Assessment of dispersive liquid–liquid microextraction for the simultaneous extraction,preconcentration, and derivatization of Hg2+ and CH3Hg+ for further determination by GC–MS

This work reports the development of a dispersive liquid – liquid microextraction method for the simultaneous extraction, preconcentration, and derivatization of Hg²⁺ and CH₃Hg⁺ species from water samples for further determination by GC – MS. Some parameters of the proposed method, such as volume and type of disperser and extraction solvent, and Na[B(C₆H₅)₄] concentration were investigated using response surface methodology. Suitable recoveries were obtained using 80 μL C₂Cl₄ (as extraction solvent), 1000 μL ethanol (as disperser solvent), and 300 μL 2.1 mmol/L Na[B(C₆H₅)₄] (as derivatizing agent). Accuracy was evaluated in terms of recovery and ranged from 87 to 99% with RSD values <7%. In addition, a certified reference material of water (NIST 1641d) was analyzed and agreed with the certified value about 107% (for Hg²⁺), with RSD values <8.5%. LODs were 0.3 and 0.2 μg/L, with enrichment factors of 112 and 115 for Hg²⁺ and CH₃Hg⁺, respectively. The optimized method was applied for the determination of Hg²⁺ and CH₃Hg⁺ in tap, well, and lake water samples.     

Sensitive and robotic determination of bromate in sea water and drinking deep-sea water by headspace solid-phase micro extraction and gas chromatography–mass spectrometry

A robotic method has been established for the determination of bromate in sea water and drinking deep-sea water. Bromate in water was converted into volatile derivative, which was measured with headspace solid-phase micro extraction and gas chromatography–mass spectrometry (HS-SPME GC–MS). Derivatization reagent and the HS-SPME parameters (selection of fibre, extraction/derivatization temperature, heating time and; the morality of HCl) were optimized and selected. Under the established conditions, the detection and the quantification limits were 0.016 μg L⁻¹ and 0.051 μg L⁻¹, respectively, and the intra- and inter-day relative standard deviation was less than 7% at concentrations of 1.0 and 10.0 μg L⁻¹. The calibration curve showed good linearity with r² = 0.9998. The common ions Cl⁻, NO₃⁻, SO₄²⁻, HPO₄²⁻, H₂PO₄⁻, K⁺, Na⁺, NH₄⁺, Ca²⁺, Mg²⁺, Ba²⁺, Mn⁴⁺, Mn²⁺, Fe³⁺ and Fe²⁺ did not interfere even when present in 1000-fold excess over the active species. The method was successfully applied to the determination of bromate in sea water and drinking deep-sea water.     

Effect of the nature and concentration of salting-out agents on the extraction of cobalt(II) from chloride solutions with trialkylamine

The effect of chlorides of Ca²⁺, Ni²⁺, Mg²⁺, Al³⁺, Li⁺, Fe²⁺, Cr³⁺, Na⁺, NH ₄ ⁺ , La³⁺, Nd³⁺ on the extraction recovery of cobalt from chloride solutions with mixtures based on trialkylamine was studied. The series of the salting-out activity of differently charged cations and the degree of their coextraction were determined.     

Ionic liquids dispersive liquid–liquid microextraction and HPLC‐atomic fluorescence spectrometric determination of mercury species in environmental waters

