Isarita Martins

Determination of parabens in shampoo using high performance liquid chromatography with amperometric detection on a boron-doped diamond electrode

Methylparaben (MePa), ethylparaben (EtPa) and propylparaben (PrPa) have been widely used, among others, as chemical preservatives in cosmetics, drugs and foods. As these compounds are linked with allergies, dermatitis and estrogenic properties, it is necessary to control the concentration of these substances in different matrices. The aim of this paper are: to evaluate the electrochemical behavior of parabens on the boron-doped diamond (BDD) electrode and the development of a chromatographic method, with electrochemical detection (HPLC-ED), for determination of parabens in shampoo. A BDD (8000 ppm) electrode was adapted in a thin layer mode analytical cell consisting of a stainless steel and a platinum wire as reference and auxiliary electrodes, respectively. Chromatographic separations were obtained with a reversed phase C8 analytical column and a mobile phase of 0.025 molL(-1) disodium phosphate, pH 7.0, and acetonitrile (40:60, v/v), delivered at a flow rate of 1.0 mL min(-1). Sample preparation was performed by solid phase extraction using C18 cartridges and acetonitrile for elution. Benzylparaben was employed as internal standard. The HPLC-ED method developed, using the BDD electrode, was validated for the determination of parabens in shampoos and presented adequate linearity (>0.999), in the range of 0.0125-0.500% (w/w), detectability 0.01% (w/w), precision (RSD of 2.3-9.8%) and accuracy (93.1-104.4%) and could be applied for routine quality control of shampoos containing MePa, EtPa and PrPa.

Simultaneous determination of multibenzodiazepines by HPLC/UV: Investigation of liquid–liquid and solid-phase extractions in human plasma

A method for simultaneous determination of seven benzodiazepines (BZPs) (flunitrazepam, clonazepam, oxazepam, lorazepam, chlordiazepoxide, nordiazepam and diazepam using N-desalkylflurazepam as internal standard) in human plasma using liquid-liquid and solid-phase extractions followed by high-performance liquid chromatography (HPLC) is described. The analytes were separated employing a LC-18 DB column (250 mm x 4.6 mm, 5 microm) at 35 degrees C under isocratic conditions using 5mM KH(2)PO(4) buffer solution pH 6.0:methanol:diethyl ether (55:40:5, v/v/v) as mobile phase at a flow rate of 0.8 mL min(-1). UV detection was carried out at 245 nm. Employing LLE, the best conditions were achieved with double extraction of 0.5 mL plasma using ethyl acetate and Na(2)HPO(4) pH 9.5 for pH adjusting. Employing SPE, the best conditions were achieved with 0.5 mL plasma plus 3 mL 0.1M borate buffer pH 9.5, which were then passed through a C18 cartridge previously conditioned, washed for 3 times with these solvents: 3 mL 0.1M borate buffer pH 9.5, 4 mL Milli-Q water and 1 mL acetonitrile 5%, finally the BZPs elution was carried with diethyl ether:n-hexane:methanol (50:30:20). In both methods the solvent was evaporated at 40 degrees C under nitrogen flow. The validation parameters obtained in LLE were linearity range of 50-1200 ng mL(-1) plasma (r>or=0.9927), limits of quantification of 50 ng mL(-1) plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15%, and recovery above 65% for all BZPs. In SPE, the parameter obtained were linearity range of 30-1200 ng mL(-1) plasma (r>or=0.9900), limits of quantification of 30 ng mL(-1) plasma, within-day and between-day CV% and E% for precision and accuracy lower than 15% and recovery above 55% for all BZPs. These extracting procedures followed by HPLC analysis showed their suitable applicability in order to examine one or more BZPs in human plasma. Moreover, it could be suggested that these procedures might be employed in various analytical applications, in special for toxicological/forensic analysis.

