Zhikun Si

Simultaneous spectrofluorimetric determination of terbium, samarium and europium with hexafluoroacetylacetone-trioctylphosphine oxide and Triton X-100

Abstract In aqueous solution, the fluorescence intensity is a linear function of concentration in the ranges 1.0 × 10 −4 -1.0 × 1.0 −6 M Sm and 1.0 × 10 −6 -1.0 × 10 −8 M Tb and Eu. The optimum conditions are 1 × 10 −3 M hexafluoroacetylacetone, 1 × 10 −4 M trioctylphosphine oxide and 0.05% Triton X-100 at pH 3.0.

Fluorescence enhancement of the europium-yttrium-diphacinone-ammonia system

Abstract A study of the enhanced (ca. 100 ×) fluorescence intensity of the Eu 3+ -diphacinone-ammonia system by Y 3+ was made using a colloidal suspension. The excitation and emission wavelengths were 330 and 612 nm, respectively. The fluorescence intensity was a linear function of the concentration of europium in the range 6.0 × 10 −11 –8.0 × 10 −7 M. The detection limit was 8.0 × 10 −14 M. The standard addition method was used for the determination of europium in rare earth oxides, with satisfactory results.

Study on sensitised luminescence of rare earths by fluorescence enhancement of the europium-gadolinium-diphacinone-ammonia complex system and its application

A study of the enhancement effect on the fluorescence intensity of the Eu3+-diphacinone(DPN)-ammonia system by La3+, Gd3+ and Y3+, has been carried out in a colloid-type suspension. Gadolinium caused the largest enhancement of the fluorescence intensity. In the presence of this element the fluorescence of the Eu-DPN-NH3 system was enhanced by a factor of about 100 at a pH of between 8.5 and 9.5. Excitation and emission wavelengths were 330 and 612 nm, respectively. Fluorescence intensity was a linear function of the concentration of europium in the range 8.0 × 10–9–1.0 × 10–11M. The detection limit was 6.0 × 10–14M. The standard additions method was used for the determination of europium in rare earth oxides and gave satisfactory results.

enhanced luminescence of terbium-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-( 1-piperazinyl) -3-quinolinecarboxylic acid with lanthanum and its application

Abstract In this paper, we found a new enhancement fluorescence system La-Tb-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid (or ciprofloxacin, CPFX)-sodium dodecylbenzenesulfonate (SDBS), and the characteristic fluorescence of the La-Tb-CPFX-SDBS system was studied in detail. The effect of the experimental conditions on the fluorescence intensity was defined. By adding a suitable amount of La3+ to the Tb-CPFX-SDBS system, the fluorescence can be enhanced approximately three-fold. The fluorescence intensity is a linear function of europium up to a limit of 5.0×10−10 mol/l. The system was used for determination of terbium in rare earth samples with satisfactory results. The mechanism of fluorescence enhancement is also discussed.

Derivative spectrophotometric determination of praseodymium in rare earth mixtures with lomefloxacin

Praseodymium forms a Pr(LMFX)(3) complex with lomefloxacin. In this paper, the absorption spectra of the complex has been investigated by applying conventional and derivative spectrophotometric methods. It was found that lomefloxacin could form a stable complex with praseodymium in the pH 6.5-8.5 media. The absorption intensity of the complex is 4.5-fold more than PrCl(3). Using the second derivative spectra, the sensitivity is 7.4 times higher for Pr than in the normal method (zero derivative spectra). The second derivative spectrophotometry for determination of praseodymium in the presence of other rare earths has been developed. The calibration curves were linear in the range of 3.5-65 mug ml(-1) for Pr. The detection limit is 0.85 mug ml(-1). The method is satisfactory for the determination of praseodymium in mixed rare earths.

Determination of some cephalosporins in pharmaceutical formulations by a fluorescence quenching method

A fluorescence quenching method for the determination of some cephalosporins is described. The method is based on the hydrolysis of the cephalosporins in sodium hydroxide to produce the sulfuret, which can quench the fluorescence intensity of fluorescein mercury. Under optimum conditions a linear relationship was obtained between the concentration of cephalosporins and the fluorescence quenching (ΔF) of fluorescein mercury. We have studied four cephalosporins: cefadroxil, cephradine, cefotaximum sodium and cefazolinum. Their detection limits are 5.0 × 10–6, 1.2 × 10–6, 1.2 × 10–5 and 6.0 × 10–5 mg ml–1, respectively. The method has been applied to the determination of some cephalosporins in pharmaceutical formulations. The results are satisfactory.

