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PubMed2002

Determination of SCN- in urine and saliva of smokers and non-smokers by SCN(-)-selective polymeric membrane containing a nickel(II)-azamacrocycle complex coated on a graphite electrode.

The construction, performance characteristics, and application of a novel polymeric membrane coated on a graphite electrode with unique selectivity towards SCN- are reported. The electrode was prepared by incorporating Ni(II)-2,2,4,9,9,11-hexamethyltetraazacyclotetradecanediene perchlorate into a plasticized poly(vinyl chloride) membrane. The influences of membrane composition, pH and foreign ions were investigated. The electrode displays a near Nernstian slope (-57.8 mV decade-1) over a wide concentration range of 1 x 10(-7)-1 x 10(-1) M of SCN- ion. The electrode has a detection limit of 4.8 x 10(-8) M (2.8 ng/cm3) SCN- and shows response times of about 15 s and 120 s for low to high and high to low concentration sequences, respectively. The proposed sensor shows high selectivity towards SCN- over several common organic and inorganic anions. The electrode revealed a great enhancement in selectivity coefficients and detection limit for SCN-, in comparison with the previously reported electrodes. It was successfully applied to the direct determination of SCN- in milk and biological samples, and as an indicator electrode in titration of Ag+ ions with thiocyanate.

Aza Compounds↗

PubMed2004

ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.

N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures.

Anti-Bacterial Agents↗

PubMed2005

Edge plane pyrolytic graphite electrodes in electroanalysis: an overview.

The recent development, behavior and scope of edge plane pyrolytic graphite electrodes in electroanalysis are overviewed. Similarities to, and advantages, over multi-walled CNT modified electrodes are noted and the wide scope of applications, ranging through gas sensing, stripping voltammetry and biosensing, illustrated.

Ascorbic Acid↗

PubMed2004

[Multiresidue analysis of pesticides in agricultural products by GC-ECD after GPC and graphitized carbon column cleanup].

A multiresidue method that enables determination of many pesticides in agricultural products by GC-ECD was studied. First, 63 pesticides were selected as agrochemicals commonly used in crop protection in this country, and/or found in agricultural products over the past 6 years (April 1996-March 2002) in Aichi Prefecture. A sample was extracted with acetonitrile and the acetonitrile layer was separated by salting-out. The extract was purified on a GPC system with a graphitized carbon columns, and then by a Florisil mini-column fractionation. The test solution was subjected to one-injection, dual-column GC with dual ECD (column: Stx-CLPesticides and Stx-CLPesticides2). The detection limits of the pesticides were in a suitable range (0.0001-0.01 microg/g) for monitoring pesticide residues in agricultural products. The method was applied to 203 commercial agricultural products to demonstrate its suitability for routine analysis.

Chromatography, Gas↗

PubMed1999

Process stability assessed by selecting Shewhart's psi statistical analysis technique of the influence of matrix modifier and furnace program in the optimization and precision of zinc determinations by graphite furnace atomic absorption spectroscopy.

The method previously used in the Toxicology Laboratories of King Faisal Specialist Hospital and Research Center for determining the zinc concentration in serum by Zeeman atomic absorption spectrometer was improved by modifying the matrix modifier and by changing the heated graphite furnace atomization (HGA) program. After trying several methods we failed to achieve the required precision and the accuracy of methods for serum zinc determination. We changed the matrix modifier to a fifty percent mixture (v/v) of 3.90 grams per liter of ammonium phosphate in Type 1 water with 0.2% nitric acid and 1.0 gram per liter of magnesium nitrate in acidic water (0.2% HNO3) with 0.1% triton X-100 was used as matrix modifier. A twenty-five fold dilution of the sample in matrix modifier was injected on the L'vov's platform of the furnace. In order to reduce the high sensitivity of Zn the furnace program was modified. The method is found very robust. The average reproducibility between inter-runs and intra-run is less than 1.59% with a high degree of accuracy. We used two levels of controls i.e. normal or low level and abnormal or high level. The linearity and the detection limit of the assay were 0.9992 and 0.010 micromol/L respectively. Average recovery of the analyte was 98.65%. The X-Bar and R charts were constructed by using Shewhart's statistical analysis technique to assess the test methodology. It was found that the assay is capable and stable for routine clinical and research analysis. The capability index (C(P)) of the assay, an indicator of the precision, was calculated.

