Showing papers on "Detection limit published in 1978"
TL;DR: A method for the concentration of dilute samples on a column and its application to the analysis of biomedical mixtures is described and the optimal choice of conditions is discussed.
112 citations
TL;DR: A fast, simple high-performance liquid-chromatographic assay for serum alpha-tocopherol, with use of a reversed-phase column and tocol as internal standard, verified by spectrophotometry, gas-liquid chromatography, and combined gas chromatography/mass spectrometry of an eluate collected from the column.
Abstract: We report a fast, simple high-performance liquid-chromatographic assay for serum alpha-tocopherol, with use of a reversed-phase column and tocol as internal standard. Only 200 microliter of serum is required. Isocratic elution of the n-hexane extract is done within 6 min; total analysis time is less than 1 h. Within-day precision (CV) was 2.3% for 24 samples of a normal plasma pool (mean concn, 10.1 mg/liter). Day-to-day precision (CV) was 3.2%, measured for 20 days for a specimen with a concentration of 10.8 mg/liter. Analytical recovery of alpha-tocopherol from fortified serum was 89 to 100%. The lower detection limit of alpha-tocopherol is estimated to be 0.6 mg/liter. The specificity of the procedure was verified by spectrophotometry, gas-liquid chromatography, and combined gas chromatography/mass spectrometry of an eluate collected from the column.
85 citations
TL;DR: Modification of a Perkin-Elmer 603 atomic absorption spectrophotometer by adding a high-intensity tungsten-halogen lamp for background correction significantly improved the detection limit for elements that have analytical wavelengths in the near-ultraviolet and visible regions.
Abstract: Modification of a Perkin-Elmer 603 atomic absorption spectrophotometer by adding a high-intensity tungsten-halogen lamp for background correction significantly improved the detection limit for elements that have analytical wavelengths in the near-ultraviolet and visible regions. Chromium in human serum and urine can be measured, with a simplified sample-handling technique, in concentrations of less than 0.1 microgram/liter. For comparison, the mean value for chromium in the serum of eight men was 0.14 microgram/liter.
64 citations
TL;DR: A method for determining manganese in biological tissues by flameless atomic absorption spectrophotometry, which is simple to perform and does not require prior extraction with solvents.
Abstract: I describe a method for determining manganese in biological tissues by flameless atomic absorption spectrophotometry, It is simple to perform and does not require prior extraction with solvents. Small tissue samples are dried for 48 h at 110 degrees C and dissolved in concentrated nitric acid; the clear acid solution is introduced into the furnace and the sequential drying (120 degrees C, 20 s), charring (800 degrees C, 70 s), and atomization (2400 degrees C, 8 s) are automatically performed. The technique of standard additions was used ot overcome matrix effect. The detection limit is 0.86 X 10(-11) g of Mn. The CV is 4.7%. Only sodium and potassium interfere at 500-fold concentrations, and their interferences were overcome by using the Deuterium Arc Background Corrector.
56 citations
TL;DR: The presence of a 5alpha-dihydrotestosterone tert-butyl-dimethylsilyl ether was detected by this method in an extract of human blood plasma during gas chromatography mass spectrometry.
Abstract: Using the combined electrostatic analyser-magnet scan facility of a double focusing mass spectrometer, the daughter ion peak for the fragmentation, [M-57]+ leads to [M-57-76]+, of a 5alpha-dihydrotestosterone tert-butyl-dimethylsilyl ether was monitored during gas chromatography mass spectrometry. The detection limit was approximately 20 pg. The steroid was detected by this method in an extract of human blood plasma.
50 citations
TL;DR: The method is applied to a human bile sample and shows excellent resolution of the dihydroxy bile acid phenacyl esters, including the cholic acid derivative, which has a detection limit of 265 pmol.
47 citations
TL;DR: Several methods for the preparation of mixed copper(II) sulfide and silver sulfide precipitates have been investigated as mentioned in this paper, and the results of these methods have been tested for their suitability as copper (II)-selective membranes.
