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radiello® Diffusive Air Sampling Application - Hydrochloric Acid (HCl)

radiello Components Used:

White diffusive body Product No. RAD120
Supporting plate Product No. RAD121
Vertical adapter Product No. RAD122 (optional)
Chemiadsorbing cartridge Product No. RAD169

Or: radiello-ready-to-use Product No. RAD1238


Cartridge RAD169 is made of stainless steel net loaded with silica gel (0.1 to 0.4 mm particle size). Gaseous hydrochloric acid is adsorbed by silica gel and subsequently extracted with water to be quantified by ion chromatography as chloride ion.

Sampling is selective for the gaseous molecules: any airborne chloride salt will not cross the diffusive membrane of radiello.

Sampling Rate

Sampling rate Q at 298 K (25 °C) and 1013 hPa is 103 ml·min-1.

Effect of Temperature, Humidity and Wind Speed

Sampling rate varies from the value at 298 K (25 °C) on the effect of temperature (in Kelvin) as expressed by the following equation:

where QK is the sampling rate at temperature K and Q298 is the sampling rate value at the reference temperature of 298 K. This yields a ± 5% variation of Q for a 10 °C variation (upwards or downwards) from 25 °C.

Sampling rate is invariant with humidity in the range 15 - 90% for short exposure time (see Exposure) and with wind speed between 0.1 and 10 m·s-1.


Let m be the mass of chloride ion in μg found onto the cartridge and t the exposure time in minutes, the environmental concentration C of hydrochloric acid in μg·m-3 is obtained according to the equation:

where QK is the sampling rate at temperature K (in Kelvin) and 1.028 is the ratio between molecular masses of HCl and Cl-(see Analysis).


Hydrochloric acid is sampled linearly in the range from 20,000 - 20,000,000 μg·m-3·min.

Workplace Environment

In workplace environment we recommend exposure time from 15 minutes to 8 hours: the ceiling values can be measured.

Outdoor Environment

We recommend exposure time from 2 hours to 2 days. Exposure time as long as 7 days is allowed if average relative humidity does not exceed 50%, taking into account the water absorbing properties of silica gel.

We also recommend to protect radiello from rain by the mountable shelter Product No. RAD196.

Limit of Detection and Uncertainty

The limit of detection is 10 μg·m-3 for 24 hour exposure. The uncertainty at 2σ is 3.5% over the whole allowed exposure range.


Gaseous chlorine is adsorbed by silica gel and is revealed as 0.02 ng of chloride ion for 1 μg·m-3·min of chlorine.


Kept in a clean environment free from gaseous hydrochloric acid, cartridge RAD169 is stable for at least 24 months before and after sampling.

If more than six months have passed since you received the cartridges, before environmental sampling campaigns, it is advisable to analyse some cartridges to check for contamination from the background. Discard the cartridges if they contain more than 5 μg of chloride ion.


Add 2 ml of deionised water to the cartridge in its tube (make sure that no trace of chloride ion is found in the water you use). Recap the tube and stir vigorously by a VORTEX stirrer for 1-2 minutes. Analyse the solution by ion chromatography. Subtract the blank value obtained from two unexposed cartridges.

Prepare the calibration solutions with sodium or potassium chloride concentrations ranging from 0.5 to 25 mg/liter
as Cl-.


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