Development of a chemiluminescence immunoassay for salivary progesterone using microtitre plates as a solid phase

Progesterone is determined in whole saliva by a direct solid-phase chemiluminescence immunoassay (CIA), which uses a monoclonal antibody raised against progesterone-11α-hemisuccinate bovine serum albumin (BSA) and the homologous marker conjugate progesterone-11α-hemisuccinate aminobutylethylisoluminol. Rabbit anti-mouse immunoglobulins (second antibody) are coated on the wells of Nunc Maxisorb microtitre plates during an overnight incubation. Then monoclonal anti-estradiol antibody is bound overnight to the second antibody and residual “binding” places are blocked with BSA. Saliva is frozen, thawed and the clear supernate obtained after centrifugation is used. The calibration graph is linear over the range 3–200 pg of progesterone and the detection limit is 1.6 pg per well (0.096 nmol l^?1). The mean recovery of added progesterone is 97%. The within-assay relative standard deviation (RSD) is 2.7–9.7% for 0.3–5.4 nmol l^?1 progesterone and the between-assay RSD is 5.7–10.6% for 0.79–3.7 nmol l^?1 progesterone. In pregnancy salivary progesterone rises from 1 nmol l^?1 (6–15 weeks) to 4 nmol l^?1 (36–40 weeks).     

Flow-injection technique for the determination of low levels of phosphorus in natural waters

An inexpensive flow-injection instrument for determining low concentrations of dissolved reactive phosphorus in natural waters is reported. The unique feature is the use of an inexpensive detector consisting of a flow cell and a simple photometer that incorporates a super-bright light-emitting diode as the source and a photodiode as the detector. The tin(II) chloride-molybdate method was optimized using a modified simplex optimization method. Silicate interference up to 5 mg Si l^?1 was removed by addition of 0.10% (w/v) tartaric acid. Using the tartaric acid-modified optimized reagents, a detection limit of 0.6 μg P l^?1 was achieved. The method was linear over the range 0–100 μg P l^?1 with an excellent precision (r.s.d. 2.9% at 2.0 and 0.5% at 50 μg P l^?1). An in-line pre-concentration anion-exchange column was used to obtain an even lower detection limit of 0.1 μg P l^?1 and applied to the analysis of real samples.     

Flow-through pH-ISFET as detector in the determination of ammonia

A simple flow-injection metod for the determination of ammonium ions in water, based on a flow-through pH-ISFET, is described. Ammonium is converted to ammonia, which diffuses through a microporous hydrophic membrane into an ammonium chloride recipient stream, forming a pH buffer which is monitored by the semiconductor detector. The linear working range extends from 0.1 to 10 mmol l^?1 with a relative standard deviation of ca. 1% at the 0.7 mmol l^?1 level.     

Automated direct determination of chromium in blood and urine by electrothermal atomic absorption spectrometry

A simple direct procedure for the determination of chromium in whole blood and urine by graphite-furnace atomic absorption spectrometry is described. Whole blood samples are diluted with 0.1% Triton-X solution before injection, whereas urine samples are injected directly. Calibration is done by direct comparison against matrix-matched standards. Between-run precision is 5.4% at 154 nmol l^?1 for urine and 3.6% at 142 nmol l^?1 for blood. The detection limits are 3.8 nmol l^?1 for urine and 11.5 nmol l^?1 for blood, each for a 20μl sample. The calibration range extends up to 770 nmol l^?1 for both blood and urine. This allows the determination of chromium in both occupationally exposed and unexposed groups. The graphite-furnace conditions for each matrix are similar. Elimination fo sample pretreatment minimizes the risk of contamination and allows a rapid sample throughput of 50–60 samples per day. The methods described are particularly suited for the screening and surveying of populations occupationally exposed to chromium.     

