Atomic Absorption Spectrometric and Spectrophotometric Trace Analysis of Indium in Environmental Samples

Abstract

Indium (III) was selectively extracted at pH 5.2–5.9 with N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA) into chloroform. BPAR [5-bromo-4(2-pyridylazo) resorcinal] was added to the extract to form an intensely red coloured ternary complex measurable spectrophotometrically at 515 nm (? = 5.81 × 10⁴ 1 mol^?1 cm^?1). The extraction system enabled enrichment of indium and determination of the metal down to 10^?4 ppm (0.1 ppb) levels. For atomic absorption spectrometric determination, indium was extracted with MFHA into methyl isobuyl ketone and measured at 303.9 nm resonance line in the air-acetylene flame. Both the methods were     

Solute Retention in Column Liquid Chromatography. VI. Enthalphy Entropy Compensation: The Column Temperature and Mobile-Phase Composition

Abstract

The concept of enthalpy-entropy compensation in “non-polar” reverse-phase (ODS) column liquid chromatography is examined in terms of the column temperature (10[ddot]-35[ddot]C) as well as mobile-phase composition (acidified water/tetrahydrofuran) for the solutes: phenol, p-nitrophenol, 2,4-dinitrophenol, o-chlorophenol, o-nitrophenol, 2,4-dimethylphenol, 2,4- dinitro-o-cresol, 4-chloro-m-cresol, and 2,4-dichlorophenol. Plots of log (solute capacity factor, k') against reciprocal column temperature, T^?1 exhibit approximate linearity only over the volume-fraction based mobile phase compositional range ?THF = 0 to 0.2. Substantial deviations occur beyond ?THF = 0.3. Plots of In k' against -ΔH[ddot] (compensation plots) yield a random distribution of data, indicating that what enthalpy-entropy compensation may exist for the systems studied is masked both in terms of temperature and mobile-phase composition. It is concluded that interaction(s) of the solutes with the stationary sorbent are more complex than has heretofore been supposed.     

Spectrophotometric determination of vanadium in petroleum crudes and derivatives

The spectrophotometric study of the complexation reaction between 5,5′methylenedisalicylhydroxamic acid and V(V) shows that two complexes are formed, the 1:1 (? = 5100 liters mol^?1 cm^?1 at 490 nm, log K_est = 5.8 ± 0.1) and the 1:2 (L:V) (? = 6250 liters mol^?1 cm^?1 at 600 nm, log K_est = 6.1 ± 0.1). A spectrophotometric method is developed for the determination of vanadium (2–9 ppm) at 2 N HCl and 495 nm, which allows its determination in petroleum crude oils with a series of advantages over the ASTM D-1548-63 method.     

Investigation of the Photochemistry and Quantum Yields of Triazines Using Polychromatic Irradiation and UV-Spectros Copy as Analytical Tool

Abstract

Photochemical reactions of atrazine, propazine, simazine, terbuthylazine, ametryn and atraton were investigated in aqueous and buffered (pH=7–9) solutions (containing a few percent of acetonitrile) using a polychromatic Xe light source at T=22[ddot]C. For terbuthylazine the photochemistry is investigated in detail, including solvent-, temperature-and pH-dependence and products found. The role of polychromatic light sources used in investigations of the photochemistry of triazines is discussed.

For the first time, quantum yield measurements were performed in the UV-band between 240–300 nm of the chlorotriazines and ametryn. Isosbestic points were found in the UV-spectra at different irradiation times, and UV-spectroscopy was used to obtain kinetic information.

Quantum yields in aqueous solutions at T=22[ddot]C for the chlorotriazines (Φ=0.048–0.062) and for ametryn (Φ=0.043) are comparable. The temperature dependence of the photoreaction of terbuthylazine leads to an activation energy of about 13 kJ mol^?1. Quantum yields in acetonitrile and hexane for terbuthylazine are about half of the values found in aqueous solution.

Atraton was not degradable under the conditions used, and the quantum yield could only be estimated to be Φ < 0.002.     

