Determination of lead in gasoline by a flow-injection technique with atomic absorption spectrometric detection

The gasoline sample is treated with iodine and Aliquat-336 and diluted with 4-methylpentan-2-one; 100 μl is injected into a flowing acetone stream for aspiration into an atomic absorption spectrometer. Calibration is linear in the range 0/2-16 mg l^?1 lead. Results for commercial gasoline samples agree well with those obtained by published titrimetric and atomic absorption methods. The precision for samples containing 300/2-400 mg l^?1 lead is ±1%; with increased recorder amplification, the limit of detection is 0.1 mg l^?1 lead. The method is rapid and economic.     

Spectrophotometric and fluorimetric determinations of trichothecene mycotoxins with reagents for formaldehyde

Several trichothecene mycotoxins, such as fusarenone-X (F-X) and T-2 toxin (T-2), readily liberate formaldehyde on heating with sulfuric acid. Spectrophotometric and fluorimetric methods for the determination of trichothecenes with reagents for formaldehyde are therefore possible. F-X (or T-2) can be determined in the 50–1000 mg l^-1 (or 50–1500 mg l^-1) range by the chromotropic acid method, in the 30–1200 mg l^-1 (or 50–2000 mg l^-1) range by the phenyl J acid method, and in the 1.25–25 mg l^-1 (or 2–40 mg l^-1) range by the J acid method. Other trichothecenes, neosolaniol, nivalenol, tetraacetylnivalenol, diacetoxyscirpenol and HT-2 toxin, etc. also give positive reactions but trichothecin and dihydronivalenol do not.     

Spectrophotometric determination of lithium ion with the chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromethylphenyl-4′-aminobenzo-14-crown-4

A spectrophotometric method of determining alkali metal ions with a chromogenice crown ether reagent was found to be more selective and sensitive than an ion-pairing method based on the same size of crown ether cavity. It is shown that in the ion-pairing method, the sensitivity toward lithium ion was 5.685 × 10^?4 absorbance/mg l^?1, with sodium interfering at 300 mg l^?1. The chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromeethylphenyl-4′-aminobenzo-14-crown-4, was much superior to benzo-14-crown-4. The sensitivity of the chromogenic crown ether was 1.69 × 10^?3 absorbance/mg l^?1. This represents a three-fold increase in sensitivity and less reagent is needed (2 × 10^?4 M for the chromogenic method versus 1.4 × 10^?3 M for ion-pairing). Interference from sodium decreased to 3000 mg l^?1. The reagent was used to determine lithium ion in treated blood serum samples in both a batch and flow injection method and results were compared with data obtained with atomic absorption; excellent agreement was obtained in all cases.     

Determination of lead in whole blood with a simple flow-injection system and computerized stripping potentiometry

An automated (24 samples/hour) procedure is described for the determination of lead (0–1000 μg l^?1) in human blood based on flow-injection stripping potentiometry. The samples are diluted 20-fold with 0.5 M hydrochloric acid containing 100 mg l^?1 mercury and 40 μg l^?1 cadmium (II), and a 1.1 ml aliquot is injected into the flow system. With a mercury-coated carbon fibre as working electrode, lead (II) is determined by using cadmium (II) as internal standard and a calibration graph prepared from bovine blood. Analyses of two human blood reference samples yielded results of 335±37 and 691±24 μg l^?1 lead, the certified values being 332 and 663 μg l^?1, respectively.     

Determination of molybdenum at μ l−1 levels by catalytic spectrophotometric flow injection analysis

A flow injection analytical method based on the catalytic action of molybdenum on the oxidation of iodide by hydrogen peroxide in acidic medium is proposed. The triiodide formed is measured spectrophotometrically at 350 nm. Molybdenum is determined in natural water samples without preconcentration at a sampling rate of 90 h^?1 with 200-μl sample injections. The detection limit is 0.7 μ l^?1 and the calibration curve is linear over the range 1–1000 μ l^?1. The relative standard deviation is 0.83% for 50 μ l^?1 molybdenum and 1.9% for 13 μ l^?1 molybdenum.     

Comparison of four chromogenic reagents for the flow-injection determination of aluminum in water

Pyrocatechol violet (PCV), aluminon, eriochrome cyanine R (ECR) and eriochrome cyanine R with cetyltrimethylammonium bromide (ECR/CTA) are compared as chromogenic reagents for the flow-injection determination of aluminium in water. The detection limit of the ECR/CTA method is 1 μg Al 1^?1. The detection limits of the PCV and ECR methods are 5 μg Al 1^?1. The aluminon method is the least sensitive, with a detection limit of 50 μg Al l^?1. Interference from iron, fluoride, phosphate and the acidity of the sample were investigated. The interference from iron is suppressed by hydroxylammonium chloride/1,10-phenanthroline in the PCV and ECR/CTA methods at concentrations less than 5 mg Fe l^?1. In the ECR and aluminon methods, iron <5 mg l^?1) is masked by ascorbic acid. Fluoride at <0.2 mg l^?1 can be tolerated in all methods. The aluminon method can tolerate up to about 500 mg l^?1 in the three other methods. All methods are sensitive to changes in acidity of the samples; the acidity should be 0.08–0.12 M HCl.     

