Lab methods: ICP-MS, ICP-OES, AAS, HPLC, FTIR, UV-Vis

Methods at a glance

ICP-MS and ICP-OES

Both use a high-temperature plasma to turn elements into ions or excited atoms. ICP-MS counts ions by mass and reaches very low detection limits, which makes it the usual choice for toxic metals such as mercury, where the GB supplement limit is just 0.1 mg/kg.^[1] ICP-OES measures emitted light and suits higher concentrations, such as common minerals. Neither distinguishes chemical forms on its own; see ICP-MS explained.

Atomic absorption spectroscopy (AAS)

AAS measures one element at a time by how much light of a specific wavelength it absorbs. It is a long-established method, still used for particular metals and sometimes as a specialised technique for mercury. It is slower for multi-element panels and, in some forms, less sensitive than ICP-MS.

HPLC (high-performance liquid chromatography)

HPLC separates a mixture into its individual compounds, which are then detected and measured. For shilajit, it can be used to profile marker compounds such as dibenzo-alpha-pyrones, and, combined with ICP-MS, to separate arsenic species for inorganic arsenic testing. It is also used for some contaminant tests, such as certain mycotoxins; see DBPs.

FTIR (Fourier-transform infrared spectroscopy)

FTIR measures how a sample absorbs infrared light, producing a spectrum that acts like a chemical fingerprint. Comparing a sample’s spectrum with reference shilajit can flag substitution or gross adulteration. It is fast and useful for screening, but it isn’t very sensitive to small amounts of an adulterant; see identity testing.

UV-Vis spectroscopy

UV-Vis measures how a solution absorbs ultraviolet and visible light. It appears in some humic and fulvic acid methods. Because results depend on the specific procedure, UV-Vis-based figures from different laboratories may not be comparable; see fulvic acid testing.

Microbiology and other methods

Microbiology uses culture methods, growing microbes on specific media, rather than instruments like these; see microbiological testing. Pesticides and PAHs are often measured by gas or liquid chromatography combined with mass spectrometry; see other contaminants.

Matching method to question

• Toxic metals at trace levelsICP-MS preferred.
• Inorganic arsenicHPLC combined with ICP-MS (speciation).
• IdentityFTIR and chromatographic profiling.
• Fulvic acidA stated humic fractionation method.

Reading the method on a report

Reports usually name the method or cite a standard method reference beside each result. If a method isn’t stated, ask. Knowing the method helps you judge detection limits and comparability; see reading a COA.

Chromatography with mass spectrometry

For pesticides, PAHs and some mycotoxins, laboratories often combine gas or liquid chromatography with mass spectrometry. Chromatography separates the compounds; mass spectrometry identifies and measures them. These methods can screen for many substances at once, which is why pesticide screens can cover hundreds of compounds; see other contaminants.

Method validation

Whatever the method, accredited laboratories validate it for the sample type, showing that it measures accurately, precisely and at a known detection limit. A complex material like shilajit can interfere with some methods, so validation for that kind of sample matters; see lab accreditation.

Putting it into practice

When you read a report, note the method beside each result. For toxic metals, look for ICP-MS or an equivalent sensitive method. For arsenic, check whether it was total or speciated. For identity, look for FTIR or chromatographic profiling. If methods aren’t named, ask.

Which methods matter most to buyers

For most buyers, the method behind the metals results matters most, because metals are the main safety question for shilajit. Look for ICP-MS or a comparably sensitive method, with detection limits well below GB limits. Next, check whether arsenic was speciated. Identity and composition methods are useful extras but don’t replace a sound metals result for your batch. If the report doesn’t make the methods clear, a short, specific question to the brand usually settles it. A brand that understands its own testing will be able to name each method without difficulty.

The bottom line

Different methods answer different questions: ICP-MS for trace metals, ICP-OES for minerals, AAS for specific metals, HPLC for compounds and speciation, FTIR for fingerprinting and UV-Vis for some composition tests. A good report uses the right method for each test and says which one.

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