Data Interpretation, Statistical↗

PubMedDate not supplied

Determination of oxalate in urine, using an amperometric biosensor with oxalate oxidase immobilized on the surface of a chromium hexacyanoferrate-modified graphite electrode.

A novel enzymatic amperometric method is described for the determination of oxalic acid in urine. An amperometric biosensor was made by immobilizing oxalate oxidase on the surface of a chromium(III) hexacyanoferrate-modified graphite electrode by using a bovine serum albumin and glutaraldehyde cross-linking procedure. The enzyme biocatalyzes oxalate decomposition in the presence of oxygen into carbon dioxide and hydrogen peroxide. The oxalate concentration, which is proportional to the amount of hydrogen peroxide, was determined amperometrically by measuring the current resulting in the reduction of hydrogen peroxide at a very low working potential (0.05 V versus the Hg ¿Hg2Cl2¿ 3M KCl electrode), which minimized the influence of the possible interferences present in human urine. All experiments were performed with succinic buffer, pH 3.8, containing 0.1M KCl and 5.4mM ethylenediaminetetraacetic acid. In an aqueous solution of pure oxalic acid, the biosensor showed good linearity in a concentration range of 2.5-100 microM without the use of a dialysis membrane. For untreated urine samples, a high correlation (R2 = 0.9949) was obtained between oxalate concentrations added to urine samples and oxalate recoveries calculated for determinations with the described oxalate biosensor.

Biosensing Techniques↗

PubMed1975

Micromethod for lead determination in whole blood by atomic absorption, with use of the graphite furnace.

I describe a micro-scale method for determining lead in whole blood by utilizing a graphite furnace. Sample pretreatment consists of fivefold dilution with a dilute surfactant. The method is directly calibrated with lead standards prepared in dilute HNO3. To eliminate a small, nonspecific absorption signal from the blood matrix, simultaneous background correction is used. Interlaboratory comparison with a flame atomic absorption technique that requires extraction yielded high correlation (r equal to 0.98). Within-run precision (coefficient of variation) ranged from 2 to 4 percent. Lead in blood can be accurately measured in as little as 20 mul of blood, hence the method is suitable for routine laboratory use and for pediatric screening.

Deuterium↗

PubMedDate not supplied

Use of a ruthenium(III), iron(II), and nickel(II) hexacyanometallate-modified graphite electrode with immobilized oxalate oxidase for the determination of urinary oxalate.

This paper describes the performance of a biosensor with an Ru(III), Ni(II), and Fe(II) hexacyanometallate-modified graphite electrode and immobilized oxalate oxidase for the determination of urinary oxalate. The addition of ruthenium enhances the electrochemical reversibility and chemical stability of the electrocrystallized layer and improves the sensitivity of the biosensor. Hydrogen peroxide, produced by the enzyme-catalyzed oxidation of oxalate, was measured at -50 mV vs an Hg Hg2CI2 3M KCl electrode in a solution of pH 3.6 succinic buffer, 0.1 M KCl, and 5.4mM ethylenediaminetetraacetic acid. The linear concentration range for the determination of oxalate was 0.18-280 microM. The recoveries of added oxalate (10-35 microM) from aqueous solution ranged from 99.5 to 101.7%, whereas from urine samples without oxalate (or with a concentration of oxalate below the detection limit) the recoveries of added oxalate ranged from 91.4 to 106.6%. The oxalate in 24 h urine samples, taken during their daily routine from 35 infants and children, was measured and found to range from 0.6 to 121.7 mg/L. There were no interferences from uric acid, acetylsalicylic acid, and urea in the concentration range investigated, but paracetamol and ascorbic acid did interfere. A good correlation (R2 = 0.9242) was found between values obtained for oxalate in real urine samples by 2 laboratories, with the proposed biosensor and ion chromatography, respectively.

Biosensing Techniques↗

PubMed2003

Electroanalytical and spectroscopic characterization of poly(o-phenylenediamine) grown on highly oriented pyrolytic graphite.

