Reference number  
DRS 384: 2018 
© RSB 2018 
 
 
 RWANDA 
STANDARD  DRS  
384 
 
First edition  
2018-mm-dd 
 
Disinfecting liquid synthetic detergents — 
Specification  
 
  DRS 384: 2018  
©RSB 2018- All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2018  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reprodu ce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw  DRS 384: 2018  
iii                ©RSB 2018- All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Term s and definitions  ................................ ................................ ................................ ..................  1 
4 Classification  ................................ ................................ ................................ ................................  2 
5 Requirements  ................................ ................................ ................................ ................................  2 
5.1 General requirements  ................................ ................................ ................................ ..................  2 
5.2 Specific requirements  ................................ ................................ ................................ ..................  2 
6 Packaging and labelling ................................ ................................ ................................ ...............  3 
6.1 Packaging  ................................ ................................ ................................ ................................ ...... 3 
6.2 Labelling  ................................ ................................ ................................ ................................ ........  3 
7 Sampling  ................................ ................................ ................................ ................................ ....... 4 
Annex  A (normative)  Determination of pH  ................................ ................................ .............................  5 
Annex  B (normative)  Stability at low and high temperature  ................................ ................................  6 
Annex  C (normative)  Cleaning efficiency  ................................ ................................ ..............................  7 
Annex  D (normative)  Determination of disinfecting activity  ................................ ..............................  10 
 DRS 384: 2018  
©RSB 2018- All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare nati onal standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS  384 was prepared by Technical Committee RSB/TC 042, Surface Active Agents . 
In the preparation of this standard, reference was made to the following standard:  
1) KS 927 , Disinfecting general purpose liquid synthetic detergents – Specification  
The assistance de rived from the above source is hereby acknowledged with thanks.  
Committee  membership  
The following organizations were represented on the Technical Surface Active Agents (RSB/TC 042) in the 
preparation of this standard.  
Paragraph of p articipants  
University of Rwanda – College of Sciences and Technology  
Rwanda Biomedical Center – Medical Procurement and Production Division  
Trust Industries Limited  
SULFO Rwanda Industries  
Private Sector Federation – Beauty Makers Association  
Mount Kenya University  
IKIZERE Initiative Hope Shines  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 384: 2018  
v                ©RSB 2018- All rights reserved  
 Introduction  
Household cleaners are some of the most widely purchased consumer products. Manufacturers of household 
cleaners have always had to keep three sometimes conflicting  goals in mind: the performance of the product, 
the safety of the ingredients fo r users, and the  costs of the ingredients. Recently, due to consumer demands, 
reducing impacts upon the  environment has been added as a fourth goal. Given the diversity of the cleaners, 
the number of  ingredients, and the difficulty in understanding the ent ire life cycle of multi -ingredient  
formulations, it is not surprising that different manufacturers have different definitions of "green"  for household 
cleaners.  
 
Among household cleaners include d isinfectants that are products whose major function is to ki ll bacteria on a 
surface, but which  are not necessarily formulated to remove dirt, stains, or other soils. Thus, these products 
are to  be distinguished from disinfecting cleaners of the types considered earlier under either general  purpose 
or bathroom clea ners.  
 
