scholarly journals PRE-CONCENTRATION AND DETERMINATION OF HEAVY METALS ON MODIFIED ACTIVATED CARBON IN REAL SAMPLES

2010 ◽  
Vol 8 (2) ◽  
pp. 130-135
Author(s):  
F. Ahmadi ◽  
K. Niknam ◽  
A. Khanmohammadi ◽  
Z. Adibmehr
Keyword(s):  
Heavy Metals ◽  
Activated Carbon ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Simple Method ◽  
Modified Activated Carbon ◽  
Real Samples ◽  
At Resonance ◽  
Simultaneous Separation

A sensitive and simple method for the simultaneous pre-concentration of nutritionally important minerals in real samples has been reported. The method is based on the formation of metal complexes by N, N'-diacetyl-4-bromo-2, 6-di (aminomethyl) phenol (DBDP) loaded on activated carbon. The metals content on the complexes are then eluted using 6mL 4M HNO3, which are detected by AAS at resonance line. In this procedure, minerals such as Ni, Cu, Co, Pb Zn and Cd can be analyzed in one run by caring out the simultaneous separation and quantification of them. At optimum condition the response are linear over concentration range of for 0.03-1.1 µg mL-1 for Ni2+ , 0.03-1.0 µg mL-1 for Cu2+, 0.02-1.0 µg mL-1 for  Pb2+ , 0.02-1.0 µg mL-1 for  Co2+,0.02-1.1 µg mL-1 Zn2+ and 0.05-1.3 µg mL-1for Cd2+. The detection limits of each element are expressed as the amount of analytes in µg mL-1 giving a signal to noise ratio of 3 are equal to 2.5, 2.4, 1.6, 2.4, 1.9 and 2.1 for Ni2+ , Cu2+, Pb2+ , Co2+,Zn2+ and Cd2+. The ability of method for repeatable recovery of trace ion are 99.9, 98.7, 99.2 , 98.7, 98.5and 95.6 with R.S.D of 1.3, 1.4, 1.2, 1.4, 1.7 and 1.4 for Ni2+ , Cu2+, Pb2+ , Co2+,Zn2+ and Cd2+. The method has been successfully applied for these metals content evaluation in some real samples including natural water and vegetable.     Keywords: Heavy Metals, N, N'-diacetyl-4-bromo-2,6-di(aminomethyl) phenol (DBDP), Activated Carbon

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Simultaneous separation and preconcentration of phosalone and chlorpyrifos in fresh vegetables using ultrasound-assisted dispersive liquid–liquid microextraction and high performance liquid chromatography

2016 ◽  
Vol 8 (18) ◽  
pp. 3795-3801 ◽  
Author(s):  
Monireh Majlesi ◽  
Mohamadreza Massoudinejad ◽  
Fateh Hosainzadeh ◽  
Nazir Fattahi
Keyword(s):  
High Performance Liquid Chromatography ◽  
High Performance ◽  
Simple Method ◽  
Fresh Vegetables ◽  
Separation And Preconcentration ◽  
Simultaneous Separation ◽  
Ultrasound Assisted ◽  
Dispersive Liquid Liquid Microextraction ◽  
Liquid Microextraction

UA-DLLME-SFO combined with HPLC-UV is a fast and simple method for the determination of pesticides and herbicides in fresh vegetables.

scholarly journals Distance scaling method for accurate prediction of slowly varying magnetic fields in satellite missions

2016 ◽  
Vol 5 (2) ◽  
pp. 281-288 ◽  
Author(s):  
Panagiotis P. Zacharias ◽  
Elpida G. Chatzineofytou ◽  
Sotirios T. Spantideas ◽  
Christos N. Capsalis
Keyword(s):  
Signal To Noise Ratio ◽  
Near Field ◽  
Magnetic Behavior ◽  
Field Measurements ◽  
High Signal ◽  
Signal To Noise ◽  
Scaling Method ◽  
Magnetic Signature ◽  
The Magnetic Field

Abstract. In the present work, the determination of the magnetic behavior of localized magnetic sources from near-field measurements is examined. The distance power law of the magnetic field fall-off is used in various cases to accurately predict the magnetic signature of an equipment under test (EUT) consisting of multiple alternating current (AC) magnetic sources. Therefore, parameters concerning the location of the observation points (magnetometers) are studied towards this scope. The results clearly show that these parameters are independent of the EUT's size and layout. Additionally, the techniques developed in the present study enable the placing of the magnetometers close to the EUT, thus achieving high signal-to-noise ratio (SNR). Finally, the proposed method is verified by real measurements, using a mobile phone as an EUT.

