Lowering the Detection Limit of Solvent Polymeric Ion-Selective Electrodes. 1. Modeling the Influence of Steady-State Ion Fluxes

1999 ◽  
Vol 71 (6) ◽  
pp. 1204-1209 ◽  
Author(s):  
Tomasz Sokalski ◽  
Titus Zwickl ◽  
Eric Bakker ◽  
Ernö Pretsch
Keyword(s):  
Steady State ◽  
Detection Limit ◽  
Ion Fluxes ◽  
Ion Selective Electrodes

scholarly journals Potentiometric Carboxylate Sensors Based on Carbazole-Derived Acyclic and Macrocyclic Ionophores

Chemosensors ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 4
Author(s):  
Ville Yrjänä ◽  
Indrek Saar ◽  
Mihkel Ilisson ◽  
Sandip A. Kadam ◽  
Ivo Leito ◽  
...  
Keyword(s):  
Detection Limit ◽  
Vinyl Chloride ◽  
Anion Exchanger ◽  
Linear Range ◽  
Ph Sensitivity ◽  
Ion Selective Electrodes ◽  
Solid Contact ◽  
Response Characteristics ◽  
Potentiometric Response ◽  
Poly Vinyl Chloride

Solid-contact ion-selective electrodes with carbazole-derived ionophores were prepared. They were characterized as acetate sensors, but can be used to determine a number of carboxylates. The potentiometric response characteristics (slope, detection limit, selectivity, and pH sensitivity) of sensors prepared with different membrane compositions (ionophore, ionophore concentration, anion exchanger concentration, and plasticizer) were evaluated. The results show that for the macrocyclic ionophores, a larger cavity provided better selectivity. The sensors exhibited modest selectivity for acetate but good selectivity for benzoate. The carbazole-derived ionophores effectively decreased the interference from lipophilic anions, such as bromide, nitrate, iodide, and thiocyanate. The selectivity, detection limit, and linear range were improved by choosing a suitable plasticizer and by reducing the ionophore and anion exchanger concentrations. The influence of the electrode body’s material upon the composition of the plasticized poly(vinyl chloride) membrane, and thus also upon the sensor characteristics, was also studied. The choice of materials for the electrode body significantly affected the characteristics of the sensors.

Detection Limit of Large Area Id Thin Film Position Sensitive Detectors Based in a-Si:H P.I.N. Diodes

1995 ◽  
Vol 377 ◽  
Author(s):  
R. Martins ◽  
G. Lavareda ◽  
F. Soares ◽  
E. Fortunato
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Steady State ◽  
Detection Limit ◽  
Large Area ◽  
Position Sensitive ◽  
Position Sensitive Detectors

ABSTRACTThe aim of this work is to provide the basis for the interpretation of the steady state lateral photoeffect observed in p-i-n a-Si:H ID Thin Film Position Sensitive Detectors (ID TFPSD). The experimental data recorded in ID TFPSD devices with different performances are compared with the predicted curves and the obtained correlation's discussed.

scholarly journals Flavylium Dye as pH-Tunable Fluorescent and CD Probe for Double-Stranded DNA and RNA

Chemosensors ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 129
Author(s):  
Ivo Crnolatac ◽  
Letícia Giestas ◽  
Gordan Horvat ◽  
António Jorge Parola ◽  
Ivo Piantanida
Keyword(s):  
Steady State ◽  
Detection Limit ◽  
Rna Secondary Structure ◽  
Binding Affinities ◽  
Cationic Form ◽  
Rna Detection ◽  
Time Resolved ◽  
Dna And Rna ◽  
Double Stranded Dna ◽  
Acidic Conditions

The interaction of 4′-(N,N-dimethylamino)-6-hydroxyflavylium cation with double stranded (ds-) DNA/RNA was studied by UV/Vis spectrophotometry, circular dichroism (CD), and also steady-state and time-resolved emission spectroscopies at neutral and weakly acidic conditions. At pH 5, the studied molecule, in its flavylium cationic form, showed considerable binding affinities (5 < logKs < 6) for all ds-DNA/RNA, contrary to chalcones forms (dominant at pH 7), which did not show binding to polynucleotides. Flavylium cation intercalated into ds-DNAs at variance to dominant groove aggregation within ds-RNA, which was reported by RNA-specific bisignate induced CD spectrum (ICD) bands. The intrinsically negligible fluorescence of flavylium was strongly increased upon the addition of DNA or RNA, whereby both the fluorescence intensity and emission lifetimes of complexes differed considerably: the strongest emission increase was observed for AU-RNA (detection limit estimated to 10 nM) followed by AT-DNAs and the much weaker effect of GC-DNAs. Both fluorescence sensitivity on the ds-DNA/RNA secondary structure and sequence-selective ICD bands make the flavylium–chalcones system an intriguing pH-switchable new probe for distinguishing between various polynucleotide sequences.