 DRS 384: 2018  
1                ©RSB 2018- All rights reserved  
 Disinfecting liquid synthetic detergents  — Specification  
1 Scope  
This Draft  Rwanda S tandard specifies requirements , sampling  and test methods for liquid synthetic detergent 
that contains a phenolic, quaternary ammonium or other type of germicide and which is intended primarily for 
general cleaning and disinfecting floors, walls , woodwork  and other hard sur faces  where the destruction of 
bacteria is important.  
2 Normative references  
The following documents are referred to in the text in such a way that some or all of  their content constitutes 
requirements of this document.  For dated references, only the edition  cited applies. For undated references, the 
latest edition of the referenced document (including any amendments) applies.  
RS ISO 862, Surface active agents — Vocabulary  
ISO 1063, Surface active agents -- Determination of stability in hard water  
RS 278, Cosmetics – Method of Sampling  
RS EAS 814,  Determination of biodegradability of surfactants — Test method  
ISO 2870, Surface active agents — Detergents — Determination of anionic -active matter hydrolysable and non -
hydrolysable under acid conditions  
ISO 2871 -1, Surface active agents — Detergents — Determination of cationic -active matter content — Part1: 
High-molecular -mass cationic -active matter  
ISO 2871 -2, Surface active agents — Detergents — Determination of cationic -active matter content — Part 2: 
Cationic -active matter of low molecular mass (between 200 and 500)  
3 Terms and definitions  
For the purposes of this standard, the terms and definitions given in RS ISO 862  and the following apply.  
3.1 
germicide  
substance that destroys microorganisms on inanimate env ironmental surfaces in the growing form but not 
necessarily the resistant spore form.   
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 3.2 
disinfectant  
substance or treatment that prevents the transmission or survival of undesirable microorganisms (usually  in the 
growing form) on inanimate environmental surfaces by causing the complete destruction or irreversible 
inactivation of such microorganisms  
4 Classification  
Disinfecting liquid synthetic detergents shall be of the following types:  
 Type 1 – Phenolic  
 Type 2 – Quaternary ammoni um compounds  (QAC)  
 Type  3 - Others  
5 Requirements  
5.1 General  requirements  
5.1.1  The product shall be a clear homogenous solution at room temperature (25 ºC ± 2 ºC). 
5.1.2  It shall not contain visible foreign matter and shall be free from objectionable odour (e.g., rancidity or 
odour of decomposition) both when received and when in solution.  
5.1.3  The product shall clean and disinfect in one operation in the presence of hard water as specified.  
5.1.4  All the ingredients used in the detergent shall be biodegradable when tested against RS EAS 814.  
5.1.5  When stored under normal conditions in sealed containers for a period equal to its shelf -life, the 
material shall remain stable and homogeneous, and shall remain free from objectionable odour.  
 
5.1.6  The product under conditions of use sha ll not cause deterioration of vinyl, asphalt, terrazzo, rubber or 
concrete cement flooring surfaces. When used on metallic or other hard surfaces the products shall cause no 
greater corrosion or harmful effects than water in the conditions.  
5.2 Specific requir ements  
The product shall also comply with the requirements given in Table 1 when tested against the methods 
prescribed therein.  
Table 1 Specific requirements  
S/N Parameters  Requirements  Test method  
1 pH of 1 part solution to 9 parts of water  4.0 to 10.5  Annex A  DRS 384: 2018  
3                ©RSB 2018- All rights reserved  
 2 Stability to hard water  Not more than 0.5 mL of 
curd shall be generated  ISO 1063  
3 Stability at low and high temperature  To pass test  Annex B 
4 Cleaning efficacy at 1 ;20 dilution with 
synthetic hard water, %, min.  70 Annex C 
5 Active detergent 
level, % m/m, min.  Phenolic s and 
Others  8.0 ISO 2870  
ISO 2871 -1 
ISO 2871 -2 Quaternary 
Ammonium 
Compounds  2.0 
6 Disinfecting activity  To pass test  Annex D 
6 Packaging and labelling  
6.1 Packaging  
The product shall be packaged in suitable containers  that are strong enough to withstand normal usage and 
transportation and that will prevent leaking, drying out and contamination of the product.  
6.2 Labelling  
Each container and each bulk package shall be legibly and indelibly marked with the following information:  
a) description of the product as “disinfecting detergent”;  
b) manufacturer’s name and physical address;  
NOTE: The name, physical address of the distributor/supplier and trade mark may be added as required.  
c) batch/lot number;  
d) net content;  
e) type of germicide used and it’s level;  
f) Instructions for use, given in imperative tense, including at least the dilution recommended for particular 
applications and an instruction not to mix with other chemicals that the manufacturer knows may affect 
the efficacy of the disinfecting compound;  
g) manufacture and expiry dates;  
h) list of ingredients in descending order of quantity;  
i) instructions for remedy in case of accidental ingestion; and  
j) country of origin.   
©RSB 2018- All rights reserved                  4 
 7 Sampling  
Sampling shall be done in accordance with RS 278 . 
 DRS 384: 2018  
5                ©RSB 2018- All rights reserved  
 Annex  A 
(normative)  
 
