Accurate analytical measurements are mandatory for:
- legal compliance with government regulations
- long-term monitoring
- baseline studies
- standardisation of laboratory performance
In agriculture, food science and environmental monitoring and accurate data on the chemical composition of raw agricultural products and foods are needed to assess the effects of farming management practices, changes in crop culture, as well as food processing of nutrient and toxic chemical content of retail food products.
Elemental concentration information is required to establish the essential nutrients or toxicology of a toxin to:
- determine the roles of nutrients in health and disease
- identify adequate, sub-adequate, or marginal intakes by the population
- establish nutrient dietary requirements
- accumulate baseline concentration data to investigate the effects on nutrient levels of various methods for food processing
- comply with legal labelling requirements.
The choice of appropriate matrix reference material plays a critical role in analytical method validation and quality control of assay results. Appropriate reference material (RM) that matches the matrix of the samples can help resolve several potential errors during the analysis. One of the most common errors are false positive and false negative results. False positive is the erroneous identification of a specific analyte, when, in fact, it is not present at a detectable level, for example, Pb (lead) in tomato leaves. False positive results may be associated with artefacts, contamination during sample preparation or analysis, or instrumental interferences. This is especially important when results contain some penalty elements and when critical decisions are being made based on the presence of these elements in the environmental or food sample. This may result in unnecessary costs and investigations.
A false negative is an opposite situation and occurs when a specific analyte, for example, cadmium in apples, is present at a detectable level in the sample is not shown in the analysis. This may be associated with poor recovery during the digestion, reduction of volatile elements during sample preparation such as ashing or digest (arsenic, mercury, sulphur), or interferences on the instrument. For instance[n3] , if a lab technician is analysing iron in wheat using pine needles as a reference material, it might not be appropriate as recovery of iron in wheat might be different to recovery in pine needles. One should ideally match both the concentration of analytes in the environmental samples and its matrix to same parameters in reference materials. There are an abundant number of reference materials available on the market with various matrices and concentrations of trace elements.