# Development of Heavy Metal Potentiostat for
## 1 Introduction and background
Both Arduino- and Raspberry Pi-based potentiostats did not possess a built-in analog to digital converter (ADC), and digital to analog converter (DAC) and the requirement for external ADC and DAC made the design more complicated. Many previous works have reported on the capability of a self-fabricated potentiostat to detect heavy metal elements. A potentiostat named CheapStat [21] was capable of detecting the arsenic (As) level in lake water. The test was conducted using a gold disk working electrode (WE), a platinum counter electrode (CE), and a silver/silver-chloride (Ag/AgCl) reference electrode (RE). A universal mobile electrochemical detector (UMED) [16] is a potentiostat which is compatible with a mobile phone and is capable of detecting cadmium (Cd), lead (Pb), and zinc (Zn). A screen-printed electrode (SPE) was used with UWED, which consists of carbon ink modified by carbon nanotubes as a WE, carbon ink as a CE, and Ag/AgCl ink as a RE. A programmable system on chip (PSoC) [22] is a commercially available integrated circuit (IC) that does not require any external electronic components to perform electrochemical experiments. The PSoC demonstrated the detection of Pb using gold wire as a WE and Ag/AgCl as a CE and RE. The latest work reported was a MiniStat [23], in which the design was developed to be suited for general electrochemical analysis in the smaller form factor. The MiniStat was tested to detect copper (Cu) using a 3 mm glassy carbon WE, a platinum wire as a CE, and Ag/AgCl as a RE. However, the potentiostats mentioned previously [16; 21; 23] demand the user to fabricate a printed circuit board (PCB) and to solder the electronic components onto the board. Since these potentiostats were designed with small surface-mounted integrated circuits (ICs), they required more skilled technicians and sophisticated tools to solder together, as compared to through-hole connections. This creates hindrances to chemists and other scientists who want to use a potentiostat. Besides, the detecting heavy metal as reported in [21; 22; 23; 24] used a three separated electrodes approach which is bulky and not suited for on-field application. The incorporation of a screen-printed electrode (SPE) eliminated the classical bulky electrodes and at the same time, enabled reduction in the sample used [25]. Although there are several reports working on modified SPE and WE [16; 25; 26; 27; 28], since heavy metals have defined redox potential, the selectivity toward specific heavy metal ions still can be achieved by bare electrodes and unmodified SPE [29]. Therefore, in the requirement of a heavy metal feature-based device for monitoring heavy metal levels in the batik industry, a Heavy Metal Potentiostat device (HMstat) incorporated with SPE was designed. The design of HMstat was based on the idea to simplify the potentiostat design by implementing a controller equipped with built-in DAC and ADC. With this, the development of electronic components in the potentiostat focused more on the main part, which is the potential control and current measurement part. Besides, the construction of the electronic component in HMstat implemented through-hole technology, which eliminates the hindrance for users who are less skilled in electronic areas in designing a potentiostat. Moreover, implementing through-hole technology enabled the design to be easily adjusted or replaced when necessary. This study will also demonstrate the capability of HMstat to implement performance tests and heavy metal measurements.