Solvent extraction of cadmium as a previous step for its determination in biological samples by electrothermal atomization atomic absorption spectrometry

A method is proposed for the solvent extraction of cadmium using 1,5-bis(di-2-pyridylmethylene)thiocarbohydrazide (DPTH) as extractant. The optimum extraction conditions were evaluated from a critical study of the effect of pH, concentration of extractant, shaking time and ionic strength. The maximum volume ratio of the aqueous to organic phase was 30:1 for a single-stage extraction of99-100% of the metal ion. The detection limit is 0.01 ng/ml cadmium, and the calibration is linear from 0.1 to 5 ng/ml. The relative standard deviation for 10 replicate measurements is 1.8% for 2 ng/ml cadmium. The extraction method was applied to the determination of cadmium in some biological materials using graphite furnace atomic absorption spectrometry.     

Kinetics of the metal-exchange reaction of deuteroporphyrin and gematoporphyrin cadmium complexes with cobalt chloride in acetonitrile

The metal-exchange reaction of cadmium deuteroporphyrin (CdDP) and cadmium gematoporphyrin (CdGP) with cobalt chloride in acetonitrile is studied spectrophotometrically. The stoichiometry of the metal-exchange reaction is determined. The results are compared with the exchange reaction of cadmium mesoporphyrin and cadmium protoporphyrin with cobalt acetate in acetonitrile. Substituents in the 2,4-positions of cadmium complexes of protoporphyrins are shown to influence the rate of the metal-exchange reaction. The increasing order of the rates of the metal-exchange reaction between protoporphyrins and cobalt chloride in acetonitrile is established.     

Estimation of cyclosporin-A in whole blood by simple and rapid reversed-phase HPLC utilizing a salting-out extraction procedure

Cyclosporin-A is a fungal cyclic undecapeptide immunosuppressive agent that is potentially active against proliferating T-lymphocytes and therefore helps the body to accept a transplanted organ. In this experiment, the drug is extracted from whole blood with acetonitrile. The extraction solvent (acetonitrile) is mixed with the whole blood at a 1:2 ratio on a vortex mixer and is centrifuged at 2000 x g. The supernatant is transferred into a fresh borosilicate culture test tube and 20 mg of zinc sulfate and 10 mg of cadmium sulfate (for 1.0 mL of whole blood) are added, vortex mixed, and centrifuged at 2000 x g. The supernatant is saturated with anhydrous ammonium sulfate and centrifuged, and salted-out acetonitrile from the aqueous mixture is injected into the HPLC system. A 60- x 4.6-mm 3-microns, slurry-packed ODS (C18) column is used with an isocratic elution of 66:2:32 (v/v), acetonitrile-isopropanol-water. The column temperature is maintained at 72 degrees C. Cyclosporin-A is detected by UV absorption at 205 nm and 0.10 to 0.002 AUFS. The limit of detection of the method is 15 ng/mL for a 100-microL injection volume, and the completion time for analysis of one sample is less than 15 min. Columns packed with different stationary phases and different dimensions are investigated to determine which column will give the maximum resolution, sensitivity, and selectivity.     

Determination of cadmium in biological samples by inductively coupled plasma atomic emission spectrometry after extraction with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide.

An inductively coupled plasma atomic emission spectrometric method for the determination of trace amounts of cadmium after extraction of the metal into isobutyl methyl ketone containing 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide is described. The optimum extraction conditions were evaluated from a critical study of the effects of pH, concentration of extractant, shaking time and ionic strength. The detection limit for cadmium is 0.1 ng ml-1 and the calibration is linear from 0.2 to 140 ng ml-1. The relative standard deviation for ten replicate measurements is 2.9% for 2 ng ml-1 of cadmium. Results from the analysis of some certified biological reference materials are given.     

分散固相萃取/高效液相色谱-串联质谱法检测大葱中虫酰肼、涕灭威及其衍生物的农药残留

采用分散固相萃取法净化(DSPE),高效液相色谱-串联质谱法(HPLC-MS/MS)在分时段多反应监测模式下对大葱中的虫酰肼、涕灭威及其衍生物进行测定,外标法定量,并对比了乙酸乙酯和乙腈作为提取剂的提取效果.结果表明,采用乙腈为提取剂时,4种农药在10～120μg/L范围内线性关系良好,且方法的定量下限(LOQ)均低于...     

