A post-column photochemical detector for use in the determination of trace metals with n-butyl-2-naphthylmethyldithiocarbamate by high-performance liquid chromatography

The determination of traces of metals by high-performance liquid chromatography of their n-butyl-2-naphthylmethyldithiocarbamate (BNMDTC) complexes on a nonpolar stationary phase, with a post-column photochemical detector is described. Metal complexes of this ligand are thermodynamically stable and kinetically inert towards dissociation. To provide low detection limits, a photochemical reactor was developed to generate a fluorescent product. A major product of the photolysis of BNMDTC complexes is identified as the highly fluorescent n-butyl-2-naphthyl-methylamine. Detection of metal ions as BNMDTC complexes at the 10^?8 M level is feasible. Iron, nickel, mercury and cobalt complexes are readily determined.     

High performance liquid chromatographic determination of copper(II) and nickel(II) by using solvent extraction and bis(acetylpivalylmethane)ethylenediimine as complexing reagent

The reagent bis(acetylpivalylmethane)ethylenediimine has been examined for the HPLC separation of copper(II), nickel(II), palladium(II) and oxovanadium(IV) chelates on reversed phase HPLC columns (250 x 4 mm) packed with Hypersil ODS, 5 mu and (150 x 3.9 mm) Nova Pak C(18) with guard column. The complexes are eluted with a binary mixture of methanol and water or methanol, acetonitrile and water. Detection is achieved with a UV detector. The solvent extraction procedure is used for the determination of copper and nickel simultaneously at microgram levels, corresponding to ng levels and pg levels respectively, per injection. The method has been applied to the determination of copper and nickel in a coin, nickel-aluminum alloy and water samples.     

Selective detection of volatile nickel,vanadium, and iron porphyrins in crude oils by gas chromatography-atomic emission spectroscopy

This report describes the selective detection of volatile nickel, vanadium, and iron metalloporphyrins in crude oil samples. An atomic emission detector (AED) was used for simultaneous detection of these metals using the Ni 301.2 nm, V 292.4 nm, and Fe 302.1 nm emission lines. Detection limits for these metals range from 0.05 to 5 pg/sec. The presence of volatile forms of these metals in several crude oil samples has been confirmed.     

A survey of ochratoxin A and aflatoxins in domestic and imported beers in Japan by immunoaffinity and liquid chromatography.

Analyses of ochratoxin A (OTA) and aflatoxins (AFs) in 94 imported beer samples from 31 producing countries and in 22 Japanese beer samples were performed by immunoaffinity column and reversed-phase liquid chromatography (LC) with fluorescence detection. Recoveries of OTA from beer samples spiked at 25 and 250 pg/mL were 86.1 and 88.2%, respectively. Recoveries of AFs were 98.4 and 98.9%, 95.4 and 95.5%, 101.2 and 97.8%, and 98.9 and 96.0%, respectively, from beer samples spiked at 4.1 and 41 pg AF B1, 4.45 and 44.5 pg AF B2, 4.7 and 47 pg AF G1, and 4.65 and 46.5 pg AF G2/mL. Detection limits were 1.0 pg/mL for OTA, 0.5 pg/mL for AFs B1 and B2, and 1.0 pg/mL for AFs G1 and G2. OTA was detected in 86 (91.5%) of 94 imported beer samples at a mean level of 10.1 pg/mL and in 21 (95.5%) of 22 Japanese beer samples at a mean level of 12.5 pg/mL. AF B1 was detected in 11 of 94 imported beer samples at a level of 0.5-83.1 pg/mL and in 2 of 22 Japanese beer samples at 0.5 and 0.8 pg/mL. Except for one beer sample from Peru, the samples contaminated with AFs were also contaminated with OTA. Although OTA was detected in most samples from various countries, AFs were detected in the beer samples from only a limited number of countries where AF contamination might be expected to occur because of their warm climate.     

