Showing papers on "Detection limit published in 1984"
TL;DR: Evidence is presented for a sensitive method useful for the detection of hydroxyl free radical generation in various systems using high pressure liquid chromatography with electrochemical detection (LCED) and hypoxanthine/xanthine oxidase plus chelated iron.
404 citations
TL;DR: A flow cytometer system was used to detect aqueous rhodamine 6G by laser-induced fluorescence and the results presented here allow a projection to single-molecule detection with reasonable improvements to the apparatus.
Abstract: A flow cytometer system was used to detect aqueous rhodamine 6G by laser-induced fluorescence. Best results were obtained with careful spectral and spatial filtering. At the detection limit, the probability of a rhodamine 6G molecule being present in the detector's probed volume of 11 pL is about 0.6 . With a flow rate of 0.42 ..mu..L/s, a detection limit of 8.9 x 10/sup -14/ M was obtained for a 1-s time constant. At the detection limit, 18 ag or 22,000 molecules of rhodamine 6G flowed through the probed volume during the signal integration period. Signal linearity extends over greater than 5 orders of magnitude limited only by saturation of the detection electronics at high concentration. The results presented here allow a projection to single-molecule detection with reasonable improvements to the apparatus. 25 references, 5 figures, 7 tables.
167 citations
TL;DR: In this paper, a new concept, the standardized chromatographic limit of detection (SCLD), is introduced to account for differences in chromatogram bandwidths of experimentally measured LODs.
Abstract: Current problems with the limit of detection (LOD) concept in chromatography are reviewed. They include the confusion of the LOD with other separate, distinct concepts in trace analysis such as the minimum detectability (MD); the use of arbitrary, unjustified models for the calculation of the LOD; the use of concentration units instead of units of amount; and the failure to account for differences in chromatographic conditions when comparing LODS. Solutions to these LOD problems are discussed. Two models are proposed for calculating the chromatographic LOD. A new concept, the standardized chromatographic LOD, is introduced to account for differences in chromatographic bandwidths of experimentally measured LODs. The standardized chromatographic LOD is shown to be a more reliable parameter than the conventional (non-standardized) chromatographic LOD.
160 citations
TL;DR: The high sensitivity enabled the method to measure both stimulants in a single human hair in actual cases, and the detection limit was about 10 pg in an injected volume.
Abstract: A detailed procedure of an extremely sensitive method for quantitation of methamphetamine and amphetamine in human hair by gas chromatography (GC)/chemical ionization (CI) mass spectrometry (MS) is presented. N-methylbenzylamine was used as an internal standard. The samples, after extraction with an organic solvent, were derivatized with trifluoroacetic anhydride before the GC/MS analysis. Quantitation was made with quasi-molecular ions of the derivatives by selected ion monitoring in the CI mode. The detection limit was about 10 pg in an injected volume. The high sensitivity enabled us to measure both stimulants in a single human hair in actual cases.
116 citations
TL;DR: In this article, a two-photon transition between the X1 and the B1 electronical states around 230 nm was used for detection of CO in different environments, including CH4/air flame and in a low pressure dc discharge.
Abstract: Laser-induced fluorescence has been used for detection of CO in different environments. The fluorescence light was obtained by using a two-photon transition between theX1?- and theB1?- electronical states around 230 nm. Cell measurements indicate a detection limit lower than 0.1 ppm. Measurements in a CH4/air flame and in a low pressure dc discharge were realized with a diode-array detector, which was used in an imaging mode, permitting single-shot CO distributions to be captured.
107 citations
TL;DR: Quantitative analysis of micro amounts of amino acids in plasma and urine by the internal standard method gave highly reproducible results with a mean coefficient of variation of less than 3% and r2 = 0.999.
99 citations
TL;DR: In this paper, a single-test-tube procedure for the fluorimetric determination of ng quantities of selenium with diaminonaphthalene, from small samples of animal origin is described.
86 citations
TL;DR: Steady-state plasma levels of bupropion and the metabolites from eight different patients are presented and 10% of the steady-state concentration of internal standard was used in single-dose pharmacokinetic studies, allowing a 10-ng/mL lower limit of detection.
83 citations
TL;DR: In this paper, a new method for the fluorometric detection of K1 and K2 vitamins using post-column electrochemical reduction is described, which is applied to the determination of vitamin K1 in human plasma samples.
77 citations
TL;DR: In this paper, a hybrid sensor for inorganic phosphate and fluoride detection was developed by coupling a potato (Solanum tuberosum) tissue slice and immobilized glucose oxidase with a Clark oxygen electrode, based on the inhibition by either ion of potato acid phosphates catalyzed glucose 6phosphate hydrolysis.
