Reference number  
DRS 392 -3: 2018  
© RSB 2018  
 
 
 RWANDA 
STANDARD  DRS  
392-3 
 
First edition  
2018 -mm-dd 
 
Skin appli ed mosquito repellents — 
Specification  — 
Part 3: 
Wipes  
  DRS 392 -3: 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 392 -3: 2018  
iii                ©RSB 2018 - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  2 
4 Requirements  ................................ ................................ ................................ ................................  4 
4.1 General  ................................ ................................ ................................ ................................ ..........  4 
4.2 Active ingredients  ................................ ................................ ................................ ........................  4 
4.2.1  Natural repellents  ................................ ................................ ................................ .........................  4 
4.2.2  Synthetic repellents  ................................ ................................ ................................ .....................  5 
4.3 Specific requirements  ................................ ................................ ................................ ..................  5 
4.4 Biological efficacy  ................................ ................................ ................................ ........................  6 
5 Packaging and labelling ................................ ................................ ................................ ...............  6 
5.1 Packaging  ................................ ................................ ................................ ................................ ...... 6 
5.2 Labelling  ................................ ................................ ................................ ................................ ........  6 
6 Sampling  ................................ ................................ ................................ ................................ ....... 7 
Annex  A (normative)  Determination of length and width  ................................ ................................ ..... 8 
A.1 Apparatus  ................................ ................................ ................................ ................................ ...... 8 
A.2 Procedure  ................................ ................................ ................................ ................................ ...... 8 
Annex  B (normative)  Determination of absorbency rate  ................................ ................................ ...... 9 
B.1 Apparatus  ................................ ................................ ................................ ................................ ...... 9 
B.2 Preparation of test specimens  ................................ ................................ ................................ .... 9 
B.3 Procedure  ................................ ................................ ................................ ................................ ...... 9 
B.4 Calculation  ................................ ................................ ................................ ................................ .... 9 
B.5 Test report  ................................ ................................ ................................ ................................ ..... 9 
Annex  C (normative)  Determination of moisture content  ................................ ................................ .. 11 
C.1 Principle  ................................ ................................ ................................ ................................ ...... 11 
C.2 Apparatus  ................................ ................................ ................................ ................................ .... 11 
C.3 Sample preparation  ................................ ................................ ................................ ....................  11 
C.4 Procedure  ................................ ................................ ................................ ................................ .... 11 
C.5 Calculations  ................................ ................................ ................................ ................................  12 
Annex  D (normative)  Determination of DEET content  ................................ ................................ ........  13 
D.1 General  ................................ ................................ ................................ ................................ ........  13 
D.2 Apparatus  ................................ ................................ ................................ ................................ .... 13 
D.3 Preparation of calibration curve  ................................ ................................ ...............................  13 
D.4 Procedure  ................................ ................................ ................................ ................................ .... 13 
D.5 Calculation  ................................ ................................ ................................ ................................ .. 14 
 DRS 392 -3: 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 o f technical committees is to prepare national 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 392-3 was prepared by Technical Committee RSB/TC 015, Pharmaceutical Products . 
In the preparation of this standard, reference was made to the following standard s: 
1) SANS 1245 , Non-woven cleaning wipes  
2) KS 2720 , Non-woven disposable wet wipes — Specification  
The assistance de rived from the above source is hereby acknowledged with thanks.  
DRS 392 consists of the following parts, under the general title Skin appli ed mosquito repellents — Specification : 
 Part 1: Lotion s, cream s, gels  and ointments  
 Part 2: Spray s and roll -ons 
Part 3: Wipes  
Part 4: Bathing Soaps  
Part 5: Bracelets , wristbands  and patches  
Committee membership  
The following organizations were represented on the Technical Committee on Pharmaceutical Products 
(RSB/TC 015) in the preparation of this standard.  
National Industrial  Research and Development Agency (NIRDA)  
National Pharmacy Council (NPC)  
University of Rwanda/College of Sciences and Technology (UR/CST)  
Pharmacie NOVA  
Rwanda Development Board (RDB)  DRS 392 -3: 2018  
v                ©RSB 2018 - All rights reserved  
 AGROPY LTD  
IKIREZI NATURAL PRODUCTS  
HORIZON/SOPYRWA  
Rwanda Social Security Board (RSSB)  
Pharmavie  
University of Rwanda/College of Medicine and Health Sciences (UR/CMHS)  
Rwanda Biomedical Center/ Malaria and Other Parasitic Diseases Division  (RBC/MOPDD)  
Society for Family Health  (SFH) – Rwanda  
Rwanda Biomedical Center/Med ical Procurement and Production Division (RBC/MPPD)  
INES - RUHENGERI  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 392 -3: 2018  
©RSB 2018 - All rights reserved                  vi 
 Introduction  
Mosquito repellents are an effective complement to bed nets in the prevention of mosquito borne diseases, 
especially malaria.  
 