Determination of pH  
A.1 Apparatus and reagents  
A.1.1 pH meter  
A.1.2 Freshly boiled and cooled distilled water  
A.2 Procedure  
Dilute a portion of the material to be tested in the proportions specified with distilled water. Measure the pH of 
the dilute solution electro -metrically at 25 ºC. For pH’s over 10, the pH instrument shall be standardized 
against a buffer solution of at le ast pH 10 in order to minimize any error due to the unsuitability of the glass 
electrode for the pH range encountered.  
 
A.3 Report  
 
Report the pH of the solution.  
 
   
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 Annex  B 
(normative)  
 
Stability at low and high tem perature  
B.1 Procedure  
Put the product at 10  ºC for low temperature, and 40 ºC for high temperature for 24 h. After  24 h remove it and 
allow it to return to room temperature (20  ºC approximately) for another 24 h during  which time it shall be well 
shaken or agitated. Pour the sample in a clean test jar and check for any  cloudiness or turbidity, visually.  
 
B.2 Report  
 
If any cloudiness, turbidity, separation or laying develops when the product is held at 10  ºC for 24 h and is 
completely eliminated when the product is returned to room temperature for 24 h and well shaken or agitated, 
then the product will have passed the test. If the cloudiness, turbidity or layering does not completely 
disappear after the product is returned to room temperature, then the product is not stable at low temperature.  
 
  DRS 384: 2018  
7                ©RSB 2018- All rights reserved  
 Annex  C 
(norma tive) 
 
Cleaning efficiency  
C.1 Principle of the method  
A solution of working strength of the product is made up with water and used in a scrubbing machine to 
remove a synthetic soil from a test panel. The reflectance of the cleaned panel is measured and ex pressed 
before application of soil.  
 
C.2 Apparatus  
 
C.2.1 Washability machine – A gardener model 105 straight line washability machine equipped with a 
sponge box. The total weight of the sponge box and sponge shall be 454 ±14 g. If necessary, sheet lead may 
be fastened to the top of the sponge box to attain this weight.  
 
C.2.2Reflectometer – Equipped with an amber tristimulus filter.  
 
C.2.3Standard white plague (reflectance approximately 80 per cent)  
 
C.2 4 Test panels – Amtico VPII white vinyl tile 230 x 230 x 3.2 mm cut to 115 x 230 mm. Only new panels 
shall be used for the test. Scrub the surface with a wet cloth and scouring powder, rinse with water, oven -dry 
at 100 ºC for 15 min and cool to room temperature. Measure  and record the reflectance(R1) of each. Use the 
template described in C.2.11. 
 
C.2.5Flat pan – Approximately 50 x 150 x 300 mm.  
 
C.2.6Sponge – A photographic grade cellulose friegrain sponge, preshrunk and cut to a dry size of about 95 x 
75 x 40 mm.  
 
C.2.7 50 mL burette  
 
C.2.8 Boston – Brandley adjustable blade, or fixed blade applicator 75 mm wide and 0.10 mm clearance.  
 
C.2.9 Water of 150 ppm hardness  
 
C.2.10 Two vinyl title squares , 115 x 115 mm.  
 
C.2.11 Template of vinyl title , 115 x 230 mm with four evenly spaced holes for making reflectancereadings.  
 
C.2.12 Forced draft oven, - 0.5 ºC 
 
C.2.13 Standard reference detergent sodium dodecylbenzene sulfonate (linear, 80 per cent active)23.5 per 
cent.  
 
