Anions in non saline waters - Determination of Anions in Natural and Treated Waters - page 88

flow injection analysis. Water samples are injected automatically into the flow system
using a flow injection sampling unit, A sampling cycle of 30s allows 120 samples per
hour to be analysed. The sample is reacted with an acid linear response buffer solution
and the pH of the resulting solution is measured with a glass electrode in a flow through
assembly.
Reagents
Unless otherwise specified all reagents are of analytical grade quality. Carrier stream,
0.1mol L −1 sodium chloride solution. Dissolve 5.844g sodium chloride in 1L distilled
water. Buffer solution. Prepare the following buffer component solutions.
(a) Add 6.01 g diethylmalonate to 7ml concentrated hydrochloric acid solution and dilute
to 500ml with distilled water.
(b) Weigh 7.88g citric acid and dilute to 500ml with distilled water.
(c) Weigh 5.22g p-nitrophenol and dilute to 500ml with distilled water.
(d) Weigh 3.87g diethylbarbituric acid and dilute to 500ml with distilled water.
(e) Weigh 2.32g boric acid, dissolve and dilute to 500ml with distilled water.
(f) Weigh 3.53g phenol, dissolve and dilute to 500ml with distilled water.
Prepare a stock buffer solution by mixing 50ml of solution (a), 50ml of solution (b), 59ml
of solution (c), 150ml of solution (d), 50ml of solution (e) and 50ml of solution (f). This
solution is made 0.10 mol L −1 with respect to sodium chloride.
Apparatus
Peristaltic pump turning at 30rpm, scientific flow-injection sampler
Fig. 2.1 Flow system for the determination of total alkalinity. Sampling rate
120 samples h −1 . Tube length and diameters are given in cm and mm
Source: Reproduced with permission from United Trades Press [22]