principles of extraction and the extraction of semivolatile organics ...

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42 Figure 2.2. Solubility, vapor pressure, and Henry’s law constant for selected chemicals [2,4]. (Reprinted with permission from Ref. 2. Copyright 6 1980 Elsevier Science.)
principles of extraction Nonvolatile: volatilization is unimportant for H < 3 10 7 atm m 3 / mol (i.e., H for water itself at 15 C) Semivolatile: volatilizes slowly for 3 10 7 < H < 10 5 atm m 3 /mol Volatile: volatilization is significant in the range 10 5 < H < 10 3 atm m 3 /mol Highly volatile: volatilization is rapid if H > 10 3 atm m 3 /mol Schwarzenbach et al. [8] illustrate the Henry’s law constant (Figure 2.3c) for selected families of hydrocarbons in relation to vapor pressure (Figure 2.3a) and solubility (Figure 2.3b). Vapor pressure (Figure 2.3a) and solubility (Figure 2.3b) tend to decrease with increasing molecular size. In Figure 2.3c, the Henry’s law constant is expressed in units of atm L/mol, whereas the Henry’s law constant in Figure 2.2 is expressed in units of atm m 3 /mol. Applying Mackay and Yuen’s, and Thomas’s volatility guidelines to the units in Figure 2.3c, the Henry’s law constant for semivolatile compounds in water lies between 3 10 4 < H < 10 2 atm L/mol (since 1 L ¼ 0.001 m 3 ). Highly volatile compounds lie above a Henry’s law constant of 1 atm L/mol. For example, Figure 2.3c illustrates that a high-molecular-weight polycyclic aromatic hydrocarbon (PAH) such as benzo[a]pyrene (C20H12) is semivolatile in its tendency to escape from water according to the Henry’s law constant, whereas a low-molecular-weight PAH, naphthalene (C10H8), is volatile. The most common gas–liquid pair encountered in analytical extractions is the air–water interface. The extraction methods discussed in this chapter are most applicable to organic solutes that are considered nonvolatile and semivolatile. However, it is possible to extend these techniques to more volatile chemicals as long as careful consideration of the tendency of the solute to volatilize is made throughout the extraction process. 2.1.2. Hydrophobicity Studies about the nature of the hydrophobic e¤ect have appeared in the literature since the early work of Traube in 1891 [14]. According to Tanford, a hydrophobic e¤ect arises when any solute is dissolved in water [15]. (Hydrophobic e¤ects, hydrophobic bonds, and hydrophobic interactions are used synonymously in the literature.) A hydrophobic bond has been defined as one ‘‘which forms when non-polar groups in an aqueous solvent associate, thereby decreasing the extent of interaction with surrounding water molecules, and liberating water originally bound by the solutes’’ [16]. In the past, the hydrophobic e¤ect was believed to arise from the attraction of nonpolar groups for each other [17]. Although a ‘‘like-attracts-like’’ interaction certainly plays a role in this phenomenon, current opinion views the strong 43
Page 1 and 2: CHAPTER 2 PRINCIPLES OF EXTRACTION
Page 3 and 4: principles of extraction Henry’s
Page 5: principles of extraction Figure 2.1
Page 9 and 10: principles of extraction forces bet
Page 11 and 12: principles of extraction Figure 2.4
Page 13 and 14: Logarithm of Aqueous Solubility (mm
Page 15 and 16: principles of extraction Figure 2.7
Page 17 and 18: where KW is the ion product of wate
Page 19 and 20: alpha 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3
Page 21 and 22: liquid-liquid extraction solving ac
Page 23 and 24: Acetone Acetonitrile n-Butyl Alcoho
Page 25 and 26: liquid-liquid extraction Table 2.3.
Page 27 and 28: Step 4. Calculate the percent of an
Page 29 and 30: additional recovery of 3.697% of th
Page 31 and 32: (a) (b) liquid-liquid extraction Fi
Page 33 and 34: liquid-liquid extraction Figure 2.1
Page 35 and 36: Step 1: Adjust aqueous sample to pH
Page 37 and 38: Fujiwara et al. [47] devised instru
Page 39 and 40: liquid-solid extraction centrate se
Page 41 and 42: liquid-solid extraction Macropore R
Page 43 and 44: solid-phase extraction The most com
Page 45 and 46: solid-phase extraction that sample
Page 47 and 48: solid-phase extraction Si O Si Si S
Page 49 and 50: solid-phase extraction meric struct
Page 51 and 52: Si O R Si O H X Si R R Si O X H X H
Page 53 and 54: solid-phase extraction ternary amin
Page 55 and 56: S i l i c a S i l i c a SO 3 − NH
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Hydrophobic inner surface solid-pha
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Monomer Print molecule Monomer Poly
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solid-phase extraction blended laye
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solid-phase extraction interact pri
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solid-phase extraction ple is a goo
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ecovery (%) 120 100 80 60 40 20 sol
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solid-phase extraction Reversed Pha
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Dependence of Desorption on Eluting
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CONDITIONING Conditioning the sorbe
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solid-phase extraction Figure 2.45.
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solid-phase microextraction 2.4.6.
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solid-phase microextraction KD ¼
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solid-phase microextraction nesses
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solid-phase microextraction Table 2
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Sample Headspace Coating (a) solid-
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Mass [ng] 180 160 140 120 100 80 60
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stir bar sorptive extraction extrac
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Recovery 1 0.9 0.8 0.7 0.6 0.5 0.4
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stir bar sorptive extraction Howeve
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eferences than LLE. The capacity fo
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eferences 26. E. Overton, Studien u
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eferences 69. C. W. Huck and G. K.
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eferences 114. J. Patsias and E. Pa
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CHAPTER 3 EXTRACTION OF SEMIVOLATIL
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introduction [5]. Di¤erent extract
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Porous Thimble Sample soxhlet and a
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ultrasonic extraction for polycycli
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ultrasonic extraction (over 20 ppm)
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pressure S T L G temperature Figure
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Weight % SiO 2 in H 2 O supercritic
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supercritical fluid extraction the
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accelerated solvent extraction for
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Solvent accelerated solvent extract
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Load Cell Fill With Solvent (0.5-1.
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Table 3.9. Solvents Recommended by
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microwave-assisted extraction a qui
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Solvent microwave-assisted extracti
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Cavity Exhausted to Chemical Fume H
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Magnetron microwave-assisted extrac
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microwave-assisted extraction Choic
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comparison of the various extractio
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93-101 1-3 84 1.5- to 2.5-g sample,
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comparison of the various extractio
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eferences 3. Book of ASTM Standards
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eferences 53. A. Hubert, K. Wenzel,
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CHAPTER 4 EXTRACTION OF VOLATILE OR
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Thermometer Screw cap Syringe Rubbe
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static headspace extraction prepara
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Peak area (counts) 12000 10000 8000
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Area A a /A is 16000 14000 12000 10
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static headspace extraction The con
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1. Dichlorodifluoromethane 2. Chlor
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dynamic headspace extraction or pur
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dynamic headspace extraction or pur
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solid-phase microextraction made co
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Coating Material solid-phase microe
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solid-phase microextraction chance
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solid-phase microextraction movemen
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1 liquid-liquid extraction with lar
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liquid-liquid extraction with large
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membrane extraction Feed Side Membr
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membrane extraction cient, C the so
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membrane extraction side volume, wh
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1 2 3 membrane extraction 1. 1,1 Di
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Benzene Toluene membrane extraction
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eferences 4.7. CONCLUSIONS There ar
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eferences 38. P. D. Okeyo and N. H.
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