7
684 Chen et al.
Asian J. Chem.
chloride background interference in the sample matrix. The
method proves to be simple, accurate, easy to handle and appli-
cable for routine analysis of iodate in iodized salt samples.
as 0.025 g/mL in deionized water. 5 mL of the salt solution
were transferred to a 20 mL stoppered glass tube and the
procedure was completed as above metioned.
RESULTS AND DISCUSSION
EXPERIMENTAL
The concentration of potassium iodate in iodized salt is
only about 20-60 mg/kg. Hence, sodium chloride constitutes
the main sample matrix. Chloride has no UV absorption, how-
ever, large amount of chloride can overload the column giving
rise to a serious interference. Under the optimal conditions,
the experimental results (Fig. 1) indicated that in the absence
of a high background salt concentration, several common
inorganic anions (except nitrite and bromide) could be well
separated (if gradient elution was applied, seven kinds of anions
could be baseline separated). On the other hand, spiking 0.1
g/mL iodized salt samples with similar concentrations of these
anions would result in the anions peaks eluted before 10 min
A Dionex (Dionex, Sunnyvale, CA, USA) Model
Ultimate-3000 High Performance Liquid Chromatograph
equipped with a LPG3400A quaternary pump, a WPS3000TSL
autosampler, a TCC-3000 Column Heater and a VWD-3100
Ultraviolet Detector was used. The instruments control and
data collection were performed with Chromeleon SR6.8
software (Dionex, USA). The analytical column was Dionex
Acclaim Mixed-Mode WAX-1 (120 Å, 250 mm × 4.6 mm ×
5
µm). HPLC-grade Acetonitrile (Sigma-Aldrich, USA) and
-1
de-ionized water of 18.2 MΩ cm achieved by a Millipore
water system (Millipore, Mosheim, France) was used through-
out. Potassium iodide (KI), potassium phosphate monobasic
(
iodate, bromate, nitrate, nitrite and bromide) being masked
(
8
(
KH
5 % hydrazine hydrate (N
NaOH) and phosphoric acid (H
and obtained from Sinopharm Chemical Reagent Co., Ltd
Shanghai, China). Potassium iodate (KIO ) crystalline was
2
PO
4
), sodium pyrophosphate decahydrate (Na
·H O), sodium hydroxide
PO ) were of analytical grade
4
P
2
O
7
·10H
2
O),
by the background chloride, but fortunately, those peaks of
iodide and thiocyanate eluted after 10 min was not subject to
any interference allowing accurate analytical peak interpre-
tation. Possible reason is that the high concentration of chloride
in the matrix occupied most of the active site of the column
stationary phase resulting in column overload masking most
of the earlier peaks (eluted before 10 min) while peaks eluted
thereafter does not suffer any interference (Fig. 1). So from
the above discussion it can be concluded that the analysis of
potassium iodate in iodized salt samples was possible after
reduction using hydrazine hydrate according to the proposed
approach without interference and with much simpler
pretreatment procedure.
2
H
3
4
2
4
(
3
purchased from Institute of Chemical Reagent in Tianjing,
China. 0.085 % hydrazine hydrate was prepared by appropriate
dilution of 85 % hydrazine hydrate solution. Iodized refined
salt, marine alga iodine salt, morton low salt and Healthy
Balance salt real samples were purchased from local market.
The standard stock solution (10 mmol/L) of potassium
iodate (KIO
3
) and potassium iodide (KI) were prepared by
or 166 mg of KI in
00 mL water. Other working solutions of 0.1, 1, 5, 10, 50,
00, 1000 µmol/L of KIO and KI were prepared by
accurately dissolving 214 mg of KIO
3
1
1
3
appropriate dilution from the stock solutions.
1
50
00
WVL-226 nm
The mobile phase was composed of a mixture of 50 mmol/L
potassium phosphate monobasic (pH 6) and acetonitrile (volume
ratio of 65:35). Flow rate was set at 1 mL/min. Column tempe-
rature was 30 °C. Injection volume was 10 µL.
5
1
3
4
6
The buffer component of the mobile phase was prepared
1
2
3
2
1
by dissolving 6.80 g of KH
2
PO
4
and 2.50 g of Na
P
4 2
7
O ·10H
2
O
0
in 1000 mL water and the pH was adjusted to 6 using 1 mol/L
NaOH. Finally, the solution was filtered through 0.45 µm
membrane filter and ultrasonically degassed for 15 min prior
to use.
Methods: Both the standards and sample solutions were
firstly deoxidized using 0.085 % hydrazine hydrate according
to the following procedure. 2 mL potassium iodate solution
–
100
–
200
(
or edible salt solution ) followed by 5 mL 0.085 % hydrazine
0
2.5
5.0
7.5
10.0
12.5 15.0 17.5 20.0
hydrate were transferred to a 20 mL stoppered glass tube, the
mixture was then heated for 6 h in an oven at 90 °C. The
produced equivalent iodide could be measured according to
its UV absorption at 226 nm. The reaction can be represented
by the following equation:
Fig. 1. Chromatograms of 7 common inorganic anions on column WAX-
.1, 0.1 g /mL iodized salt solution as a blank; 2, 0.1 g/mL iodized
1
salt solution spiked with the 7 studied anions; 3, the 7 common
anions standards plain peak profile. Peak identified: (1) iodate; (2)
bromate; (3) nitrate; (4) nitrite and bromide; (5) iodide; (6)
thiocyanate
9
6
0 °C
H
–
–
2
IO
3
+ 3NH
2
2I + 3N
2
+ 6H O
2
Column selection: In conventional reversed-phase C18
column, iodate and iodide can not be retained. Therefore, a
weak anion-exchange column (Acclaim Mixed-Mode WAX-
1, 120 Å, 4.6 × 250 mm × 5 µm) was used in this study to
Procedures for real samples were as follows: iodized
refined salt, marine alga iodine salt and Morton low salt
samples were prepared as 0.10 g /L and Healthy Balance salt
Chen, Meilan