42 citations
TL;DR: This method employs the high sensitivity of fluorescence detection together with selective extraction and reversed-phase chromatography to measure concentrations as low as 20 ng of drug/ml of plasma with a coefficient of variation of 3.91%.
36 citations
TL;DR: Correlation chromatography was applied to the high-performance liquid chromatographic separation of phenols in aqueous medium on a reversed-phase column as discussed by the authors, and the detection limit was reduced by a factor of 100.
35 citations
TL;DR: In this paper, a new detection principle for high-performance liquid chromatography is described in which the separation column is coupled to a catalytic detection system, based on the redox reaction between cerium(IV) and arsenic (III) that is catalyzed by trace amounts of iodine.
32 citations
TL;DR: In this article, a microanalytical procedure is described for the quantitative separation of Ag from natural samples by anion exchange and analysis by surface ionization mass spectrometry using silica gelatin as an emitter.
Abstract: A microanalytical procedure is described for the quantitative
separation of Ag from natural samples by anion exchange and
analysis by surface ionization mass spectrometry using silica
gel as an emitter. The isotopic composition of 50 pmol of Ag
can be measured on a Faraday detector with a precision of
0.1%. Isotopic measurements have been made on as little
as 0.15 pmol with a precision of 1% using an electron multiplier
detector. The total procedural blank for the anion exchange
Separation is 0.15 pmol. Using stable isotope dilution 0.5 pmol
of Ag, which Is 3 X 10^(11) atoms, can be measured with a
precision of better than 1% with only a 30% blank correction.
This allows the accurate determination of Ag in natural samples
down to concentration levels of 1 pmol per gram. The ionization
efficiency for Ag is about 1-2% and the detection limit
is 1 fmol. This procedure has been applied to several meteorites, and a standard terrestrial rock.
TL;DR: The method is substantially more accurate and convenient than previously described methods which required chromatographic separations, radioactive substrates, etc.
TL;DR: A rapid quantitative method has been developed for the estimation of nicotine and cotlnlne In blood and urine as discussed by the authors, which is accomplished by adsorption of the alkaloids on AmberIlte XAO-2 resin and subsequent elutlon with chloroform/ methanol.
Abstract: A rapid quantitative method has been developed for the estimation of nicotine and cotlnlne In blood and urine. Isolatlon Is accomplished by adsorption of the alkaloids on AmberIlte XAO-2 resin and subsequent elutlon with chloroform/ methanol. No solvent extraction or further purlllcatlon is required. The final determination Is made by high performanee liquid chromatography using UV detection. Absolute recovery of nicotine was at least 80% in all samples. The accuracy of the method Is estimated to be 5% on standard addition measurements. Detection limits of 2 ng/ml urine may be routinely obtained.
TL;DR: In this paper, a procedure for the gas chromatographic (GC) determination of trace amounts of inorganic mercury is described, where Hg2+ is converted into diphenylmercury (DPM) with tetraphenylborate and the DPM is extracted with toluene.
TL;DR: In this paper, a method for the identification of delta9-tetrahydrocannabinol by gas chromatography mass spectrometry has been developed, and this method has been compared with other techniques, such as detection via thin-layer chromatography using tritium labeled delta9tetraydrocannibinol and a dual gas chromatographic method.
Abstract: A method for the identification of delta9-tetrahydrocannabinol by gas chromatography mass spectrometry has been developed, and this method has been compared with other techniques, such as detection via thin-layer chromatography using tritium labeled delta9-tetrahydrocannibinol and a dual gas chromatographic method. The gas chromatographic mass spectrometric method was found to be equal or superior to other techniques and has the added advantage of being highly specific for the compound analyzed. An alternate approach using chemical ionization is also described; however, this procedure does not show significant advantages over the electron impact method. These methods show a practical lower detection limit of 500 pg ml-1 of plasma in clinical practice.
