A Method for the Determination of Octa- and Nonachloro-2-phenoxyphenols in Chicken Tissue

Abstract

A gas-liquid chromatographic method was developed capable of determining octa-and nonachloro-2-phenoxyphenols in chicken liver or muscle at 0.25 ppb and fat at 2.5 ppb. The method involves extraction with acidified acetone:hexane, cleanup with concentrated H₂SO₄ and Florisil column chromatography, methylation with diazomethane, and quantitation by capillary column gas-liquid chromatography with electron capture detection. Fortification of liver and muscle at 0.25 or 0.5 ppb and fat at 2.5 or 5.0 ppb and subsequent analysis yielded recoveries averaging 91% for octa-and 97% for nonachlorophenoxyphenol.     

High-Performance Liquid Chromatographic Determination of Trace Quantities of Azinphos Methyl and Azinphos Methyl Oxon in Various Water Sources by Direct Injection and Trace Enrichment

Abstract

A high-performance liquid chromatographic (HPLC) method is described for the determination of trace amounts of the organophosphate insecticide, azinphos methyl and its degradation product, azinphos methyl oxon, by direct injection and by trace enrichment. The compounds were analyzed on a uBondapak C₁₈ column with UY detection at 224 nm. The mobile phase for the analysis was acetonitrile-water (50:50) at a flow rate of 1.3 ml/min. Ten minutes were required for the chromatographic analysis. Water from three sources, public water supply, stream, and ocean was analyzed for azinphos methyl and azinphos methyl oxon at concentrations as low as 11.9 and 11.3 ppb, respectively, without a clean-up, concentration or derivatization step. Azinphos methyl was quantitated at 0.29 ppb and azinphos methly oxon at 0.29 ppb by employing a concentration step involving a C₁₈ Sep-Pak cartridge. The coefficients of variation for all determinations ranged from 0.77 to 9.06%. Peak heights were used for quanti-tation. Several other pesticides have been shown not to interfere with the analysis of either compound.     

Trace Enrichment and HPLC Analysis of Chlorophenols in Environmental Samples,Using Precolumn Sample Preconcentration and Electrochemical Detection

Abstract

A HPLC method has been developed for trace analysis of chlorophenols in the 0.2–2 ppb range from spiked water samples. Simple liquid-liquid extraction followed by on-line preconcentration of total mono- and dichlorophenols has been performed using a divinylbenzene-styrene copolymeric sorbent (PRP₁) as packing material for the precolumn. The chlorophenols have been eluted from the precolumn on an analytical column (5μm LiChrosorb RP-18, 12.5 cm × 4 mm) by use of a switching valve system followed by separation. Detection was carried out with an electrochemical detector. The linearity of the detector response has been proved over two orders of magnitude. The detection limit of chlorophenols by means of the electrochemical method is in the lower picogram range. The recoveries of the isomeric chlorophenols from spiked river water samples having initial concentrations of 2ppb are usually 70–90%. The procedure has been applied to drinking water and river water.     

A New Method for the Microdetermination of Molybdenum (VI) in Steel,Biological Materials and Waters

Abstract

A method is presented for the trace analysis of molybdenum (VI) in standard steel sample, plant tissues, animal tissues, and natural waters. The method is based on the extractive separation of molybdenum from complex matrices by chelating it with a new reagent N-p-methoxypheny1-2-furylacrylohydroxamic acid (MFHA) into isoamyl alcohol followed by spectrophotometric determination, Eight other new hydroxamic acids were studied for the same purpose and MFHA was chosen as it was the most sensitive of these as well as the other hydroxamic acids reported previously, The method enables rapid and reliable analysis of molybdenum at ppb lelvels in environmental matrices.     

Indirect Trace Determination of Ethylenediminetetraacetic Acid (Edta) in Water by Potentiometric Stripping Analysis

Abstract

An analytical method for indirect trace determination of ethylenediaminetetraacetic acid (EDTA) in water, by potentiometric stripping analysis is described. Excess Bi(III) was added to form a 1:1 complex with EDTA at pH 2.3. The uncomplexed Bi(III) was then deposited on a glassy carbon electrode at a potential of ?0.40 V vs. SCE and subsequently stripped potentiometrically using potassium dichromate as oxidant. The stripping time of uncomplexed Bi(III) was recorded. The Concentration of EDTA in the sample was determined from the concentration of added Bi(III) and the potentiometrically stripped Bi(III) at ?0.4 V by the standard addition method. The relative standard deviation for EDTA concentration of 95 ppb and 4.5 ppb was 1.9% and 2.6%, respectively. The detection limit was about 1 ppb EDTA for a deposition time of 3 minutes.     