An ionic liquid (IL) based dispersive liquid–liquid microextraction combined with HPLC hydride generation atomic fluorescence spectrometry method for the preconcentration and determination of mercury species in environmental water samples is described. Four mercury species (MeHg⁺, EtHg⁺, PhHg⁺, and Hg²⁺) were complexed with dithionate and the neutral chelates were extracted into IL drops using dispersive liquid–liquid microextraction. Variables affecting the formation and extraction of mercury dithizonates were optimized. The optimum conditions found were as follows: IL‐type and amount, 0.05 g of 1‐octyl‐3‐methylimidazolium hexafluorophosphate; dispersive solvents type and amount, 500 μL of acetone; pH, 6; extraction time, 2 min; centrifugation time, 12 min; and no sodium chloride addition. Under the optimized conditions, the detection limits of the analytes were 0.031 μg/L for Hg²⁺, 0.016 μg/L for MeHg⁺, 0.024 μg/L for EtHg⁺, and 0.092 μg/L for PhHg⁺, respectively. The repeatability of the method, expressed as RSD, was between 1.4 and 5.2% (n = 10), and the average recoveries for spiked test were 96.9% for Hg²⁺, 90.9% for MeHg⁺, 90.5% for EtHg⁺, 92.3% for PhHg⁺, respectively. The developed method was successfully applied for the speciation of mercury in environmental water samples.     

Indirect determination of perchlorate by atomic absorption spectrometry

A liquid-liquid extraction and determination of perchlorate by atomic absorption spectrometry is described. The method involves extraction of perchlorate with the Schiffs base complex [Co(BPTC)₂]⁺, where BPTC = 2-benzoyl pyridine thiosemicarbazone, in methyl isobutyl ketone in acidic medium and subsequent analysis of cobalt in flame AAS, hence indirectly for perchlorate. The extraction efficiency is 98%. The calibration graph was found to be linear for 1.0–11.4 g ClO ₄ ^– per ml of solvent, and the limit of detection is 30 ng ml^–1. The present method is free from interference of large number of foreign ions. The method has been applied for determination of perchlorate in human blood serum samples spiked with perchlorate, urine and commercial potassium chlorate sample.     

Solvent Extraction of Heavy Metals with a 23-Membered Macrocyclic Ionophore Attached with BF 2 + -Capped Cobalt(III) Complex

A new (E, E)-dioxime cobalt(III) complex [Co(HL)₂pyCl]containing four 23-membered macrocyclic ionophores has beenprepared. The cobalt(III) complex [Co(LBF₂)₂pyCl]bridged with BF₂ ⁺ was prepared using the precursorcobalt(III) complex and boron trifluoride ethyl ethercomplex. The solvent extraction of heavy metal cationssuch as Ni²⁺, Cu²⁺, Zn²⁺, Hg²⁺ and Pb²⁺ by the BF₂ ⁺-capped cobalt(III) complex has been investigated. The structure of the complexes is proposedaccording to elemental analyses, ¹H and ¹³C-NMR, IRand mass spectral data.     

Synergistic solvent extraction of copper, cobalt, rhodium and iridium into 1, 2-Dichloroethane at trace level by newly synthesized 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix[4]arene

A spectrophotometric method for determination of copper, cobalt, rhodium and iridium ions from nitric acid media after extraction of these ions by 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix [4] arene (THPAC) has been developed and possible synergistic effect has been investigated. The maximum enhancement was obtained in the presence of 30% 1, 2-dichloroethane in DMF and 3M nitric acid. The trace amounts of the metal were determined spectrophotometrically. Beer’s law was obeyed in concentration range 5.0–10.0 μg, 6.0–120.0 μg, 12.0–100.0 μg, and 10.0–130.0 μg/10 mL of the final solution of copper, cobalt, rhodium and iridium, respectively. The molar absorptivities (l mol^?1 cm^?1) and Sandell’s sensitivities (μg cm^?1) were calculated: Cu (II) = 0.96 × 10^4, 0.0066; Co (II) = 1.13 × 10⁴, 0.0052; Rh (III) = 0.98 × 10⁴, 0.012; and Ir (III) = 2.03 × 10⁴, 0.0095, respectively. Seven replicate analyses containing of 20.0 μg of Cu (II), 24.0 μg of Co (II), 36.0 μg of Rh (III) and 25.0 μg of Ir (III) gave mean absorbance 0.302, 0.462, 0.344, 0.264; and relative standard deviation 0.65, 0.85, 1.10, 1.08%, respectively. The interference of various ions was studied and optimum conditions were developed for determination of metals in certain alloys, environmental, pharmaceutical and synthetic samples.     