Continuous-flow extraction of organophosphorus pesticides coupled on-line with high-performance liquid chromatography

A continuous-flow extraction system coupled on-line with a high-performance liquid chromatograph with an ultraviolet detector is used to study the extraction of three organophosphorus pesticides (fenthion, azinphos methyl and diazinon) from aqueous samples with n-heptane as the organic solvent. Diazinon was not extracted significantly. The influence on the extraction of different parameters (coil length, flow rate and phase volume ratio) were studied. The calibration graphs are linear for 0.5–7 mg l^?1 and 8–20 mg l^?1 foor azinphos methyl where the percentage extraction (E%) is 90% and 70%, respectively, and up to 4 mg l^?1 for fenthion, where the E% is 33%. The detection limits and the relative standard deviations are 0.04 and 0.09 mg l^?1, and 3.4 and 5.3%, for azinphos methyl fenthion, respectively. Other pesticides and related compounds were found not to interfere. The sample throughput of this method was 15 h^?1.     

An optical-fibre laser photometer for on-line measurements

An optical-fibre laser photometer is described for measuring on-line the concentration of the different oxidation states of uranium and plutonium. It is based on a dye laser with five exchangeable curvettes containing five different dyes. The dye laser is pumped by a nitrogen laser. To compensate for the influence of the concentration of nitrate on the absorbance of the different species, the conductivity of the solution is measured to give a correction factor. Fibre optics are used to connect the dye laser, the optical flow-through cell and the photometer. The deviation for the plutonium concentration for single-sample analysis is <1 g l^?1 for concentrations up to 50 g l^?1, and in the on-line mode is <0.14 g l^?1 for the same concentration range. For uranium, the deviation is <3.07 g l^?1 for a concentration range up to 77 g l^?1 in the on-line mode.     

Determination of cobalt at picogram levels by high-performance liquid chromatography with chemiluminescence detection

A simple cation-exchange chromatographic system was used to separte cobalt from other metal ions. The cobalt thus separated was detected by the luminol chemiluminescence reaction using a spectrofluorimeter as the detector. A 3σ detection limit of 0.5 ng l^?1 was achieved, without the need for preconcentration, with a 200-μl sample. The system provided a linear analytical working range from 5 ng l^?1 to 10 μg l^?1. The cobalt content of a rice flour certified reference material was determined using the system and gave good agreement with the certificate value.     

A piezoelectric crystal detector for determination of acetoin in air

A method is presented for the determination of acetoin (3-hydroxy-2-butanone) in air with a piezoelectric crystal detector coated with semicarbazide. The response time is about 5 min, is fully reversible, and is selective for acetoin in the presence of the interferences normally found in air. The detector has a sensitivity of 12.4 Hz 1 μl^?1 for acetoin and the response varies linearly with concentration in the 50– μl l^?1 range.     

Immobilization of lactate as an electroactive indicator on pencil graphite electrode for the development of a new electrochemical biosensor for the detection of lactate dehydrogenase

A biosensor was developed for the detection of lactate dehydrogenase (LDH) enzyme using a lactate modified pencil graphite electrode (PGE). The sensor relies on the immobilization of the lactate on PGE, and LDH detection is based on the decrease of lactate peak current following oxidation to pyruvate in the presence of LDH. Square wave voltammetric technique was used for the assay of signals in the range of ?0.6 to 0.8 V and a frequency of 25 Hz for the determination of LDH. The dependence of the response was investigated in terms of reaction time, washing time and LDH and NAD⁺ amounts. Also, the electrochemical behavior of LDH treatment on the lactate modified PGE was studied. The electrode showed good selectivity, repeatability and an operational stability of about 90% of its original response for two weeks. Moreover, the sensor displayed a linear response range from 0.36?C2.13 U ??l^?1 for LDH with a detection limit of 0.16 U ??l^?1. The response time of the LDH-treated lactate modified PGE was found to be 2 s. The relative standard deviation (RSD) obtained was 3.5% (for LDH 0.71 U ??l^?1 and n = 3).     