Production of115mIn using bis(2-ethyl hexyl) phosphoric acid (HDEHP)

A rapid method for the production of^115mIn from irradiated cadmium is described. The procedure of the method is based on the extraction of^115mIn by bis(2-ethyl hexyl) phosphoric acid (HDEHP) from 0.1N sulphuric acid. Accumulated^115mIn can then be reextracted into diluted hydrochloric, hydrobromic, nitric or sulphuric acid solutions with a concentration of 1N or higher. A summary on the behaviour of cadmium and indium extraction with the solvent was given as a preliminary step in the present study. The produced^115mIn was found to be free from any cadmium as well as from any other foreign activity.     

Mass Spectrometric Analysis of Microcystins from Cyanobacterial Biomass: Optimization of the Sample Preparation Procedure

The sample preparation procedure for determination of microcystins from biomass by the LC–MS method was optimized. Treatment of freeze-dried biomass samples with acetonitrile prior to the main extraction was effectively used for decreasing the amount of protein-like matrix compounds in extracts. Use of acetonitrile–water mixtures during the main ultrasound-assisted extraction allowed increasing the total microcystins amount in the resultant extracts compared to the traditional extraction using 75% methanol.     

Sonoelectroanalysis in Acoustically Emulsified Media: Zinc and Cadmium

Dithizone (diphenylthiocarbazone) dissolved in chloroform was employed as a ligand for the solvent extraction of either cadmium or zinc from aqueous media. Acoustic emulsification was shown to be effective both in extraction and recovery or ‘back extraction’ with a fresh clean aqueous solution. Quantitative analysis of cadmium or zinc removed via double sono‐extraction from aqueous media hostile to voltammetric analysis proceeded via sono‐square wave anodic stripping voltammetry (sono‐SWASV), resulting in high sensitivity in the relatively clean medium. This technique was shown to be viable for the quantification of cadmium from surfactant containing media where direct electroanalytical techniques fail. The method was also applied to the analysis of zinc in commercial shampoo and toothpaste, giving results in close agreement with those obtained from independent analysis. Biphasic sono‐extraction synergistically coupled with sono‐SWASV therefore presents an attractive technique for cadmium or zinc analysis in electrode passsivating media. The technique likely removes contaminants present in the test solution since these will ‘prefer’ to remain in the initial aqueous phase, or will transfer to the extracting organic phase, but are unlikely to be doubly transferred into the clean final aqueous phase.     

Selective extraction and separation of cadmium using tri-n-octylamine

The extraction of cadmium by tri-n-octylamine in benzene and cyclohexane from a mixture of sulphuric acid and potassium bromide has been investigated in detail. The optimum conditions for the extraction and back-extraction of cadmium have been found. The procedure for the concentration of cadmium is described and the separation of cadmium in the presence of more than 30 metals including fission products is presented.     

A comparison of some flame atomic absorption spectrometric methods for the determination of cadmium in fertilizers and related materials

A liquid-liquid extraction procedure for cadmium in phosphate rock and phosphate-based fertilizers is described. Extraction with tri-n-octylamine and potassium iodide into methyl isobutyl ketone is shown to be simpler and less prone to interferences than the more commonly used methods based on ammonia pyrrolidine-dithiocarbamate. Iron interest strongly in the dithiocarbamate method. Addition of ascorbic acid, and extraction at low pH allows the dithiocarbamate method to operate up to 0.15 g Fe l^?1, while the amine method tolerates at least 0.2 g Fe l^?1. Direct determination is suitable on samples with a sufficiently high cadmium content. The amine extraction method has been applied successfully at an apatite containing only 0.03 mg kg^?1 cadmium.     