scholarly journals Validation of a Novel Potentiometric Method Based on a Polymeric PVC Membrane Sensor Integrated with Tailored Receptors for the Antileukemia Drug Cytarabine

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1343 ◽  
Author(s):  
Ayman H. Kamel ◽  
Abd El-Galil E. Amr ◽  
Nashwa H. Ashmawy ◽  
Hoda R. Galal ◽  
Abdulrahman A. Almehizia ◽  
...  
Keyword(s):  
Detection Limit ◽  
Biological Fluid ◽  
Pharmaceutical Formulations ◽  
Assay Method ◽  
Pvc Membrane ◽  
Therapeutic Drug ◽  
Ion Selective Electrodes ◽  
Easy Method ◽  
Potentiometric Response ◽  
Sensory Element

A simple, rapid and easy method is proposed for the detection of a cytostatic therapeutic drug, cytarabine, in real samples. The method is based on potentiometric transduction using prepared and characterized new ion-selective electrodes for cytarabine. The electrodes were integrated with novel man-tailored imprinted polymers and used as a sensory element for recognition. The electrodes revealed a remarkable potentiometric response for cytarabine over the linearity range 1.0 × 10−6–1.0 × 10−3 M at pH 2.8–4 with a detection limit of 5.5 × 10−7 M. The potentiometric response was near-Nernstian, with average slopes of 52.3 ± 1.2 mV/decade. The effect of lipophilic salts and plasticizer types on the potentiometric response was also examined. The electrodes exhibited an enhanced selectivity towards cytarabine over various foreign common ions. Validation and verification of the presented assay method are demonstrated by evaluating the method ruggedness and calculating the detection limit, range of linearity, accuracy (trueness), precision, repeatability (within-day) and reproducibility (between-days). The proposed ion-selective electrodes revealed good performance characteristics and possible application of these electrodes for cytarabine monitoring in different matrices. The electrodes are successfully applied to cytarabine determination in spiked biological fluid samples and in pharmaceutical formulations.

scholarly journals Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis

2005 ◽  
Vol 5 (6) ◽  
pp. 12403-12464 ◽  
Author(s):  
S. C. Smith ◽  
J. D. Lee ◽  
W. J. Bloss ◽  
G. P. Johnson ◽  
D. E. Heard
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Detection Limit ◽  
Diurnal Variation ◽  
Marine Boundary Layer ◽  
Chemical Conversion ◽  
Early Morning ◽  
Research Station ◽  
Solar Noon ◽  
Mean Concentration

Abstract. OH and HO2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×105 molecule cm−3 (5 min acquisition period; signal-to-noise ratio = 1). HO2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×106 molecule cm−3. The diurnal variation of OH was measured on 24 days, and that of HO2 on 17 days. The local solar noon OH concentrations ranged between (3–8)×106 molecule cm−3, with a 24 h mean concentration of 9.1×105 molecule cm−3. The local solar noon HO2 concentrations were (0.9–2.1)×108 molecule cm−3 (3.5–8.2 pptv), with a 24 h mean concentration of 4.2×107 molecule cm−3. HO2 radicals in the range (2–3)×107 molecule cm−3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HOx radicals under primarily clean marine conditions. Case study periods highlight the typical radical levels observed under different conditions. Steady state expressions are used to calculate OH and HO2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.

Potential Drifts of Solid-Contacted Ion-Selective Electrodes Due to Zero-Current Ion Fluxes Through the Sensor Membrane

2000 ◽  
Vol 12 (16) ◽  
pp. 1286-1292 ◽  
Author(s):  
Monia Fibbioli ◽  
Werner E. Morf ◽  
Martin Badertscher ◽  
Nicolaas F. de Rooij ◽  
Ernö Pretsch
Keyword(s):  
Ion Fluxes ◽  
Ion Selective Electrodes ◽  
Sensor Membrane ◽  
Zero Current
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