Page 17 - 86_04

ANALES
RANF
www.analesranf.com
may be present in the healthcare setting (8). To ensure the proper
disinfection, concentration and time of application are of great con-
cern.
Some authors have determined that bleach solutions of
0.5 g/L and 5 g/L remain stable for several days (6,9), however, the
chemical stability of 1 g/L solutions has not yet been demonstrated.
It is widely known that concentrated bleach solutions have
an expected and permitted reduction in the available chlorine con-
centration from up to 33 % during the 150 days of shelf-life (10),
which may affect significantly the concentration of diluted solutions
if they are made based on the nominal labeled concentration. In
addition, the effect of light, heat, contact with air, and the presence bleach solutions were titrated as described by FA 7 (19). Briefly, 1
of traces of metals, metal ions and organic matter can accelerate
chemical degradation (5, 7, 11,12, 13).
In Córdoba City (Argentina), drinking water comes from
different sources as lakes, damps and waterholes, and is processed
in different purification plants. Although the quality of drinking
water can be guaranteed, there is a wide range of acceptable limits
in their mineral and organic content, which could affect the chemical
stability of diluted bleach.
Finally, the unusually high demand for bleach (and other
sanitary products) during COVID-19, may exceed the control capacity
of sanitary authorities, generating a favourable field for the appe-
arance of counterfeit or adulterated products (14–16), which sug-
gests the convenience of performing some quality controls.
The objectives of this work were to determine the com-
pliance of the available chlorine concentration in trademark bleach
solutions and to propose a beyond use date (BUD) for 1 g/L bleach
solutions obtained using different drinking water sources as diluent.
2. MATERIALS AND METHODS
2.1 Water sources
Samples of drinking water were taken from five different
sources around Córdoba city, named from I to V (see table 1). To
avoid variations related to water storage conditions, samples were
taken directly from the drinking water network, from the tap located
at the previous entrance to the tank. Their conductivity and pH were
directly measured with a Mettler Toledo pHmeter, at 25 0 C using a
2-steel poles conductivity sensor and a glass electrode of Ag/AgCl,
respectively. The Chemical Oxygen Demand (COD) was determined
by the Standard Methods for the examination of water and waste-
water (5220 D) with a detection/quantification limit of 15/42 mg/L
of O2 (17) in the Center of Applied Chemistry (CEQUIMAP; Cordoba,
Argentina). Values of pH between 6.5-8.5, conductivity below 1000
µS/cm were considered acceptable. The COD levels are not establis-
hed for drinking water, however, it is known that surface waters pre-
sent values of 20 mg/L of O2 or less in unpolluted waters up to more
than 200 mg/L of O2 in waters receiving effluents (18).
3. BLEACH COMMERCIAL SOLUTIONS
Three trademark bleach presentations, with expiration
dates within the next 150 days and nominal concentration between
25 to 60 g/L, were used in this study. The new containers were ope-
ned on the day of the assay.
4. AVAILABLE CHLORINE TITRATION
Reagents: Potasium iodide (analytical grade; Pura Quí-
mica ®, Argentina), glacial acetic acid 99.5 % (pro-analysis quality,
Cicarelli ®, Argentina), sodium thiosulfate 0.05 M (normalized
analytical reagent Anedra ®, Argentina) and distilled water (Re-
gondi ®, Argentina). Starch solution was prepared dissolving 1 g
of soluble starch in 200 mL of water as described in Farmacopea Ar-
gentina 7 (FA 7) (19).
Procedure: Immediately after reception the concentrated
mL of the concentrated bleach solutions was diluted 1:50 with dis-
tilled water. An exactly measured 1 mL aliquot of this dilution was
added to a glass flask containing 5 mL of distilled water and 0.5 mL
of glacial acetic acid. Then, 0.10 g of potassium iodide were added
to react with the available chlorine species producing a stoichiometric
amount of molecular iodine (equation 5) to be titrated with 0.05 M
sodium thiosulfate (equation 6). Just before reaching the theoretical
end point, a few drops of starch solution were added. Each mL of
0.05 M sodium thiosulfate solution consumed in the reaction was
equivalent to 3.723 mg of sodium hypochlorite. Additionally, a blank
titration was performed and the volume of sodium thiosulfate con-
sumed was discounted from the volume of the end point. The titra-
tions were performed in triplicate. The pH of the solutions before
and after titration was 2.40 ± 0.05.
OCl- (ac)+2I-(ac)+2H+ ¨I2 (ac)+Cl- (ac)+H2O equation 5
2 S2O3-2 (ac) + I2 (ac) ¨2 I- (ac)+S4O6-2 (ac) equation 6
5. BUD DETERMINATION FOR DILUTED BEACH SOLUTION
The 1 g/L solutions were prepared by diluting concentrated
bleach with drinking water, based on the labeled concentration of
available chlorine. Briefly, 2.2 mL of trademark A (46 g/L of avai-
lable chlorine) were added to a 100 mL volumetric flask and taken
to final volume with drinking water coming from five different sour-
ces (I to V, see table 1).
Conformidad de lavandinas comerciales y estabilidad de diluciones
2331g/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