Francisco José Barragán

An approach to characterization of sources of urban airborne particles through heavy metal speciation

Abstract Airborne particles, collected in an urban atmosphere, influenced by surrounding farm areas (Seville), were analyzed by speciation for ten heavy metals. The use of a sequential extraction procedure allowed the subdivision of the total content of each metal into four different fractions. Statistical multivariate analysis was performed on the fractions and the main sources of metal contamination were characterized. The results show that soil aerosols make the largest contribution to pollution with Fe and Al as the most abundant metals acting as markers for this source. In addition, the close correlation between Pb and Cu suggests that these are mainly pollutants generated by traffic. The other metals permitted identification of an industrial source but always in association with a soil source. From the percentage distribution of species, we found that Fe and Al are found in the carbonate or oxide fraction (40%) and in the residual metal fraction (40%). While Pb and Cu mainly appear as oxides and carbonates (50% and 40%, respectively), Cd prevails in soluble or exchangeable form (55%).

Spectrofluorimetric determination of moxifloxacin in tablets, human urine and serum

A spectrofluorimetric method to determine the antibiotic moxifloxacin is proposed and was applied to pharmaceuticals, human urine and serum. The fluorimetric method allows the determination of 30-300 ng mL-1 moxifloxacin in aqueous solution containing phosphoric acid-phosphate buffer (pH 8.3) with lambda exc = 287 nm and lambda em = 465 nm. Detection and quantification limits were 10 and 30 ng mL-1, respectively, with a relative standard deviation (n = 10) of 2%. This method was applied to the determination of moxifloxacin in three Spanish commercial pharmaceutical formulations. Another variant of the method in micellar medium allows the direct measurement of moxifloxacin in human serum and urine by standard additions. The enhanced fluorescence of moxifloxacin in 8 mM sodium dodecyl sulfate (SDS) solution at pH 4.0 (acetic acid-acetate buffer) for lambda exc = 294 nm and lambda em = 503 nm shows the same linear range as the aqueous method with a 25% lower slope (with detection and quantification limits of 15 and 60 ng mL-1, respectively, and a relative standard deviation of 1.3%), but permits the background fluorescence for urine and serum blanks to be minimized. Hence, sufficient sensitivity is reached to determine therapeutic concentrations of the drug in urine (average recovery 102 +/- 2%) and serum (average recovery 105 +/- 2%) samples.

Terbium-sensitized luminescence determination of levofloxacin in tablets and human urine and serum

A selective and sensitive luminescence method for the determination of levofloxacin is described. The method is based in the luminescence signal from a terbium(III)-levofloxacin complex, in a micellar solution of sodium dodecyl sulfate (SDS), using a chemical deoxygenation agent (Na2SO3). The method allows the determination of 8-600 ng mL-1 of levofloxacin in 10 mM SDS solution containing 0.04 M acetic acid-sodium acetate buffer (pH 6) and 7.5 mM Na2SO3 with lambda exc = 292 nm and lambda em = 546 nm. The luminescence method was applied to the determination of the levofloxacin in a Spanish commercialized pharmaceutical formulation Tavanic (Hoechst Marion Roussel). Good concordance was found between the nominal and experimental values (500 and 488 mg, respectively), with a relative standard deviation (RSD) of 0.6%. The proposed method was shown to be 100-fold more sensitive than the spectrophotometric method, and nearly 2-fold more sensitive than the fluorescence method. The method was also applied to levofloxacin determination in human serum (by external calibration method) and urine (by standard additions method), spiked at levels found after drug administration at normal clinical doses. Average recoveries found were 90.1 (RSD 1%) and 102 (RSD 1.9%), respectively.

Fluorescence and terbium-sensitised luminescence determination of garenoxacin in human urine and serum.

Fluorescence and terbium-sensitised luminescence properties of new quinolone garenoxacin have been studied. The fluorimetric method allows the determination of 0.060-0.600mugml(-1) of garenoxacin in aqueous solution containing HCl/KCl buffer (pH 1.5) with lambda(exc)=282nm and lambda(em)=421nm. Micellar-enhanced fluorescence was also studied, leading to a higher than 400% increase in analytical signal in presence of 12mM sodium dodecyl sulphate (SDS), allowing the determination of 0.020-0.750mugml(-1) of garenoxacin. The terbium-sensitised luminescence method allows the determination of 0.100-1.500mugml(-1) of garenoxacin in 12mM SDS solution containing 0.08M acetic acid/sodium acetate buffer (pH 4.1) and 7.5mM Na(2)SO(3) (chemical deoxygenation agent), with lambda(exc)=281nm and lambda(em)=546nm. Relative standard deviation (R.S.D.) values for the three methods were in the range 1.0-2.0%. The proposed procedures have been applied to the determination of garenoxacin in spiked human urine and serum.

Determination of trovafloxacin in human serum by time resolved terbium-sensitised luminescence

A sensitive time-resolved luminescence method for the determination of trovafloxacin is described. The method is based on the time-resolved luminescence signal from the terbium(III)-trovafloxacin complex, in a micellar solution of sodium dodecyl sulfate (SDS), using a chemical deoxygenation agent (Na(2)SO(3)). The method allows the determination of 20-450 ng ml(-1) of trovafloxacin in 7.5 mM SDS solution containing 0.16 M acetic acid-sodium acetate buffer (pH 6.0) and 7.5 mM Na(2)SO(3) with lambda(exc)=270 nm and lambda(em)=546 nm. In these experimental conditions luminescence signal for trovafloxacin increases 20-fold with respect to native fluorescence of the compound in aqueous solution at pH 6.5. Terbium-sensitised luminescence was applied to trovafloxacin determination in human serum, spiked at levels found after drug administration at normal clinical doses. Recovery is 90+/-1% and day-to-day precision is 3.5%. The proposed method tolerates high concentrations of other co-administrated drugs and excipients.

Spectrofluorimetric determination of sulphide in natural and wastewaters with 1,2-naphthoquinone-4-sulphonate

A simple and sensitive spectrofluorimetric method for the determination of sulphide with 1,2-naphthoquinone-4-sulphonate (NS) has been developed. Sulphide in water samples (preserved as ZnS and then dissolved at pH 5.2 with ethylenediaminetetraacetic acid) gives a blue fluorescence (λex 235 nm and λem 470 nm) after reaction with NS, which allows the quantitative determination of this species. The samples were stored in the dark by wrapping the storage flasks in aluminium foil. Sulphide can be determined in solutions with concentrations in the range 0.08–0.48 µg ml–1 with a coefficient of variation of 3.20%(p= 0.10; n= 15) for a concentration of 0.25 µg ml–1. The proposed method is tolerant of many common cations and anions. A 280-fold excess of cyanide with respect to sulphide does not interfere with the analysis. A complementary procedure including a prior distillation step is described for samples with suspended materials or with a lower sulphide content. To test the utility of both procedures (direct and with distillation) various samples of natural waters, industrial wastewaters and municipal wastewaters were successfully analysed.

DETERMINATION OF SULPHIDE IN SEWAGE EFFLUENTS USING A NEW SPECTROPHOTOMETRIC METHOD

Abstract A suitable indirect spectrophotometric method for the determination of sulphide in water, based on the reduction of 1,2-naphthoquinone-4-sulphonate (NS) has been developed. The excess of NS is spectrophotometrically determined based on the red colour produced in its reaction with sulphanilic acid at pH 4.0–6.5. Maximum colour intensity is obtained after 40 min and the apparent molar absorptivity at 470mm is 3.5×103I.mol−1.cm−1. The sulphide concentrations can be calculated by the difference in absorption of blanks and samples.