Determination of boron in water by flow injection/inductively coupled plasma emission spectrometry

A method is described involving flow injection and inductively coupled plasma emission spectrometry for the determination of boron (0.5–25 mg l^?1) in water at a sampling rate of 320 h^?1. An 11-ml capacity cloud chamber, with a tangential aerosol outlet, was used to introduce the nebulized sample to the plasma. The sample volume injected was 300 μl. The relative standard deviation for peak height was 3% for 10 mg l^?1 of boron at a carier flow-rate of 3.5 ml min^?1. The wash-out between samples was improved by using the 11-ml cloud chamber rather than a conventional 110-ml chamber.     

Spectrophotometric determination of micro amounts of cationic polymeric flocculants by flow injection analysis

Cationic polymeric flocculants in water are determined spectrophotometrically with the anionic compound 3-(2-hydroxy-3-carboxyanilide-1-azonaphthalene)-4-hydroxybenzenesulfonic acid at pH 10 by flow injection analysis. The calibration graph at 680 nm is rectilinear from 0 to 20 mg l^?1 under optimal conditions. The relative standard deviation for 20 injections of Cat-Floc (10 mg l^?1) was 1.2%; the sample throughput was 60 h^?1.     

Peroxidase-catalysed rupture of the CF bond as and indicator reaction for enzyme immunoassay : Kinetic determination of human immunoglobulin G, α-fetoprotein and placental lactogen

A fluoride ion-selective electrode is utilized as a sensor for the kinetic determination of peroxidase label in enzyme immunoassays. The method is based on a sandwich enzyme-linked immunosorbent assay (ELISA) technique, the peroxidase-catalysed rupture of the covalent CF bond in 4-fluorophenol and the subsequent release of fluoride ions. The determination of human immunoglobulin G (lgG), human α-fetoprotein (AFP) and human placental lactogen (HPL) was investigated. The potentiometric measurement of the rate of release of fluoride ion within 5 min provided a direct correlation with the concentration of analyte present in the sample. The concentration ranges investigated for the analytes were IgG 30 μg l^?1–10mg l^?1, AFP 5–500 μg l^?1 and HPL 60 ng l^?1–1 mg l^?1. Under the given experimental conditions, the detection limits were IgG 30, AFP 12.8 and HPL 1 μg l^?1. Replacing the rate method with the fixed-time mode (15–30 min) did not improve the detection limits. The performance of the present method was found to be comparable to that of the spectrophotometric detection technique.     

Flow-injection spectrophotometric determination of palladium in catalysts and dental alloys with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropyl-amino)aniline

2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline rapidly forms a water-soluble complex with palladium in an acetate-buffered medium at pH 3.2.The molar absorptivity of the complex is 9.84×10⁴l mol^?1 at 612 nm. The calibration graph is linear over the range of 10–100 μg l^?1 palladium; the detection limit is 2 μg l^?1 and the relative standard deviation is 0.6% for 100 μg l^?1 palladium. The sample throughput is 50 h^?1. Divalent transition metals (Fe, Ni, Co) do not interfere at levels from 2 to 10 mg l^?1. Interference from copper is prevented by adding 10^?3 M EDTA solution to the carrier stream. Palladium in solutions of catalysts and dental alloys can be determined selectively, sensitively and rapidly.     

Flow-injection spectrophotometric determination of glucose in blood plasma with bindschedler's green leuco base as color reagent

The hydrogen peroxide produces in the oxidation of glucos in an immobilized glucose oxidase reactor is determined by using Bindschedler's green (leuco base) as color reagent with iron(II) as catalyst; the increase in the absorbance at 725 nm is measured. For 100-μl samples, calibration was almost linear in the range 0–2.5 mg l^?1 glucose; the relative standard deviation for 1 mg l^?1 glucose was 0.6% (n=10) and the detection limit (S/N= 2) was 0.02 mg l^?1. The injection rate was 20 h^?1. Glucose was determined satisfactorily in control sera and in real blood sera.     

