Function and design
HS 55 (Batch Mode)
12
3
Function and design
3.1
Function and measuring principle
Hydride method
The hydride method enables the matrix-free detection of the elements As; Bi; Sb; Se; Sn;
Te. It is based on the formation of gaseous metal hydrides through reduction of the
acidic samples with sodium borohydride (NaBH
4
). The carrier gas and the released hy-
drogen transport the metal hydrides to the quartz cell. There they gradually decompose
through collisions with gas particles and the glass wall at temperatures of 850 to 950 °C.
The free metal atoms absorb the primary radiation on the resonance line.
With the hydride method spectral interference is practically eliminated, because only the
element to be detected reaches the atomizer as gaseous metal hydride.
Cold vapor method
The cold vapor method is used to detect mercury. Besides sodium borohydride (NaBH
4
),
tin(II) chloride (SnCl
2
) is also used as a reduction agent. During the reaction with the
acidic sample solution, atomic Hg vapor forms, which is transported to the Hg cell by the
carrier gas argon. The free Hg atoms absorb the primary radiation on the resonance line.
The heating of the cell from room temperature to 150 °C can reduce background inter-
ference due to moisture.
HydrEA method
The HydrEA method combines the hydride or Hg cold vapor method with the graphite
tube method. It is used for the highly sensitive selective detection of the hydride-form-
ing elements As; Bi; Sb; Se; Sn; Te or Hg with the graphite tube furnace.
The Hg/hydride system generates the gaseous metal hydrides or the atomic Hg vapor,
respectively. The autosampler for the graphite tube furnace (AS-GF) transfers the ana-
lytes with the carrier gas argon into the graphite tube furnace. There the metal hydrides
are enriched on the iridium-coated standard tube for wall atomization at a preheating
temperature of 300 °C. They decompose in this process. At a temperature of 2100 °C,
the deposited metal atoms atomize again. The generated atom vapor cloud absorbs the
primary radiation on the resonance line.
The atomic Hg vapor is enriched on the gold-coated standard tube at 65 °C. At a temper-
ature of 950 °C, the Hg atoms atomize again.
Overview of Hg/hydride sys-
tems
Hg/hydride system
Function
HS 50
Simplest batch system with pneumatic operating principle
The quartz cell is heated by the acetylene-air flame.
HS 55
Batch system with electrically heated cell unit
The user fills the sample solution manually into the reaction
beaker of the Hg/hydride system. The reduction agent solution
is automatically metered by a 1-channel hose pump.
HS 60
Hg/hydride system for flow injection operation with electrically
heated cell unit
Sample and reduction agent solution, acid and waste are trans-
ported through the system by means of hose pumps.
The AS-F and AS-FD autosamplers can supply the sample solu-
tions to the Hg/hydride system in a fully automatic manner.
All Hg/hydride systems allow the detection of the hydride-forming elements and mer-
cury using the hydride and cold vapor methods.