Application of quantitative EPR

1990 ◽  
Vol 333 (1628) ◽  
pp. 37-48 ◽  
Keyword(s):  
Detection Limit ◽  
Dynamic Range ◽  
Sea Water ◽  
High Sensitivity ◽  
Nitrite Ion ◽  
Spin Concentration ◽  
Analytical Technique ◽  
Broad Dynamic Range ◽  
Aromatic Nitro

Although the high sensitivity and broad dynamic range of EPR make it an attractive analytical technique for species with unpaired electrons, the precision and accuracy of spin concentration measurements have often been low. The marked improvement in quantitative EPR is a result of improvements in instrumentation and greater attention being given to operating procedures. In 1962 the lower limit for the EPR determination of polycyclic aromatic hydrocarbons was reported to be ca . 3|ig. Using the same method these compounds have now been determined down to nanogram levels. Aromatic nitro compounds present at submicrogram levels can also be quantified by EPR. A free radical assay technique has been applied to the determination of drugs in body fluids; a morphine concentration in urine of 0.5 |ig cm -3 is detectable. Molybdenum has been determined in sea water with a relative precision of 4.7 % at the 11 pg 1 -1 level and a detection limit of 0.46 pg 1 -1 . By using the EPR signal of [FeF 6 ] 3- the total iron content of solutions containing Mn II , Fe II and Fe III has been measured, the analytical range being 10 -6 -10 -2 M with a detection limit of 6 x 10 -7 M. Diamagnetic metal ions can be estimated by EPR with the aid of spin-labelled chelating reagents, e.g. Zn II over the linear range 10 -6 -10 -3 M with a detection limit of 5.5 x 10 -7 M. Nitrite ion can be determined by EPR with a precision of 0.9% at the 0.5p.p.m. level.

scholarly journals A tandem giant magnetoresistance assay for one-shot quantification of clinically relevant concentrations of N-terminal pro-B-type natriuretic peptide in human blood

2021 ◽  
Author(s):  
Fanda Meng ◽  
Weisong Huo ◽  
Jie Lian ◽  
Lei Zhang ◽  
Xizeng Shi ◽  
...  
Keyword(s):  
Detection Limit ◽  
Giant Magnetoresistance ◽  
Dynamic Range ◽  
Point Of Care ◽  
Sample Volume ◽  
Small Sample ◽  
Broad Dynamic Range ◽  
Gmr Sensors ◽  
Gmr Sensor ◽  
Sample Volume Requirement

AbstractWe report a microfluidic sandwich immunoassay constructed around a dual-giant magnetoresistance (GMR) sensor array to quantify the heart failure biomarker NT-proBNP in human plasma at the clinically relevant concentration levels between 15 pg/mL and 40 ng/mL. The broad dynamic range was achieved by differential coating of two identical GMR sensors operated in tandem, and combining two standard curves. The detection limit was determined as 5 pg/mL. The assay, involving 53 plasma samples from patients with different cardiovascular diseases, was validated against the Roche Cobas e411 analyzer. The salient features of this system are its wide concentration range, low detection limit, small sample volume requirement (50 μL), and the need for a short measurement time of 15 min, making it a prospective candidate for practical use in point of care analysis.

scholarly journals Selective Determination of Iron(III) in Sea Water by Gold Nanoparticles Self-assembled with N-carboxyl- L-cysteine

2014 ◽  
Vol 17 (1) ◽  
pp. 001-004 ◽  
Author(s):  
Benzhi Liu ◽  
Min Wang
Keyword(s):  
Gold Nanoparticles ◽  
Detection Limit ◽  
Sea Water ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Operational Parameters ◽  
Selective Determination ◽  
Self Assembled ◽  
Optimized Conditions

Application of gold nanoparticles self-assembled with N-carboxyl- L-cysteine for the determination of iron(III) was investigated. Differential pulse adsorptive stripping voltammetry was used to detect iron(III). Various operational parameters were investigated and discussed in terms of their effects on the measurement signals. A linear range from 0.1 nM to 1.8 nM with a detection limit of 0.03 nMwas obtained under optimized conditions. The applicability of the method was successfully tested by determination of iron(III) in sea water samples.