Flow-injection spectrophotometric determination of aluminium in water with pyrocatechol violet

Optimum conditions for the adaptation of the spectrophotometric pyrocatechol violet method for aluminium to a flow-injection system are described. The detection limit is 3 μg Al l^?1 and calibration graphs are linear up to 3 or 10 mg l^?1 (with 200-μl or 10-μl injection loops, respectively). The relative standard deviation is 〈 2% at 0.1 mg Al l^?1. Potential interferences of 40 common inorganic ions and of 20 organic substances, including fulvic acid, are reported. With the use of conventional masking agents and predigestion of samples with high organic content, the method is suitable for determining total aluminium in natural waters.     

Simultaneous spectrophotometric determination of calcium and magnesium with chlorphosphonazo-III by flow injection analysis

In this flow-injection method, the total concentration of calcium and magnesium is determined by using triethanolamine/hydrochloric acid buffer (pH 7.0) and chlorphosphonazo-III (CPA-III) in the flow streams, and the concentration of calcium alone is determined by using 1.6×10^?3 M hydrochloric acid and CPA-III in the flow treams. At pH 7.0, medium, the linear calibration ranges were 0–2.00 mg l^?1 for both calcium and magnesium and the detection limits were each 0.02 mg l^?1; at pH 2.2, the linear calibration range for calcium and the detection limit were 0.20–2.00 mg l^?1 and 0.1 mg l^?1, respectively. Injection rates are 200 h. The method is suitable for analyzing natural waters.     

Continuous flow extraction of indium with bis(2-ethylhexyl)phosphoric acid in 4-methylpentane-2-one coupled on-line with flame atomic absorption spectrometry

Extraction in liquid-liquid segmented flow is used for preconcentration of indium from dilute nitric acid solutions into bis(2-ethylhexyl)phosphoric acid dissolved in 4-methylpentane-2-one. The extraction setup is coupled on-line with flame spectrometry to give a fully mechanized system. The detection limit of the method is 0.03 mg l^?1, the calibration plot is linear up to 1.75 mg l^?1. Repeatability is 1.5% RSD measured at 1 mg l^?1. Sample throughput is 60 h^?1.     

Determination of sulphur(II) compounds by flow injection analysis with application of the induced iodine/azide reaction

Sulphur(II) compounds that rapidly induce the iodine/azide reaction are determined by injection of 10-μl samples into an iodine/azide solution at a flow rate of 1.4 ml min^?1. Iodine consumption in the induced reaction is detected by biamperometry with platinum electrodes. The linear calibration ranges depend on the concentration of iodine in the iodine/azide solution pumped. The detection limit for thiosulphate, 2-mercapto-pyrimidine, 2-thiouracil, 2-thiobarbituric acid or 6-mercaptopurine is 0.1 mg l^?1 and for sulphide, cysteine, thiourea or glutathione is 0.2 mg l^?1 in the injected sample.     

The kinetic determination of clinically significant enzymes in an automated flow-injection system with fluorescence detection

An automated flow-injection manifold is described for the kinetic determination of enzyme activities by a stopped-flow procedure with fluorescence detection. The linear calibration range for alkaline phosphatase is 0/2-250 U l^?1 with a precision of 2%; sample thoughput is 35/2-40 h^?1. Linear responses were also obtained for lipase (0/2-100 U l^?1), acethylcholinesterase (0/2-500 U l^?1) and chymotrypsin (0/2-200 U l^?1). The advantages of this approach to the determination of plasma enzyme activities include sensitivity and the small sample and reagent volumes needed.     

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.     

Vergleichende untersuchungen zur titrimetrischen,photometrischen und ionen-chromatographischen hydrogencarbonat-bestimmung in trink-und mineralwässern: A comparison of titrimetric,spectrophotometric and ion-chromatographic methods for the determination of hydrogencarbonate in drinking and mineral waters

A photometric method for hydrogencarbonate determination in various natural waters is presented, based on measurements with methyl red. Accuracy of the results is demonstrated by comparison with titrimetric and ion-chromatographic methods. The photometric method is suitable for contents in the range of 1–2000 mg l^?1. The linear range of the continous flow method varies form 6–60 mg l^?1 to 12–90 mg l^?1 depending on conditions.     

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.     

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.     