Insecticides are used either for killing or controlling harmful insects. The insecticides which are applied for 
repelling insects are termed as “Repellents". Mosquito is one of the most harmful insects for mankind. To 
destroy them, many preparations are av ailable on the market in various recipes like pest killer spray, soap, oil, 
powder, repellent etc. Out of these, mosquito repellent is the most popular as it has germicidal and 
disinfectant properties and is able to repel mosquitoes and is convenient to us e. 
 
The mosquito repellent is used for warding off mosquitoes which are the most harmful insect s. Nowadays, 
mosquito repellents are used for controlling mosquito and are becoming most preferably than  other mosquito 
destroyers gradually. With the rise in th e standard of living, increasing urbanization and population, the demand 
of mosquito repellent mat is constantly increasing particularly in tropical places. It is a convenient method for 
protection against mosquito es, so it has a tremendous market potentia l. Thus , there is a very good scope for 
development of such units in the country . 
 
Skin applied mosquito repellents possess the potential to target residual transmission. Entomological evidence 
has shown that repellents provide personal protection against malaria.  Product examples that are common ly 
used  include lotions, gels, creams, ointments among others; however, many more  types of skin applied repellent 
products are now developed  in various forms such as sprays and roll -ons, wipes, soaps and bracelets , 
wristbands and patches . 
 DRS 392 -3: 2018  
1                ©RSB 2018 - All rights reserved  
 Skin applied mosquito repellents  — Specification  — Part 3: Wipes  
1 Scope  
This Preliminary Draft standard prescribes the requirements , sampling  and methods of test for skin applied 
mosquito repellents formulated and prepared as wipes  and meant to be applied directly to the skin. 
2 Normative references  
The following documents are referr ed 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 191, Refined pyrethrum concentrate ― Specification  
CIPAC 740, Determination of picaridin  
CIPAC 667, Determination of ethyl butylacetamidopropionate  
RS ISO 1833 -1, Textiles — Quantitative chemical analysis — Part 1: General principle s of testing  
RS ISO 139, Textiles — Standard atmospheres for conditioning and testing  
ISO 9073 -1, Test methods for nonwovens —Part1: Determination of mass per unit area  
ISO 9073 -18, Test methods for nonwovens — Part 18: Determination of breaking strength and elongation of 
nonwoven materials using the grab tensile test . 
 
RS ISO 3071, Textile materials; Method for determination of pH value of aqueous extracts  
ISO 20743, Textiles — Determination of antibacterial ac tivity of textile products  
ISO 21149,  Cosmetics — Microbiology — Enumeration and detection of aerobic mesophilic bacteria  
RS ISO 22717,  Cosmetics — Microbiology — Detection of Pseudomonas aeruginosa  
RS ISO 22718,  Cosmetics — Microbiology — Detection of Staphylococcus aureus  
RS ISO 18416,  Cosmetics — Microbiology — Detection of Candida albicans  
RS ISO 21150,  Cosmetics — Microbiology — Detection of Escherichia coli  
RS EAS 96, Sanitary towels — Specification  
DRS 394 -1, Mosquito repellents ― Performance Test  Guidelines ― Part 1: Skin applied repellents   
©RSB 2018 - All rights reserved                  2 
 RS ISO 2859 -1, Sampling procedures for inspection by attributes — Part 1: Sampling plans indexed by Quality 
Level (AQL) for Lot -By-Lot Inspection  
3 Terms and definitions  
For the purposes of this standard, the follow ing terms and definitions apply.  
3.1 
absorbency time  
rate at which a liquid is dispersed into the non -woven disposable wet wipe  
3.2 
acceptable  
acceptable to the authority administering this standard, or to the parties concluding the purchase contract, as 
relevant  
 
