scholarly journals The determination of N-methylcarbamate pesticides using enzyme immunoassays with chemiluminescent detection

2004 ◽  
Vol 22 (SI - Chem. Reactions in Foods V) ◽  
pp. S280-S282 ◽  
Author(s):  
B. Mičková ◽  
P. Rauch ◽  
A. Montoya ◽  
E. Ferri ◽  
F. Fini ◽  
...  
Keyword(s):  
Detection Limit ◽  
Matrix Effects ◽  
Colorimetric Detection ◽  
Fruit Juices ◽  
Analytical Performance ◽  
Experimental Comparison ◽  
Enzyme Immunoassays ◽  
Chemiluminescent Detection ◽  
Concentration Levels

In the present work, enzyme-linked immunosorbent assays (ELISAs) with chemiluminescent detection for the determination of carbofuran, carbaryl and methiocarb were developed and the analytical parameters of these assays were compared with those of ELISAs with colorimetric detection. The sensitivity of immunochemical methods was expressed as detection limit, linear working range, and I<sub>50</sub> value. In comparison with colorimetric ELISA, the ability of the chemiluminescent reagents to detect lower concentrations of HRP allowed to decrease the optimal antibody and conjugate concentrations and to reach better analytical parameters. The experimental comparison of the analytical performance of the ELISAs was carried out by analysing simply diluted fruit juices, spiked at different concentration levels with the above mentioned pesticides. Recovery values for both ELISAs were around 100% and no matrix effects were observed when fruit juices were diluted 1:20 or more.

Laser optoacoustic detection of trace concentration levels of ethylene, vinylchloride, and styrene in the atmosphere

1989 ◽  
Vol 54 (10) ◽  
pp. 2667-2673 ◽  
Author(s):  
Vojtěch Steiner ◽  
Pavel Engst ◽  
Zdeněk Zelinger ◽  
Milan Horák
Keyword(s):  
Detection Limit ◽  
Emission Line ◽  
Laser Line ◽  
Laser Source ◽  
Trace Concentration ◽  
Selective Determination ◽  
Hygienic Standard ◽  
Trace Concentrations ◽  
Concentration Levels

The optoacoustic analyzer with a tunable CO2 laser source employed in the present work permits a selective determination of ethylene in trace concentrations higher than 5 ppb (=detection limit for the 10P(14) emission line of the CO2 laser, ν = 949.5 cm-1) and of vinylchloride higher than 42 ppb (= detection limit for the 10P(22) CO2 laser line, ν= 942.4 cm-1). this method covers for both compounds the concentration range corresponding to the hygienic standard. It can be also used for the determination of styrene vapour with concentrations higher than 1.5 ppm.

scholarly journals Determination of Thiabendazole in Fruit Juices by a New Monoclonal Enzyme Immunoassay

2001 ◽  
Vol 84 (1) ◽  
pp. 156-161 ◽  
Author(s):  
Antonio Abad ◽  
Juan J Manclús ◽  
María J Moreno ◽  
Angel Montoya
Keyword(s):  
Matrix Effects ◽  
Simple Procedure ◽  
Fruit Juices ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dilution Method ◽  
Sample Throughput ◽  
Banana Juice ◽  
Routine Monitoring ◽  
Low Levels

Abstract A competitive, indirect enzyme-linked immunosorbent assay (ELISA) for thiabendazole has been developed and applied to the analysis of fruit juices spiked with this fungicide. The immunoassay is based on a new monoclonal antibody derived from a hapten functionalized at the nitrogen atom in the 1-position of the thiabendazole structure. To our knowledge, such a structure has not been previously used to obtain antibodies to thiabendazole. The l50 value and the detection limit of the ELISA for standards were 0.2 and 0.05 ng/mL, respectively. Fruit juices were analyzed by diluting samples in assay buffer, without extraction or cleanup. Samples were not even centrifuged or filtered to remove fruit pulp. Under these conditions, the immunoassay was able to accurately determine thiabendazole down to 1 ng/mL in orange and grapefruit juices, down to 5 ng/mL in banana juice, and down to 20 ng/mL in apple and pear juices. Sensitivity differences of the ELISA were caused by the minimum dilution required by each juice to minimize matrix effects: 1/10 for orange and grapefruit juices, 1/50 for banana juice, and 1/100 for apple and pear juices. In an attempt to further increase the sensitivity of the immunoassay for matrixes showing the strongest interferences, apple and pear juices spiked with thiabendazole at low levels (1–20 ng/mL) were extracted with ethyl acetate before analysis. This simple procedure entailed a significant reduction of matrix effects, which in fact allowed us to determine accurately as low as 5 ng/mL thiabendazole in apple and pear juices. Irrespective of whether samples were analyzed by the direct dilution method or after extraction, the simplicity, sensitivity, and sample throughput of this monoclonal immunoassay makes it a very convenient method for the routine monitoring of thiabendazole residues in fruit juices.