The polymerization of ortho-phenylenediamine (o-PD) on Highly Oriented Pyrolytic Graphite (HOPG) at different pH (1,3,5,7) was investigated by electroanalytical and spectroscopic methods. Cyclic voltammetry was used both to polymerize o-PD and to study the electroactivity of the resulting poly(ortho-phenylenediamine) (PPD) film. A redox couple associated to the PPD electroactivity, deeply influenced by the pH adopted during polymerization, was recorded. A correlation between this feature and the electrochemistry shown by the oligomers of o-PD, generated in solution during the polymer synthesis, was also found. A comparison between the absorption spectra, in the visible region, of the soluble oligomers and of the PPD films was also performed, suggesting that changes in both the polymer and the oligomer structure occur and are highly related to the polymerization pH. In particular, a higher degree of conjugation is exhibited by the PPD films electrosynthesised at lower pH and this likely explains the higher conductivity as well as the higher electroactivity shown by the material obtained in these conditions.

Biosensing Techniques↗

PubMed2002

[Determination of trace selenium in milk cow serum with graphite furnace atomic absorption spectrophotometry].

Trace metal selenium in milk cow serums has determined by graphite furnace atomic absorption spectrometry with matrix modifier. It's found that addition the solution of 0.1% Ni(NO3)2 as matrix modifier, the ash temperature will increase up to 1,000 degrees C. 600 degrees C is practically used for ash temperature. D2 lamp is used for background correction. Selenium in milk cow serums was directly determined after addition of 0.1% Ni(NO3)2 without digestion. The method is convenient to determine element in milk cow serum. The results show that the method has good precision and accuracy. The relative standard deviation of selenium. Determination was 4.9%, and the rates of recovery were 93.3%-104%.

Animals↗

PubMed2002

[Determination of six nutritional elements in Chinese herbal medicines by graphite furnace atomic absorption spectrometry].

Method for the determination of nutritional elements in three kinds of chinese traditional and herbal drugs including leaves of Ginkgo biloba L., Eucommiales, and Gynostemma pentaphyllum (Thunb.) Makino were studied. Samples were collected in middle of autumn, washed in water and dried by airing. About 0.5 g accurately weighed sample was digested with mixed acid of HNO3-HClO4 (4:1). Six kinds of elements of selenium, germanium, copper, zinc, iron and manganese in the digested solution were determined by graphite furnace atomic absorption spectrometry (GFAAS) respectively. Accuracy of employed AAS method was tested by the determination of Cu, Zn, Fe, Mn in standard material of peach leaves. The results obtained show proposed GFAAS method is simple, accuracy, rapid and practicable. The contents of Cu, Zn, Fe, Mn in these plant leaves are high. Especially Se in Ginkgo biloba L. and Ge in Gynostemma pentaphyllum (Thunb.) Makino were obviously higher than other herbal drugs. They are worth much more comprehensive utilization. The relation between concentrations of these nutritional elements and curative effect was also discussed.

Copper↗

PubMed2002

[Determination of lead in grape wine by graphite furnace atomic absorption spectrometry with ammonium dihydric phosphate as modifier].

Ammonium dihydric phosphate (NH4H2PO4), palladium chloride, nickelous nitrate and magnesium nitrate were used as modifiers respectively, to directly detect lead in grape wine with graphite furnace atomic absorption spectrometry(GFAAS). The results showed that NH4H2PO4 might be the best modifier. It was found that the organic matter in grape wine interfere with the determination. To remove the interference and detect lead directly with GFAAS, not only did samples need to be diluted with 4 to 10 times sample volumes of de-ionized water, but also the standard addition method was used. The method had good precision and accuracy when concentration of lead was above 10 micrograms.L-1, the relative standard deviations of lead were between -5.4% and 6.2%.

Food Contamination↗

PubMed2001

[Determination of beryllium in atmospheric particulate by graphite furnace atomic absorption spectrophotometer using aluminium as a matrix modifier agent sampling with micropore filter membrane].

Beryllium in the atmospheric particulates is collected with 0.22 micron pore diameter micropore filter membrane, which is determined by graphite furnace atomic absorption spectrophotometer using aluminium as a matrix modifier agent. This sampling method shown several advantages: easy, complete and fast digestion; low membrane blank; high elution recovery, standard addition recovery, precision and accuracy. The addition of 800 mg.L-1 aluminium to beryllium solution allows ashing temperature of 2,000 degrees C. The detection limit of 13.5 ng was obtained.

