Selling bottled water is big business with a global market estimated at 280 billion liters in 2014 and consumers in the USA averaging consumption of 128 liters per person per year. The absence of both calories and artificial additives in bottled water have driven a growth in consumption by health-conscious consumers, whilst at the same time consumption of carbonated beverages has leveled or declined.
The origin of commercial bottled waters can be quite diverse such as aquifers, springs, reservoirs or even ultra-purified tap water. In many cases the source of the water is part of the product branding, but in other instances the source may not be clearly specified on the label.
Dissolved Minerals and Salts Are Significant Indicators of Origin
To answer the headline, bottled water is not ‘just water’ and the dissolved minerals and salts reflect not only the geological source, but also handling operations including packaging. I appreciate there are many analytical techniques for analyzing minerals and salts but in this post we will concentrate our story on trace elemental analysis and isotopes. Distinct differences in dissolved elements affect the taste of bottled water and also provide evidence of geographical origin. In a recent paper Felipe-Sotelo and co-workers from the University of Loughborough in the UK, have investigated the trace elemental composition of bottled waters from the Czech Republic, Finland, France, Germany, Italy, Slovakia and UK.
Acidified aliquots of bottled water samples were analyzed directly to determine levels of major elements such as Ca, K, Mg and Na, as well as minor and trace elements (Al, As, Ba, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sr, U, V and Zn). Typically for this type of analysis inductively coupled plasma mass spectrometry (ICP-MS) or optical emission spectroscopy (OES) is employed.
Elemental Indicators of Origin of Bottled Water
In order to assess the effect on the composition of waters by factors such as geographical provenance, geological setting, type of water and packaging material, analyses of the variance (ANOVA) was performed on the results of each individual elemental parameter, as well as multivariate one-way ANOVA on the whole matrix of results. Only partial discrimination of geographical origin of bottled waters based on elemental composition was achieved using multi-variate analysis.
The best separation was between British bottled waters and other European sources with British waters not only having a lower mineral content but also having lower concentrations of heavy metals, which varied within very narrow ranges. There were some other interesting trends which were uncovered in this study, such as narrower distributions of results for the major elements, calcium, potassium, magnesium and sodium in English and Scottish bottled waters. It was speculated that this could be due to the preference of British consumers for low mineral composition in bottled water. German bottled waters showed the highest concentrations and widest distributions of nickel and manganese of which the later is considered important because of the taste and odour given to the water. The highest concentrations of lead were found in waters from the Czech Republic and Slovakia, whereas Italian bottled waters exhibited the highest levels of strontium and uranium. Waters packaged in glass containers contained higher concentrations of Al than those in PET bottles (highly read post by my colleague on this topic here), whilst higher levels of As, Sb and total organic carbon were found in water samples from PET bottles compared to glass. However, the majority of samples were in PET bottles with only three samples obtained in glass.
If you are interested in PET bottle analysis, I recommend you take a look at this highly read post written by my colleague Deepali Mohindra.
Stable Isotope Measurement of Bottled Waters
Elemental composition of bottled waters is only one tool that can be used to determine geographical origin, as hydrogen and oxygen stable isotope ratios reflect whether the water originates from mountain or lowland sources. In a 2005 publication Gabriel Bowen and co-workers found that the hydrogen and oxygen isotope ratios of 234 samples of bottled water ranged from -147‰ to +15‰ and from -19.1‰ to +3.0‰, respectively. Typically isotope ratio analysis of water can be conducted by isotope ratio mass spectrometry (IRMS) using an instrument such as the Thermo Scientific Delta V. These authors concluded that determining stable isotope ratios of bottled water can enable ultimate and proximal sources of bottled water to be distinguished and provides a tool for use in the regulatory monitoring of bottled water products
Interested in learning more about Bottled Water Analysis, including more techniques for analysis, check out the dedicated pages here.
There is some very useful information to be found in our Trace Elemental Analysis Learning Centre here and you can find a wealth of material on Isotope Analysis here.