# Development of Heavy Metal Potentiostat for
## 1 Introduction and background  
Batik is a traditional handmade textile craft in the cottage industry [1]. This industry has contributed positively to economic growth, especially in Kelantan and Terengganu in Malaysia, and has also become one of the main attractions of foreign and local tourists [2]. Batik factories are known to generate a large amount of wastewater included wax, resin, sodium, silicate, and dyes. The presence of dyes is one of the main concerns in wastewater [3]. Among all types of dyes, reactive dyes are preferred due to their convenience, transparency, and brilliant color along with ease of textile fastening [4]. Five different types of reactive dyes were studied in [5], and the results reported that each reactive dye contains heavy metal elements of cadmium (Cd), lead (Pb), arsenic (As), zinc (Zn), chromium (Cr), cobalt (Co), and copper (Cu). Amongst all, Zn and Cr are essential elements, and small doses are required by living organisms to maintain various biochemical and physiological functions [6; 7; 8; 9], while the others are non-essential elements which are highly toxic and harmful to human health and the environment, even at low concentrations [6; 7]. According to the Environmental Quality Act (EQA 1974), the permissible limit for industrial effluent discharge based on standard A (applicable to discharge into any inland waters within catchmentareas) for Cd is 0.01 ppm, As and Cr are 0.05 ppm, Pb is 0.1 ppm, Cu is 0.2 ppm, and Zn is 1.0 ppm [10]. However, as most of the batik factories were build-up with improper or without a waste management system, the level of heavy metals discharged was not determined [11]. This happened due to the lack of awareness regarding the hazardous effect of heavy metal elements toward the environment and especially concerning human health [11]. Determination of the heavy metal level before being discharged to the environmental water is crucial. Today, various heavy metal detection techniques have been established, including inductive coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma-optical emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS), atomic emission spectrometry (AES) [12], X-ray Fluorescence Spectrometry (XRF), cold vapor atomic absorption spectrometer (CVAAS), neutron activation analysis (NAA), and flameless atomic absorption spectrophotometry (FAAS) [12; 13; 14]. These techniques are highly sensitive and selective [14]. However, these techniques are inconvenient for fieldwork application, such as in a batik factory, because instruments are relatively expensive, bulky, require complex operational procedures, and long detection times [12; 13; 14]. Nowadays, electrochemical techniques hold great potential to realize the on-field detection of heavy metal elements in the batik factory. This technique has the advantages of low-cost, ease of operation, fast analysis, and is also well suited to fabricate on a small circuit for portable and on-field application [12; 13; 14; 15]. Until now, numerous research has been done in the development of electrochemical devices for various applications, which are known as potentiostats [16; 17; 18; 19; 20; 21; 22; 23]. One of the potentiostat developments is an Arduino-based potentiostat, fabricated using inexpensive components which were capable of performing simple electrochemical experiments and were suitable for an undergraduate teaching level [17; 18; 19]. For such experiments, the results and data were recorded in real-time on a Windows-based computing system via a USB interface [17]. However, a potentiostat integrated with Raspberry Pi eliminated the requirement of an external computing system. This standalone device carried out the electrochemical experiments, and the results were displayed on an LCD touch panel [20].