Air Pollutants↗

PubMed2004

Radiation dosimetry of a graphite moderated radium-beryllium source.

The Brookhaven National Laboratory Sigma Pile is a radium-beryllium neutron source imbedded in a cube of graphite blocks. The pile is approximately 2.13 m on four sides and is 3.07 m high. Thermoluminescent dosimeters were used to determine the neutron and gamma-ray dose rates in the pile. Gamma-ray dose rate measurements have also been made in the air outside of the pile, while the radium-beryllium neutron source was being withdrawn from the pile. The Monte Carlo code has been used to calculate the coupled neutron-photon transport. Measured dose rates at various locations agreed with the calculated values within 5% to 15%.

Algorithms↗

PubMedDate not supplied

Multiresidue analysis of pesticides in vegetables and fruits by gas chromatography/mass spectrometry after gel permeation chromatography and graphitized carbon column cleanup.

A multiresidue method for pesticides that enables quantitative, sequential analysis of a large number of vegetable and fruit samples by gas chromatography/mass spectrometry has been developed. First, 89 important target compounds were selected for monitoring, and then the appropriate internal standards for these pesticides, 14 stable isotopically labeled pesticides (surrogates), were used. The sample was extracted with acetonitrile, and the extract was cleaned up by a salting-out step followed by redissolution in ethyl acetate. Coextractives were removed automatically by gel permeation chromatography with a graphitized carbon column, and then by use of a tandem silica-gel/PSA cartridge column. Recoveries of 82 of the 89 pesticides from fortified spinach, tomato, apple, and strawberry were within a range from 70 to 120%, and the relative standard deviation values of 80 of the 89 pesticides were <5%. The method was applied to 188 commercial vegetable and fruit samples to demonstrate its use in routine analysis.

Chromatography, Gel↗

PubMed2004

[Direct determination of trace arsenic in coal by slurry-sampling graphite-furnace atomic absorption spectrometry].

A method for direct determination of trace arsenic in coal by slurry-sampling Graphite-Furnace Atomic Absorption Spectrometry (GFAAS) was developed, using Pd as a matrix modifier. The effects of slurry stability, particle size of sample, matrix modifiers, ashing temperature, atomization temperature, and common coexisting components on the signal intensity of arsenic were investigated. Under optimized operating conditions, the detection limits and relative standard deviation of this method were 0.054 microg x g(-1) and 8.9%, respectively.

Arsenic↗

PubMed2004

[Determination of selenium in rat's organs by graphite microwave dissolution].

The content of selenium in rat's ten organs was determined by graphite furnace atomic absorption spectrometry with microwave dissolution. Inorganic palladium modifier was added into the sample to solve the problems of selenium volatilization and matrix disturbance as selenium in the sample is liable to receive serious loss during the course of digestion and cineration. The optimistic determination conditions were shown as follow, digestion reagent of 4 mL (10:3)HNO3/H2O2, matrix modification of 50 microg x mL(-1) palladium chloride, cineration temperature of 1200 degrees C and atomization temperature of 1800 degrees C. Under such optimum conditions, the linear range is 0-80 ng x mL(-1) and the detection limit is 1.83 ng x mL(-1). The RSD is less than 8% and the average recovery rate is 97.6%. The method was shown to be precise, reliable, convenient and quick in selenium determination of various organism organs.

Animals↗

PubMed2004

[Determination of arsenic in As2O3-treated esophagoscope-transplant mouse tissue by graphite furnace atomic absorption spectrometry].

As2O3 was injected into tumour tissue of esophagoscope-transplant mouse. The concentration of As diffusing into other tissues was investigated. A method was proposed for the determination of As in tissue samples of mouse by graphite furnace atomic absorption spectrometry. After wet digestion (water-bath at 80 degrees C) with 2:1:1 (psi) of HNO3-H2SO4-HClO4, the digested tissue samples of mouse were diluted with 0.2% Triton X-100-0.4% AgNO3. The matrix-matching calibration curve of non-interference was established with standard addition method. The relative standard deviation was 3.2%-8.7%. The limit of detection was 1.57 microg x L(-1). The recoveries were 81.7%-105% Arsenic concentrations in mouse liver, kidney, brain, left-chest, and right-chest were determined after injection of arsenic at different times.

Animal Feed↗