Proficiency testing scheme for inorganic acids

The proficiency testing (PT) is offered alternatively with and without own sampling. Participants may choose whether they wish to perform sampling for inorganic acids themselves, or to have the sample carriers supplied to them [1].

The concentrations to be measured for volatile and non-volatile inorganic acids will lie within the range between 1/10 and twice the AGW¹ value [2]. (The German acronym AGW stands for Arbeitsplatzgrenzwert (Occupational Exposure Limit value – OEL). For carcinogenic substances and substances without AGW the database GESTIS - International limit values for chemical agents is used.) Since there is only a short-time limit value for nitric acid, the concentration of one test gas is in accordance with this limit value. The concentrations of the other two test gases are in accordance with the limit value of hydrochloric acid.

For HCl and HNO₃, the IFA recommends the analysis method for hazardous substances described in IFA Arbeitsmappe No. 6172 [3], DFG [4] or NIOSH [5]. For H₂SO₄ and H₃PO₄, a procedure according to IFA Arbeitsmappe 6173 [6], DFG [7] method or NIOSH [8] is recommended. (Please note: IFA Arbeitsmappe is available in German only.)

Ion chromatography should be employed for analysis.

1 Proficiency testing scheme with own sampling

A large-scale dynamic test gas stream can be found at the IFA. It is suitable for parallel sampling by up to 25 participants.

• When: 2026 or 2027 (see above)
• Where:
  Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA)
  Alte Heerstraße 111
  53757 Sankt Augustin
  Germany
• Concentration range:
  between 1/10 and two times the AGW value [2]
• Number of test series: 3
• Duration per test series: 2 hours plus preparation time and run-in period (round three will be a short time measurement) (15 min)
• Accommodations: Hotels (PDF, 45 kB, non-accessible) in Sankt Augustin

In good time, participants will receive detailed information on the PT scheme, a description of the apparatus, and the connections for the sampling devices in particular.

In addition, the participants will receive the sample kit for H₂SO₄ and H₃PO₄ (see below).

2 Proficiency testing without own sampling

The PT for inorganic acids consists of two parts [1]: The same filters are used for volatile and non-volatile acids:

• Quartz fibre filter: MK360, diameter: 37 mm, company: Munktell [3], [6]

Volatile inorganic acids: HCI, HNO₃

Loading of the sample carriers for volatile inorganic acids is performed at the dynamic test gas stream of the IFA. Alkaline impregnated* quartz fibre filters are employed as sample carriers.

* Impregnating solution: 1.0 mol/L sodium carbonate solution

1: Pre-filter: salts of the acids are trapped on the pre-filter.
2: Spacer: to separate the filter
3: Sampling filter: alkali-impregnated quartz fiber filter. Please analyse this filter!
4: Direction of air flow through the sampler

Non-volatile inorganic acids: H₃PO₄, H₂SO₄

The sample carriers quartz-fibre filters are loaded with sulphuric acid and phosphoric acid. The loaded filters are stabilised with 4 mL desorption solution (c (Na₂CO₃) = 3,1 mmol/L and c (NaHCO3) = 0,35 mmol/L) [1].

Each participant receives two sampling kits comprising of:

One sampling kit for HCI and HNO₃ comprising of

• Three loaded sample carriers (quartz fibre filters), and
• Two unloaded sample carriers for blank value adjustment.

In addition the participants will receive a sample kit for H₂SO₄ and H₃PO₄ comprising of:

• Three loaded filters stabilised immediately after loading
• Two unloaded stabilised filters for blank value adjustment.