Invalidation of the Intracavity Optogalvanic Method for Radiocarbon Detection

Radiocarbon ◽  
2016 ◽  
Vol 58 (1) ◽  
pp. 213-225 ◽  
Author(s):  
Cantwell G Carson ◽  
Martin Stute ◽  
Yinghuang Ji ◽  
Roseline Polle ◽  
Arthur Reboul ◽  
...  
Keyword(s):  
Laser Power ◽  
Limit Of Detection ◽  
Laser Cavity ◽  
Periodic Modulation ◽  
Hitran Database ◽  
Detection Thresholds ◽  
Background Contribution ◽  
Optogalvanic Spectroscopy ◽  
Pressure Glow Discharge ◽  
Ambient Levels

AbstractThe intracavity optogalvanic spectroscopy (ICOGS) method has been reported to quantify radiocarbon at subambient levels (<1 part per trillion). ICOGS uses a gas sample that is ionized in a low-pressure glow discharge located inside a 14CO2 laser cavity to detect changes in the discharge current under periodic modulation of the laser power to determine the 14CO2 concentration of the sample. When claims of detection thresholds below ambient levels were not verified by other researchers, we constructed a theoretical analysis to resolve differences between these conflicting reports and built and tested an ICOGS system to establish a lower limit of detection. Using a linear absorbance model of the background contribution of 12CO2 and data from the HITRAN database, we estimate that the limit of detection (3σx) is close to 1.5×104 Modern. By measuring a 1.5×104 Modern enriched CO2 sample in a cavity modulation ICOGS system without a clear signal, we conclude that for this system the limit of detection for ICOGS must be above 1.5×104. The implications for previous ICOGS reports are discussed.

Study on Detection of Carbaryl Pesticides by Using Surface-Enhance Raman Spectroscopy

2020 ◽  
Vol 853 ◽  
pp. 97-101
Author(s):  
Chaiwat Chakaja ◽  
Saksorn Limwichean ◽  
Noppadon Nuntawong ◽  
Pitak Eiamchai ◽  
Sukon Kalasung ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Raman Scattering ◽  
Exposure Time ◽  
Laser Power ◽  
Limit Of Detection ◽  
Surface Enhance Raman Spectroscopy ◽  
Raman Spectrometer ◽  
Surface Enhanced Raman ◽  
Solid Form ◽  
Portable Raman

In this research, the Ag nanorod structure was used as surface enhanced Raman scattering (SERS) chip which provides a sensitive detection signal for trace analysis of carbaryl pesticide. Carbaryl in solid form was measured by using the standard Raman spectroscopy to investigate the spectrum. Carbaryl at various concentrations was prepared in acetonitrile and dropped on the SERS chip for measuring Raman spectrum by a portable Raman spectrometer. The measurement condition including laser power and exposure time were studied to test the performance of SERS chip for carbaryl detection. From the results, the SERS chip useful for enhancing the Raman scattering signal which was increased depending on the laser power and exposure time. Carbaryl can be detected on SERS chip couple with the portable Raman spectrometer with the limit of detection of 10-5 M.

scholarly journals Experiments And Simulations of Thermometric Lateral Flow Immunoassay For Point-of-Care Testing

2021 ◽  
Author(s):  
Terumitsu Azuma ◽  
Yuen Yung Hui ◽  
Oliver Y. Chen ◽  
Yuh-Lin Wang ◽  
Huan-Cheng Chang
Keyword(s):  
Laser Power ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Lateral Flow ◽  
Detection Sensitivity ◽  
Lateral Flow Immunoassay ◽  
Point Of Care Testing ◽  
Incident Laser Power ◽  
Latex Beads ◽  
Fold Reduction

Abstract Temperature sensing is a promising method of enhancing the detection sensitivity of lateral flow immunoassay for point-of-care testing. A temperature increase of more than 100 °C can be readily achieved by photoexcitation of reporters like gold nanoparticles (GNPs) or colored latex beads (CLBs) on the strips with a laser power below 100 mW. Despite its promise, processes involved in the photothermal detection have not yet been well-characterized. Here, we provide a fundamental understanding of this thermometric assay by combining experiments and simulations using non-fluorescent CLBs as the reporters deposited on nitrocellulose membrane. By measuring the dependence of temperature rises on the number density of membrane-bound CLBs, we determined a 1.5-fold enhancement of the light absorption at 520 nm by the beads (diameter of 0.4 μm). The enhancement, however, was compromised by a 5-fold reduction of the incident laser power due to multiple scattering of the light in this highly porous medium. The limit of detection was measured to be 1 × 105 particles/mm2. In line with previous studies using GNPs as the reporters, the CLB-based thermometric assay provides a 10× higher sensitivity than color visualization, as demonstrated with the immunoassay for nucleocapsid proteins of the SARS-CoV-2 virus.