Spectrophotometry Determination of Cobalt after Extraction of its Ternary Complex with 3-(4-Phenyl-2-Pyridyl)-5,6-Diphenyl-1,2,4-Triazine and Tetraphenylborate into Molten Naphthalene

The reaction of 3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PPDT) and tetraphenylborate (TPB) with cobalt (II) has been studied to determine the optimum conditions for the extraction and quantitative spectrophotometry determination of this metal. The ternary complex is extracted into molten naphthalene at pH 3.6–7.4. The solid naphthalene containing the cobalt associated complex is separated by filtration and dissolved in acetonitrile. Beer's law is obeyed in the concentration range 8–140 μg cobalt in 10 ml of acetonitrile solution. The molar absorptivity and sensitivity are 4.2×10³ l·mol^?1·cm^?1 and 0.01408 μg/cm², respectively. The other factors such as pH, amounts of reagents and naphthalene, shaking and standing times, and the effect of diverse ions are studied. The method has been applied to the determination of cobalt in iron steel alloys.     

Capillary electrophoretic determination of ammonia using headspace single-drop microextraction

A new method involving headspace single-drop microextraction (SDME) and capillary electrophoresis (CE) is developed for the preconcentration and determination of ammonia (as dissolved NH₃ and ammonium ion). An aqueous microdrop (5 μL) containing 1 mmol/L H₃PO₄ and 0.5 mmol/L KH₂PO₄ (as internal standard) was used as the acceptor phase. Common experimental parameters (sample and acceptor phase pH, extraction temperature, extraction time) affecting the extraction efficiency were investigated. Proposed SDME-CE method provided about 14-fold enrichment in about 20 min. The calibration curve was linear for concentrations of NH₄⁺ in the range from 5 to 100 μmol/L (R² = 0.996). The LOD (S / N = 3) was estimated to be 1.5 μmol/L of NH₄⁺. Such detection sensitivity is high enough for ammonia determination in common environmental and biological samples. Finally, headspace SDME was applied to determine ammonia in human blood, seawater and milk samples with spiked recoveries in the range of 96-107%.     

Determination of microamounts strontium by substoichiometric isotope dilution analysis

The isotope dilution with substoichiometric separation for the determination of strontium has been investigated. Strontium can be extracted with a substoichiometric amount of bis-1,2-dicarbollylcobaltate in nitrobenzene in the presence of 15-crown-5. It has been found, that Li⁺, Mg²⁺, Ca²⁺ and Fe³⁺ do not interfere in the strontium determination but the high extraction of K⁺, Na⁺ and NH₄ ⁺ ions results in marked influence.     

Spektrophotometrische Bestimmung von Kobalt in Bleilegierungen

Zusammenfassung Die vorgeschlagene spektrophotometrische Methode beruht auf der Reaktion von Triphenyltetrazoliumchlorid (TTC) mit dem Thiocyanatokomplex des Kobalts(II). Bleilegierungen werden in Salpetersäure gelöst, das Blei mit Natriumchlorid gefällt und durch Abfiltrieren entfernt. Das Kobalt wird mit TTC und Thiocyanat in (TT)₂ [Co(CNS)₄] übergeführt, mit Chloroform extrahiert und unter Verwendung eines gelben Lichtfilters photometriert.Das Beersche Gesetz ist in den Grenzen 2–100g Co erfüllt. Die Bestimmung wird in Gegenwart von Ascorbinsäure und Thiosulfat durchgeführt und durch Ag⁺, Fe³⁺, Cu²⁺, Ni²⁺, Hg²⁺, Mo⁴⁺ und Zn²⁺ nicht gestort.Der mittlere Relativfehler der Methode ist 5,60%.

