Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 240

Table 2.41 Results of interference study the concentration of nitrite was 0.10µg mL −1

Ion

Concentration/ mg L −1 Relative peak area a

95% Confidence interval

Standard - 100.0 ±2.0 97.5-102.5
Cl − 20000 101.2±2.3 98.3-104.1
Cl − 100 99.4±2.1 96.8-102.2
Br − 100 100.4±2.2 97.7-103.1
F − 100 98.8±1.9 96.4-101.2
SO 4 2− 100 97.8±1.3 96.2-99.4
HCO 3 - 100 99.1±1.5 97.2-101.0
H 2 PO 4 − 100 98.6±2.5 95.5-101.7
NO 3 - 100 111.9±1.3 110.3-113.5
NO 3 - 10 99.6±1.8 97.4-101.8
NH 1 + 100 100.4±1.1 99.0-101.8
a Mean±standard deviation for five replicate analyses (between batch). The peak area of
nitrobenzene converted from the standard solution was arbitrarily assigned a value of 100
Source: Reproduced with permission from the Royal Society of Chemistry [542]

An electron capture detector was used to monitor the gas chromatographic effluent. The
detection limit and determination range of nitrite are 0.5µg L −1 and 1.00-1000µg L −1
respectively, which are much lower than those of the widely used colorimetric method for
the determination of nitrite (detection limit 16µg L −1 ).
The gas chromatographic method was tested in the presence of several ions normally
found in environmental samples. In Table 2.41 the peak area of nitrobenzene produced
from the standard solution containing 100µg L −1 of nitrite was arbitrarily assigned a
value of 100. The concentrations of the ions (100mg L −1 ) added to the standard nitrite
solution were much higher than those in environmental samples. The results indicated
that these anions, except for nitrate, do not interfere in this method. Moreover, chloride
added as sodium chloride at a concentration of 2.0% to the standard solution has no
effect, which suggests the possibility of applying this method to the analysis of seawater.
However, nitrate interferes positively at a concentration of 100mg L −1 although this
interference is not found at 10mg L −1 .
Derivatisation-electron capture gas chromatography has been used to determine µg L −1
quantities of nitrite in water without interference from halides, nitrate, phosphate,
sulphate, bicarbonate, ammonium and alkali metals and alkaline earth metals [543].

2.63.14 Miscellaneous

Nitrites have been determined by oxidation at a glassy carbon electrode [526,534],