Friday, October 13, 2006
Just for fun, here's the recipe for test strips:
1. The test strip is preferably a porous membrane in the form of a non-woven, a woven fabric, a stretched sheet, or prepared from a material such as polyester, polyamide, polyolefin, polysulfone, or cellulose.
2. A test strip is manufactured by mixing 40 g of an anionically stabilized (3.8 parts by weight sodium lauryl sulfate and 0.8 parts by weight dodecyl benzene sulfonic acid) water-based hydroxyl elastomer, containing about 5% by weight colloidal silica and 5 g of finely ground titanium dioxide. Then I g of tetramethylbenzidine, 5,000 units horseradish peroxidase, 5,000 units glucose oxidase, 0.12 g tris, and 10 g of water (hydroxymethyl) aminomethane (buffer) are mixed into the batch.
3. After mixing to ensure a homogeneous blend, the batch is cast onto a polyethylene terephthalate sheet for added structural integrity in a carrier matrix, and dried at 122°F (50°C) for 20 minutes.
4. Next, 100 mg of 3-dimethyl amino benzoic acid, 13 mg of 3-methyl-2-benzothiazolinone hydrazone, 100 mg of citric acid monohydrate-sodium citrate dihydrate, and 50 mg of Loval are added in dry form to a 50 ml tube.
5. These dry materials are mixed with a spatula, then 1.5 g of 10% water solution of carboxymethylcellulose is added and mixed thoroughly with the above solids.
6. Next, 2.1 g of dialyzed carboxylated vinyl acetate ethyl copolymer latex is added and thoroughly mixed.
The latex copolymer had been dialyzed (separation of larger particles from smaller particles) by placing about 100 g of carboxylated vinyl acetate/ethylene copolymer emulsion into a membrane tubing. The filled membrane was soaked in a water (distilled) bath at 68°F (20°C) for 60 hours to allow low molecular weight particles, unreacted monomer, catalyst, surfactant, etc. to pass through the membrane. During the 60 hours the water was continuously changed using an overflow system. The remaining dialyzed emulsion was then used in preparing the reagent layer.
7. Then 0.18 ml of glucose oxidase is pippeted to the tube as a liquid. Next, peroxidase is pipeted as a liquid to the tube and tartrazine is pipeted to the tube. The resulting mixture is mixed thoroughly. This mixture is allowed to stand for approximately 15 minutes.
8. A polished-matte vinyl support prior to being coated with the above solution was cut to form cell rows and then wiped clean with methanol. The mixture is pulled into a 10 ml syringe and approximately 10, 6 mm drops are placed on each cell row. The coated cell row is heated in an oven at 98.6°F (37°C) for 30 minutes followed by 113°F (45°C) for two hours. This process of coating and spreading the mixture is repeated for each cell row. The cell rows were then cut into strips of the desired size.
9. These strips were packaged with absorbent packs of silica gel and dried overnight at approximately 86°F (30°C) and 25 mm/Hg vacuum.
Now you know why they're a dollar a piece.
posted by Sydney on 10/13/2006 08:26:00 PM 0 comments