The Removal of Interference from Microwave Digestion Solution of Industrial Wastewater on the Determination of Arsenic

2014 ◽  
Vol 587-589 ◽  
pp. 625-628
Author(s):  
Ming Ming Yang ◽  
Hong Wei An
Keyword(s):  
Detection Limit ◽  
Microwave Digestion ◽  
Hydride Generation ◽  
Standard Addition ◽  
Absorption Spectrometry ◽  
Quantitative Detection ◽  
Nitrite Ion ◽  
Digestion Solution ◽  
Relative Standard

In existing literature ,there is no unified time for the evaporating excessive acid to microwave digestion solution of different samples. a new method was developed .The interference from nitrite ion and volatile nitrogen oxides which were generated during digestion were quickly removed by the adding urea and heating with boiling water. The interference from nitrate was studied. Optimized conditions of determination of arsenic with hydride generation atomic absorption spectrometry. The detection limit was 0.3μg·L-1 and minimum quantitative detection limit was 1.0μg·L-1, the relative standard deviation of standard addition method in sample was 1.1% and recovery from 98 % to 102%.

Highly Sensitive Determination of Dopamine Using Osmium/Nafion Modified Disposable Integrated Biosensor

2009 ◽  
Vol 60-61 ◽  
pp. 311-314 ◽  
Author(s):  
Chun Xiu Liu ◽  
Hong Min Liu ◽  
Qing De Yang ◽  
Nan Sen Lin ◽  
Yi Lin Song ◽  
...  
Keyword(s):  
Detection Limit ◽  
Correlation Coefficient ◽  
Gold Electrode ◽  
High Sensitivity ◽  
Differential Pulse ◽  
Redox Polymer ◽  
Highly Sensitive ◽  
Sensitive Determination ◽  
Excellent Reproducibility

A biosensor based on gold electrode modified by Pt nanaoparticles/Osmium redox polymer/Nafion trilayer film was fabricated and used for selective and sensitive determination of dopamine. The biosensor is explored for DA sensing using the cyclic voltammetry (CV), amperometric and differential pulse voltammetric (DPV) methods. The CV anodic peak currents showed a linear range with a correlation coefficient of 0.996, localized in the concentration range 0~192 μM. The differential pulse voltammetric (DPV) peak currents were linear with DA concentration during 2~425 μM with correlation coefficient of 0.99. The biosensor showed high sensitivity of 0.5 nA /nM cm2 and excellent reproducibility with the detection limit of ~10 nM (S/N=3) for the determination of DA. The easy fabrication, low detection limit and high sensitivity of the integrated biosensor making it particularly suitable for the analytical purposes.

Ultra-sensitive detection of biomarkers and applications in pharmaceutical discovery and development. Example application to rat cardiac troponin I assay via nanoparticle probes

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e14594-e14594
Author(s):  
P. Bao ◽  
T. Lubben ◽  
T. Holzman
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Dynamic Range ◽  
High Sensitivity ◽  
Cardiac Troponin I ◽  
Drug Induced ◽  
Drug Candidates ◽  
Broad Dynamic Range ◽  
Probe Test ◽  
Detection Of Biomarkers

e14594 Although specific to heart, rat cardiac troponin I (cTnI) is an example of an important biomarker for assessing drug-induced cardiotoxicity in animal models used in various phases of drug discovery and development. Current commercially available assays can only detect 10 ∼ 100 pg/mL in serum at the lowest limits. To improve the sensitivity of rat cTnI assay, we have developed a generically applicable, microarray based nano-probe test. Our rat cTnI assay algorithm uses a multi-step robotic process, which relies on non- isotropically oriented antibodies on functionalized glass as multiplexed microarrays to capture cTnI from serum. Functionalized, 130 angstrom diameter gold nano-probes (measured by static light scattering, 5 nm S.D.) also bind to the troponin through a molecular-scale complex containing antibodies. The troponin-bound molecular complex is then quantified through silver enhancement of the functionalized gold. Assays in this format can be rapidly configured and implemented for a wide array of potential biomarkers. For cTnI we have demonstrated a robust and ultra-sensitive assay with an LOD of less than 500 femtograms of rat cTnI per mL serum, and an overall CV of less than 20%. The assay also shows very low background, a broad dynamic range and over 3 logs of linear dose response. As an example of the potential of high sensitivity, the nanoparticle-based rat cTnI assay could significantly increase the effectiveness of measuring drug-induced heart damage at very low drug dosages and early times. Such sensitive and early measurements can improve examination of the safety of drug candidates while correspondingly reducing drug development time and cost. [Table: see text]

scholarly journals Multi-platforms approach for plasma proteomics: complementarity of Olink PEA technology to mass spectrometry-based protein profiling