L, 8-Dihydroxyanthraquin0Ne-Li(I) Reaction. Spectrofluorometric Determination Of Li(I) In An Ethanolic And Acetonic Media

Abstract

A spectrofluorometric study of the reaction 1, 8-Didydroxv anthraquinone-Li(I) was made in ethanol and acetone media. A new method for the spectrofluorometric determination of Li(I) is proposed, with a range between 100 and 700 ppb of Li(I) in ethanolic medium and between 50 and 450 ppb in acetone medium. The methods show errors of 2.00 and 2.90 % respectively.     

Analysis of Tetracycline,Oxytetracycline and Chlortetracycline in Plasma Extracts by Electrospray Tandem Mass-Spectrometry and by Liquid Chromatography

Abstract

Pure standards of tetracyclines (tetracycline, oxytetracycline and chlortetracycline) have been analyzed on a triple quadrupole mass spectrometer with Atmospheric Pressure Chemical Ionization (APCI) and Electrospray Ionization (ESI). ESI appeared to be considerably more sensitive than APCI. Collisional activation of the MH⁺ ions gave fragment ions at m/z values equal to MH⁺ - 35 which corresponds to loss of both H₂O and NH₃. The collisionally induced loss of 35 from MH⁺ was used in developing a mass spectrometric method based on loop injection and selected reaction monitoring (SRM) as the final analytical step. The method was tested on extracts from fortified plasma and the measurements from the MS-MS analysis were compared with results from High Performance Liquid Chromatography (HPLC) analysis of the same samples. The fortified plasma (from pig) samples were purified by chelate affinity chromatography (amberlite XAD columns). After filtration and evaporation of the solvent the redissolved residues were analyzed by HPLC and by MS-MS with ESI. The HPLC eluates (gradient of 0.01 M aqueous oxalic acid and CH₃CN) were monitored at 356 and 369 nm. The signal to noise ratio in the analyses of extracts from plasma fortified to 20 ppb suggests a detection limit for the MS-MS method below 10 ppb of tetracylines in plasma.     

Determination of Mercury in Geological Materials by Continuous-Flow,Cold-Vapor,Atomic Absorption Spectrophotometry

Abstract

To determine mercury in geological materials, samples are digested with nitric acid and sodium dichromate in a closed teflon vessel. After bringing to a constant weight, the digest is mixed with air and a sodium chloride-hydroxylamine hydrochloride-sulfuric acid solution and then Hg(II) is reduced to Hg with stannous chloride in a continuous flow manifold. The mercury vapor is then separated and measured using cold vapor atomic absorption spectrophotometry (CV-AAS). For a 100 mg sample the limit of detection is 20 parts per billion (ppb) Hg in sample. To obtain a 1% absorption signal, the described method requires 0.21 ppb Hg solution (equal to 16 ppb in sample). Precision is acceptable at less than 1.2% RSD for a 10 ppb Hg aqueous standard. Accuracy is demonstrated by the results of the analysis of standard reference materials. Several elements do interfere but the effect is minimal because either the digestion procedure does not dissolve them (e.g., Au or Pt) or the; are normally of low abundance (e.g., Se or Te).     

Spectrophotometry -Kinetic Determination of Thioketones

Abstract

A spectrophotometric-kinetic method is proposed for the assay of thioketones. The method is based on the catalysis of the sodium azide-iodine-starch reaction by thiourea at concentrations from 10 to 100 ppb. The course of the reaction is monitored spectrophotometrically by the reduction of iodine to iodide using starch iodine indicator.     

