Novel Spectrophotometric Method for Determination of Trace Germanium in Soils with Methybenzeneazosalicylfluorone using Ultrasound‐Assisted Leaching

Abstract

The research describes a very novel method for spectrophotometric determination of trace germanium in soils. The method is based on the color reaction of germanium (IV) with a new reagent, methybenzeneazosalicylfluorone (MBASF), in the presence of 6.0 M phosphoric acid and Triton X‐100. The reaction can complete rapidly and form a 1∶2 red complex with a maximum absorption at 501 nm under room temperature. The absorbance of the complex at 501 nm increases linearly with the concentration up to 18 µg of germanium (IV) in 25 mL of the solution; the apparent molar absorptivity was 2.18 ×10 ⁵ L mol⁻¹ cm⁻¹. The interference study shows the reaction system has an excellent selectivity. All common metal and interference ions reported in other literatures can be tolerated in considerable amounts. The analytical characteristics in sensitivity and selectivity are superior over all reagents reported previously. Moreover, a very simple procedure was also developed for the dissolution of soil samples in the work. The analyte was leached from soil samples by adding 2.0 mL of concentrated hydrofluoric acid to 500–1000 mg of the sample, and the mixture was then submitted to a 10‐min ultrasonic treatment. After adding 0.6 g of boric acid and 10 mL of concentrated phosphoric acid, the filtered solution was applied directly to spectrophotometric determination of trace germanium. The detection limit, calculated using three times the standard error of estimate of the calibration graph, was 2.75 ng l⁻¹. The reliability of the proposed method were verified by analyzing several certified reference materials and using the standard addition method.

Keywords:

• Germanium
• methybenzeneazosalicylfluorone
• soil
• spectrophotometry
• ultrasonic treatment