Extractor column is used to extract the solute from the aqueous solution produced by the generator column. After extraction onto a bonded chromatographic support, the solute is eluted with a solvent/water mixture and subsequently analyzed by high-performance liquid chromatography (HPLC), gas chromatography (GC), or any other analytical procedure. A detailed description of the preparation of the extractor column is given in paragraph (c)(1)(i) of this section.
Generator column is used to partition the test substance between the n-octanol and water phases. The column in figure 1 in paragraph (c)(1)(i)(A)(2) of this section is packed with a solid support and is coated with the test substance at a fixed concentration in n-octanol. The test substance is eluted from the column with water and the aqueous solution leaving the column represents the equilibrium concentration of the test substance that has partitioned from the n-octanol phase into the water phase. Preparation of the generator column is described in paragraph (c)(1)(i) of this section.
n-Octanol/water partition coefficient (Kow) is defined as the ratio of the molar concentrations of a chemical in n-octanol and water, in dilute solution. The coefficient Kow is a constant for a given chemical at a given temperature. Since Kow is the ratio of two molar concentrations, it is a dimensionless quantity. Sometimes Kow is reported as the decadic logarithm (log10Kow). In this equation, Coctanol and Cwater are the molar concentration of the solute in n-octanol and water, respectively, at a given temperature. This test procedure determines Kow at 25 ±0.05 °C. The mathematical statement of Kow is:
Equation 1:
Response factor (RF) is the solute concentration required to give a one unit area chromatographic peak or one unit output from the HPLC recording integrator at a particular recorder and detector attenuation. The factor is required to convert from units of area to units of concentration. The determination of the RF is given in paragraph (c)(3)(iii)(C)(2) of this section.
Sample loop is a 1/16 inch (in) outside diameter (O.D.) (1.6 millimeter (mm)) stainless steel tube with an internal volume between 20 and 50 [MICRO]L. The loop is attached to the sample injection valve of the HPLC and is used to inject standard solutions into the mobile phase of the HPLC when determining the RF for the recording integrator. The exact volume of the loop must be determined as described in paragraph (c)(3)(iii)(C)(1) of this section when the HPLC method is used.
Table 1-n-Octanol/Water Partition Coefficient at 25 °C for Some Reference Compounds
Chemical | Experimental log10Kow | Estimated log10Kow | Recommended log10Kow | ||||
Hansch and Leo1 | Generator Column Method | Banerjee2 | Other values | Hansch and Leo3 | Hawker and Connell4 | ||
Ethyl acetate | 0.73, 0.66 | 50.68 | - | - | 0.671 | - | 170.685 |
1-Butanol | 0.88, 0.89, 0.32, 0.88 | 50.785 | - | - | 0.823 | - | 230.852 |
1-Pentanol | 1.28, 1.40 | 51,53 | - | - | 1.35 | - | 171.39 |
Nitrobenzene | 1.85, 1.88, 1.79 | 51.85 | 1.83 | 61.82 | 1.89 | - | 171.84 |
Benzene | 2.15, 2.13 | - | 2.12 | - | 2.14 | - | 172.14 |
Trichloroethylene | 2.29 | 52.53 | 2.42 | - | 2.27 | - | 172.38 |
Chlorobenzene | 2.84, 2.46 | 72.98 | - | 82.84 | 2.86 | - | 182.80 |
o-Dichlorobenzene | 3.38 | 73.38 | 3.40 | 83.38 | 3.57 | - | 173.42 |
n-Propylbenzene | 3.66, 3.66, 3.68, 3.57 | 53.69 | - | - | 3.85 | - | 173.69 |
Biphenyl | 3.95, 4.17, 4.09, 4.04 | 73.67,93.89,103.79 | 4.04 | 63.75 | 4.03 | 4.09 | 173.96 |
