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Figure 2. Mean available chlorine concentrations determined in 1 g/L bleach solutions studied over a 14-days period. All the samples were prepared using drinking water
from different sources around Cordoba City as diluent. All samples were stored at room-controlled temperature in opaque containers, except for sample number 6, which
was stored in a transparent container and exposed to light.
Notice that the standard iodometric titration requires acidifi- These results are in agreement with those reported by Iqbal
cation of the solution in order to shift the equilibrium towards the for- et al that recommended a maximum shelf-life of 4–6 days for bleach
mation of HClO as the only species. Therefore, the results obtained solutions of 0.5 g/L and 5 g/L, prepared with drinking water and main-
correspond to the total available chlorine. tained in inactinic containers at 20-35 °C (6). Other authors informed a
longer BUD of, at least, 200 days for 5 g/L bleach solutions stored in the
Since bleach dilutions are usually performed with drinking darkness at 24 °C (9). This increase in stability could be related to the
water, which is known to contain salts, metals and organic matter, it is use of sterile distilled water, where the presence of organic matter or
important to know if the different water sources of the city have an impact other contaminants would be negligible.
on the solutions’ BUDs.
Assigning the appropriate BUD to chlorine solutions is essen-
Figure 2 shows the variation of available chlorine in 1 g/L ble- tial to quality control and to ensure the expected benefits of disinfection
ach solutions relative to their initial concentration. in both institutional and community settings. In our work, we have de-
veloped evidence-based recommendations to assign a BUD for 1 g/L
During the first 10 days of assay all the solutions protected bleach solutions prepared with drinking water. These conditions could
from light showed less than 10 % decrease in the available chlorine con- be extrapolated to the household or hospital level, provided that clean
centrations. On the 14th day, however, the concentration of available and disinfected containers are used; and must be understood as a gui-
chlorine in sample N° 5 fell below the acceptance limit for the BUD (13.5 deline to assign the BUD of bleach solutions used for disinfection purposes
%). This behaviour can be related to the higher COD value observed in that could bring several benefits.
its respective water sample. In addition, the differences in water pH and
conductivity could also explain the small variations observed among the It is important to note that degradation can be accelerated
solutions protected from light (Figure 2). In fact, it is known that the pre- under non-ideal conditions of preparation or storage, such as using con-
sence of salts, organic matter along with metal salts with redox activity, taminated water, storing solutions in open or non-opaque containers
such as Fe, Cu or Zn can affect the stability of hypochlorite solutions. (20), or exposing them to high temperatures (21). Moreover, improper
manipulation of the concentrated solutions or the more frequent opening
In the sample exposed to light (sample Nº 6), a sharp decrease of the containers could allow the external factors to have a more subs-
of available chlorine concentration was observed, with a 3.6 % decrease tantial influence in the degradation rate. In this context, the intervention
at 24 h and 20.7 % at 48 h. These results confirm the importance of light of the Pharmacy Services is recommended, providing use protocols and
protection to preserve bleach stability, whose BUD cannot be extended training and supervising staff (10). Their involvement in determining
to more than 24 h when it is not protected from light. In line with this active chlorine in both concentrated and diluted bleach solutions can also
results, Rutala et al (20) informed a decrease in available chlorine con- provide a greater certainty for its correct use in the health care settings.
centration of 50 to 60 % after a 30 days storing period in transparent
bottles.
Conformidad de lavandinas comerciales y estabilidad de diluciones
2351g/L utilizando diferentes fuentes de agua potable
María E. Gavelli, Laura C. Luciani , Carolina Bustos, María E. Olivera
An. Real Acad. Farm. Vol. 86. Nº4 (2020) · pp. 231 - 236
