Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 294

Table 2.50 The effect of surfactants on turbidimetric sulphate determination at various
sulphate concentrations

% Recovery

mg L −1 5mg L −1 SO 4 10mg L −1 SO 4 20mg L −1 SO 4

Surfactant

Cationic detergent 1000 101 103 104

Linear alkyl 0.2 99 103 100

Sulphate 0.5

2.0

107
144

103
120

100
110

Non-ionic detergent 30 112 107 104

Formulated detergent 5 109 105 102

Mixed detergent 5

20

106
120

102
118

100
105

Sodium pyrophosphate 100 103 107 110

Sodium tripolyphosphate 2

5

100
101

105
106

101
108

Soap 2 112 110 103

NTA 500 100 99 103

Source: Reproduced with permission fromVodni Hospodorstri [747]

determine sulphate in the range 30-150mg L −1 with a correlation coefficient of 0.99.

Cationic, anionic and non-ionic surfactants, polyphosphates and nitriloacetic acid are
without interference in barium-based turbidimetric methods for the determination of
sulphate (Table 2.50).
Krug et al. [748] have used continuous flow injection turbidimetry for the rapid
determination of sulphate in non saline waters.
S lanina et al. [749] and Van Raaphorst et al. [750] claim a detection limit of 0.5mg L −1
with a relative accuracy of 5% in the turbidimetric deter-mination of sulphate in rain
water.
Okawara and Kadota [751] compared the turbidimetric determination of sulphate in
non saline waters by using 2-aminoperimidine and barium sulphate as precipitating
reagents in the presence of glycerin and sodium chloride. The calibration plots were
linear over the range of 0-10mg of sulphate L −1 . Use of 2-aminoperimidine gave the
more sensitive method because of the smaller particle sizes formed. The coefficient of
variation ( n =5) was 1.4% when 2-amino-perimidine was used and 7.8% when barium
sulphate was used for sulphate concentrations of 2mg L −1 .