Principle - Hitachi ZA3000 Series Instruction Manual

2.2 Principle

Sample
Hydrochloric acid
Sodium borohydride
Argon gas
Arsenic (As), selenium (Se), antimony (Sb) and some other elements
in aqueous solution produce gaseous hydrides through reaction with
nascent state hydrogen. These elements can be analyzed with high
sensitivity by leading the gaseous hydrides into an atomizer which
thermally decomposes and atomizes them.
The Model HFS-4 Hydride Formation System produces hydrogen by
mixing sodium borohydride (NaBH
continuous flow system. The system is provided with not only a
three-liquid flow channel, in which sample, sodium borohydride, and
hydrochloric acid, but also a four-liquid flow channel, in which a
preliminary reducing agent is automatically added to the above three
liquids by the pump.
In the three-liquid flow channel, sample (or distilled water),
hydrochloric acid, and sodium borohydride are constantly flowed by
operating the pump to produce hydrogen. In addition, argon gas is
flowed at a constant rate for carrying hydride.
After the sample is delivered into the reaction coil where hydrogen is
always produced, it reacts with hydrogen (in nascent state) to form
hydrides, which are delivered to the atomizer of the atomic
absorption spectrophotometer (AAS). Then, the elements atomized
in the atomizer are quantitatively-measured by the AAS.
Fig. 2-4 shows a diagram of the three-liquid flow channel.
For measurement using the four-liquid flow channel, refer to "4
MEASUREMENT USING FOUR LIQUIDS".
Pump
Pressure
regulator
Pressure
Flow control valve
switch
Fig. 2-4 Three-liquid Flow Channel of HFS-4
) with hydrochloric acid (HCI) in a
4
Reaction coil
2 - 3
AAS
Hydride
Waste
Separator