---

The photometric determination of cobalt in lead alloys

Summary The proposed spectrophotometric method is based on the reaction of triphenyltetrazolium chloride (TTC) with the thiocyanato complex of cobalt(II). Lead alloys are dissolved in nitric acid, the lead is precipitated with sodium chloride and removed by filtration. The cobalt is converted into (TT)₂ [Co(CNS)₄] by means of TTC and thiocyanate, extracted with chloroform and photometrized with employment of a yellow light filter.Beer's law is valid between the limits 2–100g CO. The determination is conducted in the presence of ascorbic acid and thiosulfate and there is no interference by Ag⁺, Fe³⁺, Cu²⁺, Ni²⁺, Hg²⁺, Mo⁴⁺ and Zn²⁺.The mean relative error of the method is 5.60%.

     

Catalytic adsorptive stripping voltammetry versus electrothermal atomic absorption spectrometry in the determination of trace cobalt and chromium in human urine

Two methods of the determination of cobalt and chromium in human urine of non-occupationally exposed populations—highly sensitive catalytic adsorptive stripping voltammetry (CAdSV) and electrothermal atomic absorption spectrometry (ET-AAS)—are evaluated and compared. The CAdSV methods are based on adsorptive accumulation of a cobalt-nioxime (1,2-cyclohexanedione dioxime) or a chromium-DTPA (diethylenetriammine-N,N,N′,N″,N″-pentaacetic acid) complexes on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the catalytic reduction current of the adsorbed complex in the presence of sodium nitrite in case of cobalt or in the presence of sodium nitrate in case of chromium determination. In the CAdSV procedure UV-photolysis was used for the sample pre-treatment; the ET-AAS determination did not require any separate preliminary decomposition of the analyte urine samples. The accuracy of the procedures was checked by the analysis of commercially available quality control urine samples. The detection limits (3σ) were 0.13 μg l⁻¹ for Co and 0.18 μg l⁻¹ for Cr in ET-AAS determination and 0.007 μg l⁻¹ for Co and 0.002 μg l⁻¹ for Cr in CAdSV measurements. Precision (R.S.D.) was less than 5% for both methods. The study has shown that the CAdSV is a more reliable and sensitive technique for the determination of very low cobalt and chromium contents in urine, the detection of which is not possible when using the AAS technique.     

Simultaneous Determination of Ten Antibiotic Residues in Milk by UPLC

An analytical method for rapid screening and quantitative determination of ten antibiotics (chloramphenicol, thiamphenicol, tetracycline, oxytetracycline, chlortetracycline, metacycline, doxycycline, cefoperazone, ceftriaxone and cefaclor) residues in milk was developed using ultra performance liquid chromatography with photodiode array detector. After extraction with McIIvaine buffer + methanol (8 + 2), the extract was cleaned up with solid-phase extraction cartridge. The conditions of sample extraction, cleaning and separation were optimized. The average spiked recoveries of milk samples were 52.1–68.0, 70.1–81.0 and 76.2–101.0% at spiked levels of 0.1, 0.5, 2.5 μg g^?1, respectively with precisions of 3.3–15.9%. The limits of detection and quantification were 0.003–0.022 and 0.01–0.08 μg g^?1, respectively. The proposed method has been applied to the determination of antibiotics in actual milk samples with satisfactory results.     

A quick and precise heterometric microdetermination of traces of palladium in metals with nitron

A heterometric study was made of the reaction between palladium chloride and nitron in thiocyanate solutions in the presence of excesses of various masking agents.A method is presented for the hetorometric determination of ~0.5 mg palladium in 20 ml aqueous solution with nitron, which can be carried out within 5–10 mn. The solution to be analysed may in general contain ~99.5% of the following foreign metals as cations: Ca⁺², Ba⁺², Mg⁺², Zn⁺², Mn⁺², Co⁺², Ni⁺², Al⁺³, Fe⁺³, Cr⁺³, UO₂⁺², Cu⁺², Cd⁺², Hg⁺², Pb⁺², Tl⁺, Sb⁺³,Bi⁺³, Th⁺⁴, Ce⁺³ and ZrO⁺². The error is between 0 and 1%.     