Flow-injection spectrophotometric determination of fluoride based on alizarin fluorine blue in the presence of sodium dodecyl sulphate

The stopped-flow reagent-injection method proposed for the spectrophotometric determination of fluoride with lanthanum (III)/alizarin fluorine blue in the presence of sodium dodecyl sulphate at pH 4.6 (λ_max=574 nm) provides a linear calibration graph for 0.08–1.2 mg l^?1 fluoride. The relative standard deviation (n=10) was 0.2% at 0.60 mg l^?1 fluoride. The sampling rate was 60 h^?1. The method is applied to sea and bottled mineral waters with satisfactory results.     

Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 μg l^?1 of tin in the MIBK solution or 0.2–0.3 μg g^?1 in the rock. The concentration range is linear between 2.5 and 500 μg l^?1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 μg l^?1 level and < 7% at the 10–30 μg l^?1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 μg g^?1 or less.     

Determination of coumarins by voltammetric techniques in micellar and emulsified media

An electroanalytical study of the oxidation processes of umbelliferone and hymecromone at a glassy carbon electrode in micellar solution and emulsified medium by different voltammetric techniques is described. The non-ionic surfactant Triton X-405 in acetate-buffered medium at pH 4.8 was found to be the most suitable. Different ranges of linearity were obtained in the micellar solutions, depending on the technique used; the limits of determination for differential pulse voltammetry (DPV) at a stationary electrode were 2.9×10^?6 mol l^?1 and 3.3×10^?6 mol l^?1 for umbelliferone and hymecromone, respectively. In the emulsified medium formed with a mixture of toluene and ethyl acetate (3:2), the oxidation processes yielded similar results. With DPV, linear calibration plots were obtained in the ranges 1.0×10^?5–9.0×10^?7 mol l^?1 umbelliferone and 1.0×10^?5–2.0×10^?6 mol l^?1 hymecromone. The media used are predominantly aqueous so that special reference electrodes and solvent purification are not needed.     

Trace Analysis of Lead and Copper Ions in Fish Tissue Using Paste Electrodes

Abstract

DNA was immobilized onto a carbon nanotube surface through cyclic voltammetry, in which paste electrode (PE) was subjected to lead and copper trace ion analysis. Optimized conditions for square‐wave stripping voltammetry were then searched. The results indicated three other linear working ranges—3–21 mg l^?1, 2–16 µg l^?1, and 3–17 ng l^?1 Pb(II) Cu(II)—within an accumulation time of 190 s in 0.1‐M ammonium phosphate electrolyte solutions of pH 10.0. At the optimized conditions, the detection limit (S/N) was pegged at 0.4 ng l^?1 (1.93×10^?12 M Pb(II) and 6.29×10^?12 M Cu(II)). And the relative standard deviation at 10 mg l^?1 Pb(II) and Cu(II) was a 0.074 and 0.069% precision, in 15 measurements. The method can be applied to assays of fish tissue.     

Vibrational circular dichroism in the mid-infrared

Vibrational circular dichroism (VCD) has been measured for the First tune in the CH₂ bending region down to 1250 cm^?1. This advance in technique was facilitated by the addition of a carbon-rod light source, a cooled HgCdTe detector, and signal averaging to our instrument.     

Preconcentration and Spectrophotometric Determination of Chromium (VI) and Total Chromium in Drinking Water by the Sorption of Chromium Diphenylcarbazone with Surfactant Coated Alumina

Abstract

A simple and inexpensive method for determining chromium (VI) in drinking water by spectrophotometry after preconcentration with sodium dodecyl sulphate (SDS) coated alumina column is described. Chromium(VI) is reacted with diphenylcarbazide (DPC) and the Cr-DPC complex is quantitatively adsorbed onto a SDS coated alumina column from 800 ml of sample solution. The complex is then eluted with a 8 ml mixture of methanol, acetone and hydrochloric acid and determined by spectrophotometry. Total chromium can be determined after oxidation of chromium (III) to chromium (VI) by KMnO₄. The relative standard deviation (10 replicate analyses) at the 10 μg l^?1 of chromium (VI) and 10 μg l^?1 of total chromium were 3.5% and 3.4% and corresponding limits of detection (based on 3 σ) were 0.040 μg l^?1 and 0.033 μg l^?1, respectively.