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Study on Protein Profiles in Commercial
Examination Glove Production
NURUL HAYATI YUSOF*#, HASMA HASHIM*, MA’ZAM MD SAID* AND
AMIR HASHIM MOHD YATIM*
Extractable protein (EP), antigenic protein (AP) and allergenic protein (AgP) contents of
examination gloves sampled at different stages of commercial examination glove production
over a 3 months production period were determined. The EP, AP and AgP contents of gloves
at any stage of production generally increased with increasing production time. Unexpectedly
gloves collected immediately after the pre-leaching process showed higher EP contents
compared to unleached gloves. Gloves taken after post-curing at 140ºC for about 30 minutes,
gave the highest EP, AP and AgP contents. The EP, AP and AgP contents of gloves taken after
the post-leaching and the subsequent stages were considerably lower compared to gloves taken
before the post-leaching stage. There is a tendency for the AgP content of the final products to
be higher than those samples taken after the post-leaching and slurry-dip stages. It is hoped
that this study on protein profile of a commercial glove dipping line could provide a guideline
on appropriate conditions that needs to be applied at various stages of the glove production
process.
Keywords: extractable proteins; antigenic proteins; allergenic proteins; examination gloves;
pre-leaching; post-leaching; protein profile; glove line
J. Rubb. Res., 13(4), 207–217
207
*Rubber Research Institute of Malaysia, Malaysian Rubber Board, P.O. Box 10150, 50908, Kuala Lumpur, Malaysia
# Corresponding author (e-mail: hayati@lgm.gov.my)
Proteins are naturally present in natural rubber
latex (NRL). Some of the latex proteins are
water-soluble, while others are associated with
organelles such as rubber particles1,2. Some of
the water-soluble proteins that are present in
latex products such as gloves were found to
cause Type 1 allergic reaction3. In order to
deal with this problem, much effort has been
put to reduce the EP content of gloves during
product manufacturing, particularly during
the leaching process4,5. In glove production,
wet-gel leaching and post-cure leaching
are the essential, effective and well-known
methods for reduction of extractable protein
content6–8. It has also been found that slurry-
dip after drying or post-curing could initially
reduce the EP content of gloves. However,
the protein content of gloves was found to
increase with production time in the slurry
tank8. Recent work revealed that cornstarch
slurry powder has high bound affinity towards
latex proteins9. There are also some other
factors that could contribute to the increase of
EP content of gloves. One of the factors is that
certain compounding materials added into the
latex may raise the EP level10.
Previous studies7,8 on EP content reduction
were carried out only at selected sections of the
latex dipping line for the purpose of evaluating
Journal of Rubber Research, Volume 13(4), 2010
208
the effectiveness of certain manufacturing
processes where AP and AgP contents were
usually omitted. Close monitoring of protein
content of gloves taken at each section of
the glove dipping line has yet to be studied.
Hence, this paper describes EP, AP and AgP
content profiles of gloves determined at every
section of glove production at a commercial
glove dipping line. Knowing the stages of the
production that produced gloves with high EP,
AP and AgP contents, manufacturers could
give more attention to these stages by taking
appropriate actions in order to further reduce
the protein content of gloves. Even if the
protein content at several stages of the
production may be high, only one or two of
the stages may need to be critically looked
into in order to set a cost-effective process
for production of gloves with very low levels
of EP, AP and AgP contents. This paper also
compares the EP, AP and AgP content profiles
of different batches of gloves prepared at
different periods of production. It is hoped
that knowledge generated in this study could
help glove manufacturers to effectively reduce
the EP, AP and AgP contents of their gloves
without having to carry out major modification
of their dipping lines and in the process help to
lessen the allergy issues of natural rubber latex
gloves.
EXPERIMENTAL
Preparation of Gloves
Samples of compounded latex, coagulant
(L1), pre-leaching water (L2), post-leaching
water (L3) and slurry (L4) were taken from
a commercial glove production. These liquid
Figure 1. Flowchart of dipping process and process parameters, location of gloves produced and samples
labelling at different stages.
