In the UK, the Food Standards Agency is the overall regulator for food and drink, including bottled water. However, depending on whether the end product is classed as natural mineral water, spring water or bottled drinking water, different rules apply.
New regulations were introduced in 2007 that determine safe levels of trace metals under the Natural Mineral Water, Spring Water and Bottled Drinking Water Regulations 2007. This guidance is due to be revised this year.
The term ‘heavy metal’ typically refers to elements of atomic number 21 or higher that exhibit metallic properties, with many considered to be extremely toxic and relatively prevalent. Although some of these metals serve as micronutrients or metalloenzymes for humans at low concentrations, their accumulation at higher concentrations becomes toxic to most lifeforms. For example, high levels of copper have been correlated with liver damage. In addition, zinc may produce adverse nutrient interactions when present with copper-reducing immune function and levels of high density lipoproteins.
Other heavy and semi-heavy metals such as arsenic, silver, cadmium and lead are not required for the routine functioning of the human body and are toxic even at low concentrations.
Severe effects on humans include reduced growth and development, cancer, damage to organs or the nervous system, and in extreme cases, death. In addition, exposure to metals such as mercury and lead has been linked to the development of autoimmunity, which can in turn lead to joint diseases.
Children are particularly susceptible and sensitive to the toxic effects of heavy metals.
With contamination possible at all stages in the production process, routine monitoring for trace and ultra-trace levels of heavy metal impurities in bottled water is essential. Branded bottled water can be counterfeited, or contaminated at the source of the water itself due to shortcomings in preparation methods.
There are a range of techniques available to analyse bottled water. Atomic absorption (AA) and inductively coupled plasma optical emission spectrometry (ICP-OES) are traditionally used, although inductively coupled plasma mass spectrometry (ICP-MS) is becoming more favoured.
All three techniques provide the concentration of the elements, measured against a calibration standard. Graphite furnace atomic absorption (GFAA) and ICP-OES measurements are based on spectroscopic absorption or emission, while ICP-MS measures the elemental isotopes. In addition, to provide the elemental concentration of the elements, it can also be possible to verify the water source by a unique elemental ‘fingerprint’ of a given water source.
When selecting a spectroscopy technique, best practise is to choose a technique with a detection limit at least 10 times below the contamination limits specified by regulations.
A popular and cost-efficient choice for water analysis is to combine flame and graphite furnace AA. This is ideal when analysing bottled water, where the quantities of potential contaminants and the mineral content must be determined. In this configuration, the lower levels of detection achieved by GFAA are used to quantify heavy metals present at trace levels, while the flame AA is used to analyse the essential minerals that are present in higher concentrations.
A limitation of AA is that it’s a single element technique, measuring one element at the time. This means that laboratories analysing many elements and many samples may find it too slow.
ICP-OES and ICP-MS are multi-element techniques that are faster than AA for laboratories analysing several elements and numerous samples. This means that these techniques are favoured by contract laboratories. However, they have a higher initial investment cost, and in general, can be more complicated to operate.
GFAA and ICP-MS have higher detection limits than ICP-OES. As regulations become more stringent, the testing levels of heavy metal elements in drinking water are lowered over time. Therefore, these sensitive techniques are often favoured for drinking water analysis looking for low elemental concentrations.
The analysis of drinking water is fundamental to protect the health and well-being of humans and the environment. Regulatory bodies such as the Food Standards Agency set strict limits for the of heavy metals present in drinking water.
Atomic spectroscopy ensures that laboratories and environmental analysts can accurately monitor the levels of heavy metals to maintain the provision of safe bottled water.
Erik Buseth is inorganic sales development manager EMEA and India, PerkinElmer.
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