Reference

Preconcentration factor

Method

Chelating agent/solid phase adsorbent

[19]

25

AAS

1,5-Diphenyl carbazone/Amberlite XAD-16

[20]

40

ICP-AES

DuoliteGT-73 resin

[21]

5.0

CV-AAS

Dithioacetal/SiO₂

[22]

50

Spectrophotometry

Bis(2-mercaptophenyl)ethanediamide/silica gel

[23]

71

AAS

dithizone/Chromosorb-108

[24]

80

Anodic stripping voltammetry

-Aliquat-336/naphthalene

In this work

100

FAAS

3-mercapto-D-valin