Coagulant
tank
48ºC/17s
Coagulant
drying oven
Latex
tank
27-30ºC/27s
S1
S2
S3
S4S5S6
S7
Wet gel oven
120-140ºC/72s
Pre-leaching tank
(wet gelled leaching
tank)
Curing oven
140ºC
Post-leaching
tank
60-80ºC/84s
Slurry tank
48ºC/8s
Drying oven
130-150ºC/40s
Stripping
Nurul Hayati Yusof et al.: Study on Protein Profiles in Commercial Examination Glove Production
209
samples were collected at day 0 (Batch 1),
day 13 (Batch 2) and month 3 (Batch 3) of
the production. Dipping process was carried
out in the laboratory according to the similar
conditions as that of the actual glove line.
Gloves were produced and taken out from
each stage of production where wet glove
samples were taken and left to dry at RT
before carrying out the protein determinations.
The glove samples were labelled as S1-S7.
The flowchart of dipping process and process
parameters are shown in Figure 1.
Determination of EP, AP and AgP of Gloves
Extraction procedures. Cut pieces of gloves
(palm area) of 8 cm 8 cm were extracted
in 25 mM PBS buffer (pH 7.4) at room
temperature for 2 hours. Amount of buffer
used was 5 mL per gram of sample. The
extracts were then clarified by centrifugation
at 3000x g for 15 min to remove powder or
any particulate matters. Extractable protein,
antigenic protein and allergenic protein
contents were determined in duplicates11–13.
Extractable protein (EP) determination.
Extractable protein content was determined
by Lowry method using the ASTM D5712-
9911. The sample extracts were precipitated
using deoxycholic acid, phosphotungstic acid
and trichloroacetic acid. Protein pellets were
dissolved with sodium hydroxide and treated
with copper reagent to form protein-Cu2+
complex, which reduced Folin-Ciocalteu’s
phenol reagent, resulting in the development
of blue colour. For the correction method, the
same procedure was repeated but with the
copper reagent replaced by water in alkaline
tartrate solution. The colour was measured at
750 nm using micro plate reader11.
Antigenic protein (AP) determination. For
determination of the antigenic protein content,
the extracts were assayed using the ASTM
D6499-00 method12. The procedure involves
incubation of IgG antibody (raised in rabbit)
and sample extracts (containing latex proteins)
in dilution plate to form antibody-antigen
complex. The mixtures were transferred to
an assay plate. Excess IgG antibodies, which
were not bound with NRL protein, will bind to
the immobilised standard antigen in the assay
plate. Horseradish peroxidase conjugated
anti-IgG (HRP), an enzyme-substrate was
added and the reaction of enzyme on the
substrate resulted in a colour change. The
colour was measured at 490 nm using a micro
plate reader.
Allergenic protein (AP) determination.
Allergenic protein content was determined
using the IgE-ELISA Inhibition Method13.
The sample extracts were incubated with IgE
antibodies. IgE antibodies were recovered
from a human serum pool containing specific
antibodies to latex proteins. After a short
incubation, the mixtures were transferred
into an assay plate. The plate was washed
three times. Biotinylated goat anti-human
IgE and streptavidin-conjugated alkaline
phosphate were used to detect immobilised
antigen-bound specific antibody complexes.
P-nitrophenylphosphate in carbonate buffer
containing MgCl2 was added and a yellow
colour developed. The colour was measured at
405 nm using a micro plate reader.
Effect of Pre-leaching Time on EP Content
The wet gelled gloves were prepared by
immersing formers in the compounded latex
taken from the factory. According to the
conditions applied in the glove factories, the
wet gelled gloves were then dried in the wet
gel oven at temperatures ranging between
120ºC–140ºC for 72 seconds and subsequently
leached in distilled water heated at 70ºC for 5,
30, 60, 90 and 150 seconds respectively. EP
content was measured for those samples.
Journal of Rubber Research, Volume 13(4), 2010
210
RESULTS AND DISCUSSION
EP, AP and AgP Contents of Gloves Taken
at Different Stages of Glove Production
The values of EP, AP and AgP contents for
Batch 1, Batch 2 and Batch 3 gloves are shown
in Figure 2, Figure 3 and Figure 4 respectively.
The pattern or trend line of EP, AP and AgP
content profiles over the whole processing
stage was quite similar for the three batches
of gloves. However, the exact EP, AP and AgP
values, especially for Batch 3 gloves were
noticeably different compared to those shown
by Batch 1 and Batch 2 gloves.