Exploration of Pb2+ Selective Behavior of Calix[6]arene Ester Derivative

The selective behavior of calix[n]arene ester derivatives in two-phase extraction systems using polarographic technique has been investigated. Calix[4]arene tetraester derivative shows remarkable Na⁺ over Pb²⁺ selectivity; whereas calix[6]arene hexaester derivative shows Pb²⁺ over Na⁺ selectivity. The interference of some selected cations (Na⁺, K⁺, Cu²⁺ and Mg²⁺) were also examined and no significant effect on the selectivity behavior as well as extraction ability of these ionophores was found except Na⁺. The study reveals for the first time that the calix[6]arene hexaester derivative is highly Pb²⁺ selective ionophore and can be employed in the field of sensor as well as separation science and technology. The work also highlights the usefulness of polarographic technique in trace metal determination.     

Simultaneous determination of Mn(II), Cu(II) and Fe(III) as 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol complexes by adsorptive cathodic stripping voltammetry at a carbon paste electrode

A simple and precise square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for simultaneous determination of Mn(II), Cu(II) and Fe(III) in water samples using a carbon paste electrode. In 0.1 mol L⁻¹ acetate buffer (pH 5) containing 50 μmol L⁻¹ of 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol (5-Br-PADAP), Mn(II), Cu(II) and Fe(III) were simultaneously determined as metal-complexes with 5-Br-PADAP following preconcentration onto the carbon paste electrode by adsorptive accumulation at +1.0 V (vs. Ag/AgCl/3 M KCl). Insignificant interference from various cations (K⁺, Na⁺, Mg²⁺, Ca²⁺, Al³⁺, Bi³⁺, Sb³⁺, Se⁴⁺, Zn²⁺, Ni²⁺, Co²⁺, Cd²⁺, Pb²⁺, V⁵⁺, Ti⁴⁺ and NH₄⁺), anions (HCO₃⁻, Cl⁻, NO³⁻, SO₄²⁻ and PO₄³⁻) and ascorbic acid was noticed. Limits of detection of 0.066, 0.108 and 0.093 μg L⁻¹ and limits of quantitation of 0.22, 0.36 and 0.31 μg L⁻¹ Mn(II), Cu(II) and Fe(III), respectively, were achieved by the described method. The described stripping voltammetry method was successfully applied for simultaneous determination of Mn(II), Cu(II) and Fe(III) in ground, tap and bottled natural water samples.     

Tuning the selectivity of polymeric ionic liquid sorbent coatings for the extraction of polycyclic aromatic hydrocarbons using solid-phase microextraction

A new generation polymeric ionic liquid (PIL), poly(1-4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm⁺ NTf₂⁻)), was synthesized and is shown to exhibit impressive selectivity towards the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from aqueous samples when used as a sorbent coating in direct-immersion solid-phase microextraction (SPME) coupled to gas chromatography (GC). The PIL was imparted with aromatic character to enhance π–π interactions between the analytes and the sorbent coating. For comparison purposes, a PIL with similar structure but lacking the π–π interaction capability, poly(1-vinyl-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide) (poly(HDIm⁺ NTf₂⁻)), as well as a commercial polydimethylsiloxane (PDMS) sorbent coating were evaluated and exhibited much lower extraction efficiencies. Extraction parameters, including stir rate and extraction time, were studied and optimized. The detection limits of poly(VBHDIm⁺ NTf₂⁻), poly(HDIm⁺ NTf₂⁻), and PDMS coatings varied between 0.003–0.07 μg L⁻¹, 0.02–0.6 μg L⁻¹, and 0.1–6 μg L⁻¹, respectively. The partition coefficients (log K_fs) of eight PAHs to the three studied fiber coatings were estimated using a static SPME approach. This study represents the first report of analyte partition coefficients to any PIL-based material.     