Robust method for the analysis of phytochelatins in rice by high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry based on polymeric column materials

A sensitive and robust high‐performance liquid chromatography coupled with electrospray tandem mass spectrometry method for the identification and quantification of glutathione and phytochelatins from rice was developed. Homogenized samples were extracted with water containing 100 mM dithiothreitol, and solid‐phase extraction using polymer anion exchange resin was employed for sample purification. Chromatography was performed on a polymeric column with acetonitrile and water containing 0.1% formic acid as the mobile phase at the flow rate of 300 μL/min. The limit of quantitation was 6–100 nM. This assay showed excellent linearity for both glutathione and phytochelatins over physiological normal ranges, with correlation coefficients (r) > 0.9976. Recoveries for four biothiols were within the range of 76–118%, within relative standard deviations less than 15%. The intraday precision (n = 7) was 2.1–13.3%, and the interday precision over 15 days was 4.3–15.2%. The optimized method was applied to analyze tissue samples from rice grown using nutrient solutions with three different cadmium concentrations (0, 50, and 100 μM). With increasing cadmium concentrations, the content of phytochelatin 2 and phytochelatin 3 in rice roots increased, in contrast to most phytochelatins, and the content of glutathione in rice stems and roots decreased significantly.     

Liquid-liquid extraction and spectrophotometric determination of cadmium with 1,10-phenanthroline and thymol blue

A simple and highly sensitive extraction spectrophotometric method was developed for the determination of traces of cadmium. The method is based on the preconcentrative extraction of ternary-ion-association complex of cadmium—1,10-phenanthroline-thymol blue into chloroform and subsequent determination by spectrophotometry. The ternary ion associate is stable for 20 h and cadmium content as low as 0.1 g in 90 ml of sample can be determined. The method is precise and has been applied to the determination of cadmium in sea water, solder and high purity zinc and indium materials.     

Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l⁻¹, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis.     

Extraction and determination of zinc in pharmaceutical samples

A systematic study of extraction of zinc salicylate is reported. Optimum conditions for the extraction and determination of zinc are evaluated from a critical study of the effect of pH, sodium salicylate concentration and triphenylphosphine oxide concentration. The effect of foreign ions on the extraction is also discussed. The probable composition of the species has been deduced from the extraction data. The method has been used to separate zinc from cadmium and mercury in binary mixtures and for the determination of zinc in various pharmaceutical products.     

Indirect atomic-absorption determination of boron by solvent extraction as tris(1,10-phenanthroline)cadmium tetrafluoroborate

An indirect atomic-absorption method for boron has been developed. Boric acid is converted into tetrafluoroborate and extracted into nitrobenzene with Tris(1,10-phenanthroline)cadmium(II). The cadmium in the extract is determined by its atomic-absorption at 228s>d8 nm. A fivefold molar excess of the cadmium chelate is necessary for the extraction from pH 4>d3-6>d0 medium. The sensitivity for boron is thus made about the same as that of cadmium, 0>d005 ppm. Metal ions that react with fluoride or phenanthroline interfere. A procedure is described for determination of boron in steel.     

Development of a new QuEChERS method based on dry ice for the determination of 168 pesticides in paprika using tandem mass spectrometry

This study describes a new QuEChERS method referred to as the dry ice-partitioning QuEChERS method. This current method can be differentiated from the other QuEChERS methods in the sense that it uses dry ice rather than salts or buffers to extract and partition pesticides in the first extraction step. The dry ice-partitioning QuEChERS method consists of extraction method A (for detection of the acetonitrile layer) and extraction method B (for detection of both acetonitrile and aqueous layers). The extraction efficiency was then compared with the citrate-buffering QuEChERS method by means of recovery. Recovery values of the tested 168 pesticides were above 76%, with relative standard deviations of less than 20%. Certain problematic pesticides, including benfuracarb, carbosulfan, dichlofluanid, probenazole, pymetrozine, tolylfluanid, TFNA, and TFNG evidenced acceptable recoveries via the dry ice-partitioning QuEChERS method compared to the less than 70% recoveries of the citrate-buffering QuEChERS method examined herein. The matrix effect of paprika on the method developed herein was not significant, and matrix-matched calibration was performed well, with an r(2)≥0.99. The dry ice-partitioning QuEChERS method is capable of detecting the aqueous layer as well as the acetonitrile layer; this interesting feature makes it worth in application as an alternative QuEChERS method for the multiresidue analysis of pesticides within a broad polarity range in various matrices.     

