Mettler Toledo GA42 Operations Instructions download pdf (Page 26)

24 METTLER TOLEDO DL36

9.2 Tips for sample addition

The titration cell of the DL36 is set up for the injection of samples.

1. During sample preparation and sample addition, work as quickly as possible to keep the

effect of atmospheric moisture to a minimum. As most samples are stored and transport-

ed under standard conditions of temperature and pressure, you should also weigh in and

inject under these conditions.

• You can cool readily volatile samples before sampling (notice: moisture could then

condense on the syringe!), viscose samples can be warmed.

• With hygroscopic liquids, you should never take samples from the surface as the

moisture content is highest at this point.

• Samples in which moisture is present in the form of a dispersion can possibly be treated

in an ultrasonic bath before addition.

2. Never remove the Teflon stopper to add solid samples! This would result in an excessive

amount of moisture entering the cell.

• For determination of the moisture content in solids, you can dissolve these in an

appropriate solvent or extract them and then inject the solutions. You must determine

the moisture content of the corresponding solvent/extraction agent beforehand and

enter it as a blank value (see Section 7.3.2).

• With solids for which no suitable solvent is available for the titration, e.g. polymers,

moisture can be driven off only by heating. METTLER TOLEDO offers drying ovens for

such situations which lead the resulting water vapor through tubing to the titration cell of

the DL36, where it can be determined.

3. Adjust the amount of sample to the expected moisture content to achieve short titration

times and allow as many titrations as possible to be performed with the same reagent

solutions. The following table provides an overview of the amount to be weighed in.

Moisture content Sample weight

50 - 100%........................... <0,01 g

10 - 50%........................... 0,02 → 0,01 g

1 - 10% ........................... 0,05 → 0,01 g

0,1 - 1%........................... 0,1 → 0,01 g

0,01 - 0,1%........................ 1,0 → 0,1 g

0,001 - 0,01%...................... 5 → 1,0 g

0,0001 - 0,001%................. 10 → 5 g

Sample determinations

not suitable for coulometry

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 43 44

No comments

Mettler Toledo GA42 Operations Instructions Page 26