Sodium Tripolyphosphete, anhydrons — 40.0 per cent  
Sodium  metasilicate, pentahydrate — 7.0 per cent  
Sodium sulfate,anhydrons — 29.5 per cent.  
 
C.3 Preparation of soiled panels  
C.3.1  Soil          Parts by weight   
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  Metallic brown, ASTM D & 4, Class 1    20 
  Kerosene          12 
  Stoddard solvent         12 
  Liquid petroleum         1 
  Lubricating oil         1 
  Hydrogenated vegetable shortening     1 
 
C.3.2 Soiling procedure  
 
Dissolve oils and shortening in kerosene -stoddard solvent and then disperse metallic brown in this solution. 
While the bulk lot of soil is continuously stirred to ensure uniformity, remove a sample of approximately 4 g 
and apply along the entire length of vinyl panel. Use a ‘doctor’ blade, of fixed -blade applicator, set at 0.10 mm 
to provide an even spread. Air dry soiled panel in forced d raft oven set at 80 ºC for 15 min.  
 
Allow panels to cool to room temperature, use between 20 and 24 h after removal from oven.  
 
C.3.3 Synthetic hard water  
 
Prepare a litre of synthetic hard water as described in RS EAS 127 -1. 
 
C.3.4 Checking soiled panels – Clean 2 C.3.3 sets of 3 soiled panels by the procedure detailed in E4. with 
the exceptions that , in the case of set N0. 1, the wash solution shall be distilled water, and in the case of No. 
2, the wash solution shall be a 1. 0 per cent solution standard. Reference detergent in 150 ppm hard water. 
Measure the reflectance of the cleaned panels and calculate cleaning efficiencies. Cleaning efficiency with 
distilled water shall be less than 30 percent and with the standard deterge nt shall exceed 80 per cent. If the 
criteria given above are not met in at least 2 of the 3 determinations, the lot of soiled panels shall be reflected. 
This checking procedure shall be followed with each lot of soiled panels.  
 
C.4 Procedure  
 
C.4.1 Make up  1 litre of a 2 percent solution of the cleaner or detergent in 150 ppm hard water, and use at 
25°C.  
 
C.4.2 Fit sponge into washability apparatus housing box 95 x 75 mm.  
 
C.4.3 Soak test panel for 60 s in sufficient wash solution to cover entire panel.  
 
C.4.4 Wet sponge with 25°C tap water and squeeze damp -dry by hand.  
 
C.4.5 Add 50 mL of wash solution to damp -dry sponge and insert into sponge housing box.  
 
C.4.6 Centre test panel on washability apparatus by use of two 115 x 115 mm pieces of vinyl tile, one  on 
either end of the test panel.  
 
C.4.7 Start washability apparatus, set at one stroke per second (a complete cycle) back and forth is two stroke 
while dripping wash solution from a burette onto the centre of test panel.  
 
C.4.8 Time wash operation so that  12 mL wash solution from burette onto the centre of test panel.  
 
C4.9 Wash panel for 100 strokes (50 cycles).  
 
C.4.10 Stop apparatus.  
 
C.4.11 Remove washed panel and rinse under a light stream of 25°C tap water.  
 DRS 384: 2018  
9                ©RSB 2018- All rights reserved  
 C.4.12 Drain water from panel and immediately replace on apparatus in a reverse direction.  
 
C.4.13 Rinse sponge in 25°C tap water, squeeze damp -dry by hand, and replace sponge in box with unused 
side facing test panel.  
 
C.4.14 Repeat wash cycle and rinse panel as before.  
 
C.4.15 Allow washed, rinsed panel to air dry.  
 
C.4.16 Make triplicate runs for each cleaning solution tested. Use a fresh sponge for each different detergent 
tested, but the same sponge, may be used for replicator runs on any one product. The first test result obtained  
from using a new sponge for the first time shall be reflected.  
 