For all batches, generally, the trend of EP,
AP and AgP content of S1 glove, samples
taken after the latex tank and S2 samples
taken after the wet gel oven were quite
similar. These samples were found to contain
relatively high EP, AP, and AgP content, as
these samples did not undergo the leaching
process. However, for Batch 1 and Batch 2
gloves, the EP content of S3 samples taken
after the pre-leaching tank was about 500
µg/dm2 higher than that of S2 samples.
As for Batch 3 gloves, the EP content of
S3 samples was about 600 µg/dm2 higher
than that of S2 samples. The AP and AgP
contents of S3 samples also appeared to be
rather similar as those S2 samples for all
batches. Furthermore, it is noteworthy that
the AgP content showed high values from the
beginning until S4 samples for all the three
batches of gloves. The comparatively high
EP content at the S3 stage could in part be
due to the effect of evaporation after the
pre-leaching stage. This could be explained
by work done previously where after the pre-
leaching stage (wet-gelled leaching stage),
evaporation process of water from gloves
occurred14. It is possible that the evaporation
process mitigated the migration of soluble
proteins to the glove surface and Ca2+ ions
that remain in the glove film might have
trapped the protein within the film matrix.
Other contributing factors include rate of
water overflow and agitation, which have a
bearing on the concentration of proteins in the
leaching tank.
Further increase of EP, AP and constantly
high AgP content was observed for S4
samples, taken after the curing oven.
It showed the highest protein content
among the glove samples. This is probably due
to the effect of heating over a long period of
curing. Proteins may possibly degrade causing
breakdown of protein chains, making them
more soluble during heating where the rate of
degradation which may be relatively high at the
initial stage of heating as the samples contain
substantial amounts of water. In addition,
the heating process would promote more
proteins to migrate towards the surface of
glove film and be made readily extractable14.
However, S5 samples which were post-
leached samples, showed remarkably low
EP, AP and AgP contents. At this stage, it is
probable that most of the soluble proteins,
which accumulated on the glove surface,
were extracted into the post-leaching tank and
hence the EP, AP and AgP contents dropped
substantially.
The EP, AP and AgP contents of S5, S6 and
S7 glove samples taken after the post-leaching
and the subsequent stages were considerably
lower compared to gloves taken before the
post-leaching stage, S1-S4, for all batches of
gloves.
Hence, from the pattern shown by the
graphs, the processing stages from latex
dipping to oven drying/curing stages are
important stages as the gloves produced at
these stages showed high levels of EP, AP
and AgP contents. It is at these stages where
process design that could enhance protein
removal or suppress protein denaturation be
used to produce low protein gloves.
Figure 2. Extractable protein (EP), antigenic protein (AP), and allergenic protein (AgP) content of Batch 1
(0 day production)
Figure 3. Extractable protein (EP), antigenic protein (AP) and allergenic protein (AgP) content of Batch 2
(13 days production)
1200
1000
800
600
400
200
0
300
350
EP99
AP
AgP 250
200
150
AgP (AU/mL)
EP, AP (µg/dm2)
100
50
0
S1 S2 S3 S4 S5 S6 S7
1200
1000
800
600
400
200
0
1000
1200
EP99
AP
AgP 800
600
AgP (AU/mL)
EP, AP (µg/dm2)
400
200
0
S1 S2 S3 S4 S5 S6 S7
1200
1000
800
600
400
200
0
300
350
EP99
AP
AgP 250
200
150
AgP (AU/mL)
EP, AP (µg/dm2)
100
50
0
S1 S2 S3 S4 S5 S6 S7
1200
1000
800
600
400
200
0
1000
1200
EP99
AP
AgP 800
600
AgP (AU/mL)
EP, AP (µg/dm2)
400
200
0
S1 S2 S3 S4 S5 S6 S7
Figure 4. Extractable protein (EP), antigenic protein (AP) and allergenic protein (AgP) content of Batch 3
(3 months production).
