PURPOSE
A quick
screening method based on the use of dimethylglyoxime, suitable for the
qualitative evaluation of nickel release. The result is indicative and provides
guidelines when evaluating objects for nickel release. Dimethylglyoxime reacts
with released nickel ions and gives a pink colour complex.
EQUIPMENT
• Distilled
water
•
Dimethylglyoxime powder, analytical grade
• Ethanol
>95%
• 25%
Ammonia solution
• Volumetric
flask with stopper, 1000 ml
• Measuring
cylinder
• Magnetic
stirring
• Balance,
accuracy 0.01 g
• Funnel
• Safety
gloves
• Safety
goggles
• Cotton
swabs
•
Well-ventilated area for performing the test
TEST
SPECIMEN
• Test all parts with skin contact separately.
• Metal parts without skin contact shall not be tested.
• Test the piecing part on the test specimen and the
outer part separately.
• For
spectacles all parts with skin contact shall be tested.
Rub directly with the cotton swab immersed with the two solutions on the
metal part that have skin contact. Make sure the metal is clean since it
otherwise could be difficult to judge the result.
METHOD
NOTE: If you purchase ready-made solutions, also make sure to apply any
procedure recommended by the supplier.
Preparation
solutions
Dimethylglyoxime,
0.8%
a) Weigh (8.0g±0.5)g of dimethylglyoxime into a 1000 ml
flask with stopper.
b) Add ~900 ml ethanol (>95%) and place the flask on
magnetic stirring until the dimethylglyoxime is solved.
c) Add
ethanol so the total volume is exactly 1000 ml.
Ammonia
solution, 10% (m/m)
a) Measure 420 ml of ammonia solution (25%) and mix with
500 ml distilled water.
b) Stir and allow cooling to room temperature (if
necessary).
c) Add
distilled water so the total volume is exactly 1000 ml.
The ammonia
and dimethylglyoxime solutions are stable for 6 months at a temperature below
25°C. After this time there is a risk that the solutions will not work
correctly. If possible it is best to keep the solutions in a refrigerator.
Test method
1. Moisten a cotton swab with two drops of each solution.
It is important that it is exactly two drops of each solution and not more or
less. It does not matter which chemical is added first, but the two chemicals
shall be mixed on the cotton swab.
2. Rub quite
hard on the area to be tested for 30 seconds, not shorter and not longer. Use a
clock that shows seconds. The appearance of pink colour, from light pink to
strong cerise indicates nickel release. Other colours, green, grey, brown or
blue indicates other metals or dirt: in these cases the sample is OK.
1. Put two
drops of each solution on a cotton swab. It does not matter which one you put
on first, but the two solutions shall mix together on the swab.
2. Rub quite
hard on the object for 30 seconds, not shorter or longer.
RESULTS
If the
cotton swab turns pink it should be reported as “ + “ ( = NOT OK).
If the
cotton swab does not turn pink it should be reported as “ – “ ( = OK).
SAFETY
The chemicals used shall be handled with care!