C.4.17 Measure the reflectance of the washed panels as described in C.2.4. Average the results obtained (4 
readings on each of thee panels).  
 
C.5 Calculation and report  
 
 
 Cleaning  efficiency  (% CE) = 𝑅2
𝑅1 𝑥 100 
 
 Where, R1 = reflectance of unsoiled, unwashed panel , 
 
                    R2 = reflectance of soiled, washed panel.  
   
©RSB 2018- All rights reserved                  10 
 Annex  D 
(normative)  
 
Determination of disinfecting activity  
D.1 Outline of the method  
D.1.1 The disinfectant detergent is tested at the recommended ‘use’ -dilution’ and concurrently at 0.5 and 1.5 
times that dilution. The test consists of challenging the diluted disinfectant with bacterial moculum, 
withdrawing a sample in a suit recovery medium. After the sampling, the mixt ure is again challenged by a 
second moculum and after a second interval, is again sampled for curruting. This process is then repeated to 
provide a third challenge.  
 
D.1.2 The sample is considered to have passed or failed the test according to the extent of growth shown in 
the first two cultured samples.  
 
D.2 Apparatus  
 
D.2.1 Facility for incubation at 37 °C ± 1 °C. 
 
D.2.2 Facility for incubation at 27 °C ± 1 °C. 
 
D.2.3 Stopclock  
 
D.2.4 Facility for refrigeration at 4 ± 1 °C. 
 
D.2.5 Universal containers ― Made of glass and having metal tops with rubber liners. Plastic containers or 
glass containers with plastic tops shall not be used.  
 
D.2.6 Test tubes — 19 mm X 150 mm.  
 
D.2.7 Filter paper , No. 4 whatman (sterile) or equivalent.  
 
D.2.8 Autoclave , 121 ± 1 °C. 
 
D.2.9 Pipette , capable of dispensing 0.02 °C ± 1 °C 0.005 mL.  
 
D.2.10 pH meter  
 
D.2.11 Sterilizer ,  (by filtration ) 
 
D.2.12 150 μm test sieve . 
 
D.2.13 Oven , capable of maintaining temperature at 100 °C ± 1 °C. 
 
D.3 Media  
 
D.3.1 Growth media for test organisms.  
        Wright and Mundy Broth with Dextrose (WMBD).  
 
D.3.1.1 Dispense 10 mL and 6 mL quantities of the Wright and Mundy Broth into universal bottles, and 
autoclave at 121 °C ± 1°C for 12 minutes.  DRS 384: 2018  
11                ©RSB 2018- All rights reserved  
 D.3.1.2 Add to this medium, 10 per cent (M/v) de xtrose solution sterilized by filtration, to give a final dextrose 
concentration of 0.1 per cent (m/v), (i.e. to 10 mL broth add 0.1 dextrose solution and to 6.0 mL broth add 0.06 
mL dextrose solution).  
 
D.3.2 Recovery medium ― A nutrient broth prepared as  follows:  
 
D.3.2.1 Composition  
 
  10 g of Beef extract  
  10 g of Peptone  
  5 g of Sodium chloride  
  30 g of Polyoxyethylene sorbitan mono -oleate.  
 
D.3.2.2 Preparation – Add the ingredients to 1000 mL of water. Mix well. Dispense 10 mL quantities intotest 
tubes and autoclave at 121 ± 1°C for 15 minutes.  
 
D.3.3 Hard water – Standardhard water with 342 mg/L (ppm) hardness prepared as follows:  
Dissolve 0.304 g of anhydrous calcium chloride hexahydrate ( MgCl2-6H2O) in distilled water and make up the 
volume to one litre. Sterilize the standard hard water by autoclaving at 121 °C ± 1 °C for 15 minutes . Allow this 
to reach room temperature before use.  
 