scholarly journals Ratiometric Colorimetric Detection of Nitrite Realized by Stringing Nanozyme Catalysis and Diazotization Together

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 280
Author(s):  
Mengzhu Wang ◽  
Peng Liu ◽  
Hengjia Zhu ◽  
Bangxiang Liu ◽  
Xiangheng Niu
Keyword(s):  
Detection Limit ◽  
Signal Analysis ◽  
High Efficiency ◽  
Colorimetric Assay ◽  
Low Cost ◽  
Colorimetric Detection ◽  
Health It ◽  
Practical Applications ◽  
Higher Sensitivity

Due to the great threat posed by excessive nitrite in food and drinking water to human health, it calls for developing reliable, convenient, and low-cost methods for nitrite detection. Herein, we string nanozyme catalysis and diazotization together and develop a ratiometric colorimetric approach for sensing nitrite in food. First, hollow MnFeO (a mixture of Mn and Fe oxides with different oxidation states) derived from a Mn-Fe Prussian blue analogue is explored as an oxidase mimic with high efficiency in catalyzing the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation to blue TMBox, presenting a notable signal at 652 nm. Then, nitrite is able to trigger the diazotization of the product TMBox, not only decreasing the signal at 652 nm but also producing a new signal at 445 nm. Thus, the analyte-induced reverse changes of the two signals enable us to establish a ratiometric colorimetric assay for nitrite analysis. According to the above strategy, facile determination of nitrite in the range of 3.3–133.3 μM with good specificity was realized, providing a detection limit down to 0.2 μM. Compared with conventional single-signal analysis, our dual-signal ratiometric colorimetric mode was demonstrated to offer higher sensitivity, a lower detection limit, and better anti-interference ability against external detection environments. Practical applications of the approach in examining nitrite in food matrices were also verified.

Determination of Ethylenethiourea in Grapes and Wine

1985 ◽  
Vol 68 (4) ◽  
pp. 741-745
Author(s):  
Jana Chovancova ◽  
Eva Matisova ◽  
Vojtech Batora
Keyword(s):  
Gas Chromatography ◽  
Detection Limit ◽  
Electron Capture ◽  
Paper Chromatography ◽  
Capillary Gas Chromatography ◽  
Electron Capture Detection ◽  
Flame Ionization Detection ◽  
Flame Ionization ◽  
Concentration Levels

Abstract Residues of ethylenethiourea (ETU) in grapes and wine were deter- [ mined by capillary gas chromatography and paper chromatography, without a cleanup step, and after derivatization to 5-benzyl-ETU. The ! detection limit was 0.0002 mg/kg for flame ionization detection, 0.008 mg/kg for paper chromatography with photodensitometric evaluation of the detected spot. Results were compared with a generally used GC method specifying electron capture detection of trifluoroacetylated S- benzyl-ETU. The recoveries of ETU in grapes and wine at different j concentration levels were determined. ETU residues were determined J in treated grapes but no residues were detected in wine

X-Ray Fluorescence Determination of Barium and Strontium in Geologic Samples

1971 ◽  
Vol 25 (3) ◽  
pp. 316-318 ◽  
Author(s):  
Brent P. Fabbi
Keyword(s):  
Detection Limit ◽  
Matrix Effects ◽  
Analytical Line ◽  
X Ray ◽  
First Order ◽  
Fluorescence Determination ◽  
Geologic Samples ◽  
Line Iron

It is possible to accurately determine barium and strontium in a variety of geologic samples by the XRF method proposed herein after correcting for matrix effects. The first-order (I) titanium Kα1 line interferes spectrally with the barium first-order (I) Lα1 analytical line. Iron significantly absorbs the emitted strontium x-ray quanta. Both of these effects were investigated in detail and a method of correcting for them developed. Detection limit for both elements is about 10 ppm.

scholarly journals Chemiluminescent and Colorimetric Detection of Erwinia amylovora by Immunoenzymatic Determination of PCR Amplicons from Plasmid pEA29

Plant Disease ◽  
2000 ◽  
Vol 84 (1) ◽  
pp. 49-54 ◽  
Author(s):  
M. Merighi ◽  
A. Sandrini ◽  
S. Landini ◽  
S. Ghini ◽  
S. Girotti ◽  
...  
Keyword(s):  
Erwinia Amylovora ◽  
Colorimetric Detection ◽  
Infected Plant ◽  
Detection Threshold ◽  
Diagnostic Technique ◽  
Molecular Diagnostic ◽  
Enzyme Linked Immunosorbent Assay ◽  
Chemiluminescent Detection

