Determination of heavy metals present in DLSU-Manila's drinking fountains using differential pulse-anodic stripping voltammetry (DPASV)

• Main Authors: Bautista, Islene Hazel D. R., Isnit, Pamela Camille M., Uytanlet, Chloe Jane C.
• Format: text
• Language: English
• Published: Animo Repository 2008
• Subjects: Drinking water > Analysis; Water quality > Measurement; Water quality management > Philippines; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/6725
• Institution: De La Salle University

The presence of toxic heavy metals, specifically arsenic, cadmium, lead and mercury in DLSU-Manila's drinking water fountains was determined by using the Differential Pulse Anodic Stripping Voltammetry (DPASV). Glassy carbon electrode was used as the working electrode with platinum wire and standard calomel electrodes as the auxiliary and reference electrode respectively. The water samples were taken from the drinking fountains of La Salle, Velasco and Yuchengco buildings primarily because of their construction dates. The specific time of day the samples were taken, the height of the drinking fountain with respect to the location of the overhead tanks and the acquisition date of the drinking fountain units were taken into consideration. These samples were tested using DPASV at the same day that they were taken to avoid expiration of the samples. The last batch of samples was then tested using Atomic Absorption Spectrophotometry (AAS) and the results were compared with that of DPASV. Tap water and commercially available bottled distilled water samples were tested with both DPASV and AAS and the results were compared with the results gathered from the drinking fountain water samples. Tap water samples were gathered from the first floor of both La Salle and Velasco buildings and the second floor of the Yuchengco building and the commercially available bottled distilled water used was Absolute distilled drinking water. The results that were obtained by comparing DPASV and AAS showed that determining the amounts of the four metals were very inaccurate when AAS is to be used. This was mainly because AAS cannot detect too small concentrations of different metals accurately where concentrations above 100ppb would be optimal. This is the reason why AAS was not able to determine the concentrations of mercury in the samples whose concentrations are only along 0.5ppb to 3.5ppb. Similarly, arsenic was not determined in the samples using both methods since the supporting electrolyte used for DPASV would not yield any values of arsenic and for the same reason as mercury, arsenic would be too small to be detected by AAS. Therefore, since the concentrations of the metals in this study ranges only from 2ppb to 20ppb, trace analysis would be more accurate if DPASV method would be chosen. The electrolyte used in the whole study was made constant to 0.1M HCI solution. The results yielded by the electrode showed that the peaks of cadmium, lead and mercury are shown in different voltages which are -1.4V, -1.1V and -1.545V respectively. Finally, after evaluating the amount of cadmium, lead, and mercury in the water samples, it could be observed that the drinking fountain water and the tap water of DLSU-Manila almost have the same concentrations, bringing into conclusion that the filters installed together with the drinking fountain units do not remove the heavy metal contents of the water. Also, it was observed that the metals present in DLSU-Manila's drinking fountain water exceeded by 0.177ppb to 15.802ppb for cadmium, 0.0006ppb to 3.194ppb for lead, and 0.011ppb to 1.381ppb for mercury, to the concentrations prescribed by the Environmental Protection Agency (EPA) of 5ppb for cadmium, 15ppb for lead, and 2ppb for mercury.