Preparation and Characterization of an Unusual Di-Cobalt Complex; X-Ray Crystal Structure of Co(CO)2(μ-CO)(μ:η2,η4-C4Ph4)Co(CO)2(PPh3)

Reaction of [MoCo(CO)₅(PPh₃)₂(η⁵-C₅H₅)] (1) with diphenylacetylene in tetrahydrofuran at 50 °C yielded two heterobimetallic compounds, [MoCo(CO)₄.(PPh₃){μ-PhC ? CPh}(η⁵-C₅H₅)] (4) and [MoCo(CO)₅{μ-PhC ? CPh} (η⁵-C₅H₅)] (5). However, an unexpected product, Co(CO)₂(μ-CO)(μ:η₂,η⁴-C₄Ph₄)Co(CO)₂(PPh₃) (6), was observed while attempting to grow the crystals for structural determination of 4. The X-ray crystal structure of 6 was determined: triclinic, $ {\rm P}\bar 1 $, a = 11.654(2) Å, b = 12.864(2) Å, c = 13.854(2) Å, α = 89.67(2)°, β = 86.00(2)°, γ= 83.33(2)°, V = 2057.9(6) ų Z=2. In 6, two cobalt fragments are at apical and basal positions of the pseudo-pentagonal pyramidal structure, respectively. The electron count for the apical cobalt fragments is 20, which is rather unusual. It is believed that 6 was formed after the fragmentation and recombination of the fragmented species of 4.     

Trace determination of manganese(II) by temperature-controlled/assisted ionic liquid-based dispersive liquid-phase microextraction and electrothermal atomic absorption spectrometry

A microextraction method, namely temperature-controlled/assisted ionic liquid-based dispersive liquid-phase microextraction (DLPME) for manganese(II) determination in environmental water samples is presented. Manganese(II) was extracted from aqueous solution into an ionic liquid (IL) after complexation with 1-(2-thiazolylazo)-2-naphthol (TAN) and directly introduced for electrothermal atomic absorption spectrometry (ETAAS) determination. Several factors that might affect ETAAS signal and extraction efficiency, such as pyrolysis and atomization temperature; and pH adjustment, concentration of TAN, extraction time, volume of IL and stirring rate were studied. Within optimal experimental conditions, the detection limit (3σ), the quantification limit (10σ), the enrichment factor and the relative standard deviation for five replicate determinations at 0.5 μg L^?1 of manganese(II) were calculated as 0.023 μg L^?1, 0.076 μg L^?1, 58.7 and 6.3 %, respectively. The presented method was also successfully applied to the determination of manganese(II) in real samples. The main benefits of the method are simplicity, low cost, rapidity, high recovery, powerful extraction efficiency and the proposed approach is free of volatile organic solvents.     

Electrochemical metal-ion sensor based on a cobalt phthalocyanine complex captured in Nafion® on a glassy carbon electrode

This article describes an electrochemical metal-ion sensor based on a cobalt phthalocyanine (CoPc) complex and determination of its sensor activity for some transition metal ions. Ag⁺ and Hg²⁺, among several transition metal ions, coordinate to the sulfur donors of CoPc and alter the electrochemical responses of CoPc in solution, indicating possible application of the complex as Ag⁺ and Hg²⁺ sensor. For practical application, CoPc was encapsulated into a polymeric cation exchange membrane, Nafion, on a glassy carbon electrode and used as an electrochemical coordination element. This composite electrode was potentiometrically optimized and potentiometrically and amperometrically characterized as transition metal-ion sensors with respect to reproducibility, repeatability, stability, selectivity, linear concentration range, and sensitivity. A µmol?dm^?3 sensitivity of the CoPc-based sensor indicates its possible practical application for the determination of Ag⁺ and Hg⁺² in waste water samples.