This manuscript deals with a compact setup for photometric determination of chemical species, requiring a heating step prior to measurement. This setup consists of a flow-batch device and a LED based photometer. The flow-batch device, machined in a stainless steel piece, was designed to be used in analytical procedures without requiring the use of a fluid for heat exchange. The resistive heating element and the temperature sensor were embedded in holes perforated in the stainless steel device, allowing temperature control to be performed by software. Aliquots of sample and reagent solution were inserted into the heated cavity, using solenoid valves controlled by software. While reaction development proceeded, the compound formed was monitored, using a homemade LED-based photometer coupled to the flow-batch device with an optical fiberglass cable. All steps of the analytical procedure were performed employing a microcontroller (PIC 18F4553). The effectiveness of the proposed flow-batch device was evaluated by using it for the photometric determination of manganese in plant materials. Accuracy was assessed by comparing results with those achieved using a reference method, and no significant difference at 95% confidence level was observed. Other useful features such as an analytical throughput of 40 determinations per hour, a linear response ranging from 5 mg L−1 to 30 mg L−1 (r = 0.999), a relative standard deviation 2.0%(n = 11), a reagent consumption of 31 mg NaIO4 and a waste generation of 800 μL per determination were achieved.