Study of the fluorescence of the europium–thenoyltrifluoroacetone–cetyltrimethylammonium bromide–Triton X-100 system

The europium–thenoyltrifluoroacetone (TTA)–cetyltrimethylammonium bromide (CTAB)–Triton X-100 system at pH 5.5–7.5 was studied and used for the spectrofluorimetric determination of europium. The excitation and emission wavelengths were 370 and 612 nm, respectively. Fluorescence intensity was a linear function of the concentration of europium in the range 1.0 × 10–7–1.0 × 10–9 mol dm–3. The detection limit was 2.0 × 10–12 mol dm–3. The standard additions method was used for the determination of europium in synthetic rare earth oxides and gave satisfactory results. The molar ratio method was carried out spectrofluorimetrically for the determination of the stoichiometric composition of the fluorescent species. A ratio of 1 : 4 : 1 for the ternary Eu–TTA–CTAB complex was found.

Selective determination of neodymium and erbium in mixtures with other lanthanides by second-derivative spectrophotometry of complexes with benzoyl-indan-1,3-dione and cetylpyridinium chloride

The absorption spectra of 4f electron transitions of the neodymium and erbium complexes with benzoyl-indan-1,3-dione and cetylpyridinium chloride have been studied by conventional and derivative spectrophotometry. The second-derivative spectrum has been used to eliminate the interference of the other lanthanides, and to increase the sensitivity by a further factor of 4–6. Beers Law is obeyed for 6–29 μg/ml Nd and 7–33 μg/ml Er. The relative standard deviations evaluated from 10 independent determinations of 5.0 μg/ml Nd and Er were 1.1% (Nd) and 1.6% (Er). The detection limits obtained from the sensitivity of the calibration graphs and 3sb, (standard deviation of the blank,n = 11) were 0.63 μg/ml Nd and 0.61 μg/ml Er. The quantification limits (10sb) were 2.1 μg/ml Nd and 2.0 μg/ml Er. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.

Study of the fluorescence enhancement system europium-gadolinium-thenoyltrifluoroacetone-cetyltrimethylammonium bromide-Triton X-100 and its application

Abstract A fluorescence enhancement phenomenon on adding Gd3+ to the europium-thenoyltrifluoroacetone-cetytrimethylammonium bromide-Triton X-100 fluorescence system was observed and studied in detail. The fluorescence intensity of this system was 60 times greater than that of the system without gadolinium. The optimum conditions are a Gd3+ concentration of 2.0 × 10−5 M and pH 7.5–8.5; the fluorescence intensity is a linear function of the concentration of europium in the range 6.0 × 10−11 −1.0 × 10−7 M and the detection limit is 2.0 × 10−12 M europium. This system was used for the determination of trace amounts of europium in rare earth samples with satisfactory results.

Derivative spectrophotometric determination of holmium in rare earth mixtures with 2-(diphenylacetyl)indan-1,3-dione and octylphenyl poly(ethyleneglycol) ether

The zero-order and second-order derivative absorption spectra of the system of holmium with 2-(diphenylacetyl) indan-1, 3-dione and octylphenyl poly(ethyleneglycol) ether have been determined by derivative spectrophotometry. The molar absorptivity of absorption spectra and the derivative spectra are calculated respectively. The absorbances at the absorption maxima for the holmium complex are 48.5 (at 450 nm) and 14.5 (at 460 nm) times greater than for the corresponding chloride. The derivative spectra have been used to eliminate the interference of other lanthanides, and the sensitivity is again increased by a factor of about 5. The calibration graph is linear up to ∼ 25 μg/ml of holmium. The detection limit, obtained from the sensitivity of the calibration graph and for 3Sb (Sb = standard deviation of a blank without holmium,n = 11), was 0.37 μg/ml of holmium. The quantification limit (10Sb was 1.2 μg/ml. The method has been applied successfully to synthetic and reference samples of rare earths.