Planar electromagnetic sensors are widely used in many applications due to its low cost, simple architecture, and fast response. Currently, there are many types of membranes which have been introduced to remove contaminants from an aqueous solution. Hence, the water quality could be maintained and safe to consume. The objective of this paper is to apply and investigate the effectiveness of a selective membrane in detecting nitrate, phosphate, zinc, and nickel ions by means of planar electromagnetic sensors array (PESA). The samples have four different concentration levels, 5 ppm, 25 ppm, 75 ppm, and 100 ppm. The selective membrane's performance is evaluated based on absolute average sensitivity (|Z%|). This performance is compared with conventional coating such as incralac. The developed membrane consists of two elements which are polymer and solvent. Modified silica is selected as a polymer material while N-(2-Aminoethyl)-3 Aminipropyltrimethoxysilane is selected as a solvent. The selection of these materials is based on their ability to attract the contaminants in the aqueous solution and hence increased the selectivity. The proposed sensor with a membrane shows its higher sensitivity compared to incralac. The highest sensitivity is 338 % which observed in the presence of membrane for the nickel detection. Meanwhile, the lowest sensitivity using membrane is 12 % for zinc detection.