢ – 5.81 6.00 5.86 5.78 5.91105 2,3,3¢,4,4¢ 6.93 6.65 6.60 6.78 6.74 6.82106 2,3,3¢,4,5 6.89 6.64 6.74 6.68 6.63 6.61107 2,3,3¢,4,5¢ – 6.71 6.72 6.64 6.60 6.58108 2,3,3¢,4,6 – 6.71 6.59 6.39 6.33 6.35109 2,3,3¢,4¢,5 – 6.48 6.43 6.66 6.61 6.58110 2,3,3¢,4¢,6 – 6.48 6.18 6.46 6.40 6.52111 2,3,3¢,5,5¢ – 6.76 6.75 6.52 6.47 6.32112 2,3,3¢,5,6 6.25 6.45 6.40 6.36 6.31 6.33113 2,3,3¢,5¢,6 – 6.54 6.22 6.35 6.29 6.25114 2,3,4,4¢,5 – 6.65 6.72 6.73 6.69 6.71115 2,3,4,4¢,6 6.38 6.49 6.48 6.46 6.40 6.44116 2,3,4,5,6 6.32 6.33 6.53 6.44 6.39 6.43117 2,3,4¢,5,6 6.37 6.46 6.39 6.43 6.38 6.43118 2,3¢,4,4¢,5 – 6.74 6.63 6.69 6.65 6.61119 2,3¢,4,4¢,6 6.35 6.58 6.40 6.38 6.32 6.31120 2,3¢,4,5,5¢ – 6.79 6.64 6.55 6.50 6.36121 2,3¢,4,5¢,6 6.28 6.64 6.43 6.23 6.17 6.06122 2¢,3,3¢,4,5 – 6.64 6.55 6.71 6.67 6.73123 2¢,3,4,4¢,5 – 6.74 6.60 6.67 6.62 6.60124 2¢,3,4,5,5¢ – 6.73 6.68 6.64 6.59 6.54125 2¢,3,4,5,6¢ – 6.51 6.13 6.39 6.33 6.42126 3,3¢,4,4¢,5 – 6.89 6.93 7.04 7.01 6.95127 3,3¢,4,5,5¢ – 6.95 6.96 6.91 6.88 6.70128 2,2¢,3,3¢,4,4¢ 6.73 6.74 6.74 7.01 6.98 7.14129 2,2¢,3,3¢,4,5 6.71 6.73 6.72 6.93 6.89 6.98130 2,2¢,3,3¢,4,5¢ – 6.80 6.78 6.87 6.84 6.88131 2,2¢,3,3¢,4,6 – 6.58 6.41 6.65 6.60 6.73132 2,2¢,3,3¢,4,6¢ – 6.58 6.23 6.69 6.64 6.83133 2,2¢,3,3¢,5,5¢ – 6.86 6.86 6.73 6.69 6.62134 2,2¢,3,3¢,5,6 – 6.55 6.36 6.61 6.56 6.71135 2,2¢,3,3¢,5,6¢ – 6.64 6.27 6.53 6.48 6.55136 2,2¢,3,3¢,6,6¢ – 6.22 5.98 6.34 6.28 6.54137 2,2¢,3,4,4¢,5 6.71 6.83 6.83 6.89 6.85 6.86138 2,2¢,3,4,4¢,5¢ 6.74 6.83 6.75 6.92 6.88 6.90139 2,2¢,3,4,4¢,6 – 6.67 6.66 6.63 6.58 6.61140 2,2¢,3,4,4¢,6¢ 6.66 6.67 6.54 6.63 6.58 6.65141 2,2¢,3,4,5,5¢ 6.71 6.82 6.81 6.84 6.80 6.80142 2,2¢,3,4,5,6 – 6.51 6.46 6.66 6.62 6.73143 2,2¢,3,4,5,6¢ 6.55 6.60 6.27 6.61 6.56 6.70144 2,2¢,3,4,5¢,6 – 6.67 6.57 6.57 6.51 6.55145 2,2¢,3,4,6,6¢ – 6.25 6.31 6.36 6.30 6.46146 2,2¢,3,4¢,5,5¢ – 6.89 6.81 6.78 6.74 6.66147 2,2¢,3,4¢,5,6 – 6.64 6.55 6.59 6.54 6.59148 2,2¢,3,4¢,5,6¢ – 6.73 6.57 6.47 6.42 6.38149 2.2¢,3,4¢,5¢,6 – 6.67 6.32 6.59 6.54 6.62

1868

Table 6 (Contd.)

