Before a sample can be analysed, several steps for sample preparation are necessary. These includes dilution, addition of standards and buffer solutions, filtration, concentration, purification, and deposition in a suitable sample vial. Depending on the sample volume, there are simple accessories for manual processing but also devices and systems for interactive support or automation.
A very high concentrated sample/analyte can cause incorrect measurement results depending on the type of analysis (e.g., overloading or overrange). For this reason, the sample should be diluted. For dilution, it is extremely important to use very accurate and precise volumetric dosing and measuring systems to obtain accurate and reproducible analytical results.
Types of dilution:
|manually||Pipette & volumetric flask|
|semi-automatic||Dual Syringe Dilutor Microlab 600 / 700|
|automatically||Dual Syringe Dilutor & Sample station Liquid Station|
Standards are often added to the sample in order to evaluate quantitatively the individual process steps of sample preparation.
In some cases, special additives have to be added to the sample, e.g., to stabilize (buffer reagent) or to make it measurable (labelling, derivatization).
Samples may contain interfering substances that influence the analytical result. These can be removed by specific purification, thus improving the measurement result.
If the sample concentration is too low, specific enrichment methods increase the amount of sample required for detection.
Particles are removed from the sample, thus preventing a negative influence on the analysis system or the measurement result.
The selection of the suitable sample vial is also an important step in sample preparation. It has to be ensured that the sample does not change during the time from preparation to analysis. This guarantees that the sample can be reliably measured in the respective analysis system and that there are no negative interactions between the sample and the sample vial.
Repeat the steps for single or dual dilution with varying dilution ratios and the same final volume.
Repeat the steps for single or dual dilution and use the resulting dilution as the sample for the next dilution.
Automated dilution & measurement of the sample
The application was designed to produce a diluted sample with a desired absorbance, in order to measure it in another analyser system. In a first step, the sample is diluted with a defined ratio and then measured photometrically. If the determined absorbance is not in the required range, the necessary dilution is calculated and the sample is diluted accordingly and repeatedly checked by the photometer. As soon as the desired absorbance has been achieved, the dilution is transferred to the designated sample vial.
pH regulation + time-controlled sampling + automated dilution incl. standard addition
When developing materials for implants, the corrosion behaviour in body fluids must be tested. The solid sample material is in the test medium in a temperature-controlled and pH-regulated reaction vial. A sample is automatically taken from the reaction vial, and a standard is diluted and added according to predefined, but not equidistant, time intervals. The generated analysis substance is subsequently measured by element analysis.
Automated, time-controlled enzymatic reaction and sample addition in the analyser system
The hydroxyproline concentration in meat and sausage products has to be analysed. The protein hydroxyproline cannot be measured directly photometrically and must be converted in an enzymatic detection reaction. Different media are added at defined times. After a certain reaction time, the sample is automatically transferred into the measuring system.
Automated time-controlled reagent addition, sample extraction and dilution
Different amounts of various reagents are added to a reaction vial at defined times to influence and control the reaction. To evaluate the reaction progress and behaviour, samples are taken from the reactor at regular intervals. The sample is automatically diluted during transfer to a special sample vial so the sample can be processed ready for use in the corresponding analyser system later on.
DURATEC is a supplier and manufacturer of products and services for the fields of instrumental analysis, chemical analysis technology and technical, industrial or scientific processes or applications.