A Green Approach to Ammonia Determination in Human Saliva Using Natural Reagent via Gas-Diffusion Flow-Injection Spectrophotometry

A simple and cost-effective analytical approach is proposed based on a gas diffusion-flow injection procedure for determining ammonia in human saliva. The proposed procedure utilizes purple sweet potato extract as an acceptor reagent. The principle of determining ammonia is based on the total ammonia in saliva, which is transformed to ammonia gas in the NaOH donor stream, which diffuses through the gas diffusion membrane to the acceptor stream containing purple sweet potato extract. The presence of ammonia changed the color of the extract, which was detected at a wavelength of 604 nm, with absorbance proportional to the ammonia concentration. Optimization of standard parameters produced optimal results under 1.5 M NaOH, 10% extract, and 50 cm mixing coil with 300 μL sample volume. The results of the procedure were selective against phosphate, magnesium, and calcium, with less than a 5% bias value. The result was valid when applied to human saliva and supported by a 101–103% recovery. The proposed gas diffusion-flow injection procedure offers on-site assay and green chemical analysis with relatively high throughput.