Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 89

(Breda), Orion model 601 pH meter, Beckman micro blood electrode consisting of a
micro sensor assembly (Beckman Part No 580621), and a pH-electrode (Beckman Part
No. 39045), Hitachi model QPD 53 potentiometric recorder.
Procedure
A schematic flow diagram for the system is shown in Fig. 2.1. Tygon tubing of 0.50mm
diameter was used and all connectors were made from Perspex. The tube lengths used are
as indicated in Fig. 2.1.
Automatically inject water samples into the flow system by using a flow injection
sampling unit. Use a sampling cycle of 30s between successive samples giving a capacity
of 120 samples per h. Actuate the valve system on a time basis which is correlated with
the sampler unit. The sampling valve actuates every 28 s after movement of the sampler
to the next sample.
Fig. 2.2 shows the appearance of recorder tracing as well as calibration curves when
analysing a series of standards in the range 20-300mg L −1 bicarbonate solution. Although
the calibration curve is not linear over the complete concentration range, experimental
results indicate linearity in the range 30-75 mg L −1 .