The determination of dissolved manganese and cadmium in sea water at low nmol 1−1 concentrations by chelation and extraction followed by electrothermal atomic absorption spectrometry

The development and application of a method suitable for the determination of dissolved manganese and cadmium in sea water at the low concentrations typical of the open ocean is described. A mixed dithiocarbamate/Freon TF extraction system is used to separate trace metals from major constituents, prior to back extraction into a final dilute nitric acid solution and subsequent determination of the metals by graphite-furnace atomic absorption spectrometry. The procedure also separates dissolved Co, Cu, Fe, Ni, Pb and Zn from a sea-water matrix. A mechanized system for the extraction step and measures to control contamination are described. The detection limits (3 σ) for manganese and cadmium are 0.10 and 0.04 nmol l^?1, respectively.     

Separation and determination of Cd in biological materials by continuous-flow fluid extraction coupled to flow-injection ICP-AES

An FI-ICP-AES method for the determination of trace levels of cadmium in biological samples is described based on the complexation of the metal ion with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH) and its subsequent on-line extraction into isobutyl methyl ketone (IBMK). The detection limit for cadmium is 8.7 ng/ml and the calibration is linear at least from 10 to 2000 ng/ml. The relative standard deviation for 7 replicate measurements is 3.4% for 100 ng/ml of cadmium. Results from the analysis of some certified biological reference materials are given.     

Hydrophobic solvent induced phase transition extraction to extract drugs from plasma for high performance liquid chromatography–mass spectrometric analysis

Novel sample preparation approaches for HPLC bioanalysis based on the phenomenon that acetonitrile can be separated from water by adding salts or cooling at subzero temperatures have been reported. These two methods are superior to conventional liquid–liquid extraction since the separated acetonitrile phase can be directly injected to the RP–LC system. However, the salting-out method suffers from a potential problem that the remained salt in the acetonitrile phase may harm the MS detector, while the subzero-temperature method is troublesome to operate. Here, we have reported a similar phase separation phenomenon that the acetonitrile aqueous mixture can be separated by adding a hydrophobic solvent; and capitalising on this phase transition phenomenon, we have proposed an alternative approach, named solvent induced phase transition extraction (SIPTE), to extract drug from plasma for HPLC–MS analysis. The proposed SIPTE method is much simpler and avoids contaminating the MS detector. Three structurally diverse drugs were selected as test compounds to design the SIPTE method and to validate the efficiency of this method. The four goals of plasma sample pretreatment for HPLC–MS analysis, i.e. removal of proteins, removal of other low-molecular interferences, preconcentration of the analytes of interest, and matching the sample solvent with the HPLC–MS system, can be rapidly performed in a very simple step by using the SIPTE method.     

Electrochemically controlled solid-phase microextraction (EC-SPME) based on overoxidized sulfonated polypyrrole

A method for the extraction and selective determination of cations is proposed using electro-synthesized overoxidized sulfonated polypyrrole film. The polymer film is used for the selective extraction of trace levels of nickel and cadmium ions by solid-phase microextraction (SPME). The cation uptake and release properties of the overoxidized sulfonated polypyrrole film electrode were examined under both open circuit and controlled potential conditions for prospective applications in electrochemically controlled solid-phase microextraction. Increased extraction efficiency and selectivity toward cations were achieved in high saline content of water. Simple preparation of film coatings on a platinum wire was possible using a constant potential method. Applied positive and negative potentials facilitated the extraction and desorption of cations, respectively. Nickel and cadmium ions were desorbed into sample aliquot and determined by electrothermal atomic absorption spectrometry (ETAAS). The cation uptake and release mechanism is affected both by the cation exchange at the negative sulfonate and carboxylate moiety on the film and the altered solution pH occurring at the counter electrode caused by the applied potential. The method was validated using a standard reference material and tested for the determination of cadmium ion in commercial table salt samples.