3.3 
length of piece  
distance between the beginning and the end of the sample in the lengthwise or machine direction  
3.3 
overall width of piece  
distance between the outermost edges of the sample measured perpendicular to the longitudi nal edges  
3.4 
usable width of piece  
width of the fabric excluding any selvedge materials, marks, pin -holes or other non -homogeneous areas of  
the fabric.  
3.5 
non-woven  
non-wovens are structures of textile materials, such as fibres, continuous filaments, or chopped yarns of any  
nature or origin, that have been formed into webs by any means, and bonded together by any means, 
excluding the interlacing of yarns as in woven fabric, knitted fabric, laces, braided fabric or tufted fabric  
3.6 
mosquito  DRS 392 -3: 2018  
3                ©RSB 2018 - All rights reserved  
 any of numerou s arthropod animals of the class mosquito, having an adult stage characterized by three pairs 
of legs and a body segmented into head, thorax, and abdomen and usually having one or two pairs of wings. 
Mosquito include the flies, crickets, insects, beetles, butterflies, and bees.  
3.7 
mosquito repellent  
substance applied to skin, clothing, or other surfaces which discourages mosquito  (and arthropods  in general) 
from landing or climbing on that surface  
3.8 
wipe 
clean or dry (something) by rubbing with a cloth, a piece of paper, or one's hand.  
3.9 
natural repellents/biopesticides  
repellents that contain natural, plant -based active ingredient or other products approved  by a competent 
authority  
3.10 
synthetic repellents  
conventional repellents containing synthetic chemical active ingredients  
3.11 
DEET  
N,N-Diethyl -meta -toluamide  or diethyltoluamide  
3.12 
IR3535  
ethyl butylacetyla minopropionate  
3.13 
Picaridin  
1-(1-methylpropoxycarbonyl) -2-(2-hydroxyethyl) piperidine or 2 -(2-hydroxyethyl) -1-piperidinecarboxylic acid 1 -
methylpropyl ester   
©RSB 2018 - All rights reserved                  4 
  
4 Requirements  
4.1 General  
4.1.1 The product shall con stitute a mosquito repellent  that is formulated as wipes and shall be essentially 
a product which has  active ingredient (s) added to a certain level.  
 