TL;DR: A high-performance liquid chromatographic procedure is described for the determination of octopamine and a sensitive assay of dopamine beta-monooxygenase (EC 1.14.17.1) activity in human serum with tyramine as the substrate.
TL;DR: In this article, the effects of mobiel phase pH, flow-rate, column temperature, etc., on the separation of catecholamines by high-performance liquid chromatography (HPLC) on Zipax SCX and Zorbax ODS columns were investigated.
TL;DR: Fluorine is measured in a bone matrix using cyclic activation in a reactor system that includes an accurate method for correction of sodium matrix interference due to20F by measurement of the24Na and23Ne photopeaks.
Abstract: Fluorine is measured in a bone matrix using cyclic activation in a reactor system. The detection limit and hence precision is considerably improved when compared with other neutron activation techniques and includes an accurate method for correction of sodium matrix interference due to20F (T=11 s) by measurement of the24Na and23Ne photopeaks. In an interference free matrix the sensitivity is 0.6 μg F. Cyclyc activation, also applied to standard biological materials, will detect ≥10 other elements simultaneously.
TL;DR: Attempted extraction of cytosine arabinoside from plasma with various organic solvents was unsuccessful, but protein precipitation with ethanol or trichloroacetic acid followed by washing of the aqueous residue with organicsolvents to remove as many of the interfering substances as possible gave satisfactory results.
TL;DR: The experimental limit of detection and the interferences for any assembled gas sensor are the analytical features of greatest interest as mentioned in this paper, and theoretical and practical studies of CO2 and SO2 gas sensors are reported.
TL;DR: In this paper, an investigation into the applicability of the Grimm glow-discharge source for the determination of gold, platinum, palladium and certain base metals in silver was undertaken.
Abstract: An investigation into the applicability of the Grimm glow-discharge source for the determination of gold, platinum, palladium and certain base metals in silver was undertaken. An integrated sputtering factor was used as an internal standard. The accuracy of the results and the limit of detection of the method are acceptable. The silver was also determined by this method, with relative standard deviations of better than 0.09%. The precision for gold, palladium, platinum and copper was better than 5% within the analytical ranges determined.
TL;DR: In this article, a method for the determination of hydrazine residue in water is described, which is based on gas chromatography using a nitrogen/phosphorus detector, and the limit of detection is 0.1 part per billion (10 9 ).
TL;DR: A chromatographic method is described, in which 3,4-dihydroxybenzylamine is used as the internal standard, for determining free methyldopa in human urine, which is readily adaptable for use in studies of the pharmacokinetics of methyLDopa and to routine clinical laboratory use.
Abstract: We describe a chromatographic method, in which 3,4-dihydroxybenzylamine is used as the internal standard, for determining free methyldopa in human urine. The drug was adsorbed onto alumina, eluted, and the eluate directly injected onto a reversed-phase column (octadecyl-bonded silica stationary phase), with dilute acetate buffer (pH 2.7) as the mobile phase and ultraviolet detection at 280 nm facilitated. Methyldopa is well separated from other urinary biogenic amines present in the alumina extract, and other commonly used antihypertensives and diuretics do not interfere with the analysis. The sensitivity of the method is adequate to quantify 8.0 mg of methyldopa per liter in 30 ml of sample; the lower limit of detection is 25 ng. Analytical recovery for methyldopa varied from 95 to 102% with within-run and day-to-day coefficients of variation of 2.7 (n = 10) and 3.8% (n = 5), respectively. This procedure is readily adaptable for use in studies of the pharmacokinetics of methyldopa and to routine clinical laboratory use.
LGC1
TL;DR: A method has been developed for the separation, identification and estimation of six mycotoxins in foods at the μg kg−1 level and it has been tested using a range of foods including total diet samples.