Figure 5. EP content of pre-leached film versus leaching time
2500
2000
1500
1000
500
0
1200
EP99
AP
AgP
1000
800
600
AgP (AU/mL)
EP, AP content (µg/dm2)
400
200
0
S1 S2 S3 S4 S5 S6 S7
300
200
35%
Unleached
250
150
100
50
0
Extractable protein (EP) content (µg/dm2)
0 50 100
Leaching time (min)
150 200
2500
2000
1500
1000
500
0
1200
EP99
AP
AgP
1000
800
600
AgP (AU/mL)
EP, AP content (µg/dm2)
400
200
0
S1 S2 S3 S4 S5 S6 S7
300
200
35%
Unleached
250
150
100
50
0
Extractable protein (EP) content (µg/dm2)
0 50 100
Leaching time (min)
150 200
Nurul Hayati Yusof et al.: Study on Protein Profiles in Commercial Examination Glove Production
213
Pre-leaching Time versus EP Content
Since the above section stated that pre-
leached gloves, S3 showed high EP content
compared to S2 samples taken after the wet
gel oven, a study on the effect of leaching time
upon EP content reduction was conducted in
the laboratory with the same conditions as the
glove factory. Longer leaching time extracted
more proteins from the pre-leached gloves as
shown in Figure 5. At 5 minutes of leaching
time, about 35% of EP content was reduced
when compared to the control (unleached)
gloves. Hence, it can be said that leaching
time of <50 s which is practiced by most
glove factories is insufficient for proteins to be
removed efficiently from the gloves. Prolonged
pre-leaching time is recommended in order to
reduce further EP content in the final product
of gloves.
EP, AP and AgP Contents of Gloves Sampled
at Different Periods (Batch) of Production
The EP and AP contents for Batch 1 and
Batch 2 gloves as shown in Figure 6 and
Figure 7 respectively, were found to be rather
similar. However, the EP and AP contents of
Batch 3 gloves were found to be substantially
higher that those of Batch 1 and Batch 2 gloves.
The differences in results between Batch 1 and
2 to Batch 3 might be due to several factors
such as;
• the accumulative effect of inefcient
former cleaning and build up of proteins
in leaching water with time
• water in the pre-leaching and post-
leaching tanks were not changed
regularly but merely replenished
• the accumulation of proteins in the
coagulant
• the accumulation of proteins in the
latex tank associated with the old latex
compound
• sedimentationoflatexcompound
• hydrolysis of proteins in the latexwith
production time.
The results for the AgP content however
were quite in contrast to those of the EP and AP
results as shown in Figure 8. Batch 1 gloves
showed the lowest AgP content compared to
Batch 2 and Batch 3 gloves at all stages of
production. The AgP content of Batch 2 and
Batch 3 gloves for all the production stages
were consistently higher than Batch 1 by
about 50% and 20%–30% respectively. An
interesting observation is that the AgP content
of S1, S2, S3 and S4 gloves for the production
periods of 2 weeks (Batch 2) and 3 months
(Batch 3) were similar, which was on the high
side of 1000 AU/mL. Comparing results in
Figure 6 and Figure 8 for Batch 2 gloves, it
appeared that there were situations where gloves
with a relatively low level of EP content could
still show a significantly high AgP content.
The allergenic proteins appeared to exist in
the latex compound and its concentration
increased rapidly to a maximum value within
a relatively short production period. The
localised heating of latex compound by the hot
glove formers and the prevailing pH conditions
perhaps promote denaturation of proteins with
prolonged production time.
Protein Concentration of Coagulant, Pre-
leaching water, Post-leaching water and
Slurry
The coagulant (L1), pre-leaching water
(L2), post-leaching water (L3), and slurry
(L4) were found to show erratic values likely
because several adjustments had been made to
these samples. One of the adjustments made
was changing or topping up of old solutions
with fresh solutions.
Table 1 shows the EP, AP and AgP contents
of L1, L2, L3 and L4 for all batches. Protein
Figure 6. Extractable protein (EP) content for Batch 1, Batch 2 and Batch 3.
Figure 7. Antigenic protein (AP) content for Batch 1, Batch 2 and Batch 3
2500
2000
1500
1000
500
0
EP content (µg/dm2)
Batch 1 Batch 2 Batch 3
S1
S1
S2
S2
S3 S3
S4
S4
S5
S5
S6
S6
S7
S7
S1
S2
S3
S4
S5
S6
S7
160
120
140
80
100
60
40
20
0
AP content (µg/dm2)
Batch 1 Batch 2 Batch 3
S1
S2
S3
S4
S5
S6
S7
2500
2000
1500
1000
500
0
EP content (µg/dm2)
Batch 1 Batch 2 Batch 3
S1
S1
S2
S2
S3 S3
S4
S4
S5
S5
S6
S6
S7
S7
S1
S2
S3
S4
S5
S6
S7
160
120
140
80
100
60
40
20
0
AP content (µg/dm2)
Batch 1 Batch 2 Batch 3
S1
S2
S3
S4
S5
S6
S7
Nurul Hayati Yusof et al.: Study on Protein Profiles in Commercial Examination Glove Production
215
concentration of coagulant (L1) was found
to be low. This could be due to the effect of
calcium precipitating the proteins, and that
calcium has been shown to interfere with
ELISA assays15,16.