Stripping voltammetric determination of traces of catechol compounds preceded by adsorptive accumulation of metal complexes

Catechol compounds are quantified by controlled adsorptive accumulation of their metal complexes onto a hanging mercury drop electrode followed by stripping voltammetry. By using tin(IV) as a redox marker for quantifying the surface-bound species, selectivity can be improved relative to conventional oxidative methods; dopamine can be quantified in the presence of ascorbic acid. The method allows measurements of micromolar levels of catechol, dopamine, l-dopa, 3,4-dihydroxyphenylacetic acid and caffeic acid. The adsorptive stripping response is evaluated with respect to preconcentration time and potential, tin(IV) and analyte concentrations, stripping mode, reproducibility and possible interferences. Analogously, solochrome violet RS and dimethylglyoxime can be quantified after accumulation of their iron(III) and nickel(II) complexes, respectively. Detection limits are 7×10^?9 M for solochrome violet RS and 5×10^?8 M for caffeic acid (1- and 5-min preconcentration, respectively).     

Determination of organometallic compounds by capillar gas chromatography – inductively coupled plasma mass spectrometry

The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC-ICP-MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC-ICP-MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400).     

Determination of diphenyltin and dialkyltin homologues by HPLC with morin in the eluent

A sensitive and selective method has been developed for the simultaneous determination of diphenyltin and dialkyltin compounds. The compounds were separated by HPLC on a cyanopropyl-bonded silica column with toluene containing 1-5% acetic acid, 1-5% ethanol or methanol and 0.0015% morin. The organotins were eluted as morin complexes and detected by a fluorescence spectrophotometer. Detection limits ranged from 1 to 4 pg. Data reported include capacity factors, separation efficiencies and linearity of detection.     

Separation and determination of Ni(II), Co(II) and Cu(II) by RP-HPLC with hexadecyltrimethylammonium bromide/n-propanol mobile phases

Summary The effect of the presence of a cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), and a short chain alcohol,n-propanol, in the mobile phase on the chromatographic retention of Co(II), Ni(II) and Cu(II) diethylammonium diethyldithiocarbamate complexes, has been studied. A simple isocratic reversephase method for the determination of the metals is proposed, using a mobile phase of composition CTAB 0.03 M/n-propanol 45 %v/v. Detection limits at pg levels were obtained for all solutes. The method was applied to the determination of the complexes in tap water samples at three different concentrations, with recoveries close to 100%. In order to evaluate the interaction between the metal complexes and the aggregates formed, the values of solute binding constants are calculated.     

Determination of sulfur,nickel and vanadium in fuel and residual oils by x-ray fluorescence spectrometry

The determination of sulfur, nickel and vanadium in fuel and residual oils by wavelength-dispersive x-ray fluorescence spectrometry is reported. Calibration is initially established with matrix-matched synthetic standards, and maintained free of instrumental drift by daily normalization to a reference standard. An epoxy-cast reference standard pellet offers mechanical rigidity and chemical stability for at least nine months. Matrix effects of sulfur and carbon are studied and corrected. Results for NBS SRM oils fall within the NBS certified values, with imprecision (% RSD) for S, Ni, and V of 1.1, 1.5 and 1.0%, respectively. Detection limits (3 s.d.) are 20 μg g^?1 for sulfur and 0.8 μg g^?1 for Ni and for V.     

Simultaneous determination of arsenic and antimony species in environmental samples using bis(trifluoroethyl)dithiocarbamate chelation and supercritical fluid chromatography.

Simultaneous separation and quantitation of arsenic(III) and antimony(III) can be achieved by extraction with lithium bis(trifluoroethyl)dithiocarbamate followed by supercritical fluid chromatographic (SFC) analysis. Arsenic(V) and antimony(V) are extracted after reduction with potassium iodide and sodium thiosulfate. Detection limits of 7 pg As and 11 pg Sb are achieved using this extraction method and SFC. Application to natural water and biological sample analysis is discussed.     

A highly sensitive laser two-photon ionization detector for liquid chromatography

A highly sensitive detector for liquid chromatography using the laser two-photon ionization technique is described. Detection limits for several aromatic molecules, such as pyrene and chrysene, with a nitrogen laser (337 nm) are in the range 5–30 pg, which is considerably below the limits attainable with a commercial u.v. absorption detector.     