Analysis of Phosmet and Azinphos-Methyl in Apples by High-Performance Liquid Chromatography

Abstract

A high-performance liquid chromatography (HPLC) method has been developed to analyze two organophosphate insecticides (phosmet and azinphosmethyl) in apples. The procedure includes a novel extraction whereby whole apples are sonicated for 2 min in 100 ml of MeOH to remove the pesticides. Reversed-phase HPLC separation was accomplished with an Ultremex C18 column and acetonitrile:methanol:water as the eluent. Detection was at 224 nm for phosmet and 300 nm for azinphos-methyl. For both pesticides the limit of detection was 0.5 ppb and the linearity was from 1 to 405 ng injected. Average recoveries were 80% for phosmet and 86% for azinphos-methyl. Thirteen apple varieties comprising 240 apples were analyzed from supermarkets and roadside stands for phosmet (amount found ranged from none detected to 1233 ppb) and azinphos-methyl (amount found ranged from none detected to 388 ppb). Confirmation of phosmet and azinphos-methyl was made by UV spectral scans.     

Combination of solid phase extraction and in vial solid phase derivatization using a strong anion exchange disk for the determination of nerve agent markers

Alkylphosphonic acids (APAs) are degradation products and chemical markers of organophosphorous (OP) nerve agents (chemical warfare agents). Anion exchange disk-based solid phase extraction (SPE) has been combined with in vial solid phase derivatization (SPD) and GC–MS analysis for the determination of APAs in aqueous samples. The optimization of critical method parameters, such as the SPD reaction, was achieved using statistical experimental design and multivariate data analysis. The optimized method achieved quantitative recoveries in the range from 83% to 101% (n = 13, RSD from 4% to 10%). The method was sensitive, with LODs in SIM mode of 0.14 ppb, and demonstrated excellent linearity with an average R² ≥ 0.99 over the concentration range of 0.07–1.4 ppm in full scan mode and from 0.14 ppb to 14 ppb in SIM mode. For forensic applications, aqueous samples containing APAs at concentrations exceeding 14 ppb were concentrated and target analytes were successfully identified by spectral library and retention index matching. Method robustness was evaluated using aqueous samples from the official OPCW Proficiency Test (round 19) and all APAs present in the sample were conclusively identified. The SPE disk retained the underivatized APAs in a stable condition for extended periods of time. No significant losses of APAs from the disk were observed over a 36-day period. Overall, the method is well suited to the qualitative and quantitative analysis of degradation markers of OP nerve agents in aqueous matrices with simplicity, a low risk of cross-contamination and trace level sensitivity.     

Determination of Biacetyl in Beer by Liquid Chromatography with Sensitized Phosphorescence Detection

Abstract

A new determination method for biacetyl in beer is developed. After a simple sample preparation method and separation by HPLC, biacetyl is detected by sensitized room temperature phosphorescence. A detection limit of 0.5ppb biacetyl in beer can be obtained. The linearity of response is 0.5–150ppb; the relative standard deviation is 4.2% at the 16ppb level. Prepared samples are stable for at least 20 hours when kept in closed vials. The separation of biacetyl and 2,3-pentanedione, an α-diketone also present in beer, is described. It is found that sensitized phsophorescence detection is about a factor of 30 less sensitive for 2,3-pentanedione. The reliability of the method is demonstrated by comparison with a routine head space gas chromatography method.     

Method for the Determination of DES,Hexestrol and Dienestrol Residues in Bovine Urine Using GC-MSD

Abstract

A method is described to determine Diethylestilbestrol, Hexestrol and Dienestrol residues in bovine urine, using GC-MSD, working with the SIM system. The urine was centrifuged and the pH adjusted to 9 with 32% NaOH, then subjected to a solid phase extraction procedure using C-18 columns (Baker, spe-500). These columns were eluted with methanol, the alcohol extract was evaporated to obtain a solid residue. The derivation of the stilbene was performed with BSTFA:TMCS 99:1, incubated 15 min at 70°C. The final extracts were dissolved in acetonitrile and injected in a GC-MSD apparatus (quadrupol electronic impact). Three characteristic ions were monitored for each product studied. The detection limit achieved is 2 ppb for Diethylestilbestrol and Hexestrol and 3 ppb for Dienestrol.     

Determination of Low Level Mercury in Organic Samples

Abstract

This report describes work done to develop a method for the determination of low-level mercury in organics from a chemical plant. The method developed is based on heating the sample with phosphoric acid, collecting the atomic mercury produced on a gold-plated Nichrome wire, followed by thermally releasing the mercury through a UV spectrophotometer. The method is useful down to a few ppb mercury.     

