Concentration (C) of a solution is the amount of solute in a given amount of solvent or solution and can be expressed as a weight/weight or weight/volume relationship. The conversion from a weight relationship to one of volume incorporates density as a factor. For dilute aqueous solutions, the density of the solvent is approximately equal to the density of the solution; thus, concentrations expressed in milligrams per liter (mg/L) are approximately equal to 10-3 g/103 g or parts per million (ppm); those expressed in micrograms per liter ([MICRO]g/L) are approximately equal to 10-6 g/103 g or parts per billion (ppb). In addition, concentration can be expressed in terms of molarity, normality, molality, and mole fraction. For example, to convert from weight/volume to molarity molecular mass is incorporated as a factor.
Density is the mass of a unit volume of a material. It is a function of temperature, hence the temperature at which it is measured should be specified. For a solid, it is the density of the impermeable portion rather than the bulk density. For solids and liquids, suitable units of measurement are grams per cubic centimeter (g/cm3). The density of a solution is the mass of a unit volume of the solution and suitable units of measurement are g/cm3.
Extractor column is used to extract the solute from the saturated solutions produced by the generator column. After extraction onto a chromatographic support, the solute is eluted with a solvent/water mixture and subsequently analyzed by high-pressure liquid chromatography (HPLC), gas chromatography (GC), or any other suitable analytical procedure. A detailed description of the preparation of the extractor column is given in paragraph (c)(1)(i)(D) of this section.
Generator column is used to produce or generate saturated solutions of a solute in a solvent. The column, see figure 1 in paragraph (c)(1)(i)(A) of this section, is packed with a solid support coated with the solute, i.e., the organic compound whose solubility is to be determined. When water (the solvent) is pumped through the column, saturated solutions of the solute are generated. Preparation of the generator column is described in paragraph (c)(1)(i)(A) of this section.
Response factor (RF) is the solute concentration required to give a 1 unit area chromatographic peak or 1 unit output from the HPLC recording integrator at a particular recorder 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)(ii)(B)(2) of this section.
Sample loop is a 1/16 inch (in) outer 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)(ii)(B)(1) of this section when the HPLC method is used.
Saturated solution is a solution in which the dissolved solute is in equilibrium with an excess of undissolved solute; or a solution in equilibrium such that at a fixed temperature and pressure, the concentration of the solute in the solution is at its maximum value and will not change even in the presence of an excess of solute.
Solution is a homogeneous mixture of two or more substances constituting a single phase.
Table 1-Water Solubilities at 25 °C of Some Reference Chemicals
Reference chemical | Water solubility (ppm at 25 °C) | ||
Wasik (generator column method) | Yalkowski15 | Other literature references | |
2-Heptanone | 24080 | 4300 | 54330 |
1-Chlorobutane | 2873 | 872.9 | 7666 |
Ethylbenzene | 2187 | 208 | 7162 |
1,2,3-Trimethylbenzene | 265.5 | 75.2 | 748.2 |
Biphenyl | 3106.71 | 7.48 | 86.62 |
Phenanthrene | 41.002 | 1.212 | - |
2,4,6-Trichlorobiphenyl | 3100.226 | 0.225 | 80.119 |
2,3,4,5-Tetrachlorobiphenyl | 3100.0209 | 0.01396 | 80.0192 |
Hexachlorobenzene | - | 0.004669 | 90.00996 |
2,3,4,5,6-Pentachlorobiphenyl | 3100.00548 | 0.004016 | 80.0068 |
1 Preferred water solubility at 25 °C by Yalkowski et al. (1990) in paragraph (e)(12) of this section based on a critical review of all the experimental water solubility data published.
2 Tewari et al. (1982) in paragraph (e)(10) of this section.
3 Leifer et al. (1983) in paragraph (e)(3) of this section.
4 May, Wasik, and Freeman (1978, 1978a) in paragraphs (e)(5) and (6) of this section.
5 Yalkowski et al. (1990) in paragraph (e)(12) of this section.
6 Hansch et al. (1968) in paragraph (e)(2) of this section.
7 Sutton and Calder (1975) in paragraph (e)(9) of this section.
8 Mackay et al. (1980) in paragraph (e)(4) of this section.
9 The elution chromatographic method from Organization for Economic Cooperation and Development (OECD) (1981) in paragraph (e)(8) of this section.
10 Miller et al. (1984) in paragraph (e)(7) of this section.
FIGURE 1-GENERATOR COLUMN
FIGURE 2-SETUP SHOWING GENERATOR COLUMN ENCLOSED IN A WATER JACKET AND OVERALL ARRANGEMENT OF THE APPARATUS USED IN THE GC METHOD
Table 2-Constituents of Artificial Seawater1
Chemical | Amount |
NaF | 3 mg |
SrCl2,6H2O | 20 mg |
H3BO3 | 30 mg |
KBr | 100 mg |
KCl | 700 mg |
CaCl2.2H2O | 1.47 gram (g) |
Na2SO4 | 4.00 g |
MgCl2.6H2O | 10.78 g |
NaCl | 23.50 g |
Na2SiO3.9H2O | 20 mg |
NaHCO3 | 200 mg |
1 If the resulting solution is diluted to 1 L, the salinity should be 34 ±0.5 g/kilogram (kg) and the pH 8.0 ±0.2. The desired test salinity is attained by dilution at time of use.
FIGURE 3-SCHEMATIC OF HPLC-GENERATOR COLUMN FLOW SYSTEM
Equation 1:
Equation 2:
FIGURE 4-WATER RESERVOIR FOR GC METHOD
Equation 3:
Equation 4:
Equation 5:
40 C.F.R. §799.6786