Copper(II) and nickel(II) complexes of mono-oxocyclam(5-oxo-1,4,8,11-tetraazacyclotetradecane). Synthetic and potentiometric studies

Summary The macrocyclic mono-oxotetraamine, 5-oxo-1,4,8,11-tetraazacyclotetradecane (mono-oxocyclam=LH) has been prepared by reaction of methyl acrylate with 2,3,2-tetra(1,9-diamino-3,7-diazanonane). The protonation constants of the ligand are log K₁=9.40, log K₂=6.65 and log K₃=2.87 at 25 °C (I=0.1 mol dm^–3 NaClO₄). Detailed potentiometric studies of the interaction of the base with copper(II) and nickel(II) have been carried out. In the pH range 2.5–7.0 two complexes, [CuLH]²⁺ and [CuL]⁺, form; the deprotonated complex being 100% abundant at pH 7. For nickel(II), only [NiL]⁺ forms (log _11–1 = 3.90), the yellow low spin nickel complex reaching its maximum concentration above pH 6. The [CuL][ClO₄] · H₂O and [NiL][ClO₄] 0.5 H₂O complexes have been characterised in the solid state. The nickel(II) complex is square planar with a d-d band at 22625 cm^–1.     

Mixed complexes of palladium(II) with 1-aminoethylidene-1,1-diphosphonic acid and glycine

The complexing of palladium(II) with two biological active reagents: glycine (Gly, HA) and 1-aminoethylidene-1,1-diphosphonic acid (AEDP, H₄L) at concentrations of chloride ions (0.15 mol/L) corresponding to physiological levels is studied by means of spectrophotometry, pH potentiometry, and ³¹P NMR spectroscopy. The formation constants for mixed complexes with compositions of [PdH₂LA]^? (log?? = 43.7) and [PdHLA]^2? (log?? = 39.05) are determined. The both ligands are found to be coordinated to palladium(II) in a bidentant-cyclic manner: through amine nitrogen and the oxygen atom of the carboxyl group (in the case of Gly), or through the phosphonic group (in the case of AEDP). A diagram of the distribution of equilibrium concentrations of the complexes depending on pH is calculated for the system K₂[PdCl₄]: Gly: AEDP = 1: 1: 1. It is demonstrated that there are complexes with compositions of [PdHLA]^2?, [PdA₂], and [Pd(HL)₂]^4? in solutions with $C_{Cl^ - } = 0.15 mol/L$ and pH 6?C7.     

Spectrophotometric Studies on the Proton Transfer from the Protonated DNA to 5,10,15,20-Tetrakis[4-(trimethyammonio)-phenyl]porphine

Abstract

The interaction of nucleic acids with 5, 10, 15, 20-tetrakis[4-trimethy-ammonio)phenyl]porpine (TAPP) were investigated on the basis of a mechanistic discussion, and a spectrophotometric method for DNAs was accordingly proposed in the present paper. Depending on the acidity of the solution, TAPP can interact with nucleic acids, producing different absorption features. When the pH of the solution is higher than 6.39, TAPP can interact with both DNAs and RNA, giving a new absorption band at 420.3 nm. If the pH is lower than 6.39, however, the interactions with DNAs (but not RNA) can give an absorption band centered at 436.3 nm. It was found that the absorption band at 436.3 nm originates from the proton transfer from the protonated double-stranded structure of DNA to TAPP. At optimal conditions, the absorbance at 436.3 nm is in proportion to the concentration of the DNAs. Calibration curves were linear in the range of 0±3.0 μg.ml^?1 for calf thymus and 0±3.2 μg.ml^?1 for fish sperm DNA. No interference of 4-fold of RNA was found for the determination of DNAs. The limits of determination (3[sgrave]) were 34.6 ng.ml^?1 for calf thymus DNA and 33.2 ng.ml^?1 for fish sperm DNA, respectively. Four synthetic samples were determined with satisfaction.     