4.1.2 The product shall be of acceptable uniform make and finish . 
4.1.3 The product shall be free from defects that might impair their  appearance or serviceability (or both).  
4.1.4 When applied to the skin, the product shall have the benefit of repelling mosquitoes  and shall not cause 
harmful effect to th e skin 
4.2 Active ingredients  
4.2.1  Natural repellents  
4.2.1.1  Active ingredients used in natural repellents shall be natural and plant based compounds such as 
essential oils or any other  plant extract approved as mosquito repellents.  
4.2.1.3  The manufacturer  shall provide adequate data on the repellence of such ingre dients.  
4.2.1.4  The manufacturer  shall have adequate data justifying the proportion of ingredient(s) for which claims 
are made, used in the product.  
4.2.1.5  The essential oils  and other plant extracts  used in natural repellents shall be, but not limited to :  
a) Cedarwood oil ; 
b) Tea tree oil ; 
c) Geranium oil ; 
d) Rosemary oil ; 
e) Lemongrass oil ; 
f) Citronella oil ; 
g) Eucalyptus oil ; and  
h) Cinnamon oil . DRS 392 -3: 2018  
5                ©RSB 2018 - All rights reserved  
 i) Neem oil  
4.1.2.6  The proportion of single or blended active ingredient (s)  in natural repellent shall be set by the 
manufacturer i n accordance with specific standard  and records shall be availed.  
4.1.2.7  Pyrethrum extracts such as pyrethrin s shall be considered in natural repellents. The limits of pyrethrin s 
in natural repellents shall not be less than 0.5 % and the extract used shall meet the requirements of RS 191.  
4.2.2  Synthetic repellents  
4.2.2.1  Synthetic repellents shall contain synthetic chemical compounds which are able to discourage 
mosquitoes and send th em flying or crawling away.  
4.2.2.2  If the synthetic active ingredient  is blended with other active ingredient (s), either natural or synthetic, 
the proportion shall be set by the manufacturer based on scientific research and records shall be availed.  
4.2.2.3 Active ingredients and their content in synthetic repellents shall meet the requirements prescribed in 
table 1.  
Table 1 – Active ingredients for wipes formulated as mosquito repellents  
S/N Ingredients  Limits  Test methods  
i.  DEET , % m/m.  4 –50 Annex E 
ii.  Picaridin , % m/m  5 – 20 CIPAC 740  
iii.  IR3535 , % m/m  7.5 –20.07  CIPAC 667  
4.2.2.4  Synthetic repellents and their active ingredients shall be approved and registered by competent 
authority  before being released to the market . 
4.3 Specific requirements  
The product shall comply with the requirements given in table 2 . 
Table 2 – Specific requirements for wipes repellents  
S/N  Parameters  Requirements  Test method  
1 Fibre composition, %  A blend of at least 20% 
cellulose and the 
remaining percentage of 
80% polyester  RS ISO 1833 -1 
2 Size, mm  Length  As declared on the label  Annex A 
Width  
3 Grammage , g/m2, min.  
 36 ISO 9073 -1 
4 Breaking 
strength, 
N, min.  Machine 
direction  Dry  60 ISO 9073 -18 
Wet 30 
Cross 
section  Dry 3.5 
Wet 2.5 
5 Absorbency time, sec, max  (for 
manufacturer)  5 Annex B 
6 pH 5.5 – 8.0 RS ISO 3071   
©RSB 2018 - All rights reserved                  6 
 7 Moisture content , % Above 50  Annex C  
8 Anti-Bacterial activity (A), min.  2 ISO 20743  
9 Total viable count, cfu/g  100 ISO 21149  
10 Pseudomonas aeruginosa, cfu/g  Not detectable per gram 
of sample  RS ISO 22717  
11 Staphylococcus aureus  Not detectable  RS ISO 22718  
12 Candida albicans  Not detectable  RS ISO 18416  
13 E. coli  Not detectable  RS ISO 21150  
14 Number of wipes, pcs  As declared  Sensory  
15 Flushability  Pass the test  RS EAS 96  
4.4  Biological efficacy  
When tested in accordance with DRS 394-1, the product shall have repelled 100 % of the mosquitoes from 
landing or climbing on that surface, within  protection time indicated by the manufacturer.  
5 Packaging and labelling  
5.1 Packaging  
5.1.1 The product  shall be pack aged in a suitable package that shall protect them from any form of  
contamination  and damage.  
5.1.2 The primary pack age seal shall be secure and allow resealing as many times as possible  ensuring wet 
wipe is not dry.  
5.1.3 The product  shall be delivered in a clean and dry condition.  
5.1.4 Only wipes of the same size shall be packed together in secondary pack.  
 
5.2 Labelling  
5.2.1 The primary pack ages  shall be marked with legible and indelible pre -printed marking bearing the  
following information:  
 
a) manufacturer’s name, address and/or trade mark;  
b) import er/distributors name, address ( if applicable) ; 
c) number of wipes in a pack;  
d) intended use , e.g repellent ; 
e) size of wipe in the pack ; 
f) ingredients “fibre content” or “material content”  and active ingredient used ; DRS 392 -3: 2018  
7                ©RSB 2018 - All rights reserved  
 g) instruction for use, storage and disposal;  
h) country of origin;  
i) date of manufacture and expiry; or best before;  
j) batch number ; 
k) safety caution ; and  
l) special population  whose exposure is prohibited (children and pregnant women) . 
5.2.2 Secondary packaging  
 
The outside of each secondary pack shall bear the following information in legible and indelible marking:  
a) the manufacturer’s name and/or registered trade mark;  
b) the words “non woven disposable wet wipes” ; and  
c) the number of packages . 
6 Sampling  
Random samples of the product shall be drawn for test in accordance with  RS ISO 2859 -1 from the market, 
factory or anywhere else.  
  
©RSB 2018 - All rights reserved                  8 
 Annex  A 
(normative)  
 
Determination of length and width  
A.1 Apparatus  
A.1.1  Steel scale that is of a length exceeding the width of the fabric to be measured, and is graduated in 
centimeters and millimeters.  
 
A.1.2  Marking pen . 
 
