Chemistry Reference
In-Depth Information
exchange columns. Column packings used were
Table 2.13
ICP response factor for various phosphorus compounds
Compounds
Response factor
Purity
KH
2
PO
4
Orthophosphate
1.00
1.00
Na
4
P
2
O
7
−
· 10H
2
O
Pyrophosphate
1.01
1.02
Na
5
P
3
O
10
Tripolyphosphate
1.00
1.00
(NaPO
3
)
Metaphosphate
1.02
0.93
C
10
H
12
N
5
O
7
PNa · 6H
2
O
-
0.98
1.14
C
10
H
12
N
5
O
10
P
2
-
1.03
0.98
C
10
H
14
N
5
O
13
P
3
Na
3
· 3H
2
O
-
1.02
0.97
Source: Reproduced with permission from the American Chemical Society [237]
Table 2.14
HPLC variables
Column
µ-Bondapak-NH
2
1/8in×1ft
Nucleosil N(CH
3
)
3
1/8in×1ft
Eluant
Tartaric acid (0.1 mol L
−1
)+MgSO
4
, (0.01 mol
−1
)+NaOH (0.1 mol
−1
)
Buffers
Oxalic acid (0.1 mol
−1
)+MgSO
4
(0.01 mol
−1
)+NaOH (0.1 mol
−1
)
Ammonium formate (0.1mol
−1
)+MgSO
4
(0.01 mol
−1
)+HCl (0.1 mol
−1
)
Acetic acid (0.2 mol
−1
)+NaOH (0.1 mol
−1
)
Tris(hydroxymethyl)amine (0.3mol
−1
)+H
2
SO
4
(0.075mol
−1
)
Source: Reproduced with permission from the American Chemical Society [237]
µ-Bondapak-NH
2
and Nagel SA. The outlet of the liquid chromatograph was connected
to the crossflow nebuliser of the ICP spectrometer (Jarrell-Ash-Atom-Comp 750) with
Teflon tubing (1/16in×5in). Eluant flow rate was set at 1ml min
−1
.
Phosphorus was monitored at 214.9nm (second order). The analog signal was taken out
through the profile mode of a computer program. In order to filter noise, a 50kΩ resistor
and 20µF condenser were installed before the recording, giving an approximate time
constant of 1s.
The ICP operational parameters were RF power 1.3kw, coolant gas 18L min
−1
, sample
gas 0.5L min
−1
, plasma gas 0.1min
−1
and observation height in plasma 15mm.
The results in Table 2.13 indicate that under these conditions the detection response is
substantially independent of the chemical form of the phosphorus compounds.
Optimum chromatographic conditions are summarised in Table 2.14.
Among the eluants examined, oxalate plus magnesium gave the best resolution, tartrate
plus magnesium gave the second best but formate plus magnesium and acetate plus
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