Online Novel Techniques for Selective Simultaneous Determination of Alkalinity/Bicarbonate and Hardness in Drinking Water by Skalar San++ Segmented Flow Analysis.
Creators: name: Mouaz A. Ghani, H Elmahadi Omer,  B. Hafez, M. Siroor Alshamsi,
Publisher: name: Moroccan Journal of Chemistry
Year: 2020
Subjects: segmented flow analysis, alkalinity/bicarbonate, hardness, drinking water, online calibration curve, Selectivity, Evaluation of carbonate concentration, Smart systems; Continuous Flow techniques.

description: The procedures of the current novel automated technique for the determination of hardness, Carbonate, bicarbonate and alkalinity in drinking water have been modified from both classical batch titration and the method of the flow analysis Skalar San++ method (classical scalar current). The forms of standards in the current methods have been modified. The calcium chloride used previously in the current method for the determination of both calcium and total hardness was replaced by a mixed standard that contains calcium and magnesium carbonate in an aqueous solution. Likewise, calcium carbonate and sodium bicarbonate standards currently used in determination of alkalinity and bicarbonate respectively were replaced by using only one standard of calcium, sodium carbonate salt, and the required bicarbonate concentrations were derived from the same calcium carbonate formula mathematically in the stoichiometry equation. The new approach method was validated and applied successfully for analysis of drinking water and proficiency tests samples (PTS).The technique is used for an automatic online analysis of total, calcium hardness, total alkalinity and bicarbonate in drinking water covering a range of 10 - 100 ppm for total hardness and calcium hardness and a range of 5-100 ppm for alkalinity and bicarbonate mg/L as CaCO3. The method gave a distinct merit over the manual titration method and the current skalar method, with enhanced detection limit, high precision (RSD) which was found to be less than 1%) and accuracy of ( ± 1-2%), as well as a high spectral peak resolution and sample throughput.. Moreover, additional merits of the proposed method over the classical skalar one, other than being economic in use, as there is some chemical cut off, is the feasibility of the automatic determination of carbonate ions concentrations in the same run, which could not be achieved automatically by the classical skalarc method, as it always needs mathematical subtraction of bicarbonate concentration from alkalinity concentrations from multi runs. The latter approach is tedious, involved lots of reagents and procedures, time consuming, and could impact the overall method precision and accuracy. The methoddemonstrated selectivity as online automated approach for selective determination of total hardness and calcium hardness in one run and determination of total alkalinity and bicarbonate from the same standard in the second run, when keeping all of the four chemistry reagents aspirated automatically. Sole analysis for every parameter as in the current method was achieved demonstrating simultaneous analysis without discernment, the recovery was found to be comparable with the novel proposed method, but the latter gave a marked enhancement in precision and peak resolution.. Analysis for drinking water samples gave quantitative results with Z score of less than ± 1.2. Accuracy of the automated analysis was investigated by multiple techniques including recovery by standard addition method, run of CRM and t test statistical analysis. The merit of the accuracy for this proposed method has been demonstrated successfully through applications to real samples.
description: Moroccan Journal of Chemistry, Vol. 8, No 1 (2020)