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The measurement results of K, Na, Ca, and Mg in water samples by LCGD-AES are basically in agreement with the reference values measured by IC. The limits of detection and precision (RSD, in 1 mg L –1) of K, Na, Ca, and Mg are 0.20, 0.02, 0.01, and 0.01 mg L –1 and 0.9, 1.5, 0.6, and 1.2%, respectively. However, it is not used to further evaluate the analytical performance due to instability of plasma after adding CTAC. With the addition of 0.5% cetyltrimethylammonium chloride (CTAC), the emission intensity of elements can enhance significantly. Low-molecular-weight organic substances do not have a remarkable enhancement on signal intensity. High concentrations of some metals may interfere with the detection of Ca and Mg.
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The results showed that the optimized operating parameters are a 660 V discharge voltage, pH = 1.0 HNO 3 as the supporting electrolyte, and a 4.0 mL min –1 solution flow rate. Moreover, the measurement results of water samples using LCGD-AES were verified by ion chromatography (IC). The discharge stability and parameter influencing the analytical performance of LCGD-AES were systematically examined. A liquid cathode glow discharge (LCGD) was developed as a low-power and miniaturized excitation source of atomic emission spectrometry (AES) for the determination of K, Na, Ca, and Mg in water samples from rivers and lakes.