Correction of EP determination for
coagulant was carried out in this study. The
corrected values showed consistently lower
EP values compared to the uncorrected values.
The percentage of EP reduction ranges from
90%–100%. This correction method showed
that calcium nitrate was not only interfering
with the ELISA assays but also with the Lowry
assays15–17.
Pre-leaching water (L2) was found to
contain similar protein contents compared to
post-leaching water (L3) except for Batch 3.
Considering Batch 2 and Batch 3 production
data, the EP, AP and AgP contents in the
slurry (L4) were much lower compared to
those in the post-leaching water. Despite the
differences, the S5 and S6 glove samples
showed comparatively similar levels of EP,
AP and AgP contents. It is possible that in
the samples taken after slurry tank stage,
the extractable proteins in the gloves were
already at relatively stable levels and it was not
extracted much by the slurry.
CONCLUSIONS
A profile of EP, AP and AgP protein contents of
gloves at various stages in the glove production
line was obtained in this study. The results
showed that distinct increase in protein contents
was found on gloves collected immediately
after the pre-leaching process compared with
the unleached gloves. The gloves collected
immediately after drying and curing stage
gave the highest protein contents whilst the
glove samples collected immediately after the
post-leaching were at minimum levels of EP,
AP and AgP contents. Moreover, the gloves
taken before the post-leaching stage gave
considerably higher values of EP, AP and AgP
contents compared to gloves taken after post-
leaching stage for all batches of production.
Figure 8. Allergenic protein (AgP) content for Batch 1, Batch 2 and Batch 3.
1200
1000
800
600
400
200
0
AgP content (AU/mL))
Batch 1 Batch 2 Batch 3
S1 S1
S2
S2
S3
S3
S4
S4
S5
S5
S6
S6
S7 S7
Journal of Rubber Research, Volume 13(4), 2010
216
Through the knowledge generated from
this work, it is hoped that more attention could
be paid and appropriate actions on certain
critical stages in the production dipping line
could be considered by manufacturers in
order to enhance protein removal and lessen
protein allergies amongst users. Among
positive measures that can be considered are
prolonging the pre-leaching process, high
temperature of leaching water, provide two or
three short leaching tanks instead of one long
tank, constant agitation in tanks, usage of clean
and running water, frequent change of water
and etc.
ACKNOWLEDGEMENTS
The authors thank Vijayalakshmi K., Mohd
Yusof Rais and Haridas for their excellent
technical assistance. We also thank Hashima
Idris for her statistical assistance and Abd
Latiff Mustari and Zulkifli Ahmad, from
Kilang Barangan Getah Felda, Dioh for their
co-operation in collecting the samples.
Date of receipt: January 2010
Date of acceptance: June 2010
REFERENCES
1. HASMA, H. (1987) Proteolipids of Natural
Rubber Particles. J. Rubb. Res., 2(2), 129.
2. HASMA, H. (1993) Proteins in Natural Rubber
Latex. Proceedings IRTC 93 Workshop on
Latex Proteins.
3. ONG ENG LONG, ESAH YIP AND LAI
PIN FAH (1998) Latex Protein Allergy and
Your Gloves. RRIM, Malaysian Rubber
Board.
4. GAZELEY, K.F. (1985) Leaching Behaviour
of Prevulcanised Natural Rubber Latex
Films. NR Technology, Vol. 3, Part 3.
5. ENG, A.H., KODAMA, S. AND KAWASAKI,
H. (1999) Reduction of Water Extractable
Proteins in Natural Rubber Latex Films by
Ultrasonic Leaching System, J. Rubb. Res.,
2(1), 23–28.
6. SUBRAMANIAM, A., YIP, E., NG, K.P. AND
MOK, K.L. (1993) Extractable Protein
Content of Gloves from Prevulcanised
Natural Rubber Latex. Proceedings IRTC
93 Workshop on Latex Proteins.
7. AMIR HASHIM MD. YATIM (1993) Effect of
Leaching on Extractable Protein Content.