PCB-congenerno.

Structure log Kow(HPLC) Bro4 [5]

log Kow(TSA) [22]

log Kow(HQSAR) [36]

log Kow (GC)(C18- 50%+EVA)

log Kow (GC)(C18- 50%+Bro4)

log Kow (GC)(Phenyl- 35%+Bro4)

150 2,2¢,3,4¢,6,6¢ – 6.32 6.35 6.35 6.29 6.36151 2,2¢,3,5,5¢,6 6.51 6.64 6.44 6.53 6.47 6.52152 2,2¢,3,5,6,6¢ – 6.22 6.09 6.30 6.24 6.42153 2,2¢,4,4¢,5,5¢ 6.74 6.92 6.76 6.82 6.78 6.70154 2,2¢,4,4¢,5,6¢ 6.64 6.76 6.63 6.53 6.48 6.43155 2,2¢,4,4¢,6,6¢ 6.57 6.41 6.72 6.27 6.20 6.17156 2,3,3¢,4,4¢,5 7.53 7.18 7.25 7.26 7.24 7.19157 2,3,3¢,4,4¢,5¢ – 7.18 7.10 7.26 7.24 7.24158 2,3,3¢,4,4¢,6 – 7.02 6.86 6.95 6.92 6.90159 2,3,3¢,4,5,5¢ – 7.24 7.27 7.11 7.08 6.93160 2,3,3¢,4,5,6 – 6.93 6.87 6.94 6.90 6.89161 2,3,3¢,4,5¢,6 – 7.08 6.88 6.78 6.74 6.65162 2,3,3¢,4¢,5,5¢ – 7.24 6.56 7.13 7.10 6.97163 2,3,3¢,4¢,5,6 – 6.99 6.83 6.93 6.89 6.90164 2,3,3¢,4¢,5¢,6 – 7.02 6.56 6.90 6.86 6.90165 2,3,3¢,5,5¢,6 – 7.05 6.85 6.76 6.72 6.62166 2,3,4,4¢,5,6 – 6.93 6.87 7.02 6.99 7.01167 2,3¢,4,4¢,5,5¢ – 7.27 7.11 7.16 7.14 7.01168 2,3¢,4,4¢,5¢,6 – 7.11 6.74 6.83 6.79 6.71169 3,3¢,4,4¢,5,5¢ 7.61 7.42 7.59 7.53 7.52 7.35170 2,2¢,3,3¢,4,4¢,5 – 7.27 7.27 7.45 7.44 7.48171 2,2¢,3,3¢,4,4¢,6 7.06 7.11 6.96 7.16 7.14 7.21172 2,2¢,3,3¢,4,5,5¢ – 7.33 7.34 7.31 7.29 7.19173 2,2¢,3,3¢,4,5,6 – 7.02 6.85 7.17 7.14 7.24174 2,2¢,3,3¢,4,5,6¢ – 7.11 6.72 7.09 7.06 7.14175 2,2¢,3,3¢,4,5¢,6 – 7.17 6.98 7.05 7.02 6.94176 2,2¢,3,3¢,4,6,6¢ – 6.76 6.70 6.81 6.76 6.89177 2,2¢,3,3¢,4¢,5,6 – 7.08 6.89 7.12 7.09 7.18178 2,2¢,3,3¢,5,5¢,6 – 7.14 6.91 6.96 6.92 6.90179 2,2¢,3,3¢,5,6,6¢ – 6.73 6.54 6.75 6.70 6.85180 2,2¢,3,4,4¢,5,5¢ – 7.36 7.28 7.35 7.34 7.24181 2,2¢,3,4,4¢,5,6 7.11 7.10 7.06 7.15 7.12 7.13182 2,2¢,3,4,4¢,5,6¢ – 7.20 7.01 7.03 7.00 6.95183 2,2¢,3,4, 4¢,5¢,6 7.07 7.20 7.02 