Spectroscopic and HPLC methods for the determination of alendronate in tablets and urine

Two methods (spectrophotometric and HPLC) have been developed and validated for the analysis of alendronate sodium in tablet dosage form. Both methods depend on the ability of alendronate sodium to react with o-phthalaldehyde (OPA) at basic pH to produce a light-absorbing derivative. The derivative was found to possess absorption maximum at 330 nm where neither the derivatizing agent nor the analyte had any absorption. Thus, spectroscopic method was based on the derivatization-induced absorption of alendronate sodium at 333 nm. The HPLC method was based on separation of the formed derivative from other ingredients in tablets with detection at 333 nm. Both methods were satisfactory with regard to accuracy, prescion and linearity. Moreover, a HPLC method with fluorescence detection (HPLC-FD) was developed for the quantification of alendronate sodium in urine. The method was also based on the derivatization of alendronate with OPA, but fluorescence detection was employed. Linearity, recovery, selectivity, prescision and sensitivity were satisfactory for the proposed HPLC-FD method. Yet a new quantification limit (0.6 ng ml⁻¹) for alendronate in urine was achieved.     

Supramolecular assembler based on cucurbit[8]uril: Photodimerization of a styryl dye in water

Photolysis of aqueous solutions of styryl dye 1 in the presence of cucurbit[8]uril (CB[8]) has been studied by optical spectroscopic methods for the molar ratios n = c _CB[8]/c ₁ in the range of 0 ≤ n ≤ 6. It has been found that the inclusion complexes (1)₂@CB[8] dominate in the solution at n ≤ 0.5, whereas the complexes 1@CB[8] dominate at n ≥ 1. The stability constants have been determined for the 1: 1 (log K ₁ = 6.2 (L mol^?1)) and 2: 1 (log β = 11.9 (L² mol^?2)) complexes. The fluorescence decay kinetics of dye 1 in the presence of CB[8] is two-exponential, with the average lifetime increasing substantially at n ≥ 1. It has been shown that the system can operate in the cyclic mode as an assembler (or supramolecular catalyst) in the photodimerization reaction of dye 1 to form cyclobutane derivative 2. The stability constant of the complex 2@CB[8] (log K ₃ = 5.9 (L mol^?1)) and the quantum yield of cycloaddition (? ≈ 0.07 at n ≈ 0.5) have been determined.     

Second Derivative Spectrophotometric Determination of p-Aminophenol in the Presence of Paracetamol

Abstract

A second derivative spectroscopic method for the determination of p-aminophenol in paracetamol powder is described. Second derivative absorbance (d²A/dλ²) values were measured at 223.8 nm (Δ = 4.2 nm) where p-aminophenol showed derivative responses obeying Beer's Law but paracetamol had negligible derivative absorption. The concentrations of p-aminophenol solutions prepared in 0.1 N HCl (0.12–7.61 mcg/ml), containing constant amounts of paracetamol (20 mcg/ml) related linearly with the d²A/dλ² values and gave a straight line (r = ?0.9999). The method allowed determination of 0.5% to 38% of p-aminophenol in paracetamol without prior separation, it is rapid, precise and accurate.     

Effect of Pyruvate on the Redox Behavior of the Iron (III)-(II) Couple

Abstract

Evidence for the formation of Fe(III) and Fe(II) complexes with pyruvate ion is presented. Complexes with a 1:2 ratio of Fe(II) to pyruvate and 1:1 ratio of Fe(III) to pyruvate were identified by spectrophotometry. The complexation results in partial kinetic control of the electrochemical oxidation of Fe(II) in citrate buffer. In addition, Fe(III) was found to be chemically reduced by pyruvate. The apparent first order rate constant at 25[ddot]C is 7.12 × 10^?2 s ^?1in pH 4.0 pyruvate buffer and 1.24 × 10^?1 s ^?1 in pH 3.2 pyruvate buffer. In pH 4.0 citrate buffer the reaction is not first order and is significantly slower.     

Spectrophotometric Investigation of Iron(III)-N-Phenylcin-namohydroxamic Acid System

Abstract

N-Phenylcinnamohydroxamic acid, PCHA, was found to react with iron (III) to form complex species of different colour depending upon the reaction environment. The reaction conditions for the formation of the complex species were studied in aqueous-ethanolic medium. The general spectral properties of the species were investigated. The absorption curves were found to have two isobestic points. The number and composition of the complexes were determined and found to have composition 1:1, 1:2, 1:3 (Fe: PCHA). The wavelengths of the maximum absorbances were figured out to be 535, 495, and 445 nm for the I, II, and III complex species, respectively. It was verified that the Beer's law holds for these complexes at all wavelengths, and for the mixtures at the wavelengths of the isobestic points in a wide range of pH. The stepwise stability constants have been determined by the method of isobestic point and found to be log K₁ = 11.55, log K₂ = 10.11, and log Kg₃ = 7.44 for the I, II, and III complex species, respectively. The distribution diagrams (nomograms) of the complex species as a function of pH were constructed and the molar extinction coefficients of the three consecutive complexes have also been determined.     

