Some factors affecting the concentration of available chlorine in commercial sources of sodium hypochlorite

Aims To evaluate the availability, effect of storage, dilution and heating on some commercial sources of sodium hypochlorite (NaOCl). Methodology All pharmacies in a Regional Health Authority were telephone su rveyed to establish the proprietary and nonproprietary NaOCl products avail able, their cost and concentration. Ninety-six freshly produced bottles of a commercially available thin household bleach (J, Sainsbury's) were random ly stored in four different modes (full 1L bottles in dark at room temperat ure, half-empty 1 L bottles under the same conditions, full 200 mt bottles under the same conditions, full 200 mt bottles stored at 37 degreesC) up to 6 months. The available chlorine in the bleach solutions was evaluated at specific time intervals (0, 1, 2 weeks, 1, 2, 3, 4, 6 months) using iodomet ric titration. Four brands of commercially available bleaches (J. Sainsbury 's Thin Household Bleach, Tesco's Value Bleach, Tesco's Red Label Bleach, S afeway's Savers Bleach) were diluted (by 1:1, 1:2 or 1:3 dilution factors) and samples taken from each dilution for titration to test predictability. NaOCl solutions (5% w/w) were heated in covered or uncovered beakers up to 60-85 degreesC. Samples were taken from each beaker at time 0 and each h up to 4 h, for titration. Results Of the 116 pharmacies, 33% could supply a proprietary product and 5 3% a nonproprietary product. In all, 78% were able to supply a NaOCl produc t. There was no significant difference (P< 0.05) in available chlorine at b aseline between the different modes of storage. After storage at room tempe rature for 6 months, there were no significant differences (3% of original; P > 0.05) between the different modes of storage. When the storage tempera ture was 37 degreesC, however, there was a significant difference (38% of o riginal: P < 0.01) at 6 months, Comparison of baseline with the concentrati ons of available chlorine at 6 months showed significant differences (P < 0 .01) for all conditions. The available chlorine concentration in four brand s of 'thin' supermarket bleaches could be predictably reduced according to the dilution factor. When 5%, NaOCl was heated to 60-85 degreesC for up to 4 h, the available chlorine was increased to 6% in covered solutions and 9% in uncovered solutions. Conclusions Both proprietary and nonproprietary solutions of NaOCl should b e relatively easily obtainable in the UK. Stored under appropriate conditio ns, commercially available thin bleaches and nonproprietary solutions of Na OCl may he diluted to obtain predictable concentrations. Heating solutions of NaOCl may cause unpredictable changes to the concentration, depending up on conditions.