How can the homogenisation of trace elements (below 5 % RSD) in food supplements be validated with process reliability?
Validating the homogenisation of trace elements in food supplements with process reliability requires systematic evidence from representative sampling, validated elemental analysis and statistical evaluation. At low dosages of selenium, chromium, molybdenum or iodine, it is not only the mixing quality itself that is critical but also the sampling and analytical variance. The process assessment must therefore not rest on a single measured value.
1. Plan sampling to be statistically robust
Sampling should be stratified across the entire mixing and filling process, that is, at defined points in time and at various positions within the batch. The aim is to capture both local inhomogeneities and segregation effects. In practice, several samples are taken per batch and per sampling position.
The sample quantity should correspond as far as possible to the single dose, so that the later assessment of uniformity remains close to practice. The sampling strategy should be risk-based and statistically justified.
2. Validate the elemental analysis
Trace elements require a sufficiently sensitive and selective method, usually ICP-MS for very low contents and ICP-OES for higher concentrations. The sample is generally dissolved completely by means of a suitable, validated digestion, so that matrix effects and recovery losses are minimised.
The analytical method must be validated before the homogeneity assessment, in particular with regard to accuracy, precision, linearity, limit of detection and limit of quantification, specificity and robustness. Method precision should be considerably better than the homogeneity target, so that the process variance is not masked by measurement uncertainty.
3. Separate process variance from method variance
What matters is not only whether a sample scatters, but why it scatters. An analysis of variance components is therefore useful in order to distinguish analytical scatter, sampling error and genuine process scatter from one another.
If the method variance is too high, an apparently poor RSD may wrongly be attributed to the mixing process. Only the statistical separation of these contributions permits a robust statement about the actual homogeneity.
4. Define acceptance criteria clearly
An RSD below 5 % is a common acceptance criterion for blend uniformity approaches and is frequently combined in practice with additional limits for individual values. It is advisable also to check the mean against the target content, for example within the range of 90–110 % of the target value, and to assess outliers or systematic positional differences.
Confidence or tolerance intervals are also helpful for a robust process assessment, because they represent not only the sample but also the expected quality of future units.
5. Secure the critical process parameters
Homogeneity depends substantially on the critical process parameters, above all mixing time, rotational speed, fill level, order of addition and pre-mixing. For trace elements with very low dosages, a premix or geometric dilution strategy is frequently required in order to avoid dosing errors and segregation.
Particle size distribution, differences in density, moisture and electrostatic effects must also be taken into account, because they significantly influence the tendency to segregate.
6. Validate across several batches
Homogeneity validation should not be tied to a single batch, but should take place within the framework of process validation across several consecutive batches. An assessment during process qualification with predefined sampling points and documented acceptance criteria is customary.
How amixon® solves validatable trace element homogenisation in food supplements
amixon® precision mixers are designed to achieve a technically ideal mixing quality even at very small dosing quantities. That is the decisive basis for validating trace elements such as selenium, chromium, molybdenum or iodine, because the ingredients distribute very evenly throughout the mixing chamber and homogeneity remains reproducible.
The gentle mode of operation is particularly important here. amixon® mixes without appreciable heat input and with an adjustable tool speed matched to the product. Sensitive ingredients such as vitamins, probiotics, encapsulated active substances and delicate carriers are thereby preserved.
A further advantage is the robust mixing performance across differing fill levels and batch sizes. This makes amixon® particularly interesting for flexible production environments and contract manufacturers who frequently switch between different batch sizes.
amixon® also offers design advantages for hygiene, purity and batch integrity. Mixing chambers executed free of joints, very high residual discharge and minimised carry-over between recipes support clean process management and reduce the risk of cross-contamination.
Process reliability in documentation is another clear plus. Mixing programs can be stored, process data recorded without gaps and batches clearly assigned. Validation thereby becomes robust not only technically but also in documentary terms.
In the pilot plant, customers can test with original products and secure the mixing parameters directly for the production scale. Trace elements, premixes and sensitive recipes can thus be developed and validated realistically before production starts.
What makes amixon® special
- Technically ideal mixing quality for trace elements and micro-dosages.
- Gentle mixing without appreciable heat input.
- Suitable for sensitive ingredients such as vitamins, probiotics and encapsulated active substances.
- Very good dischargeability and low carry-over.
- Hygienic, validation-friendly design.
- Reproducible processes through documentable mixing programs.
- Product-oriented validation in the pilot plant with the original product. In the Paderborn pilot plant alone, amixon® has 35 test mixers available. These have a volume of 5 to 3,000 litres.