Abstract: A method has been developed for the separation, identification and estimation of six mycotoxins in foods at the μg kg−1 level. The food is extracted by using aqueous acetonitrile and the extract is then washed with 2,2,4-trimethylpentane and any mycotoxins re-extracted into chloroform. The extract is then purified using grooved t.l.c. plates coated with silica gel. After chromatography, any fluorescent bands are removed and examined by h.p.l.c. using a fluorescence detector. The method has been tested using a range of foods including total diet samples. Recoveries at twice the detection limit varied from 40 to 95%.
TL;DR: The method has been applied to the determination of the level of copper in the plasma ultrafiltrate of patients with rheumatoid arthritis andInterferences from the salt matrix, the use of background correction and the problems of contamination caused by the low level of Copper are discussed.
Abstract: A method for the direct determination of the level of copper in plasma ultrafiltrate using atomic-absorption spectrometry with carbon furnace atomisation is reported. The relative standard deviation and the detection limit expressed as 2δ were 3.6%(50 µl of 0.05 µg ml–1 copper solution) and 0.0036 µg ml–1, respectively. Interferences from the salt matrix, the use of background correction and the problems of contamination caused by the low level of copper are discussed. The method has been applied to the determination of the level of copper in the plasma ultrafiltrate of patients with rheumatoid arthritis.
TL;DR: Results suggest that the difference in concentration factors between the gills and digestive gland may be based on a quantitative difference in macromolecular binding sites, and that although the soluble protein content of the tissue may influence the final concentration factor, it does not appear to affect the rate at which this equilibrium is achieved.
Abstract: From previous work, the equilibrium concentration factor for dissolved mercury in the digestive gland of Ostrea edulis Linnaeus was found to be three to four times higher than that in the gills. In the present study, an analysis of soluble protein revealed values of 49.3±14.2 mg g wet tissue-1 for the digestive gland and 0.7 ±0.1 mg g wet tissue-1 for the gills. Starvation significantly reduces the soluble protein level of the digestive gland to 31.1±6.4 mg g-1 and that of the gills to below the limit of detection. These results suggest that the difference in concentration factors between the gills and digestive gland may be based on a quantitative difference in macromolecular binding sites. However, the uptake of dissolved mercury over a period of 48 h was considerably greater in the gills, so that although the soluble protein content of the tissue may influence the final concentration factor, it does not appear to affect the rate at which this equilibrium is achieved. A more detailed investigation of the mechanism of dissolved mercury uptake by oyster gills has been carried out using isolated tissues. The process is inhibited by 5mM 2–4 dinitrophenol, by the absence of a readily metabolizable substrate (dextrose) in the uptake medium, and by 30mM K+. The effect of K+ necessitated further investigation with a specific inhibitor of K+ transport. Strophanthin G (ouabain), at a concentration of 0.01 mM, caused a significant increase in mercury uptake.
TL;DR: The characteristics of the ninhydrin amino acid detection system such as sensitivity, detection limit and reproducibility are described and detection limits in the picomole range are obtained.
Abstract: The choice of optimal conditions for the ninhydrin reaction detection of amino acids was studied. By increasing the temperature to 140°C it was possible to reduce the necessary reaction time to about one minute. By using a glass-bead packed bed reactor, peak broadening could be lowered to a level corresponding to a standard deviation of 18 mm3. This allows fast and sensitive amino acid analysis without significant loss in resolution due to the flow reactor. The characteristics of the ninhydrin amino acid detection system such as sensitivity, detection limit and reproducibility are described. Detection limits in the picomole range are obtained.
TL;DR: In this article, a high-performance liquid chromatography (HPLC) separation of tetracycline and its degradation products on a C18-reversed phase column with the mobile phase water, in two steps with varying amounts of acetonitrile, is dascribed.
TL;DR: In this paper, the authors reported improved or new detection limits for the measurement of the atomic emission of involatile elements with a HGA 2200 carbon-furnace atomizer incorporating maximum power heating and temperature control.
TL;DR: The hormones used in practice can be determined with improved sensitivity by coupling to the diazonium compound Fast Dark Blue R Salt and zeranol, estradiol, estriol and estrone are analysed as azo dyestuffs.