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Troubleshooting
70
Large blanks in cyanide
Large blanks in cyanide are probably caused by contaminated MgCl
pure or other ultra-pure grade. A good grade (better than A.C.S.) of sulfuric acid also helps.
Bumping (violent boiling) in the sample tube
This may sometimes actually push the membrane and ring up in the collector tube.
Add one Hengar granule or other small (ca. 1 mm diameter) boiling stone to the sample tube.
Results from Micro Dist™ do not agree with other methods
Try calibrating the analytical method with Micro Distilled standards. If the recoveries improve
for reference samples, then use Micro Distilled standards. Remember that analytical methods
which follow the distillation must be scaled down in proportion to the smaller Micro Distilled
sample.
Block takes hours to come up to temperature
The red light goes out on the block when it's at temperature. If it takes more than 30–40
minutes, contact the Lachat Technical Support Department.
Can't break the collector tube or solution spills all over when they break
Purchase a pair of pruning shears or poultry scissors and cut the collector tube at the
break point.
Membrane caking
When solid samples or sludges are distilled, foam comes up through the membrane, or scum
cakes over the underside of the membrane causing it to be pushed up.
This occurs when the sample has a lot of organics in it such as grease or oils. The scum or
foam is organic surfactants which wet the hydrophobic membrane. This causes it to lose its
hydrophobicity and thus not function properly.
The placement of the membranes on all collector tubes is elevated such that the matrix foam
normally will not come into contact with the membrane.
Be careful of scummy organic material caking the membrane or actually oozing through the
membrane as this causes pressure to build up in the sample tube. The pressure is not large
but it is sufficient to cause spattering of the hot sample when the sample tube is removed. In
some cases the distillation membrane may pop out of the ring.
Running Solid Samples with Micro Dist
The Micro Dist is capable of handling many different kinds of solid samples from sands
to sludges.
As a general guideline, if the sample is high in organic content use only 0.5 g or less sample. If
the sample is low in organic content, one can use up to 1 g of sample.
Experiment with samples to determine the best weight of sample to add for each matrix type.
The sample will be diluted with DI water (5 to 6 mL) per the Micro Dist manual.
Calculating the amount of sample in mg/kg after analysis:
Multiply the determined concentration in mg/L by (1 L / l000 mL) * dilution vol. in tube = mg
analyte in sample.
Divide by g of original sample * 1000 g / kg to give mg analyte / kg sample.
. Always use 99.9999%
2
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