A.2 Procedure  
A.2.1 Procedure for width  
A.2.1.1  Lay the test sample flat and full width (without subjecting it to tension) on a plane surface and 
condition it in that state for at least 24 h in accordance with RS ISO 139.  
A.2.1.2  Take, to the nearest 1 mm, five measurements across the overall width or b etween theinnermost 
selvedge threads (as relevant) of the conditioned test sample at approximately equalintervals throughout its 
length.  
A.2.1.3  Calculation  
Calculate the arithmetic mean of the five measurements and record it as the width of the sample.  
A.2.2  Procedure for length  
A.2.2.1  Take a laboratory sample as specified in the relevant product specification. Where no specification 
exists, take the laboratory sample as agreed upon between the test laboratory and the manufacturer to ensure 
a reasonable  and acceptable reliability at a reasonable and acceptable confidence level.  
 
A.2.2.2  Lay the laboratory sample flat and full width (without subjecting it to tension) on a plane surface and 
condition it in that state for at least 24 h in accordance with RS  ISO 139.  
 
A.2.2.3  From the conditioned laboratory sample cut a test specimen across the full width of the laboratory 
sample along a datum line drawn (see 3.1) at right angles to the selvedges and as close as possible to the 
beginning and the end of the la boratory sample.  
 
A.2.2.4  Take, to the nearest millimeter, five measurements (see B.1.2) of the length of the test specimen at 
approximately equal intervals across its width.  
 
A.2.2.5  Calculation  
Calculate the arithmetic mean of the five measurements and r ecord it as the length, in metres (accurate to the 
nearest centimeter), of the laboratory sample.  DRS 392 -3: 2018  
9                ©RSB 2018 - All rights reserved  
 Annex  B 
(normative)  
 
Determination of absorbency rate  
B.1 Apparatus  
A.1.1  Water tub , of a depth of at least 100 mm and maintained at room temperature.  
A.1.2  Stop watch , with an accuracy of 0.2 s  
A.1.3  Cylindrical basket , weighing 2.7 ± 0.3 g of height 80 mm, diameter 50 mm with square opening of 
15 mm to 20 mm , made of copper wire of 0.4 mm diameter.  
 
A.1.4  Weighing machine  
 
A.1.5  Forceps  
 
B.2 Preparation of test specimens  
Take three test specimens, each of mass at least 1 g and composed of a number of pinches of fibres taken 
from widely separated parts of the conditioned laboratory sample.  
 
B.3 Procedure  
B.3.1  Compress the first test specimen to a volume of approximately 20 mL.  
B.3.2  By means of the forceps (see 3.2), place the test specimen lightly on the surface of the distilled water 
(see 3.3) and simultaneously start the stopwatch (see 3. 3). 
 
B.3.3  Using the stop watch, measure the time it takes the basket  and its contents to sink below the surface 
of water in seconds.  
 
B.3.4  Record the absorption period to the nearest 0.1 s.  
 
B.3.5  Repeat the test for at least three test specimens.  
B.4 Calculation  
Calculate, to the nearest second, the arithmetic mean of the th ree test results.  
B.5 Test report  
Report the following information:   
©RSB 2018 - All rights reserved                  10 
 a) all the data needed to identify the laboratory sample tested;  
b) confirmation that the test was carried out in accordance with this standard;  
c) any deviation from this standard; and  
d) the mean absorbency rate, expressed in seconds, of the absorbent cotton wool.  DRS 392 -3: 2018  
11                ©RSB 2018 - All rights reserved  
 Annex  C 
(normative)  
 
Determination of moisture content  
C.1 Principle  
A specimen of specified mass of filler material of the non -woven disposable wet wipe is dried in an oven at 
specified temperature  and the moisture content is determined.  
C.2 Apparatus  
C.2.1  Balance , with an accuracy of 0.05% of the weighed mass  
C.2.2  Sample container , waterproof when sealed, will be used for transfer of analyzed material and during 
weighing  
C.2.3  Oven , well ventilated with a temperature of 102 ºC to 105 ºC  
C.3 Sample preparation  
C.3.1  Take a sufficient number of dry sample containers, number them and take their masses after they 
are held open for a short period of time so that they will have the same air pressure as the sur rounding 
atmosphere. Then leave them open until you take the test piece.  
 
C.3.2  Take 5 random pieces of the wet wipe . The test pieces shall weigh 5 g.  
 
C.3.3  If the surrounding atmosphere is hot and humid, prevent water condensation on the internal and 
external surfaces of the container.  
 
