Direct determination of trace amounts of sodium in water-soluble organic pharmaceuticals by microwave induced plasma atomic emission spectrometry

The direct determination of trace sodium by microwave induced plasma atomic emission spectrometry (MIP-AES) in water-soluble organic substances utiliz ed in pharmaceutical preparations was developed. No decomposition of the or ganic constituents was required. Samples were dissolved with water and intr oduced to the plasma after ultrasonic nebulization without desolvation. A l imit of detection (3 sigma) of 0.91-3.0 ng ml(-1) was obtained under experi mental conditions. The quantitative MIP-AES procedure involved the standard addition method. The sodium content determined in reference material NIST SRM 1568A Rice Flour agreed with the certified value (6.6 +/- 0.8 mug g(-1) ). Physical and chemical interferences were investigated. It was found for the microwave plasma that it is possible to introduce organic substances so lutions of concentration up to 5% without sensitivity losses. This direct t echnique is fast and sensitive and helps to reduce contamination connected with the sample preparation procedure. (C) 2001 Elsevier Science B.V. All r ights reserved.