TABLE 1. EP-CORRECTION, AP AND AgP CONTENT OF COAGULANT (L1),
PRE-LEACHING WATER (L2), POST-LEACHING WATER (L3) AND SLURRY (L4) FOR
BATCH 1, BATCH 2 AND BATCH 3
Batch 1 Batch 2 Batch 3
Samples EP AP AgP EP AP AgP EP AP AgP
(µg/mL) (µ/mL) (AU/mL) (µg/mL) (µg/mL) (AU/mL) (µg/mL) (µg/mL) (AU/mL)
L1 12 >2 58 27 >2 178 14 >2 107
L2 5 <0.0312 6 48 0.08 208 24 0.04 24
L3 <4.7 <0.0312 5 52 0.15 516 45 0.3 271
L4 <4.7 0.04 0.4 15 0.09 248 10 0.3 94
*>2 µg/g is max conc. of std. antigen
*<0.0312 µg/g is min conc. of std. antigen
*4.7µg/mL is LOD for ASTM D5712-99
Nurul Hayati Yusof et al.: Study on Protein Profiles in Commercial Examination Glove Production
217
Proceedings IRTC 93 Workshop on Latex
Proteins.
8. NG, K.P., YIP, E. AND MOK, K.L. (1994)
Production of Natural Rubber Latex Gloves
with Low Extractable Protein Content:
Some Practical Recommendations. J. nat.
Rubb. Res., 9(2), 97–95.
9. HASMA, H. AND WAN ROSLINAH (2005)
Binding Propensity of Modified Corn
Starch and Oat Starch for NR Latex Proteins
and Ways to Minimise the Interaction. J.
Rubb. Res., 8(2), 79–89.
10. MOK, K.L., NORHAYATI, M., ROSMA-
HANI, C.I., NURUL HAYATI, Y.
AND HASMA, H. (2005) Interference
Correction in the Lowry Micro Assay
for Measurement of Extractable Protein
(EP) in Natural Rubber Latex Products,
Malaysian Rubb. Tech. Dev., 5, 3–7.
11. AMERICAN SOCIETY FOR TESTING AND
MATERIALS (1999) Standard Test Method
for the Analysis of Aqueous Extractable
Protein in Natural Rubber and its Products
using the Modified Lowry Method. ASTM
D5712-99.
12. AMERICAN SOCIETY FOR TESTING AND
MATERIALS (2000) Standard Test Method
for the Immunological Measurement of
Antigenic Protein in Natural Rubber and
its Products ASTM D6499-00.
13. PALOSUO, T., MAKINEN-KILJUNEN,
S., ALENIUS, H., REUNALA, T., YIP,
E. AND TURJANMAA, K. (1998)
Measurement of Natural Rubber Latex
Allergen Levels in Medical Gloves by an
Allergen specific IgE ELISA Inhibition,
RAST Inhibition and Skin Prick Test.
Allergy 5, 3, 59.
14. YEANG, H., SUNDERASAN E. AND
HAFSAH MOHD GHAZALY (1995)
Latex Allergy Studies: Extraction of
Natural Rubber Latex Proteins with
References to Film Thickness, Latex DRC
and Protein Migration Behaviour, J. nat.
Rubb. Res., 10(1), 46–62.
15. HASMA, H., NURUL HAYATI, Y., LAU,
C.H., RUHIDA, A.R. AND AMIR
HASHIM, M.Y. (2004) Correlation
between Total Extractable Protein and
Antigen Contents with Allergen Content
of NR Gloves and Chemical Interference
on Protein Assays. J. Rubb. Res., 7(1),
56–70.
16. MOK, K.L., LAI, P.F., HASMA, H. AND
AMIR, M.Y. (2004) Recent Studies
on Interferences in NR Latex Protein
Measurement. International Latex
Conference 2004.
17. MOK, K.L., NORHAYATI MORIS,
ROSMAHANI CHE ISA, HASMA
HASHIM, NURUL HAYATI YUSOF
(2005) Interference Correction in
Lowry Micro Assay for Measurement of
Extractable Proteins in Natural Rubber
Latex Products. Malaysian Rubb. Tech.
Dev., p. 3–7.
