Carbon and diamond paste microelectrodes based on Mn(III) porphyrins for the determination of dopamine

Nejem

et al. 2012

Analyst

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Monocrystalline diamond (natural diamond, synthetic-1 and synthetic-2) based electrochemical electrodes were designed for the analysis of L- and D-fucose. Response characteristics of the electrochemical electrodes were determined using cyclic voltammetry and differential pulse voltammetry (DPV). L-fucose was determined using DPV with electrodes based on natural diamond, synthetic-1 and synthetic-2, respectively, at 240 mV using NaCl as the electrolyte (pH 3.0); at 160 mV using KNO(3) (pH 10.0) and at 80 mV using KCl as the electrolyte (pH 10.0) while D-fucose was analyzed at 120 mV using KCl as the electrolyte (pH 1.0); at 140 mV using KNO(3) as the electrolyte (pH 1.0) and at 160 mV using NaNO(3) as the electrolyte (pH 3.0). The linear concentration ranges for L-fucose were between 10(-13) and 10(-9) mol L(-1) (natural diamond), 10(-11) and 10(-8) mol L(-1) (synthetic-1) and 10(-6) and 10(-3) mol L(-1) (synthetic-2) with detection limits of 10(-14), 10(-12) and 10(-8) mol L(-1) magnitude order, respectively. For D-fucose, the linear concentration ranges were 10(-6) to 10(-3) mol L(-1) (natural diamond), 10(-5) to 10(-3) mol L(-1) (synthetic-1) and 10(-9) to 10(-3) mol L(-1) (synthetic-2) with detection limits of 10(-7), 10(-7) and 10(-10) mol L(-1) magnitude order, respectively. The sensors were used for the assay of L-fucose in serum and urine samples.

Section: Introductionmentioning

confidence: 99%

Determination ofl- and d-fucose using amperometric electrodes based on diamond paste

Nejem

et al. 2012

Analyst

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“…Their utilization in biomedical analysis represents a good alternative to chromatographic methods1213141516171819202122. Stochastic response is based on channel conductivity, according to the mechanism described previously by Stefan-van Staden and Moldoveanu21.…”

mentioning

confidence: 99%

“…The monocrystalline form of diamond was preferred due to the diamond monocrystal properties proprieties, such as enhanced holes and electron mobilities2526. Monocrystallin diamond paste sensors have been used in differential potentiometric voltammetry mode for the assay of biological compounds such as: L-fucose and D-fucose15, sildenafil citrate1314, and neurotransmitters16171819. To our knowledge, the approach has not been used previously to assay steroid hormones in biological matrices such as saliva.…”

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confidence: 99%

Pattern recognition of estradiol, testosterone and dihydrotestosterone in children's saliva samples using stochastic microsensors

Gugoaşă

Calenic

et al. 2014

Sci Rep

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Stochastic microsensors based on diamond paste and three types of electroactive materials (maltodextrin (MD), α-cyclodextrin (α-CD) and 5,10,15,20-tetraphenyl-21H,23H porphyrin (P)) were developed for the assay of estradiol (E2), testosterone (T2) and dihydrotestosterone (DHT) in children's saliva. The main advantage of utilization of such tools is the possibility to identify and quantify all three hormones within minutes in small volumes of childen's saliva. The limits of quantification obtained for DHT, T2, and E2 (1 fmol/L for DHT, 1 pmol/L for T2, and 66 fmol/L for E2) determined using the proposed tools allows the utilization of these new methods with high reliability for the screening of saliva samples from children. This new method proposed for the assay of the three hormones overcomes the limitations (regarding limits of determination) of ELISA method which is the standard method used in clinical laboratories for the assay of DHT, T2, and E2 in saliva samples. The main feature of its utilization for children's saliva is to identify earlier problems related to early puberty and obesity.

“…Reliable methods of analysis are a need for the assay of dopamine in biological fluids and its pharmaceutical formulations. Therefore, different methods of analysis were proposed for the assay of dopamine: electrochemical methods based on GC electrodes, 5,6 gold-palladium binary system based electrodes, 7 plastic membrane based electrodes, 8 screen-printed electrodes, 9 modified carbon 10,11 and diamond paste; 10 capillary zone electrophoresis, 12 and HPLC. 13 Dot microsensors represents a new concept in the technology of microsensors which combined with the stochastic concept 14 enhanced the capability of sensor for qualitative and quantitative analysis of single molecules of biomedical importance.…”

mentioning

confidence: 99%

Stochastic Dot Microsensors for the Assay of Dopamine in Pharmaceutical Samples and Biological Fluids

Balasoiu

2012

J. Electrochem. Soc.

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Stochastic dot microsensors based on the complexes of Mn(III) with porphyrins and modified diamond or carbon pastes were employed for the assay of dopamine in pharmaceutical and biological samples. The advantage of using such sensors for the assay of dopamine is the possibility of qualitative and quantitative assay of dopamine in one run of the experiment. The covered linear concentration range for these sensors was between 10 −10 and 10 −3 mol/L with high sensitivities. The proposed dot sensors were used reliably (RSD < 1%) for the assay of dopamine from different samples for more than 8 months, with a recovery higher than 93.00%.The first stochastic sensors were designed by Hladky and Haydon 1 in 1970 and were based on granomycin. The advantages of stochastic sensors are that they can monitor individual binding of the molecules in the nanochannels characterized through t on as well as unbinding events characterized through t off ( Figure 1). t on is a measure of the quantity of the analyte in the sample (1/t on = f(concentration)), and t off is a signature of the analyte to be determined. 2 The mechanism of the response of such sensors is very complex; there are binding and unbinding events, redox processes, traveling through the nanochannels and while the nanochannel is blocked by the analyte it is losing its conductivity -this being illustrated by the value of the intensity of the current which is getting to zero (Figure 1). Dopamine (DA) is a very important substance for the body. The ability to determine dopamine concentration in vivo would allow mapping the dopamine concentration in the brain. Low levels of DA indicate the presence of diseases such as Parkinson's, schizophrenia and Huntington's. 3,4 Medication based on DA is supplied with precaution as it can cause the rising of blood pressure. Reliable methods of analysis are a need for the assay of dopamine in biological fluids and its pharmaceutical formulations. Therefore, different methods of analysis were proposed for the assay of dopamine: electrochemical methods based on GC electrodes, 5,6 gold-palladium binary system based electrodes, 7 plastic membrane based electrodes, 8 screen-printed electrodes, 9 modified carbon 10,11 and diamond paste; 10 capillary zone electrophoresis, 12 and HPLC. 13 Dot microsensors represents a new concept in the technology of microsensors which combined with the stochastic concept 14 enhanced the capability of sensor for qualitative and quantitative analysis of single molecules of biomedical importance. In this paper we proposed 6 stochastic dot microsensors based on the complexes of Mn III with (I) 5,10,15,20-tetratolyl-21H,23H-porphyrin, (II) 5,10,15,20-tetraphenyl-21H,23H-porphyrin and (III) 5,10,15,20-tetrakis(3,4-dimethoxiphenyl)-21H,23H-porphyrin and carbon and/or diamond paste for the assay of dopamine in pharmaceutical products and urine. The selection of Mn III complexes with porphyrins as electroactive compounds for the design of the microsensors was done based on the nanostructured channels formed by their mo...