Determination of glutathione and glutathione disulfide in human whole blood using HPLC with coulometric detection: A comparison with fluorescence detection

2011 ◽  
Vol 76 (4) ◽  
pp. 277-294 ◽  
Author(s):  
Roman Kanďár ◽  
Pavla Žáková ◽  
Miroslava Marková ◽  
Halka Lotková ◽  
Otto Kučera ◽  
...  
Keyword(s):  
Detection Limit ◽  
Whole Blood ◽  
Trichloroacetic Acid ◽  
Signal To Noise Ratio ◽  
Glutathione Disulfide ◽  
Simple Method ◽  
Human Whole Blood ◽  
Coulometric Detection ◽  
Coefficients Of Variation

We describe a relatively simple method for the determination of glutathione (GSH) and glutathione disulfide (GSSG) in human whole blood. We have used an HPLC with coulometric electrochemical detection for the simultaneous measurement of GSH and GSSG. Diluted and filtered trichloroacetic acid extracts were injected directly into the HPLC system and were eluted isocratically on a Polaris 5u C18-A, 250 × 4.6 mm analytical column. Glutathione in samples extracted with trichloroacetic acid and diluted with 1.0 mMhydrochloric acid was stable at 4 °C for at least 8 h. The analytical performance of this method is satisfactory: the intra-assay and inter-assay coefficients of variation were below 10%. Quantitative recoveries from spiked whole blood samples were at intervals 91.6–97.6% for GSH and 85.0–104.4% for GSSG. The linear range is 5.0–2000.0 μmol/l, with a detection limit of 2.1 μmol/l (signal-to-noise ratio = 3) for GSH and 2.0–250.0 μmol/l, with a detection limit of 0.9 μmol/l for GSSG.

scholarly journals Determination of Flumequine in Channel Catfish by Liquid Chromatography with Fluorescence Detection

1999 ◽  
Vol 82 (3) ◽  
pp. 614-619 ◽  
Author(s):  
Steven M Plakas ◽  
Kathleen R El Said ◽  
F Aladar Bencsath ◽  
Steven M Musser ◽  
Calvin C Walker
Keyword(s):  
Liquid Chromatography ◽  
Fluorescence Detection ◽  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Solid Phase ◽  
Signal To Noise Ratio ◽  
Methanol Solution ◽  
Signal To Noise ◽  
Relative Standard

Abstract Rapid methods are described for determination of flumequine (FLU) residues in muscle and plasma of farm-raised channel catfish (Ictalurus punctatus). FLU residues were extracted from tissues with an acidified methanol solution, and extracts were cleaned up on C18 solid-phase extraction cartridges. FLU concentrations were determined by liquid chromatography (LC)using a C18 analytical column and fluorescence detection (excitation, 325 nm; emission, 360 nm). Mean recoveries of FLU from fortified muscle were 87–94% at 5 levels ranging from 10 to 160 ppb (5 replicates per level). FLU recoveries from fortified plasma were 92–97% at 5 levels ranging from 20 to 320 ppb. Limits of detection (signal-to-noise ratio, 3:1)for the method as described were 3 and 6 ppb for muscle and plasma, respectively. Relative standard deviations (RSDs) for recoveries were ≤12%. Live catfish were dosed with 14C-labeled or unlabeled FLU to generate incurred residues. Recoveries of 14C residues throughout extraction and cleanup were 90 and 94% for muscle and plasma, respectively. RSDs for incurred FLU at 2 levels in muscle and plasma ranged from 2 to 6%. The identity of FLU in incurred tissues was confirmed by LC/mass spectrometry.

DETERMINATION OF SIGNAL AND NOISE STATISTICS USING CORRELATION THEORY

Geophysics ◽  
1970 ◽  
Vol 35 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Bibhu P. Dash ◽  
K. Ahmed Obaidullah
Keyword(s):  
Signal To Noise Ratio ◽  
Random Series ◽  
Signal To Noise ◽  
Time Duration ◽  
Optimum Time ◽  
Seismic Wavelet ◽  
Correlation Theory ◽  
Noise Ratio ◽  
Noise Statistics

A seismic trace may be represented as the sum of a signal and noise series. Each of the series may further be represented by convolution of a finite wavelet and a random series. With this representation, and provided that the signal and noise are uncorrelated, it is possible, in theory, to extract signal and noise statistics from two adjacent traces of a reflection seismogram. Some experiments are shown on model seismic traces, and it is shown that within the time‐duration of the seismic wavelet, the estimates of signal and noise statistics are reasonable for low signal‐to‐noise ratio. There remains, however, the problem of determining the optimum time lengths of the estimates.

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