A molecular diagnostic technique (polymerase chain reaction enzyme-linked immunosorbent assay [PCR-ELISA]) for detection of Erwinia amylovora was developed. The protocol is based on the immunoenzymatic determination of PCR products. For in vitro amplification, we used previously published primers able to detect the cryptic plasmid pEA29, which is ubiquitous in E. amylovora. Amplicons were labeled with 11-digoxigenin (DIG)-dUTP during the amplification reaction, captured by hybridization to a biotinylated oligonucleotide in streptavidin-coated ELISA microplates, and then detected with anti-DIG-Fab′-peroxidase conjugated antibodies. The specificity of the assay was verified using E. amylovora strains from different host plants and geographical origins in addition to other plant-associated bacteria (either phytopathogenic or saprophytic) belonging to the genera Erwinia, Pseudomonas, and Agrobacterium. In detection threshold experiments with pure cultures, as few as 30 and 3 CFU/reaction tube were detected when the ABTS (colorimetric) and ECL (chemiluminescent) detection assays, respectively, were used. PCR-ELISA coupled with chemiluminescent detection was able to detect as few as 4 × 102 CFU/g of artificially infested pear twigs. The assay was further shown to be suitable for detection of E. amylovora in naturally infected plant organs, and the results were compared to those obtained using standard PCR assays with electrophoretic separation of amplicons.

Colorimetric determination of Salmonella typhimurium based on aptamer recognition

2016 ◽  
Vol 8 (35) ◽  
pp. 6560-6565 ◽  
Author(s):  
Changqing Zhu ◽  
Ying Hong ◽  
Zhen Xiao ◽  
Yang Zhou ◽  
Yuan Jiang ◽  
...  
Keyword(s):  
Detection Limit ◽  
Salmonella Typhimurium ◽  
Colorimetric Detection ◽  
Colorimetric Determination

A sensitive colorimetric detection of S. typhimurium based on aptamer recognition with a detection limit of 10 cfu mL−1.

scholarly journals Colorimetric Detection of Mercury Ions in Water with Capped Silver Nanoprisms

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1533 ◽  
Author(s):  
Fouzia Tanvir ◽  
Atif Yaqub ◽  
Shazia Tanvir ◽  
Ran An ◽  
William A. Anderson
Keyword(s):  
Detection Limit ◽  
Coal Combustion ◽  
Matrix Effects ◽  
Colorimetric Detection ◽  
Industrial Processes ◽  
Rapid Testing ◽  
Mercury Ions ◽  
Reagent Solution ◽  
Testing Methods ◽  
Silver Nanoprisms

The emission of mercury (II) from coal combustion and other industrial processes may have impacts on water resources, and the detection with sensitive but rapid testing methods is desirable for environmental screening. Towards this end, silver nanoprisms were chemically synthesized resulting in a blue reagent solution that transitioned towards red and yellow solutions when exposed to Hg2+ ions at concentrations from 0.5 to 100 µM. A galvanic reduction of Hg2+ onto the surfaces is apparently responsible for a change in nanoprism shape towards spherical nanoparticles, leading to the change in solution color. There were no interferences by other tested mono- and divalent metal cations in solution and pH had minimal influence in the range of 6.5 to 9.8. The silver nanoprism reagent provided a detection limit of approximately 1.5 µM (300 µg/L) for mercury (II), which compared reasonably well with other reported nanoparticle-based techniques. Further optimization may reduce this detection limit, but matrix effects in realistic water samples require further investigation and amelioration.

scholarly journals Synthesis of 1,5-diphenylcarbazide-immobilized alginate/pectin films for colorimetric detection of Cr(VI)

2020 ◽  
Keyword(s):  
Detection Limit ◽  
Optimum Condition ◽  
Optical Sensor ◽  
Potential Application ◽  
Colorimetric Detection ◽  
Ion Pairs ◽  
Direct Determination ◽  
Violet Color ◽  
Sensitive Sensor

<p>An optical sensor for colorimetric detection of Cr(VI) has been synthesized by immobilizing 1,5-diphenylcarbazide (DPC) into alginate/pectin films. The addition of cationic surfactant (CTAB) was used to increase the effectiveness of DPC immobilization by forming hydrophobic-ion pairs. At optimum condition, the films has good selectivity for Cr(VI) compare to other interference metals. The formation of violet color in the films showed its potential application for visual colorimetric detection of Cr(VI). The developed films in this study was found to be simple, rapid and sensitive sensor for direct determination of Cr(VI) with detection limit as low as 0.233 mg L–1 and time response was 8 minutes.</p>

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