Multianion analysis, applications of ion chromatography - Determination of Anions in Natural and Treated Waters - page 670

Fig. 12.32 Dual suppressor column flow system
Source: Reproduced with permission from the American Chemical
Society [58]

the separator column of the ion chromatograph, those loaded by pump having replaced
the injection loop and remained in place during loading and analysis.
Studies on this method have shown the following.

(1) Sample ions are quantitatively retained (<7% RSD) in the concentrator, both when
large volumes of µg L −1 levels or small volumes of mg L −1 levels are loaded. Only the
total number of milliequivalents is important.
(2) Detector response is linear over a large range (2-103µg L −1 ) of ion concentration.
(3) Reproducibility for identical samples in the 5-20µg L −1 range loaded remotely on
different concentrators is 18% RSD for phosphate and nitrate and 25% RSD for
chloride and sulphate.
(4) Concentrators can be loaded and then stored for at least 7 days at room temperature
before analysis without significantly affecting results.

Tables 12.15-12.18 show that response for phosphate, nitrate and sulphate was linear
over four orders of magnitude (2-10 4 µg L −1 ). Responses for chloride ion was linear over
three orders of magnitude (2-10 3 µg L −1 ). Correlation coefficients for a linear least
squares fit were between 0.9887 and 0.9999.
Table 12.19 lists the results obtained from remotely loaded concentrators analysed
immediately after loading vs 7 days after loading. Results show that samples can be
stored for at least 7 days without significantly affecting accuracy. The difference in
determined concentrations between the immediate and the postponed analyses is less than
the RSD for the remotely loaded concentrators.

Table 12.15 Chloride response using a concentrator column

Concentration (µg
L −1 )

Sample vol.
(mL)

Micro-
equivalents

Scale µmho
cm −1

Response µmho
cm −1

14.1×10 −1

1000 5 100 758.46