Table 1 Investigated digestion methods for samples containing SiO2.

From: A hydrofluoric acid-free method to dissolve and quantify silica nanoparticles in aqueous and solid matrices

Method

Digestion

Analysis

max. SiO2 (mg L−1)

max. KOH (M)

range of molar ratio KOH: SiO2

Digested by

max. Si (mg L−1)

max. KOH (mM)

Analyzed by

High SiO2

4110

0.958

0.6–60.1

Microwave

1921

958

DLS

KOH0.1

8.53

0.06

423–1922

1.98

30

ICP

KOH0.5

70

0.5

0.4–1.7

0.75

100

KOH1.0

4.50

0.60

8017–36916

1.05

300

RT + KOH0.1

100

0.1

60.1

RT

4.45

10

UV-Vis

RT + KOH1.0

2.61

0.6

13803–14704

0.57

300

ICP

85

1

462–707

2.39

39

UV-Vis

  1. High_SiO2: high SiO2-NP concentrations were used to find the lowest KOH concentration leading to complete solubilization. KOH0.1, KOH0.5, KOH1.0: different KOH concentrations were tested to assess Si recovery in simple and complex matrices. RT + KOH0.1, RT + KOH1.0: the solubilization of SiO2-NPs at room temperature (RT) was tested (recoveries: refer to Table 2).
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