D.3.4 Yeast suspension  
 
D.3.4.1 Weigh to the nearest gram about 65 g of active dry yeast. Cream by the gradual addition of sterile 
hard water using a heavy glass rod for stirring. Decant the creamed portion into a flask, add more hard water 
to any lumpy residue remaining and repeat the creaming and decantation until no re sidue remains, and 500 
mL of hard water has been used.  
 
D.3.4.2 Shake the contents of the flask vigorously and strain -through a 150 μm sieve ( F2.12 ) breaking down 
any remaining lumps.  
 
D.3.4.3 Add 500 mL sterile hard water, shake vigorously.  
 
D.3.4.4 Transfer 50 mL or 100 mL portions into screw capped bottles, screw the caps tightly and autoclave at 
121 °C ± 1°C for 15 minutes. Allow the autoclave to cool without releasing the pressure. Store cold but 
notfreezing.  
 
D.3.4.5 Dry two glass petri -dishes to  constant mass. Into each of these dishes, pipette 25 mL of sterilized 
yeast suspension and dry to constant mass at 100°C. Calculate the average solids content of the suspension.  
 
D.3.4.6 Before use, pipette 25 mL of the sterilized yeast suspension into a beaker. Determine the pH using a 
glass electrode, and determine the volume of 40 g/L sodium hydroxide solution needed to adjust the pH to 7.0 
± 0.1.  
 
D.3.4.7 Immediately before use, add to each bottle of sterilized yeast suspension a volume of sterile hard  
water and a volume of 40 g/L sodium hydroxide calculated to adjust the concentration of dry yeast to 5 per 
cent (m/v) and the pH to 7.0 ± 0.1. Discard prepared yeast, two weeks after preparation.  
 
D.3.5 Ringers solution, 25 per cent (v/v) ― Dissolve 9.00 g of sodium chloride, 0.42 g of potassium 
chloride, 0.24 g of anhydrous calcium chloride and 0.20 g of sodium bicarbonate in water and dilute to 1000 
mL. 
Add 1 volume of this solution to 3 volumes of water to give a 25 per cent solution. Dispense into test  tubes 
fitted with suitable closures and sterilized by auto -claving at 121 °C ± 1°C for 15 minutes.  
 
D.4 Selection of the most resistant organism by the minimum inhibitory concentration test  
 
D.4.1 The following organisms shall be used for the test:   
©RSB 2018- All rights reserved                  12 
 Pseudomonas aeruginosa (NCTC 6749 or equivalent)  
Proteus vulgaris (NCTC 4635 or equivalent)  
Stophyloccus aureus (NCTC 4163 or equivalent)  
 
These organisms may be obtained as freeze dried cultures. Once sub -cultured, the organisms shall be 
maintained on aga r slopes of suitable nutrient medium at 4 ± 1°C.  
 
D.4.2 Subculture each organism daily into a universal bottle containing 6 mL of growth medium ( D.3.1 ) and  
Incubate for 24 ± 2 h at 37 °C ± 1°C.  
 
D.4.3 Dilute one part of freshly grown sub -culture of each organism, which is at least a fifth sub -culture and 
not more than a fourteenth, with ten parts of the growth medium ( D.3.1 ) before dilution, the P. aeruginosa , 
culture shall be filtered using a whatman No.4 filter paper.  
 
D.4.4 Prepared three sets of ten, doubling dilutions of the disinfectant in universal containers ( D.2.5 ). For this 
purpose dilute the neat disinfectant in the growth medium ( D.3.1 ) or the recovery medium ( D.3.2 ) to give a 
final volume of 5 mL of the diluted disinfectant for each dilution.  
 
D.4.5 Inoculate each dilution in one set with 0.02 mL of a diluted culture of one organism (see D.4.3 )). 
 
D.4.6 Incubate all the three sets of inoculate dilutions at 37 ± 1°C for 72 hours, and examine to determine the 
organism most resistant to the disinf ectant, that is the organism for which the minimum inhibitory 
concentration is highest.  
 