C.3.4  Handle the test pieces gently to prevent dirt or changes in water content. Don’t touch the test pieces 
with your bare hands. Put the test pieces in a container just after taking them and close the container 
immediately.  
C.4 Procedure  
C.4.1  Dry the test pieces in an oven with a temperature of 102ºC to 1050C. Open the containers lid and dry 
the specimen inside the container. Open the container for a moment, to balance the air pressure inside the 
container with the surrounding pressure, weigh the container that holds the specimen again and calculate the 
weight of the specimen.  
 
C.4.2  First cycle of drying will last at least 30 minutes. Return the container with the test pieces to the oven, 
for at least half the first  cycles drying time. Take the container out and take the mass with the test pieces 
inside. Repeat the drying and weighing cycles. When the drying time on every cycle is at least half of the total 
previous drying cycle times. Continue the process until the difference between two consecutive masses does 
not exceed 0.1 % of the original mass of the specimen.   
©RSB 2018 - All rights reserved                  12 
 C.5 Calculations  
Calculate the moisture content using the following formula and round the results up to the nearest 0.1 %.  
` 𝑉=100𝑎−𝑏
𝑐 
Where,  
a is weight of the container with the specimen before drying (in grams);  
b is weight of the container with the specimen after drying (in grams);  
c is weight of the container (in grams); and  
V is water content (in weight %).  DRS 392 -3: 2018  
13                ©RSB 2018 - All rights reserved  
 Annex  D 
(normative)  
 
Determination of DE ET content  
D.1 General  
The sample is dissolved in carbon disulfide and the difference in absorbance at 14.18 µm and at 14.48 µm is 
determined. The quantity of meta -isomer is obtained from this value by means of a calibration curve prepared 
by the use of a reference standard.  
D.2 Apparatus  
D.2.1  Double -beam infrared spectrophotometer. Perkin -Elmer model 21 or equivalent.  
D.2.2  Two equivalent infrared absorption cells, with sodium chloride windows and a path length of 
approximately 0.4 mm.  
D.3 Preparation of calibration curve  
D.3.1 Weigh (to the nearest 0.1 mg) into four volumetric flasks sufficient amounts of the reference DEET 
standard of known  purity to give concentrations of approximately 20, 40, 60 and 80 g/L when dissolved in carbon 
disulfide.  
D.3.2  Fill the reference cell with carbon disulfide and the sample cell with each of the standard solutions in 
turn, and record the spectra. The spectrum may be scanned rapidly, except for the region 12 – 15 µm, where a 
normal speed should be used. Carry out a blank  measurement with carbon disulfide to correct for any inequality 
in the paired cells and to determine whether a cell correction is required.  
D.3.3 Measure the absorbance at 14.18 µm and at 14.48 µm and calculate the difference between these 
value s, ΔA, for  each of the solutions. Plot the values of ΔA against the concentration (g/l) of the meta -isomer.  
 
D.3.4  If a cell correction is required, the value of ΔA is determined from the formula:  
 
  ΔA = [A 14.18 – A14.48]ref. - [A14.48]blank 
 
  Where ref. = determination with reference standard  
    blank = determination on CS 2 blank  
 
D.4 Procedure  
Weigh (to the nearest 0.1 mg) about 0.5 g of the sample, transfer quantitatively to a 10 mL volumetric flask, 
and make up to the mark with carbon disulfide. Measure the  infrared absorption at 14.18 μm and 14.48 μm 
using the same conditions as described in section A.3. Determine the concentration of meta -isomer by 
comparing this value with the calibration curve. A standard sample should be run each day to check the 
calibr ation of the instrument.   
©RSB 2018 - All rights reserved                  14 
 D.5 Calculation  
DEET content (g/kg) =𝐶1 𝑥 𝑃 
𝐶2 
Where,  
 C1 = concentration (g/L) of standard DEET found from calibration curve  
 C2 = concentration (g/L) of sample taken  
 P = purity (g/kg) of the reference standard.  DRS 392 -3: 2018  
15                ©RSB 2018 - All rights reserved  
 Bibliography  
[1] USPC/USP Pharmacopeial Forum 2009 (Vol. 35 (3),  Topical and Transdermal Drug Products  
[2] Manual on development and use of FAO and WHO specifications for pesticides , November 2010, 2nd 
Edition.  
[3] Product Performance Test Guidelines. OPPTS 810.3700: Insect Repellents to be applied to human 
Skin 
 DRS 392 -3: 2018  
ICS 65.100  
 
 
©RSB 2018 - All right s reserved