Abstract: A biosensor for inorganic phosphate and fluoride has been developed by coupling a potato (Solanum tuberosum) tissue slice and immobilized glucose oxidase with a Clark oxygen electrode. Measurement is based on the inhibition by either ion of potato acid phosphates catalyzed glucose 6-phosphate hydrolysis. The precision is 1.7% and 6.5% and the lower detection limit 2.5 X 10/sup -5/ M and 1 X 10/sup -4/ M for phosphate and fluoride, respectively. For phosphate determination the hybrid sensor is stable for 28 days or 300 assays. With a higher limit of detection the sensor can be applied in a commercial enzyme electrode based device. Its application for phosphate determination in fertilizer and urine samples is described.
77 citations
TL;DR: A high-sensitivity, low-dead-volume laser-induced fluorescence detector has been designed for use in capillary column liquid chromatography and exhibits femtogram detection limits and a linear dynamic range spanning five orders of magnitude.
TL;DR: In this article, the 1, 10-phenanthroline-hydrogen peroxide-sodium hydroxide system containing a cationic surfactant micelle was used to detect the ultratraces of copper (II) with a detection limit of 0.3 pg.
Abstract: Flow injection analysis, with chemiluminescence detection, is used to determine ultratraces of copper (II) by means of the 1, 10-phenanthroline-hydrogen peroxide-sodium hydroxide system containing cationic surfactant micelle to increase the sensitivity. This permits the determination of copper (II) more selectively than any other chemiluminescent system with a detection limit of 0.3 pg (20-μl sample injection). Lead (II) (10−4 M), the strongest catalyst after copper (II), provides a signal 25% of that for copper (10−8 M).
TL;DR: In this paper, a spectrophotometric detection system was proposed for determinations of transition and rare earth metal ions by post-column mixing with the colour-forming reagents PAR and Arsenazo I, respectively, measuring the absorbance at 498 and 600 nm.
Abstract: Conventional ion chromatography excludes the analyses of anionic species with pK > 7, and transition metals that can form hydroxide precipitates at neutral pH. These limitations come from the combined characteristics of the suppressor column and the electrical conductivity detector. By suitable selection of the detection system, an extension of analytical limits can be achieved. For fast and accurate analyses of cyanide and sulphide ions, with an electrochemical method involving a silver sulphide based ion-selective electrode and a high pH buffered eluent, the detection limit can reach the p.p.b. level. For determinations of transition and rare earth metal ions, a spectrophotometric detection system is proposed. By post-column mixing with the colour-forming reagents PAR and Arsenazo I, respectively, transition metal and rare earth metal ions can be monitored by measuring the absorbance at 498 and 600 nm. The detection limit can reach the 0.1 p.p.m. level with good precision. The working principle and reaction mechanism of the proposed methods are also discussed in detail.
TL;DR: The absolute detection limit, 0.6 ng of bromide, makes this liquid-chromatographic method the most sensitive assay for serum bromides yet reported.
Abstract: In this liquid-chromatographic method for the determination of bromide in human serum, an important and unique feature is pre-analysis ultrafiltration of the sample, which effectively removes proteins. The chromatographic system consists of an anion-exchange column (Whatman Partisil SAX 10-micron particles), an isocratic phosphate-buffered mobile phase, and ultraviolet detection at 195 nm. The absolute detection limit, 0.6 ng of bromide, makes this method the most sensitive assay for serum bromide yet reported. The day-to-day CV ranged from 1.6% to 4.9%. Analytical recovery of bromide added to serum samples ranged from 96.2% to 108.8%. Data on bromide in serum are presented for adults and newborns and for adults given bromide orally.
TL;DR: In this paper, a peroxyoxalate chemiluminescence detection system for liquid chromatography is described, which is used for the detection of the dansyl derivative of a drug with a secondary amine functional group in serum samples.
Abstract: A peroxyoxalate chemiluminescence detection system for liquid chromatography is described. The excitation of fluorophores is generated by the reaction of bis-(2,4,6-trichlorophenyl)oxalate or bis(2,4-dinitrophenyl)oxalate and hydrogen peroxide, which are added to the column effluent. The influence of the solvents and the concentrations of the reagents have been investigated. The influence of the flow cell volume on sensitivity and on band broadening have also been studied and a “chemical band narrowing effect” has been observed. Different types of apparatus have been compared for detection of the emitted light. The system has been used for the detection of the dansyl derivative of a drug with a secondary amine functional group in serum samples. The detection limits are in the 1–10pg range.
TL;DR: A rapid and simple assay for catechol-O-methyltransferase (COMT) activity by high-performance liquid chromatography with electrochemical detection is described, which is very suitable for screening of COMT activity as well as for determining the meta/para product ratios.
TL;DR: In this article, the chemiluminescence (CL) post-column reaction to microbore column (250 × 1 mm I.D., 10 μm) high-performance liquid chromatography is described for the sensitive detection of Dns-amino acids.
TL;DR: The method yields a linear response over at least three orders of magnitude, and in most cases the detection limits are better than those obtained by fluorescence detection with the same fluorometer.
