Eluant sodium phthalate

It is appropriate to refer here to the development of non-suppressed ion chromatography. A simple chromatographic system for anions which uses a conductivity detector but requires no suppressor column has been described by Fritz and co-workers.28 The anions are separated on a column of macroporous anion exchange resin which has a very low capacity, so that only a very dilute solution (ca 10 4M) of an aromatic organic acid salt (e.g. sodium phthalate) is required as the eluant. The low conductance of the eluant eliminates the need for a suppressor column and the separated anions can be detected by electrical conductance. In general, however, non-suppressed ion chromatography is an order of magnitude less sensitive than the suppressed mode. 

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]).

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. 

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