Optimized Box-Behnken Design Combined Response Surface Methodology to Determine Calcium and Iron Contents Using Visible, Atomic Emission and Atomic Absorption Spectrophotometry in Vegetables and Wastewater Samples

Abstract

Background: Calcium and iron are crucial essential minerals. Iron is mainly responsible for transporting oxygen in the body and the immune system. In comparison, calcium's primary function is in human bones and teeth. Due to that, it is vital to quantify the amount in vegetables.

Objective: Optimization and validation of three analytical procedures, visible, atomic emission spectrophotometry (AES), and atomic absorption spectrophotometry (AAS), were developed to determine calcium and iron in vegetables and wastewater samples using response surface methodology (RSM) via Box-Behnken design (BBD). The design helps to reduce experiment trials with selected variables to find a correlation between them and their respective dependent variables.

Methods: Method I was developed to quantify calcium in vegetables mixed with concentrated 3M HNO3 and heated to reflux as per the BBD. Then it was cooled, filtered, and completed with 3M HNO3 to be carried out utilizing AES and AAS. For method II, vegetables were mixed with nitric acid and sulfuric acid solution with an optimized 5M KSCN solution, which was computed using the AAS and visible spectrophotometry.

Results: First, percentage of water content was calculated for all vegetables, higher in malabar spinach and lower in peas. The calcium and iron contents were present within 0.59-2.68 mg and 35.8-211.5 mg, respectively, in 100 g of vegetables. The results showed a higher amount of iron was available in spinach and a lower amount in okra. In contrast, the highest calcium amount was present in broccoli and the lowest amount was in peas. The calcium and iron content were between 0.015-137.25 and 0.01-147.85 µg/mL in the wastewater samples.

Conclusions: These methods can help to determine the amount of calcium and iron for the quality control samples in research and development, food, and the environmental industry.

Highlights: Three validated analytical techniques quantify calcium and iron in vegetables and wastewater samples. The RSM-BBD optimized the method and determined its crucial factors.