TL;DR: A Finnigan 4500 mass spectrometer was modified to perform direct liquid introduction high-performance liquid chromatography (DLI-HPLCMS) as discussed by the authors, which provided molecular weight information with sub microgram detection limits and greatly increased specificity over HPLC detection.
TL;DR: In this article, a post-column detection system using the bis(2,4,6-trichlorophenyl) oxalate-hydrogen peroxide chemiluminescence reaction was described for the analysis of sixteen Dns-amino acids.
TL;DR: By the proposed method, ng ml levels of phosphorus can be determined, and the detection limit is about 0.1 ng ml , and the method can also be applied to the determination of phosphorus in river water and sea-water.
TL;DR: A technically simple, rapid and sensitive high performance liquid chromatographic assay for cis-dichlorodiammineplatinum (II) in human plasma ultrafiltrate and urine is described and the detection limit was less than 50 ng/ml using only 1 ml of biological fluid.
TL;DR: A sensitive and specific procedure for quantifying plasma catecholamines using on-line trace enrichment high performance liquid chromatography with electrochemical detection (HPLC-EC) is described, which yields a lower working limit of detection of 25 pg norepinephrine and epinephrine per milliliter plasma.
TL;DR: A highly sensitive and specific liquid chromatographic procedure with peroxyoxalate chemiluminescence detection has been developed for the determination of fluocortin butyl, a 3 alpha-ketocorticosteroid, in blood plasma.
TL;DR: In this article, a postcolumn fluorescence detection system was introduced for the detection of oxidizable anions in anion-exchange chromatography, and the anions (nitrite, thiosulfate, and iodide) were analyzed by this system using their reaction with Ce(IV) to produce the fluorescent species Ce(III).
Abstract: A postcolumn fluorescence detection system is introduced for the detection of oxidizable anions in anion-exchange chromatography. The anions (nitrite, thiosulfate, and iodide) are analyzed by this system using their reaction with Ce(IV) to produce the fluorescent species Ce(III) in a postcolumn-packed bed reactor. In addition, the nitrate and nitrite anions are determined simultaneously by using a postcolumn copperized reductor to reduce nitrate to nitrite prior to its oxidation with Ce(IV). The detection limit of this method is at the low ppb level with a linear dynamic range covering 2-3 orders of magnitude.
TL;DR: In this paper, a sensitive and selective method was developed for the determination of serum concentrations of erythromycin A by high performance liquid chromatography with electrochemical detection, which was extracted from alkalinized serum samples with methyl t-butyl ether, and the samples were reconstituted in acetonitrile/ammonium acetate and washed with hexane.
Abstract: A sensitive and selective method has been developed for the determination of serum concentrations of erythromycin A by high performance liquid chromatography with electrochemical detection. Erythromycin was extracted from alkalinized serum samples with methyl t-butyl ether. After evaporation of the ether, the samples were reconstituted in acetonitrile/ammonium acetate and washed with hexane. Aliquots were injected onto a Sepralyte diphenyl column. The mobile phase consists of acetonitrile/sodium perchlorate/ammonium acetate/methanol under isocratic conditions. Eluted peaks were detected by dual coulometric electrodes operated in the oxidative screen mode. The recovery of erythromycin from serum was 84%. Assay limit of quantification was 0.05 μg/ml serum, and dynamic linear range was 0.05–1.5 μg/ml. This method was used to quantitate both erythromycin and its gastric degradation products from human serum. Additionally, other macrolide antibiotics could be quantified by electrochemical detection. A...
TL;DR: In this paper, high-resolution gas chromatography of the butylated acids isolated on an anion exchange resin was used to identify Nitrilotriacetic acid in waters and waste-waters.
TL;DR: In this article, small precolumns packed with a resin-based strongly acidic cation exchanger were successfully used for the preconcentration of nine polar anilines, with subsequent determination by liquid chromatography with UV absorbance or electrochemical detection.
TL;DR: An analytical technique is described for the determination of nitrated polycyclic aromatic hydrocarbons (nitro-PAH) in diesel particulates using capillary gas chromatography and the presence of PAH and related derivatives does not interfere with the analysis.
Abstract: An analytical technique is described for the determination of nitrated polycyclic aromatic hydrocarbons (nitro-PAH) in diesel particulates. It involves the use of capillary gas chromatography for the separation of nitro-PAH and subsequent detection by chemiluminescence. The detection limit of the method is determined to 10-25 pg injected on-column. 1-Nitronaphthalene, 2-nitronaphthalene, 2-nitrofluorene, and 1-nitropyrene were selectively detected in the sample. The presence of 1-nitronaphthalene and 1-nitropyrene were unequivocally confirmed by mass spectrometry. Because of detector selectivity to nitro compounds, the presence of PAH and related derivatives does not interfere with the analysis. The technique is useful for the screening of nitroaromatics in complex environmental samples. 35 references, 3 figures, 2 tables.
TL;DR: In this article, a method was developed for the determination of several munitons components (nitro-organic compounds) in environmental waters based on Porapak resin adsorption of the munitions components.