Imaging the composition of homeopathic granules by ToF-SIMS

Born at the end of the 18th century, homeopathy was conceived by Samuel Hahnemann who described its fundamental principles. This principle is based on the law of similitude and is described by its founder as follows: "any substance capable of inducing pathological symptoms in a healthy person in large doses is likely, in specially prepared doses, to cause similar symptoms to disappear in the patient who presents them.

In short, substances that cause disease in the healthy patient in large doses can cure the patient with the same symptoms when used in minute quantities.

This introduces the second principle on which homeopathy is based: infinitesimality. The active substances, called "strains" in homeopathy, can come from three families: plant, mineral and animal. These strains are diluted according to the Hahnemannian technique (noted DH to the tenth and CH to the hundredth) or according to the Korsakovian technique (noted K).

These active substances are then incorporated into a neutral carrier, generally consisting of lactose and sucrose.

The ToF-SIMS in ionic imaging mode will allow to map the different elements and molecular compounds contained in a homeopathic granule, with a submicronic resolution. 

The primary ion beam reduced to a small diameter spot scans the surface of the sample to be imaged. The secondary ion extraction and mass analysis optics allows the reconstruction of chemical images by synchronizing the detection of the secondary signal with the scanning of the primary beam. The lateral resolution of the images depends on the size of the micro-beam (from 100 nm to 3 µm in diameter depending on the analysis conditions).

The ToF-SIMS allows to detect with a very high sensitivity traces of elements up to ppb and molecules up to femtomole, in extreme surface (< 1 nm) of solid samples. 

A pulsed source of mono or multi-atomic primary ions (Ga⁺, Bi_n⁺, Au⁺, C₆₀⁺, ...) with an energy of a few keV bombards the sample surface. The secondary ions resulting from the interaction between the primary ions and the sample are then focused and accelerated with the same kinetic energy towards the time-of-flight analyser which separates them according to their m/z ratio with a very good mass resolution (ΔM/M > 10 000 at mass 28). The resulting mass spectra represent the number of secondary ions as a function of their travel time to the detector, which is proportional to the square root of the m/z ratio.

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Figure 1: 2D ToF-SIMS image of sucrose (C₃H₅O⁺ in red) and lactose (C₃H₇O₃⁺ in blue) Figure 2: 2D ToF-SIMS image of Sucrose (C₃H₅O⁺ in red) and Lactose (C₃H₇O₃⁺ in blue) and K+ (in green)
 

Molecular analyses on pure samples of lactose and sucrose were carried out in order to identify the tracer ions differentiating these two sugars, used in the manufacture of granules. 

It has been shown that lactose presents more intensely some characteristic fragment ions: C₃H₇O₃⁺, C₁₂H₂₂O₁₁Na⁺, C₈H₁₃O₇^-, C₁₀H₁₁O₄^-.
Sucrose shows more intensely other characteristic fragment ions: C₆H₁₄O₂⁺, C₇H₈O₄⁺, C₁₂H₂₂O₁₁K⁺, C₁₂H₂₁O₁₁^-.

The chemical images obtained on the section of a homeopathic granule (Figures 1 and 2) indicate that lactose is present as dense 'grains' and that sucrose forms the 'cement' around them. In addition to the fragment ions characteristic of the two sugars, contaminations could also be localized: Na⁺, dibutylamine (C₈H₂₀N⁺), PO₃^- and Cl^- at the level of Lactose, as well as K⁺ dispersed in the sucrose matrix and at the interfaces with the Lactose grains.

In figure 1, the superposition of Saccarose (in red) and Lactose (in blue) is presented with C₃H₅O⁺ and C₃H₇O₃⁺ as tracers.

In figure 2, you visualize Sucrose (C3H5O+ in red), Lactose (C₃H₇O₃⁺ in blue) and potassium (K⁺ in green).

In this example, the ToF-SIMS imaging mode revealed visual information on the sub-micron scale arrangement of constituents on the surface of a homeopathic granule.

ToF-SIMS allows to map the distribution of the different elements and compounds present in a sample with a submicronic resolution.

For more applications of ToF-SIMS analysis or our other techniques, please ask us for information.

Other complementary techniques can be used to study the surface structure of a sample (TEM, SEM) and to analyse their chemical composition such as EDX and XPS.