Rapid TLC Separation of some Closely Related 1-(2-Benzothiazolyl)-3- Methyl-5-Phenyl Pyrazole Derivatives

Abstract

Some closely related 1-(2-Benzothiazolyl)-3-methyl-5-phenyl pyrazole derivatives have been separated by TLC on silica gel-G[ddot] Most suitable solvent systems tried are (A) Pet. ether (40[ddot]-60[ddot])- Benzene (1:3) and (B) cyclohexane: ethylacetate (50:3).     

Recognition Studies of a Pyridine-Pendant Calix[4]arene with Neutral Molecules: Effects of Non-covalent Interactions on Supramolecular Structures and Stabilities

A new calix[4]arene derivative containing hydrogen bond acceptors,5,11,17,23-tetra-tert-butyl-25,27-bis[(4-pyridylmethyl)oxy]-26,28-dihydroxycalix[4]arene (L), has been synthesized. ¹H-NMR titrations in chloroform-d werecarried out to investigate the host–guest chemistry ofL towards neutral molecules containing a widevariety of hydrogen bond donor groups such as aldehydederivatives of p-tert-butylcalix[4]arenes(compounds 3 and 4), acetylacetone,1,2-diaminoethane, 2,6-diaminopyridine, catechol,resorcinol, hydroquinone, phthalic acid, isophthalicacid and terephthalic acid. L can formcomplexes with resorcinol, phthalic acid and catecholin 1 : 1 (log K = 3.13), 1 : 1 (log K = 5.41) andpolymeric fashions, respectively. In addition, thesolution structures of these complexes have beenrevealed by NOESY experiments. L forms a 1 : 1complex with resorcinol by hydrogen bonding and vander Waals interactions resulting in a supramolecularframework. The phthalic acid molecule interacts withL via hydrogen bonding and is included into thelower rim cavity of L.     

Hydroxy Naphthol Blue as a Spectrophotometric and Fluorometric Reagent for the Uranyl Ion

Abstract

The utility of hydroxy naphthol blue (HNB) as a spectrophotometric and fluorometric reagent for the uranyl ion has been investigated. In phthalate buffer (at a pH of 4.0), UO₂ ²⁺ forms a brown complex of low absorptivity with the red form of HNB. By following the decrease in HNB absorbance at 530 nm (which has ε = 4.1 × 10³) uranyl ion can be determined to levels as low as 1.1 × 10^?6 M (0.30 μg/ml). HNB also emits at 460 nm when excited at 365 nm at these pH values, while the UO₂ ²⁺ complex exhibits greatly reduced emission. Examination of the quenching of HNB emission by UO₂ ²⁺ allows the determination of uranyl ion to levels as low as 3.2 × 10^?6 M (0.86 μg/ml). A 1:1 type complex was formed between UO₂ ²⁺ and HNB, and a formation constant of 9.77 × 10³ (log K₁ = 3.99) was measured for the complex.     

1, 8-Dihydroxyanthraquinone-Ca(II) Reaction. Spectrofluorimetric Determination of Traces of Ca(II)

Abstract

1, 8-Dihydroxyanthraquinone (1, 8-DHAn) shows a fluorescent reaction with Ca(II) ion in ethanol-water mixtures and ammoniacal medium.

In the present work the 1, 8-DHAn-Ca(II) complex has been studied spectrofluorimetrically. The complex shows two excitation maxima at 485 nm and 495 nm and its emission maximum is centered at 615 nm. A 2:1 (R:C) stoichiometry and a log K_est of 7.38±0.22 for the overall equilibrium have been found for the complex.

A new method for the spectrofluorimetric determination of Ca(II) between 50 and 550 ngml^?1 has been proposed. The interference level of foreign ions has been established.     

