Total Digestion with HF in HVT Vessels and Complexation of Fluoride with Saturated Boric Acid

In wet chemical analysis complete dissolution of the samples is required for the determination of total concentration of elements. Especially for silicate-containing samples the usage of hydrofluoric acid is a necessity.

1 Introduction

In order to digest and extract all metals quantitatively from matrices containing silicates and oxides, normally digestion with hydrofluoric acid is carried out in a two-step-procedure.

The first step is the digestion with an acid mixture containing HF. However, to avoid excessive losses of reagents by acid venting, the maximum allowed setting for the maximum temperature is 185 °C, if HNO3 is combined with HCl or HF.

So if a higher temperature for the oxidation is required, the first step shall be filled with HNO3 alone and programmed with a setting for the max. temperature of up to 200 °C in Multiwave GO (Limit 205 °C in Multiwave PRO). HF will be added in a second step with a lower limit of 185 °C.

The last step is the complexation of the remaining HF with boric acid.

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