Eluant sodium nitrate

Plot a graph of the total effluent collected against the concentration of halide in each fraction (millimoles per litre). The sum of the titres using 0.3 M sodium nitrate eluant (less blank for each titration) corresponds to the chloride, and the parallel figure with 0.6M sodium nitrate corresponds to the bromide recovery. 

For ionic samples it is recommended that salt/buffer systems be used as eluants. The salts most commonly used are sodium sulfate, sodium nitrate, and sodium acetate because these cause little corrosion to stainless steel column hardware even at low pH. Ionic strength is varied according to sample type but generally does not exceed 1.0 M because increasing salt concentration promotes hydrophobic interaction. Often a buffer is used to allow pH to be controlled. 

Van Os et al. [41] achieved complete separations in 6min of l-30mg L 1 concentrations of bromide, chloride, nitrite, nitrate and sulphate using a Zipax SAX separation column, with eluent suppression and electrical conductivity detection [42], The necessary high pressure packing techniques for packing the separation column have been described [43], With sample pieconcentration, detection limits were reduced to about 5pg L 1 but calibration graphs for chloride and nitrate were not linear. Sodium adipate and 1.410 3M disodium succinate are used as eluants, both at pH7. 

When using conventional ion chromatographic separation techniques, it is possible that other matrix anions also common to non saline waters may coelute with bromide. For example, bromide and nitrate elute simultaneously using a standard anion separator column (Dionex No. 30065), standard anion suppressor (Dionex No. 30366) and standard eluant (0.003M sodium bicarbonate/0.0024M sodium carbonate). 

Jones and Tarter [11] have applied this technique to the simultaneous determination of metals (sodium, potassium, calcium, magnesium) and anions (chloride, sulphate, nitrate, bromide) in potable waters. The technique uses a cation separator column, a conductivity detector, an anion separator column and an anion suppressor column. Two different eluants were used lithium carbonate-lithium acetate dihydrate, and copper phthalate. 

Sodium chloride has the advantage of lowest reagent cost. Nitrate eluant has the advantage of providing the highest uranium concentration in the eluate. However, chloride and nitrate eluants require conversion of resin back to sulfate form with sulfuric acid to improve uranium recovery in the next adsorption cycle. 

Surface-functionalized PS/DVB polymers are also commercially available. For example, Hamilton (Reno, USA) introduced an anion exchange resin rmder the trade name PRP-XIOO. This resin features spherical PS/DVB particles, which are surface-aminated with trimethyl amine [21, 22]. As can be seen from Fig. 3-4, seven inorganic anions, which are commonly referred to as standard anions , can be separated within a short time. Sodium p-hydroxybenzoate was used as the eluant. Similar stationary phases are also available from SYKAM (Gilching, Germany) under the trade name LCA AOl. The different elution order of anions on LCA AOl as compared with the PRP-XIOO is due to the use of a carbonate/ bicarbonate eluant (Fig. 3-5). In addition, Sykam offers a stationary phase under the trade name LCA A04, on which bromide and nitrate elute behind sulfate. 

Fig. 3-4. Separation of various inorganic anions on PRP-XIOO. - Eluant 4 mmol/L sodium p-hydroxybenzoate (pH 8.6) flow rate 3 mt/min detection direct conductivity injection volume 100 pL solute concentrations 20 mg/L each of fluoride (1), chloride (2), nitrite (3), bromide (4), nitrate (5), orthophosphate (6), and sulfate (7) (taken from [22]).

Fig. 7-36. Indirect photometric detection of various inorganic anions. — Separator column 250 mm X 4 mm i.d. SAR-40-0.6 eluant 1 mmol/L sodium phthalate (pH 7 to 8) flow rate 2 mL/ min detection UV (285 nm, indirect) injection volume 20 pL solute concentrations 106 mg/L chloride (1), 138 mg/L nitrite (2), 400 mg/L bromide (3), 310 mg/L nitrate (4), and 480 mg/L sulfate (5) (taken from [65]).

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