Books
in black and white
Main menu
Home About us Share a book
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

Chromatografy Methods for Environmental - Ando D.J.

Ando D.J. Chromatografy Methods for Environmental - Wiley publishing , 2003. - 265 p.
Download (direct link): chromatography2003.pdf
Previous << 1 .. 37 38 39 40 41 42 < 43 > 44 45 46 47 48 49 .. 83 >> Next

dielectric constant. It is observed (Table 7.2) that hexane has a small dielectric constant and therefore is unsuitable on its own as a solvent for MAE.
A typical procedure used for microwave-assisted extraction is shown in Figure 7.12.
7.6.2 Example 7.4: Atmospheric Microwave-Assisted Extraction of Polycyclic Aromatic Hydrocarbons from Contaminated Soil
7.6.2.1 Extraction Conditions These are as follows:
Sample: 2 g
Solvent: 70 ml dichloromethane
aMAE conditions: power, 99% (for a 300 W system); extraction time, 20 min
Solids
127
Comments Contents of extraction vessel filtered through a GF/A glass microbore filter. Extracts were concentrated to 5 ml using a rotary evaporator, before addition of internal standards.
7.6.2.2 Analysis by GC
Separation and identification of the individual PAHs was carried out on a Carlo Erba HRGC 5300 Mega Series gas chromatograph, with on-column injection and flame ionization detection. A 30 m x 0.32 mm id x 0.1 ^m film thickness DB-5 HT capillary column was used with temperature programming from an initial temperature held at 50C for 2 min before commencing a 15Cmin-1 rise to 90C; the latter temperature is held for 2 min, and then increased at a rate of 6Cmin-1 to 300C, with a final hold time of 8 min. The detector temperature was set at 290C.
7.6.2.3 Typical Results
These are shown in Figure 7.13 [1].
DQ 7.10
Comment on the results obtained in this study (see Figure 7.13).
350 _ 300
i? 250
o>
E
200
c
0
1 150
c Cl)
? 100
o O
50 0
Figure 7.13 Results obtained for the atmospheric microwave-assisted extraction of various polycyclic aromatic hydrocarbons from contaminated soil, and comparison with those obtained from Soxhlet extraction: ?, Soxhlet; ?, aMAE: 1, naphthalene; 2, ace-naphthylene; 3, acenaphthene; 4, fluorene; 5, phenanthene; 6, anthracene; 7, fluoran-thene; 8, pyrene; 9, benz[a]anthracene; 10, chrysene; 11, benzo[fc,k]fluoranthene; 12, benzo[a]pyrene; 13, indeno[1,2,3-cd]pyrene; 14, benzo[ghi]pyrene [1] (cf. DQ 7.10).
Polycyclic aromatic hydrocarbon
128
Methods for Environmental Trace Analysis
Answer
It is found that the recoveries of polycyclic aromatic hydrocarbons from soil are similar irrespective of the extraction method used. In addition, similar precision is achieved in both cases.
7.6.3 Example 7.5: Pressurized Microwave-Assisted Extraction of Polycyclic Aromatic Hydrocarbons from Contaminated Soil
7.6.3.1 Extraction Conditions These were as follows:
Sample: 2 g
Solvent: 40 ml acetone
pMAE conditions: power, 30% (for a 950 W system); temperature, 120C; extraction time, 20 min
Comments Extraction vessels allowed to cool after extraction process. Contents of vessels were then filtered through a GF/A glass microbore filter, and extracts concentrated to 5 ml by using a rotary evaporator before the addition of internal standards.
7.6.3.2 Analysis by GC
Separation and identification of the individual PAHs was carried out on a Carlo Erba HRGC 5300 Mega Series gas chromatograph, with on-column injection and flame ionization detection. A 30 m x 0.32 mm id x 0.1 film thickness DB-5 HT capillary-column was used with temperature programming from an initial temperature held at 50C for 2 min before commencing a 15Cmin-1 rise to 90C; the latter temperature is held for 2 min, and then increased at a rate of 6Cmin-1 to 300C, with a final hold time of 8 min. The detector temperature was set at 290C.
7.6.3.3 Typical Results
These are shown in Figure 7.14 [1].
DQ 7.11
Comment on the results obtained in this study (see Figure 7.14).
Answer
As already observed for atmospheric microwave-assisted extraction (see Figure 7.13 above), it is found that the recoveries of polycyclic aromatic hydrocarbons from soil are similar irrespective of the extraction method used. In addition, similar precision is achieved in both cases.
Solids
129
Polycyclic aromatic hydrocarbon
Figure 7.14 Results obtained for the pressurized microwave-assisted extraction of various polycyclic aromatic hydrocarbons from contaminated soil, and comparison with those obtained from Soxhlet extraction: ?, Soxhlet; H, pMAE: 1, naphthalene; 2, ace-naphthylene; 3, acenaphthene; 4, fluorene; 5, phenanthene; 6, anthracene; 7, fluoran-thene; 8, pyrene; 9, benz[a]anthracene; 10, chrysene; 11, benzo[fc,k]fluoranthene; 12, benzo[a]pyrene; 13, indeno[1,2,3-cd]pyrene; 14, benzo[ghi]pyrene [1] (cf. DQ 7.11).
7.7 Pressurized Fluid Extraction
Pressurized fluid extraction uses heat and pressure to extract analytes rapidly and efficiently from solid matrices. For background information on pressurized fluid extraction, see Box 7.2.
Box 7.2 Pressurized Fluid Extraction
Theory
Liquid solvents at elevated temperatures and pressures should provide enhanced extraction capabilities when compared to their use at or near room temperature and atmospheric pressure for two main reasons, namely (i) solubility and mass-transfer effects, and (ii) disruption of surface equilibria [5].
Previous << 1 .. 37 38 39 40 41 42 < 43 > 44 45 46 47 48 49 .. 83 >> Next