D.5 Preparation of inoculums  
 
D.5.1 Daily sub -cultures of the test organism selected as in D.4.6 shall be grown in 6 mL quantities of the 
growth medium ( D.3.1 ) and incubated at 37 ± 1°C for 24 ± 2 hours.  
 
D.5.2 The day before the test, inoculate 10 mL of the growth medium ( D.3.1 ) with the test organism from a 
daily sub -culture and not more than a fourteenth. Incubate the inoculated, broth at 37 °C ± 1°C for 24 ± 2 
hours. 
 
D.5.3 Add 6 mL of the test organism culture ( D.5.1 ) and ( D.5.2 ) to 4 mL of the yeast suspension ( D.3.4 ) thus 
making a final concentration of 2 per cent (m/v) of yeast in the yeast/organism suspension. If a culture of P. 
aeruginosa is used, it shall b e filtered using a whatman No.4 filter paper before addition.  
 
D.5.4 Shake the yeast/organism suspension for one minute with a few sterile glass beads. Immediately before 
the test, count the number of viable organisms in the inoculum by decimal dilutions i n 25 per cent Ringers 
solution (see D.3.5 ) and by the drop plate method. The viable count shall be not less than 108 organisms/mL 
or more than 1010 organisms/mL or the test results are considered invalid.  
 
D.6 Preparation of the disinfectant dilutions  
 
Prepare three dilutions of the disinfectant in hard water ( D.3.3 ) based on the recommended ‘use dilution’ of 
the disinfectant, as follows  
 
A = 0.5 times the recommended ‘use -dilution’  
B = 1.0 times the recommended ‘use -dilution’  
C = 1.5 times the recommended ‘use -dilution’  
 
The disinfectant dilutions shall be prepared and tested on the same day.  
 
D.7 Test procedure  
 
D.7.1 The test shall be carried out at 27 °C ± 1°C.  DRS 384: 2018  
13                ©RSB 2018- All rights reserved  
  
D.7.2 Dispense 3 mL of each dilution of disinfectant ( D.6) into separate universal bottles labelled A, B, and C, 
then allow to equilibrate to 27 °C ± 1°C.  
 
D.7.3 Add 1 mL of the inoculum to A, B and C at 0, 1 and 5 min respectively and mix by swirling gently.  
 
NOTE : Although D.7.4 to D.7.7 inclusive relate to a single sample, in practice all three dilutions are tested 
concurrently and a protocol for this is given in D.7.7 . It is recommended that before commencing the test, 
universal containers holding the disinfectant dilutions are arranged in a rack together wit h a fourth container 
holding the inoculum. The tubes of the recovery broth, labeled A1, A2 and A3, B1, B2 and B3; C1, C2 and C3 
are placed nearby and using a copy of the test protocol, each step is ticked off as it is completed.  
 
D.7.4 Eight minutes after the addition of the inoculum, remove a sample of the inoculum/disinfectant mixture 
and put 0.02 mL into each of the first group of five tubes of recovery broths. Return the remainder of the 
mixture in the pipette to the universal container.  
 
D.7.5 Ten minu tes after the first addition of the inoculum, add another 1 mL of the inoculum to each of the 
disinfectant dilutions and mix by swirling gently.  
 
D.7.6 Eight minutes later, remove a sample of the mixture as put before ( D.7.4 ) and put 0.02 mL into each of 
the second group of five tubes of recovery broths.  
 
D.7.7 Swirl the recovery broths and incubate at 37 °C ± 1°C for 48 ± 2 h. Examine the growth and record the 
results.  
 
D.8 Interpretation of results  
 
D.8.1 The disinfectant, shall be regarded as having passed the test at the recommended ‘use dilution’ if there 
is no growth in at least two of the five recovery broths for the first and second additions of the inoculum.  
 
D.8.2 To be acceptable, a disinfectant shall pass the test on three separate occasions using freshly prepared 
inoculum on each occasion.  
 
 DRS 384: 2018  
ICS 71.100.35  
 
 
©RSB 2018 - All right s reserved