SPI-Chem HPMA Water Soluble Embedding Kit
Instructions for Use:
CAUTION: Thoroughly read all instructions and warnings on container labels
prior to use of this kit.
INTRODUCTION
HPMA or 2-hydroxypropyl methacrylate embedding media is a water soluble monomer that is finding
increasing applications in field of electron histochemistry as well as in the materials sciences
where observations of water soluble coatings and binders must be evaluated using thin section
techniques. The HPMA kit contains the following components:
1. Hydroxypropyl methacrylate (HPMA)
2. Azo-bis-iso-butyronitrile
3. 2, 4-Dichlorobensoyl Peroxide
Briefly, the specimen is dehydrated and impregnated (infiltrated) stepwise with prepolymerized HPMA containing successively less water (20'1 and 3.0%) and 0.1% Azo-bis-iso-butyronitrile or 2, 4-Dichlorobenzoyl Peroxide as a catalyst for subsequent Polymerization with ultraviolet (UV) light or heat.
FORMULATION
The preparation and mixing of type resin component must be thorough and always performed in a fume hood.
Prepolymerization of HPMA:
According to the procedure of ¹Leduc and Bernhard and Leduc and ²HOlt, quantities of up to
30ml of HPMA, containing 0.1% of azonitrile catalyst are partiality polymerized by heating to
about 90°C or until it starts to steam, with constant stirring. Once it starts to steam, cool
the beaker in an ice bath to rapidly cool it.
Repeat the process to obtain the desired viscosity (that of free flowing syrup consistently)
Dehydration and Impregnation of Sample:
Water is then added to separate liquids of the HPMA pre-polymer, to make 80% and 97% HPMA
solutions. A typical impregnation using the above pre-polymers includes 2 changes, 1
hour each for both the 80% and the 97% HPMA.
About 5ml of fluid is used for each specimen, placed in glass vials and agitated for the duration
of the impregnation. Should the HPMA turn cloudy from excess water, replace the wet HPMA with a
fresh aliquot before proceeding further. Each change of HPMA contains 0.1% of azonitrile to ensure
complete impregnation of samples with catalyst.
Embedding and Polymerization:
The samples are then placed in fresh 97% pre-polymer in gelatin capsules. To obtain a softer and less brittle final polymer, up to 10% water can be used during the: final polymerization (e.i.,90% pre-polymerized HPMA).
The capsules must be filled to capacity, to ensure the exclusion bf air, when their tops are pushed down tight.
Polymerization can be accomplished exposing the capsules to long wavelength UV light (3150A), in the cold (I-3°C) for 12 to 24 hrs. Alternately, for heat polymerization, the capsules can be maintained at 56-60°C for 2 to 3 days.
DISCLAIMER
The information given in this bulletin is to the best of our knowledge accurate, but no warrant is
expressed or implied. It is the user's responsibility to determine the suitability for his own use
of the products described herein; and since conditions of use are beyond our control, we disclaim
all liability with respect to the use Qt any material supplied by us. Nothing contained herein
shall be construed as a recommendation to practice any patented invention or as a recommendation
to use any product or to practice any process in violation of any law or any government regulation.
1) Leduc, E.H. and Bernard, W.V, J. Ultrastruct. RES. 19, 196 (1967)
2) Leduc, E.H. and Holt, S.J., J. Cel Biol. 26, 137 (1965)
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Monday July 07, 2008
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