Sequential flow-injection determinations of calcium and magnesium in waters

A tubular PVC membrane electrode for calcium without inner reference solution and a device for location of the reference electrode are described. In the flow-injection system, calcium is determined potentiometrically and then magnesium is determined by atomic absorption spectrometry. The electrode provides linear response to calcium in the range 5 × 10^?5/2-10^?1 M. On-line dilution of the sample allows magnesium determination in the range 0/2-10 mg l^?. Flow rates between 3 and 6 ml min^?1 are possible. The sampling frequency is 60/2-90 h^?1.     

Spectrophotometric determination of vanadium(V) with methoxypromazine maleate and its application to vanadium steels and minerals

The reagent in 8-fold excess forms a violet species with vanadium(V) instantaneously in 1–3 M phosphoric acid. The absorption maximum is at 565 nm; the molar absorptivity is 1.65 × 10⁴ l mol^?1 cm^?1. Beer's law is obeyed over the range 0.1–6.5 mg l^?1 vanadium (V); the optimum range is 0.3–6.0 mg l^?1; the Sandell sensitivity is 3.1 ng cm^?2. The method is simple and selective. The method is applicable for the determination of vanadium in vanadium steels and minerals.     

Biotransformation of arsenate to arsenosugars by Chlorella vulgaris

Chlorella vulgaris was cultivated in a growth medium containing arsenate concentration of <0.01, 10, 100 and 1000 mg l^?1. Illumination was carried out in 12 h cycles for 5 days. The health status of the culture was monitored by continuous pH and dissolved oxygen (DO) readings. Destructive sampling was used for the determination of biomass, chlorophyll, total arsenic and arsenic species. The chlorophyll a content, the DO and pH cycles were not significantly different for the different arsenate concentrations in the culture. In contrast, biomass production was significantly (p < 0.05) increased for the arsenic(V) treatment at 1000 mg l^?1 compared with 100 mg l^?1. The arsenic concentration in the algae increased with the arsenate concentration in the culture. However, the bioconcentration factor decreased a hundred‐fold with increase of arsenate from the background level to 1000 mg l^?1. The arsenic species were identified by using strong anion‐exchange high‐performance liquid chromatography–inductively coupled plasma mass spectrometry analysis after methanol/water (1 : 1) extraction. The majority (87–100%) of the extractable arsenic was still arsenate; arsenite was found to be between 1 and 6% of total extractable arsenic in the algae. In addition to dimethylarsinic acid, one unknown arsenical (almost co‐eluting with methylarsonic acid) and three different arsenosugars have been identified for the first time in C. vulgaris growing in a culture containing a mixture of antibiotics and believed to be axenic. The transformation to arsenosugars in the algae is not dependent on the arsenate concentration in the culture and varies between 0.2 and 5% of total accumulated arsenic. Although no microbiological tests for bacterial contamination were made, this study supports the hypothesis that algae, and not associated bacteria, produce the arsenosugars. Copyright © 2003 John Wiley & Sons, Ltd.     

Picomole‐level Formaldehyde Determination in Gaseous and Beer Samples Using Flow Injection Chemiluminescence Analysis

Based on the linear enhancement of formaldehyde (FA) within 7.0 ～ 1000 pmol l^?1 on luminol—bovine serum albumin (BSA) chemiluminescence (CL) system, FA determination in air and beer samples using CL with flow injection (FI) was proposed. The detection limit was 2.5 pmol l^?1 (3σ) and the relative standard deviations were less than 4.5% (n = 7). At a flow rate of 2.0 mL min^?1, a whole analysis from sampling to washing only needed 32 s, offering a sample throughput of 112 h^?1. This proposed method was successfully utilized to determine FA vapor pressure in liquid (121.8 ± 3.8 Pa), FA content in real air sample (8.93 ± 0.03 mg m^?3), and FA levels in beer (199.5 ± 5.6 ～ 225.2 ± 3.5 mg l^?1), giving determination recoveries from 90.7% to 109.3%. The mechanism of BSA—FA interaction was also investigated, showing FA binding to BSA was a spontaneous process mainly through hydrogen bonding and van der Waals force by FI‐CL, with binding constant K of 1.89 × 10⁶ l mol^?1 and the number of binding sites n of 0.86. Molecular docking analysis further revealed FA could enter into the pocket at subdomain IIA of BSA, with K of 1.71 × 10⁵ l mol^?1 and ΔG of ‐29.68 kJ mol^?1.     

Utilisation of kinetic-based flow injection methods for the determination of chlorine and oxychlorine species

Automated selective iodometric methods for the determination of chlorine and oxychlorine species have been developed for use in the drinking water industry. By utilising kinetic-based methods, linear ranges observed were: chlorine, 0.2–10 mg l^?1; chlorine dioxide, 0.3–10 mg l^?1; chlorite ion, 0.08–5 mg l^?1; and chlorate ion, 0.08–5 mg l^?1.