Evaluation of dicationic reagents for their use in detection of anions using positive ion mode ESI-MS via gas phase ion association

Twenty-three different dications were investigated for their effectiveness in pairing with singly charged anions, thereby allowing the electrospray ionization mass spectrometry (ESI-MS) detection of anions as positively charged complexes. Nitrate, iodide, cyanate, monochloroacetate, benzenesulfonate, and perfluoro-octanoate were chosen as representative test anions as they differ in mass, size-to-charge ratio, chaotropic nature, and overall complexity. Detection limits were found using direct injection of the anion into a carrier liquid containing the dication. Detection limits are given for all six anions with each of the 23 dications. Each anion was easily detected at the ppb (microg/L) and often the ppt (ng/L) levels using certain dicationic reagents. The ability of dicationic reagents to pair with anions and produce ESI-MS signals varied tremendously. Indeed, only a few dications can be considered broadly useful and able to produce sensitive results. Liquid chromatography (LC)-ESI-MS also was investigated and used to show how varying the dicationic reagent produced significantly different peak intensities. Also, the use of tandem mass spectrometry can lead to even greater sensitivity when using imidazolium based dications.     

Solution equilibria between ethylenediamine-N,N'-di-3-propionate and some transition metal(II) ions

Solution equilibria between the ligand ethylenediamine-N,N'-di-3-propionate (eddp(2-)) and copper(II), nickel(II) or cobalt(II) ions were studied by glass electrode pH-metric and spectrophotometric measurements in 0.1 M NaCl ionic medium at 298.0+/-0.2 K. In the concentration limits 1.0相似文献   

Investigation of separation and identification possibilities of some metal-DEDTC complexes by sequential TLC-IR system

The separation and identification possibilities of some metal-diethyldithiocarbamate (DEDTC) complexes are investigated by thin-layer chromatography-IR sequential system. DEDTC complexes of metal cations are prepared in a predetermined optimum pH or pH range. Optimum separation conditions of these complexes and the reproducibilities of their retention factor (Rf) values are investigated on a series of precoated or laboratory-made TLC plates. Rf values are determined using the one-dimensional ascending technique. The precision of the procedures is determined for five replicates in terms of standard deviation. Detection limits are also determined for each of the metal complexes. The IR spectra are scanned and interpreted for their precise identifications after preconcentration with a wick-stick procedure for the complexes, giving the overlapped Rf values. The complexes could be identified by the aid of IR absorption bands. It has been determined that these IR absorption bands can also be used as reference spectral bands in possible quantitative studies. It is concluded that an efficient and successful qualitative analysis is possible for incompletely-separated complex compounds using an IR spectrophotometer as the TLC detector.     

Direct determination of nickel traces on modified cellulose by diffuse reflection spectroscopy and using chromaticity characteristics

Diffuse reflection spectroscopy has been used for the direct determination of nickel traces after preconcentration on cellulose (Cel). The experimental parameters (optical characteristics, acidity of aqueous solution, shaking time, volume of aqueous solution, nickel and tartaric ion concentrations, etc.) affecting sorption of nickel species with immobilized dimethylglyoxime (DG) and benzyldioxime (BD) have been optimized. Diffuse reflection coefficient and chromaticity characteristics of the nickel sorbates indicated the same dependence on studied factors, but their sensitivity is different. The linear relations of variations of these quantities with the nickel contents were determined. Detection limits were 0.1 μg/mL and 0.2 μg/mL for BD and DG, respectively. The procedures were used for the analysis of natural and waste waters.     

Evaluation of kel-f—graphite electrodes as detectors for continuous flow systems

A new electrode material, fabricated from Kel-F powder and graphite powder by pressing at 250°C and 1000 p.s.i., is applied as a detector in a thin-layer, flow-through cell, for applications to continuous flow streams. The detector is useful in a wide range of solvents for a wide range of species. Applications are described for 1,1'-bis(hydroxymethyl) ferrocene (BHMF), ascorbic acid, ferrocene, phenol, and hydroquinone, using various aqueous and methanolic solvent/electrolyte compositions. Detection limits range from 800 pg for BHMF to less than 20 pg for phenol. Background current fluctuations are used to estimate flow rate stability, which is the dominant factor in setting detection limits.     