7.06 7.03 6.99184 2,2¢,3,4,4¢,6,6¢ – 6.85 7.06 6.77 6.72 6.72185 2,2¢,3,4,5,5¢,6 7.00 7.10 6.94 7.08 7.05 7.06186 2,2¢,3,4,5,6,6¢ – 6.69 6.64 6.84 6.80 6.95187 2,2¢,3,4¢,5,5¢,6 – 7.17 6.93 7.02 6.99 6.96188 2,2¢,3,4¢,5,6,6¢ – 6.82 6.87 6.71 6.66 6.68189 2,3,3¢,4,4¢,5,5¢ – 7.71 7.77 7.71 7.71 7.56190 2,3,3¢,4,4¢,5,6 – 7.46 7.30 7.49 7.48 7.45191 2,3,3¢,4,4¢,5¢,6 – 7.55 7.23 7.38 7.36 7.27192 2,3,3¢,4,5,5¢,6 – 7.52 7.31 7.33 7.31 7.16193 2,3,3¢,4¢,5,5¢,6 – 7.52 7.23 7.35 7.33 7.24194 2,2¢,3,3¢,4,4¢,5,5¢ – 7.80 7.82 7.86 7.86 7.75195 2,2¢,3,3¢,4,4¢,5,6 – 7.56 7.38 7.66 7.66 7.71196 2,2¢,3,3¢,4,4¢,5¢,6 – 7.65 7.43 7.55 7.54 7.49197 2,2¢,3,3¢,4,4¢,6,6¢ – 7.30 7.41 7.26 7.24 7.24198 2,2¢,3,3¢,4,5,5¢,6 – 7.62 7.39 7.50 7.49 7.41199 2,2¢,3,3¢,4,5,5¢,6¢ – 7.20 7.07 7.50 7.49 7.45200 2,2¢,3,3¢,4,5,6,6¢ 7.36 7.27 7.26 7.28 7.26 7.36201 2,2¢,3,3¢,4,5¢,6,6¢ – 7.62 7.36 7.19 7.17 7.19202 2,2¢,3,3¢,5,5¢,6,6¢ 7.31 7.24 7.16 7.13 7.10 7.13203 2,2¢,3,4,4¢,5,5¢,6 – 7.65 7.42 7.56 7.56 7.47204 2,2¢,3,4,4¢,5,6,6¢ 7.45 7.30 7.42 7.24 7.22 7.19205 2,3,3¢4,4¢,5,5¢,6 – 8.00 7.70 7.90 7.91 7.76206 2,2¢,3,3¢,4,4¢,5,5¢,6 7.94 8.09 7.84 8.03 8.04 7.94207 2,2¢,3,3¢,4,4¢,5,6,6¢ 7.86 7.74 7.79 7.71 7.71 7.68208 2,2¢,3,3¢,4,5,5¢,6,6¢ 7.78 7.71 7.67 7.64 7.64 7.63209 2,2¢,3,3¢,4,4¢,5,5¢,6,6¢ 8.28 8.18 8.18 8.15 8.16 8.10

The RRT values for the stationary phase C18 (50%) were also correlated with the evaluated log Kow values of Li et al. [32]. TheKow(HPLC)Bro4 [5], the Kow(TSA) [22], and the Kow(HQSAR) values [36] are given as references for comparison. The numbering of thePCB congeners follows Ref. [34]

1869

Kow values for a group of congeners or structurallyrelated compounds.

References

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