A novel highly sensitive voltammetric quetiapine fumarate (QF) sensor based on a glassy carbon electrode (GCE) modified with carbon black nanoparticles (CB) was successfully developed.

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Levothyroxine sodium (LS, L-T4) is a sodium salt of natural thyroid hormone thyroxine (T4), commonly used in treatment of hypothyroidism. In this work a new voltammetric method of levothyroxine sodium (LS) determination using renewable mercury film electrode is presented. A linear voltammetric response was obtained for analyte in the concentration range from 0.025·10−6 mol L−1 (1.99·10−5 g L−1) to 4.0·10−6 mol L−1 (3.19·10−3 g L−1), with a detection limit of 1.8·10−8 mol L−1 for preconcentration time of 30 s. Repeatability of method was determined as RSD % for levothyroxine sodium concentration of 0.2·10−6 mol L−1 as 1.4% (n = 9). The proposed method was successfully applied and validated by studying the recovery of levothyroxine sodium in different pharmaceutical products.

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[a] 1IntroductionGlucocorticoids are group of important medications with wide variety of use,m ainly due to their anti-inflammatory and immunosuppressive properties.H uman body produces natural corticoids which are necessaryf or propers ecretion of other hormones and keeping homeostasis. However, affecting the balance of adrenalh ormones excretion may cause diseases connected with necessity of using their synthetic analogs in very little and controlled doses.T aking drugs containingc orticoids is connected with the risk of serious adversee ffects,t hus quality control of medications consisting this group of active substances shouldb ev ery precise [1,2].Prednisolone ((11b)-11,17,21-trihydroxypregna-1,4-diene-3,20-dione [8].P rednisolone derivative is also used in ophthalmologya sacontent of eye drops used to reducea llergic reactionsa ffecting eyes, such as swellinga nd itching [ 9,10].D ue to its immunosuppressive properties is also widely use after organ transplantation [11] and as ah ormone substitution for patients unable to produce proper amounts of corticosteroids on its own [12].L ong term usage of this corticoid may cause serious side effectsl ike gaining weight, high blood pressure,m usclew eakness,o steoporosis,h igh glucose level in body fluids or mentalh ealth problems [13][14][15][16].Numerous studies have been presented withd ifferent prednisolone determination methods including spectroscopy [17],s pectrophotometry [18,19],g as chromatography [20][21][22],c hemiluminescence [23] and high performance liquid chromatography (HPLC) coupled with various detector [24][25][26][27].H owever these methods generate lots of chemical wastesa nd also require time consuming sample preparation connected with risk of its contamination.S uch inconveniences can be eliminated using electrochemical methods,w hich provide high sensitivity,l ow limit detectiona nd simple procedure of sample preparation.C lassical polarography [28,29] and different voltammetry techniques were used for prednisolone determination.R ecently,t wo voltammetric methodsw ere developed for the analyte determinationi nd rug samples based on oxidation of prednisolone at glassy carbon electrode [30] . One of the methodso fa chieving high sensitivity in voltammetry is development in the working electrode constructionf ield. Va rious typeso fm etal film electrodes were constructed recently.A mongt hem lead, gallium and mercury were most frequently used [35][36][37].I nteresting solution of renewable mercury film electrode was proposed by Baś and Kowalski[ 38].W ith the renewable Abstract:F ast and sensitive method of prednisoloned eterminationa tr enewable mercury film electrodeu sing differentialp ulse adsorptive stripping voltammetry (DPAdSV) was successfully developed. Thee ffects of various factors such as:p reconcentration potential and time, pulse height, step potential and supporting electrolyte composition were optimized.Alinear voltammetric response for analyte was obtained in the concentration), with ad etectionl imit of 0.01 mmolL À1 ...