2-Chlorobiphenyl | - | 74.50,94.38 | - | 103.90,113.75,124.59,134.54 | - | 4.99 | 194.49 |
1,2,3,5-Tetrachlorobenzene | - | 74.65 | 4.46 | - | 4.99 | - | 174.70 |
2,2'-Dichlorobiphenyl | - | 94.90 | - | 94.90,103.63,113.55,144.51, 155.02 | - | 4.65 | 204.80 |
Pentachlorobenzene | - | 75.03 | 4.94 | - | 5.71 | - | 244.99 |
2,4,5-Trichlorobiphenyl | - | 75.51,95.81 | - | 105.67,105.86,155.77 | - | 5.60 | 175.70 |
2,3,4,5-Tetrachlorobiphenyl | - | 46.18,75.72 | - | - | - | 6.04 | 175.98 |
2,2',4,5,5'-Pentachlorobi-phenyl | 6.11 | 96.50,75.92 | - | 136.11,126.85 | - | 6.38 | 176.31 |
2,2',3,3',6,6'-Hexachloro-biphenyl | - | 45.76,76.63,96.81 | - | - | - | 6.22 | 176.36 |
2,2',3,3',4,4',6-Heptachlorobiphenyl | - | 76.68 | - | - | - | 7.11 | 176.90 |
2,2',3,3',5,5',6,6'-Octachlorobiphenyl | - | 77.11,97.14 | - | 128.42 | - | 7.24 | 217.16 |
2,2',3,3',4, 4',5,6,6'-Nona-chlorobiphenyl | - | 47.52 | - | - | - | 7.74 | 177.63 |
2,2',3,3',4, 5,5'6,6'-Nona-chlorobiphenyl | - | 78.16 | - | - | - | 7.71 | 177.94 |
Decachlorobiphenyl | - | 78.26,98.20 | - | 129.60 | - | 8.18 | 228.21 |
1 Hansch and Leo (1979). Shake-flask method in paragraph (e)(8) of this section.
2 Banerjee, Yalkowski, and Valvani (1980). Shake-flask method in paragraph (e)(1) of this section.
3 Hansch and Leo (1984). Estimates log10Kow using the CLogP3 computer program in paragraph (e)(9) of this section.
4 Hawker and Connell (1988). Generator column method and an estimation method correlating log10Kow with the total surface area of the molecule in paragraph (e)(8) of this section.
5 Tewari et al. (1982). Generator column method in paragraph (e)(14) of this section.
6 Veith, Austin, and Morris (1979). Reverse-phase HPLC method in paragraph (e)(16) of this section.
7 Miller et al. (1984). Generator column method in paragraph (e)(11) of this section.
8 Chiou and Schmedding (1982). Shake-flask method in paragraph (e)(4) of this section.
9 Woodburn, Doucette, and Andren (1984). Generator column method in paragraph (e)(19) of this section.
10 Rapaport and Eisenreich (1984). Reverse-phase HPLC method in paragraph (e)(13) of this section.
11 Woodburn (1982). Reverse-phase HPLC method in paragraph (e)(18) of this section.
12 Bruggemann, Van der Steen, and Hutzinger (1978). Shake-flask method in paragraph (e)(2) of this section.
13 Tulp and Hutzinger (1978). Shake-flask method in paragraph (e)(15) of this section.
14 Chiou, Porter, and Schmedding (1983). Shake-flask method in paragraph (e)(5) of this section.
15 Bruggemann, Van Der Steen, and Hutzinger (1982). Reverse-phase thin-layer chromatography in paragraph (e)(2) of this section.
16 Chiou et al. (1977). Shake-flask method in paragraph (e)(3) of this section.
17 Average value using all the data.
18 Average value using all the data except the datum point 2.46.
19 Average value using all the data except the data points 3.90 and 3.75.
20 Average value using all the data except the data points 3.63 and 3.55.
21 Average value using all the data except the datum point 8.42.
22 Average value using all the data except the datum point 9.60.
23 Average value using all the data except the datum point 0.32.
24 Average value using all the data excluding the estimated datum point 5.71.
FIGURE 2-SETUP SHOWING GENERATOR COLUMN ENCLOSED IN A WATER JACKET AND OVERALL ARRANGEMENT OF THE APPARATUS USED IN GC METHOD
FIGURE 3-SCHEMATIC OF HPLC-GENERATOR COLUMN FLOW SYSTEM
Equation 2:
Equation 3:
FIGURE 4- WATER RESERVOIR FOR GC METHOD
Equation 4:
Equation 5:
Equation 6:
40 C.F.R. §799.6756