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 .. 21 22 23 24 25 26 < 27 > 28 29 30 31 32 33 .. 83 >> Next

Parameter
S etting/Condition
Hollow-cathode lamp current
Wavelength
Sample volume
Background correction required Graphite tube
Graphite furnace programme (gas
6 mA 286.3 nm
5 ^l
Yes
Lanthanum coated
Step 1: 50°C for 10 s Step 2: 85°C for 10 s Step 3: 600°C for 5 s Step 4: 900°C for 5 s Step 5: 2700°C for 7 s
flow of 50 mlmin 1 argon is on
during Steps 1-4)
(absorbance recorded)
CH3(CH2)-
CH3(CH2)3
CH3(CH2)3 -CH3(CH2)3
:sn o Sn
CH3(CH2)3
CH3(CH2)3
Figure 5.12 The molecular structure of bis(tributyltin) oxide (TBTO); the molecular weight of this compound is 596.12, while the atomic weight of tin is 118.69.
is carried out using bis(tributyltin) oxide (TBTO) (Figure 5.12), by accurately weighing 0.0502 g of TBTO, dissolving in glacial acetic acid and making up to a final volume of 200.00 ml with more acid. A search of the scientific literature will undoubtedly identify a range of procedures for the extraction and separation of organotin species. A summary of the methods used for the determination of organotin compounds in sediments is shown in Table 5.4. A recent review, however, highlights the determination of organotin compounds by using high performance liquid chromatography [17].
SAQ 5.3
By reference to Table 5.4, can you identify any similarities between the different extraction methods used for butyltin determination from sediments?
5.6.3 Arsenic
Arsenic occurs in many chemical forms in the environment, i.e. arsenite As(iii), arsenate As(v), monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), arsenobetaine (AsB) and arsenochloine (AsC) (Table 5.5), with a
Table 5.4 Summary of the various methods used for butyltin determination in sediments [16]
Extraction technique“
Separation Detection“ technique6
1 g of sample extracted with 20 ml acetic acid, followed by centrifugation at 4000 rpm for 15 min. Extract derivatized with GC QFAAS 10% NaBH4 in 1% NaOH
2 g of sample extracted with 20 ml acetic acid and stirred for 12 h, followed by centrifugation at 4000 rpm for 15 min. GC QFAAS
Extract derivatized with 5% NaBELj
2 g of sample extracted with 10 ml acetic acid and mechanically stirred for 16 h, followed by centrifugation at 4000 rpm GC QFAAS
for 5 min. Extract derivatized with 4% NaBH4
2 g of sample, pre-wetted with 2 ml water, extracted with 8 ml of 0.1% NaOH in methanol and back-extracted into 2 ml cGC FPD
hexane. Extract derivatized with NaBH4, followed by back-extraction into hexane
1 g of sample extracted with 5 ml HC1 and 10 ml toluene, with mechanical shaking for 15 h. Extract derivatized with cGC FPD
2% NaBEt4.
3.5 g of sample extracted using SFE with CO2 and 20% methanol, after HC1 addition. Extract derivatized with Grignard cGC FPD
reagent, using 2 moll-1 EtMgCl in tetrahydofuran
5 g of sample, stirred for 1 h with 50 ml of a HBr-water mixture and then extracted for 2 h with tropolone/pentane, cGC FPD
followed by centrifugation at 1000 rpm for 10 min. Organic phase was then dried with Na2S04 and reduced in volume to 0.5 ml. Extract derivatized with Grignard reagent, using 1 moll-1 pentylmagnesium chloride in diethyl ether, for 1 h.
Then, excess Grignard reagent destroyed by dropwise addition of H2S04. Organic layer extracted twice with 5 ml pentane; all extracts combined and dried with anhydrous Na2S04. Resultant extract evaporated to 0.5 ml and purified by passing through a ‘Florisil’ column with pentane. The latter extract reduced in volume to 0.5 ml under N2
2 g of sample ultrasonically extracted for 30 min with 4 ml deionized water, 2 ml acetic acid, 2 ml DDTC in pentane and cGC QFAAS
25 ml hexane. Hexane phase was collected and sediment was back-extracted with 25 ml hexane. Combined hexane
extracts evaporated to dryness, and then re-dissolved with 250 ml «-octane. Extract derivatized with Grignard reagent, using 2 moll-1 pentylmagnesium bromide in diethyl ether
1 g of sample ultrasonically extracted with 20 ml diethyl ether/HCl in tropolone. Extract derivatized with Grignard reagent, cGC MS
using 2 moll-1 pentylmagnesium bromide in diethyl ether
0.5 g of sample extracted with methanol/tropolone after addition of HC1. Extract derivatized with Grignard reagent, using cGC MS
2 moll-1 pentylmagnesium bromide in diethyl ether, followed by clean-up with silica gel
2 g of sample extracted with acetic acid and back-extracted into toluene. Extract pre-concentrated by solvent evaporation HPLC ICP-MS
25 g of sample leached with 150 ml HC1 (0.5 moll-1) for 24 h at room temperature. Slurry centrifuged at 1500 rpm for — Polarography
30 min. Solid material washed with 0.5 moll-1 HC1, followed by centrifugation. Combined supernatant filtered and then extracted with dichloromethane. Organic phase was added to 5 ml LiCl electrolyte (0.2 moll-1) in ethanol
“SFE, supercritical fluid extraction; DDTC, diethyldithiocarbamate.
6GC, gas chromatography; cGC, capillary gas chromatography; HPLC, high performance liquid chromatography.
“QFAAS, quartz-fumace atomic absorption spectroscopy; FPD, flame photometric detection; MS, mass spectrometry; ICP-MS, inductively coupled plasma-mass spectrometry.
Previous << 1 .. 21 22 23 24 25 26 < 27 > 28 29 30 31 32 33 .. 83 >> Next