Determination of fluoride impurities in Leuprolide. Comparison of analytical methods

Application of microextraction techniques for indirect spectrophotometric determination of fluorides in river waters

The present study is dedicated to development of improved method for determination of trace amounts of fluorides in natural waters which is based on the interaction of fluorides with ion associate (IA) of Al(III), salicylic aldehyde acylhydrazones (benzhydrazone (SABH) and 4-picolinhydrazone (SAPH)) and polymethine dye Astra Phloxine FF (AP). Comparison of analytical forms [Al(SABH)₂]⋅AP and [Al(SAPH)₂]⋅AP showed that the analytical system Al(III)-SAPH-AP is more effective, namely, a higher level of preconcentration of the analytical form is ensured by and extraction equilibrium is achieved faster. Based on the study, we propose a new, fast, simple, reliable, sensitive, and accurate method of the indirect UV-Vis-spectrophotometric determination of fluorides grounded on the interaction of fluorides with IA of Al(III), SAPH and AP with the utilization of vortex-assisted liquid-liquid microextraction (VALLME). The method is based on the discoloration of the microextract of IA of Al(III), SAPH and AP (Al-SAPH-AP) in presence of fluoride ions due to the formation of fluoride complexes of aluminum with higher stability. The effect of various factors has been studied. The optimal conditions of the UV-Vis-spectrophotometric determination of fluorides were defined as: pH 7.0-10.0, 1.0⋅10^-6 mol⋅L^-1 Al(III); 4.0⋅10^-5 mol⋅L^-1 SAPH; 1.0⋅10^-6 mol⋅L^-1 AP; λ = 560 nm. VALLME have been carried out in 250 μL of CCl₄ at 20:1 vol ratios of aqueous and organic phases, with vortexing at 3000 rpm for 15 s followed by centrifugation at 2000 rpm for 2 min. The determination of fluorides is feasible in the presence of various interferences. The calibration curve shows the linear dependence in the range of 0.3-114 μg⋅L^-1 of the fluorides concentration (R² = 0.993) with the limit of detection of 0.086 μg⋅L^-1 and the limit of determination of 0.284 μg⋅L^-1. The accuracy of the proposed protocol of fluorides determination was verified towards a reference method on the samples of natural rivers waters (RSD 2.6-3.1%, recovery 98.3-101.4%).

Recent Developments in Methods of Analysis for Fluoride Determination

This review covers current analytical techniques, instruments, and methodologies used in the analysis of fluoride in various matrices. Our comprehensive literature search showed that there is no recently published review article about analytical methodologies for fluoride. In this review, we explore chromatographic, spectroscopic, and electrochemical innovations appearing in the recent literature.

Determination of bioavailable fluoride from sepiolite by “in vivo” digestibility assays

This work presents a study of the bioavailability and distribution of fluoride in tissues of animals (Wistar rats) which were fed with a poultry feeding that contains sepiolite as an additive. The determination of fluoride concentration was carried out by potentiometric measurements using a fluoride selective electrode. The quantification was done using the standard addition method with enough accuracy and precision in all the assays. The results demonstrate that fluoride present in sepiolite is not bioavailable. The digestion process does not extract all the fluoride from sepiolite, so sepiolite can be use in poultry feedings without any risk. These studies have contributed to the discussions at EU level about extraction procedures and F(-) determination in feed material of mineral origin.

Determination of fluoride in toothpaste using headspace solid-phase microextraction and gas chromatography–flame ionization detection

A new method for determination of fluoride in toothpaste employing the headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/flame ionization detection (GC/FID) has been proposed. It is a development of the method for determination of fluoride using trimethylchlorosilane (TMCS) as the derivatization reagent to form trimethylfluorosilane (TMFS), with the liquid/liquid extraction (LLE) step replaced by HS-SPME. To introduce the latter, it was necessary to determine the conditions of the reaction and to optimize the two stages of the SPME procedure: extraction and desorption. The parameters of the SPME analysis using carboxen/polydimethylsiloxane (CAR/PDMS) fiber were defined and compared with the corresponding ones for the LLE method, used as a reference. Also, these two methods were compared with respect to their linearity, precision, and accuracy. Results from toothpaste analyses using these two methods were highly correlated, indicating the potential to use the SPME extraction as an inexpensive and solventfree alternative to the LLE method.

Generic ciprofloxacin tablets contain the stated amount of drug and different impurity profiles: A 19F, 1H and DOSY NMR analysis

The objective of this study was to control the purity of 16 commercial formulations of ciprofloxacin tablets purchased in different countries or via the Internet using 19F and 1H nuclear magnetic resonance (NMR). Twelve out of the sixteen commercial formulations of ciprofloxacin measured by 19F NMR contain the active ingredient within 100+/-5% of stated concentration. Three formulations have a lower ciprofloxacin content between 90 and 95% and one shows a higher concentration superior to 105%. The impurity profile was characterised using 19F and 1H NMR, and is characteristic of the manufacturer. Four to twelve fluorinated impurities among them fluoride ion and two already known compounds were detected and quantified in the sixteen formulations analysed by 19F NMR. Two other non-fluorinated impurities were observed in the seven formulations analysed with 1H NMR. The total content of impurities as well as their individual levels are in agreement with those reported previously in the few studies devoted to ciprofloxacin purity. However, all the formulations do not comply with the limits for impurities given in the ciprofloxacin monograph of the European Pharmacopeia. Finally, a "signature" of the formulations was obtained with Diffusion-Ordered SpectroscopY (DOSY) 1H NMR which allowed the characterisation of some excipients present in the formulations studied.

Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

Articles about the development of derivative spectrophotometric methods and analytical applications of derivative spectrophotometry (DS) published in the last nine years (since 1994) are reviewed.

An overview of the recent trends in development of HPLC methods for determination of impurities in drugs

An extensive survey of the literature published in various analytical and pharmaceutical chemistry related journals has been conducted and the high-performance liquid chromatography (HPLC) methods which were developed and used for determination of process-related impurities in drugs have been reviewed. This review covers the time period from 1995 to 2001 during which around 450 analytical methods including all types of chromatographic and hyphenated techniques were reported. HPLC with UV detection was found to be the technique of choice for many workers and more than 200 methods were developed using LC-UV alone. A critical analysis of the reported data has been carried out and the present state-of-art of HPLC for determination of impurities of analgesic, antibiotic, anti-viral, anti-hypertensive, anti-depressant, gastro-intestinal and anti-neoplastic agents has been discussed.