SERUM TRIIODOTHYRONINE DETERMINATION BY SATURATION ANALYSIS

1973 ◽  
Vol 72 (4) ◽  
pp. 714-726 ◽  
Author(s):  
A. Burger ◽  
B. Miller ◽  
C. Sakoloff ◽  
M. B. Vallotton
Keyword(s):  
Ionic Strength ◽  
Limit Of Detection ◽  
Improved Method ◽  
Accuracy Of Measurement ◽  
Tracer Amount ◽  
The Mean ◽  
Physiological Values ◽  
Hyperthyroid Patients ◽  
Solvent Blank

ABSTRACT An improved method for the determination of serum triiodothyronine (T3) has been developed. After addition of a tracer amount of the hormone, T3 was extracted from 1 ml serum under conditions of pH and ionic strength which favoured T3 extraction (89%) over thyroxine (T4) extraction (58%). Chromatography of the extracted material on Sephadex LH-20 separated T3 completely from residual T4. The T3 eluate was dried, then re-dissolved in 0.5 ml NaOH 0.04 n. To 0.2 ml duplicate aliquots, a standard amount of TBG was added for the competitive protein analysis. After one hour incubation at 4°C, separation of bound from free T3 was achieved on small Sephadex G-25 columns. Overall recovery was 67 ± 10.8% and correction for the loss was made. The solvent blank was 37 ± 27 (sd) ng/100 ml. Accuracy of measurement of known quantities of T3 added to serum was 98.4%. The coefficient of variation within the assay was 6.2% and between the assays it was 11.4%. The limit of detection (0.1 ng) corresponded to a concentration of 25 ng/100 ml. T4 added to serum did not interfere with T3 determination until high non-physiological values were reached. The mean ± sd serum T3 in 54 euthyroid subjects was 153 ± 58 ng/100 ml and in 24 hyperthyroid patients it was 428 ±186 ng/100 ml; 4 out of the 24 hyperthyroid values were within 2 sd of the mean euthyroid group. All the values found in the euthyroid group were well above the limit of detection of the method.

Position Paper on Treatment of Hepatitis C in Romania, 2017. Part One

2017 ◽  
Vol 26 (2) ◽  
pp. 171-181 ◽  
Author(s):  
Liana Gheorghe ◽  
Ioan Sporea ◽  
Speranţa Iacob ◽  
Roxana Şirli ◽  
Anca Trifan ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Liver Disease ◽  
Hepatitis C ◽  
Limit Of Detection ◽  
Position Paper ◽  
Hcv Infection ◽  
Fixed Dose ◽  
Diagnostic Tools ◽  
End Stage Liver Disease ◽  
End Stage

Background & Aims: Hepatitis C Virus (HCV) infection is a common condition with endemic prevalence in some areas of the world. In Romania, the mean prevalence is about 3%. New treatments became available on the market in recent years and new drugs are in the pipeline. A re-evaluation of HCV therapy was considered mandatory. The Romanian Society of Gastroenterology and Hepatology undertook this task for the practitioners of this country.Methodology: A group of recognized experts was created who screened the available literature and the major available guidelines. A list of items requiring attention has been created. These items were discussed and rated. Decisions were taken by consensus.Recommendations: We present here the first of the two parts of our Society’s recommendations for chronic HCV infection treatment. An agreement was reached regarding the diagnostic tools, the assessment of severity and the up-dated therapy schedules.Conclusions: This Position Paper represents a guide for the assessment and the therapy of HCV infection. The recommendations are in concordance with other guidelines but are applied to the real-life conditions in this country.Abbreviations: DAAs: Direct-acting antivirals; DDIs: Drug-drug interactions; ESLD: End-stage liver disease; ESRD: End-stage renal disease; eGFR: Estimated glomerular filtration rate; EASL: European Association for the Study of the Liver; EMA: European Medicines Agency; FDA: US Food and Drug Administration; FDC: Fixed-dose combination; GT: Genotype; GRADE: Grading of Recommendations Assessment, Development and Evaluation; HCV: Hepatitis C virus; HCC: Hepatocellular carcinoma; LT: Liver transplantation; LLD: Lower limit of detection; MELD score: Mayo-Clinic End-Stage Liver Disease score; ANMDM: National Agency of Medicines and Medical Devices; PPIs: Proton pump inhibitors; PWID: People who inject drugs; RCT: Randomized controlled trial; RDT: Rapid diagnostic test; RAS: Resistance-associated substitution; SRGH: Romanian Society of Gastroenterology and Hepatology; SAE: serious adverse events; SPC: Summary of Product Characteristics; SVR: Sustained virologic response.

Production of Atmospheric-Pressure Glow Discharge

2003 ◽  
Vol 79 (10) ◽  
pp. 1002-1008 ◽  
Author(s):  
Koichi TAKAKI ◽  
Tamiya FUJIWARA ◽  
Fumiyoshi TOCHIKUBO
Keyword(s):  
Glow Discharge ◽  
Atmospheric Pressure ◽  
Atmospheric Pressure Glow Discharge ◽  
Pressure Glow Discharge
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