Free fluoride determination in honey by ion-specific electrode potentiometry: Method assessment, validation and application to real unifloral samples

Abstract

Surprisingly, a reliable method for measuring the concentration of free fluoride ions in honey is still missing from the literature, notwithstanding the generally recognized importance of the analyte and the matrix. To fill this gap, this study proposes and validates a straightforward ion-specific electrode potentiometric method for this task. The method offers very low detection and quantification limits (6.7 lg kg À1 and 25 lg kg À1 , respectively), good linearity (R 2 > 0.994), good sensitivity (typically 55 ± 3 mV for an order of magnitude of concentration) in an unusually low concentration interval (between 0.020 and 1 mg L À1 ), and acceptable precision and bias. The method was applied to 30 unifloral (thistle, eucalyptus and strawberry tree) honey samples from Sardinia, Italy. The amount of free fluoride ions found in these honeys appears to be lower than Abbreviations: FISE, fluoride ion-selective electrode; TISAB, total ionic strength adjusting buffer; EDTA, ethylenediaminetetraacetic acid disodium salt; CDTA, 2-[2-[bis(2-hydroxy-2-oxoethyl)amino]cyclohexyl]-(2-hydroxy-2-oxoethyl)aminoethanoic acid; EC, external calibration method; MSA, multiple standard additions method; CRM, certified reference material; LOD, limit of detection; LOQ, limit of quantification * Corresponding author.

Potentiometric Determination of Free Fluoride Content in Wines from Dalmatia Region (Croatia)—A Comparative Study of Direct Potentiometry and Standard Addition Method

“…This is also evident from the calibration curve (Figure 1) and even more so from the comparison of the fluoride content obtained when calculating the results of the dp-AcB_DS and dp-TISAB_DS used, which were 9.5% and 5.4%, respectively (Figure 3). This is consistent with the conclusions of numerous groups of authors proposing TISAB as the optimal buffer for fluoride determination [35][36][37]. Additionally, the higher values of fluoride concentration in the tested wine samples obtained with dp-TISAB_DS (0.19 mg/L) compared to the results obtained with dp-AcB_DS (0.16 mg/L) are logically due to chelation [36].…”

“…In the first phase of the research, the influence of the composition of the solution on the FISE response was studied by direct potentiometry. Since some groups of authors used acetate buffer [33,34] while others suggested TISAB as optimal for fluoride determination [35][36][37], both were investigated in this study by comparing their influence on fluoride determination. Evaluation of the direct potentiometry method and the standard addition method in the determination of fluoride was also performed.…”

An Analytical Protocol for the Differentiation and the Potentiometric Determination of Fluorine-Containing Fractions in Bovine Milk

“…Unfortunately, this protocol is currently absent in the literature. Hence, pursuing the interest of this research group in the development and validation of original FISE methods applicable either in dental research [ 57 , 65 , 66 , 67 , 68 ] or in food analysis [ 69 ], the aim of this study is to develop for the first time (and validate, where possible) a comprehensive analytical protocol for the FISE determination of the fluorine contained in different fractions of bovine milk.…”

Determination of trace fluoride in water samples by silylation and gas chromatography/mass spectrometry analysis

“…Meanwhile, excessive fluoride intake can lead to human poisoning, 3 and there is a small gap between a safe dose and a harmful one 4 . According to Regulation 98/83/EEC of the Council of the European Communities, the fluoride content of drinking water is required to be less than 1.5 μg/mL 5 . In view of the ubiquity of fluorides, it is of great significance to determine the content of fluoride ion in drinking water, surface water and sewage, for the purpose of environmental protection and people's health 6 …”