GC-MS Derivatization Studies: The Formation of Dexamethasone MO-TMS

Abstract

The 16α-methyl group in dexamethasone increases drastically the steric hindrance to reaction of both the 20-ketone and 17α-hydroxyl groups, as shown by kinetic studies with GC-MS techniques. A procedure is described for the preparation of the MO derivative (reaction et 60[ddot]C for 3 hr) and complete conversion of all hydroxyl groups to TMS ether groups (reaction at 100[ddot]C for 6 hr). The resulting MO-TMS derivative is thermostable and suitable for use in GC-MS methods. The procedures usually employed in urinary steroid studies are satisfactory for prednisone and prednisolone.     

Extraction—spectrophotometric determination of traces of cadmium with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of cadmium is described. The ion-associate formed between the cadmium-PAR anionic chelate and cetyldimethylbenzylammonium chloride (CDBA) is extracted with chloroform at pH 10. The absorption maximum of the extracted species occurs at 505 nm, the molar absorptivity being (9.82 ± 0.30) × 10⁴ l mol^-1 cm^-1. The optimal concentration range for measurements is 0.2–1.0 μg Cd ml^-1; Beer's law is obeyed. The composition of the ion-associate is estimated to be CdPAR₂-2CDBA. The conditional extraction constant is log K'_ex ≈ 8. The stability constant of the cadmium—PAR chelate in aqueous solution is log β₂ = 17.5 ± 0.3. Extraction with N-benzoyl-N-phenylhydroxylamine is used to avoid several interferences. Moderate amounts of zinc are masked with sodium hydroxide.     

Development and Validation of Derivative Spectrophotometric Method for Determination of Rabeprazole Sodium in Pharmaceutical Formulation

Abstract

The aim of this work is to develop and validate the derivative spectrophotometric method for determination of the proton pump inhibitor rabeprazole sodium in pharmaceutical formulations. The technique was applied using water (pH 10.0) as diluent. The first‐order derivative spectra were obtained at N=5, Δλ=4.0 nm, and determinations were made at 304 nm. The method showed high specificity in the presence of formulation excipients and good linearity in the concentration range of 6.0 to 18.0 µg/mL^?1. The intra‐ and interday precision data demonstrated the method has good reproducibility [Relative Standard Deviation ((RSD)=1.0 interdays)]. Accuracy was also evaluated and results were satisfactory (mean recovery of 99.15%). The detection and quantitation limits were 0.055 and 0.17 µg/mL^?1, respectively. The method was demonstrated to be adequate for routine analysis in quality control.     

Anion Recognition with Hydrogen‐Bonding Cyclodiphosphazanes

Modular cyclodiphosph(V)azanes are synthesised and their affinity for chloride and actetate anions were compared to those of a bisaryl urea derivative ( 1 ). The diamidocyclodiphosph(V)azanes cis‐[{ArNHP(O)(μ‐tBu)}₂] [Ar=Ph ( 2 ) and Ar=m‐(CF₃)₂Ph ( 3 )] were synthesised by reaction of [{ClP(μ‐NtBu)}₂] ( 4 ) with the respective anilines and subsequent oxidation with H₂O₂. Phosphazanes 2 and 3 were obtained as the cis isomers and were characterised by multinuclear NMR spectroscopy, FTIR spectroscopy, HRMS and single‐crystal X‐ray diffraction. The cyclodiphosphazanes 2 and 3 readily co‐crystallise with donor solvents such as MeOH, EtOH and DMSO through bidentate hydrogen bonding, as shown in the X‐ray analyses. Cyclodiphosphazane 3 showed a remarkably high affinity (log[K]=5.42) for chloride compared with the bisaryl urea derivative 1 (log[K]=4.25). The affinities for acetate (AcO^?) are in the same range ( 3 : log[K]=6.72, 1 : log[K]=6.91). Cyclodiphosphazane 2 , which does not contain CF₃ groups, exhibits weaker binding to chloride (log[K]=3.95) and acetate (log[K]=4.49). DFT computations and X‐ray analyses indicate that a squaramide‐like hydrogen‐bond directionality and C_α?H interactions account for the efficiency of 3 as an anion receptor. The C_α?H groups stabilise the Z,Z‐ 3 conformation, which is necessary for bidentate hydrogen bonding, as well as coordinating with the anion.