*Occurrences of Cadmium, Arsenic, Lead, and Mercury in Potable Water in Greater Gaborone… DOI: http://dx.doi.org/10.5772/intechopen.113716*

Samples were collected in 50 mL precleaned polyethylene bottles and spiked with ~3 drops of 50% HNO3 (1:1, HNO3, v/v). Water samples were collected from the different stages of the drinking water supply chain, which included (i) raw untreated water reservoir tanks, (ii) treated water reservoir tanks, (iii) household outdoor taps representing the end of the distribution line (**Figure 2b**), and (iv) indoor drinking water taps (**Figure 2a**). In all instances, samples were collected in triplicates. Sample collection times were during the morning, peak usage, and midday to represent low to moderate usage. Temperature, pH, and total dissolved solids (TDS) were measured immediately after sampling using a pre-calibrated multimeter capable of measuring these parameters to the required accuracy. In each instance, samples were collected without flushing taps first [65]. The samples were preserved at ~4°C in an insulated cooler box and transported to the lab for processing. **Figure 2** exemplifies the sample collection process.