2020 ◽  
Author(s):  
Agnese Petrera ◽  
Christine von Toerne ◽  
Jennifer Behler ◽  
Cornelia Huth ◽  
Barbara Thorand ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Plasma Proteins ◽  
Biomarker Discovery ◽  
Dynamic Range ◽  
High Sensitivity ◽  
Living Organism ◽  
Protein Profiling ◽  
German Population ◽  
Plasma Proteome ◽  
Broad Dynamic Range

AbstractThe plasma proteome is the ultimate target for biomarker discovery. It stores an endless amount of information on the pathophysiological status of a living organism, which is however still difficult to comprehensively access. The high structural complexity of the plasma proteome can be addressed by either a system-wide and unbiased tool such as mass spectrometry (LC-MS/MS) or a highly sensitive targeted immunoassay such as the Proximity Extension Assays (PEA). In order to address relevant differences and important shared characteristics, we tested the performance of LC-MS/MS in data-dependent and -independent acquisition modes and PEA Olink to measure circulating plasma proteins in 173 human plasma samples from a Southern German population-based cohort. We demonstrated the measurement of more than 300 proteins with both LC-MS/MS approaches applied, mainly including high abundance plasma proteins. By the use of the PEA technology, we measured 728 plasma proteins, covering a broad dynamic range with high sensitivity down to pg/ml concentrations. In a next step, we quantified 35 overlapping proteins with all three analytical platforms, verifying the reproducibility of data distributions, measurement correlation and gender-based differential expression. Our work highlights the limitations and the advantages of both, targeted and untargeted approaches, and prove their complementary strengths. We demonstrated a significant gain in proteome coverage depth and subsequent biological insight by platforms combination – a promising approach for future biomarker and mechanistic studies.

scholarly journals A Cell-Free Approach Based on Phospholipid Characterization for Determination of the Cell Specific Unbound Drug Fraction (fu,cell)

2019 ◽  
Vol 36 (12) ◽  
Author(s):  
Andrea Treyer ◽  
Sandra Walday ◽  
Hinnerk Boriss ◽  
Pär Matsson ◽  
Per Artursson
Keyword(s):  
Dynamic Range ◽  
Cell Types ◽  
Drug Binding ◽  
Small Scale ◽  
Intracellular Fraction ◽  
Drug Molecules ◽  
Cellular Assays ◽  
Broad Dynamic Range ◽  
The Impact

Abstract Purpose The intracellular fraction of unbound compound (fu,cell) is an important parameter for accurate prediction of drug binding to intracellular targets. fu,cell is the result of a passive distribution process of drug molecules partitioning into cellular structures. Initial observations in our laboratory showed an up to 10-fold difference in the fu,cell of a given drug for different cell types. We hypothesized that these differences could be explained by the phospholipid (PL) composition of the cells, since the PL cell membrane is the major sink of unspecific drug binding. Therefore, we determined the fu,cell of 19 drugs in cell types of different origin. Method The cells were characterized for their total PL content and we used mass spectrometric PL profiling to delineate the impact of each of the four major cellular PL subspecies: phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI). The cell-based experiments were compared to cell-free experiments that used beads covered by PL bilayers consisting of the most abundant PL subspecies. Results PC was found to give the largest contribution to the drug binding. Improved correlations between the cell-based and cell-free assays were obtained when affinities to all four major PL subspecies were considered. Together, our data indicate that fu,cell is influenced by PL composition of cells. Conclusion We conclude that cellular PL composition varies between cell types and that cell-specific mixtures of PLs can replace cellular assays for determination of fu,cell as a rapid, small-scale assay covering a broad dynamic range.

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