Determination of Arsenic in Beverages and Foods by Hydride Generation Atomic Absorption Spectroscopy

Abstract

The determination of the arsenic content of foods and beverages by a technique involving a magnesium nitrate aided dry ashing step followed by an arsine generation atomic absorption finish is described. Recoveries of various arsenic species added prior to ashing was excellent. Total arsenic concentrations found in samples of beverages ranged from less than 10 to 265 ppb and in foods from 20 to 9290 ppb. The sensitivity of the technique is approximately ten-fold better than obtainable with commercially available hydride generation atomic absorption units.     

Determination of Germanium in Zinc by Differential Cathode Ray Polarography

Abstract

A differential cathode ray polarographic method is described for determining traces of germanium in zinc and its compounds. The germanium was previously extracted with carbon tetrachloride from the sample solution in hydrochloric acid. After reextraction with water the germanium content was determined polarographically in 1.4 M perchloric acid ? 5.10^?2 M pyrogallol. The detection limit was 0.0012 μg/ml, allowing to detect about 4 ppb of germanium in zinc using 5 g samples.     

Specific Spectrophotometric Determination of Palladium with N,N'-Diphenylbenzimidoylthiourea

ABSTRACT

A specific method for the spectrophotometric determination of palladium with N.N'-diphenylbenzimidoylthiourea (DPB1TU) is described. The method in new, simple, rapid and applicable over 0.3-1.0 M HC1 and free from interferences of the precious metals i.e.

Ag, Au, Pt, Ir, Rh, Ru, Os. The value of molar absorptivity of the complex in the term of Pd is (2.50)x10⁴ L mole^?1 cm^?1at λ_max 365 nm in chloroform. The detection limit of the method at 3 σ a is 80 ppb Pd. The composition of the complex and effect of diverse ions in the determination of Pd are discussed. The application of the method has been tested for the analysis of the metal in catalytic material.     

Reagentless - Continuous Determination of Aqueous Ozone with Glass Tube Separator - Thin Film Semiconductor

Abstract

A method without any reagent for the determination of ultra-trace aqueous ozone utilizing a glass tube-separation process and a thin film semiconductor is proposed. The glass tube was used as the separator to transfer ozone from water into a gas phase. Ozone was transfered into clean air flowing in the tube and then was continuously monitored at the thin film semiconductor. Signals were proportional to concentration of aqueous ozone more than 5 ppb. Detection limit (S/N=3) was 0.02 ppt for aqueous ozone. The relative standard deviation (n=7) was 3.8 % at 7.6 ppb. The interference from hydrogen peroxide. monochloramine. and dichloramine were completely eliminated. The sensitivity of aqueous ozone was 45 times greater than that of hypochlorite.     

Dosage des Traces d'Arsenic par Voltametrie et Redissolution Cathodique dans les Solutions Industrielles de ZnSO4

Abstract

A method is described for the determination of traces of arsenic in industrial ZnSO₄ solutions for electrolysis by cathodic stripping voltammetry. The limit of detection is of the order of 1 ppb.     

Optical detection of cyanide by palladium(II)-dithiazolopyridine probe at the parts per billion level

Abstract

The ensemble of 2,6-bis(2-chlorophenyl)dithiazolo[4,5-b:5',4'-e]pyridine 1 with Pd²⁺ ions (1?Pd²⁺) was prepared for the detection of cyanide ions (CN^¯) in 50% aqueous methanol. Among the tested metal ions, only Pd²⁺ sensitively induced the red shift of the absorption bands and the complete decrease of fluorescence emission. The detection limit toward Pd²⁺ was 2?ppb. The ensemble 1?Pd²⁺ selectively and rapidly detected a low concentration of cyanide ions by a colorimetric change (40?ppb) as well as a “turn-on” fluorescent response (5?ppb). Job’s plot revealed the complex formation with 1:1 stoichiometry. The binding and replacement mode of 1?Pd²⁺ and CN^¯ were also confirmed by ¹H NMR titrations and IR analysis. In general, a fast and selective recognition of CN^¯ is reported.