Sample Preparation

In the case of solid samples that are going to be analyzed by XRF for the determination of major chemical elements, the most advisable method is fusion. In this type of preparation, finely ground samples (particle size < 60 µm) are calcined at 950ºC to eliminate all organic matter and volatile components. The calcined material is then melted with the help of a flux at high temperature (1200º C) and finally transferred to a mold where it cools. The final result is known as a pearl, which is a solid with a glassy appearance. Since the process involves the use of high temperature, this type of preparation is not recommended for the determination of minor, trace or volatile elements. Among the advantages of this type of preparation, we highlight that by melting the material, an effective particle size of approximately atomic size is achieved and the mineralogy of the sample is eliminated, and therefore the matrix effect is minimized. Another advantage is that standards can be prepared from oxides, carbonates, phosphates, etc., so calibrations can be adjusted to each type of sample. The fluxes used in the Service are lithium tetraborate and lithium metaborate. The amount of sample needed for the preparation of each bead is approximately 2.5-3 g.

Equipment:

Claisse Perlator.

We call dry sample preparation the process of eliminating organic matter, applying in our case high temperatures, and subsequent dissolution of the residue by treatment with diluted acids.

It is used in various samples such as soils, plants, marine products, etc. It cannot be used for the determination of volatile analytes such as Hg, Pb, As, Sn, Se, etc.

Sample requirements:

In the case of plants, geological materials and similar, the samples must be well dried.

In the case of food, fresh samples are accepted.

Homogeneous in all cases.

Representative.

Equipment:

Carbolite ELF 11/6B muffle furnace.

We call wet sample preparation the process by which, starting from a solid, colloidal or heterogeneous liquid sample, we can obtain a homogeneous aqueous solution with the analytes of interest in solution. For this, we use an attack with strong acids in a closed system, with the application of heat and, in general, pressure higher than atmospheric to increase the attack speed.

Its use is mandatory for the determination of volatile elements that cannot be prepared dry (Hg, As, Sn, etc.) and for complex matrices that can only be broken down in this way.

It is applied to various samples such as geological materials, plant and animal tissues, sludge, food, etc.

Sample requirements:

In the case of plants, geological materials and similar, the samples must be well dried.

In the case of food, fresh samples are accepted.

Homogeneous in all cases.

Representative.

Equipment:

Savillex Teflon Dischargers

Sample requirements and limitations:

Documentation to be submitted: Application Form duly completed.

Minimum sample quantity required: depends on the technique to be used ( consult us ).

Maximum number of samples per request: depends on the technique to be used ( consult us ).

Collection period for measured samples: 1 month.

Refrigeration of analyzed samples: 1 week after delivery of results.

Sample requirements and limitations:

Documentation to be submitted: Application Form duly completed.

Minimum sample quantity required: depends on the technique to be used ( consult us ).

Maximum number of samples per request: depends on the technique to be used ( consult us ).

Collection period for measured samples: 1 month.

Refrigeration of analyzed samples: 1 week after delivery of results.

Technical bases:

Most samples that are determined by analytical techniques are too complex or too diluted to be introduced directly into the equipment. Therefore, sample extraction and concentration techniques are used to eliminate the components of the matrix that are not of interest (interferences), as well as concentrate the analyte of interest so that it can be detected.

Depending on the mechanism or process to be employed, we can classify the extraction techniques into:

Extraction method.

Liquid-liquid (LL).

Solid-liquid (SL).

Solvent-accelerated (SA).

Solid-phase (SPE).

Analytical supercritical (SCE).

Microwave-assisted (MAE).

Using chromatographic techniques, such as Liquid Chromatography or Thin Layer Chromatography.

Using classical techniques: crystallization, precipitation, distillation, filtration, etc.

Complementary techniques such as: dialysis and microdialysis or ultrafiltration.

Applications:

Pharmaceuticals: antibiotics, sedatives, steroids, analgesics.

Biochemistry: amino acids, proteins, carbohydrates, lipids.

Food: artificial sweeteners, antioxidants, additives.

Contaminants: pesticides, herbicides, phenols, PCBs.

Clinical medicine: bile acids, drug metabolites, urine extracts, estrogens.

Forensic chemistry: drugs, poisons, blood alcohol, narcotics.

Sample requirements and limitations:

Documentation to be submitted: Application Form duly completed.

Minimum sample quantity required: depends on the technique to be used ( consult us ).

Maximum number of samples per request: depends on the technique to be used ( consult us ).

Collection period for measured samples: 1 month.

Refrigeration of analyzed samples: 1 week after delivery of results.

Equipment:

Solid Phase Extraction Cartridges, Reversed Phase, Normal Phase and Ion Exchange.

Chromatographic equipment and fraction collector.

Microwave assisted digester.

Refrigerated centrifuges, distillation and filtration equipment.

Accelerated solvent extraction system.