Determination of metallo-cyanides by capillary electrophoresis after concentration on supported liquid membranes

A method for the determination of traces of metallo-cyanide complexes by capillary zone electrophoresis is described. The suitability of preconcentration procedures based on supported liquid membranes in a flow system is investigated. Methyltrioctylammonium chloride in dibutyl ether is used as the active component of the membrane liquid. Due to ion-pairing mechanisms enrichment factors ranging from 50 to 600 can be achieved for cyanide complexes of Fe(II), Fe(III), Ni, Co, Pd, Pt, Cr, Au and Ag. The final capillary electrophoretic separation of the metallo-cyanides is performed off-line with a phosphate-triethanolamine buffer at pH 8.5 as the carrier electrolyte. Its separation selectivity and compatibility with the preconcentration procedure are optimized by addition of hexamethonium bromide, sodium perchlorate and sodium cyanide. Detection limits in the low nmol range can be achieved by direct UV detection at 214 nm. An approach for the analysis of free and labile cyanide is discussed which involves the conversion of these species into the nickel cyanide complex. Applications in the fields of environmental monitoring and industrial process control are possible.     

Direct determination of nickel traces on modified cellulose by diffuse reflection spectroscopy and using chromaticity characteristics

Diffuse reflection spectroscopy has been used for the direct determination of nickel traces after preconcentration on cellulose (Cel). The experimental parameters (optical characteristics, acidity of aqueous solution, shaking time, volume of aqueous solution, nickel and tartaric ion concentrations, etc.) affecting sorption of nickel species with immobilized dimethylglyoxime (DG) and benzyldioxime (BD) have been optimized. Diffuse reflection coefficient and chromaticity characteristics of the nickel sorbates indicated the same dependence on studied factors, but their sensitivity is different. The linear relations of variations of these quantities with the nickel contents were determined. Detection limits were 0.1 μg/mL and 0.2 μg/mL for BD and DG, respectively. The procedures were used for the analysis of natural and waste waters. Received: 30 July 1998 / Revised: 4 November 1998 / Accepted: 7 November 1998     

Determination of Nickel and Palladium in Environmental Samples by Low Temperature ETV-ICP-OES Coupled with Liquid-liquid Extraction with Dimethylglyoxime as Both Extractant and Chemical Modifier

A novel method for the determination of nickel and palladium in environmental samples by low temperature ETV-ICP-OES with dimethylglyoxime(DMG)as both the extractant and chemical modifier has been developed.In this study,it was found that nickel and palladium can form complexes with dimethylglyoxime(0.05%,mass fraction)at pH 6.0 and can be extracted into chloroform quantitatively.The complexes can be evaporated into plasma at a suita-ble temperature(1400 ℃)for ICP-OES detection.Under the optimized conditions,the detection limits of nickel and palladium are 0.48 and 0.40 ng/mL,respectively,while the RSD values are separately 5.0% and 3.1%(ρ=50 ng/mL,n=7).The proposed method was applied to the determination of the target analytes in environmental samples with satisfactory results.     

High performance liquid chromatographic separation and UV determination of cobalt, copper iron and platinum in pharmaceutical preparations using bis(isovalerylacetone)ethylenediimine as complexing reagent

The reagent bis(isovalerylacetone)ethylenediimine(H₂IVA₂en) has been examined for HPLC separation and UV determination of cobalt, copper, iron and platinum using off-line precolumn derivatization and extraction in chloroform. The complexes of cobalt(II), cobalt(III), iron(II), iron(III) and the reagent have been subsequently separated on a Microsorb C-18 column. The complexes were eluted isocratically using ternary mixtures of methanol/water/acetonitrile. Detection was achieved by UV monitoring. Detection limits for Co(II), Co(III), Fe(II) and Fe(III) were 2.5–5.0 ng/injection, based on 0.5–1.0 g/ml with 5 l/injection. The concentration of cobalt(II) and cobalt(III) in aqueous solution have been determined. The presence of oxovanadium(IV), platinum(II), and nickel(II) did not affect the determinations. The HPLC method developed has been applied to the determination of cobalt, copper, iron and platinum in pharmaceutical preparations at the 30 g/g to 15 mg/g level and the obtained results were compared to those of atomic absorption spectrometry.