Molecularly imprinted solid phase extraction of urinary diethyl thiophosphate and diethyl dithiophosphate and their analysis by gas chromatography–mass spectrometry

An analytical method involving molecularly imprinted solid phase extraction (MISPE) and gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of organophosphates metabolites (diethyl thiophosphate--DETP and diethyl dithiophosphate - DEDTP) in human urine samples. A DETP molecularly imprinted polymer (MIP) was synthesized using 4-vinylpiridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. The conditioning step of the MISPE was conducted by running 3 mL of acetonitrile, 3 mL of 0.1 mol L⁻¹ dibasic phosphate buffer at pH 11 and 2 mL of water through the molecularly imprinted polymer (MIP) cartridge. The extraction step was executed using 1.0 mL of a urine sample, with the pH previously adjusted to 3.0. Finally, the analytes were eluted with 3 mL of acetonitrile and derivatized with 3% 2,3,4,5,6-pentafluorobenzyl bromide solution at room temperature for 1h. The sample was analyzed by GC-MS in the SIM (selected ion monitoring) mode. Analytical calibration curves for DETP and DEDTP were constructed using a pool of urine samples and six levels of concentration. The method was found to be linear from 10 to 500 μg L⁻¹ (r>0.99) with limits of quantification of 10 μg L⁻¹ for both analytes. The within-day and between-day precisions were evaluated (as %RSD) and all the results were <15% for both analytes. The method was accurate (relative error<±15%), with good robustness.

Analysis of ortho-cresol in urine by solid phase microextraction-capillary gas chromatography

Neste trabalho foi desenvolvido um metodo usando a microextracao em fase solida (SPME) para analise cromatografica em fase gasosa capilar com detector de ionizacao por chama (CG/IC) de orto-cresol urinario, metabolito do tolueno. Apos otimizacao das variaveis da SPME e da validacao do metodo, foram analisadas amostras de urina de 27 trabalhadores expostos a solventes em oficinas de reparo automotivo. As melhores condicoes de extracao foram obtidas com a hidrolise acida da urina, extracao em fibra de carbowax/divinilbenzeno (CW/DVB) 70 µm por 20 min em pH neutro, com adicao de 3 g de Na2SO4, sob agitacao. O metodo mostrou linearidade entre 0,1 e 1,5 mg L-1 de o-cresol em urina, LOQ de 0,1 mg L-1, repetibilidade entre 6,8 e 7,8%. O valor medio de o-cresol em urina dos trabalhadores foi de 0,35 ± 0,23 mg L-1. O metodo SPME/CG/DIC mostrou ser rapido, simples e aplicavel para fins de biomonitorizacao de trabalhadores expostos.

Liquid-liquid extraction combined with high performance liquid chromatography-diode array-ultra-violet for simultaneous determination of antineoplastic drugs in plasma

A liquid-liquid extraction (LLE) combined with high-performance liquid chromatography-diode array detection method for simultaneous analysis of four chemically and structurally different antineoplastic drugs (cyclophosphamide, doxorubicin, 5-fluorouracil and ifosfamide) was developed. The assay was performed by isocratic elution, with a C18 column (5 µm, 250 x 4.6 mm) and mobile phase constituted by water pH 4.0- acetonitrile-methanol (68:19:13, v/v/v), which allowed satisfactory separation of the compounds of interest. LLE, with ethyl acetate, was used for sample clean-up with recoveries ranging from 60 to 98%. The linear ranges were from 0.5 to 100 µg mL-1, for doxorubicin and 1 to 100 µg mL-1, for the other compounds. The relative standard deviations ranged from 5.5 to 17.7%. This method is a fast and simple alternative that can be used, simultaneously, for the determination of the four drugs in plasma, with a range enabling quantification of the drugs in pharmacokinetics, bioequivalence and therapeutic drug-monitoring studies.

Valores de referência para carboxiemoglobina

INTRODUCTION The reference values (RV) of biological indicators are used in the interpretation of the results of such indicators in individuals occupationally exposed to chemical agents. The Brazilian Group for the Establishment of Reference Values has worked on these definitions for the purpose of establishing RVs for several bioindicators in various regions of the country. In the present study, the RV for carboxyhemoglobin (COHb) was determined for the South of Minas Gerais. MATERIAL AND METHOD The COHb was analyzed by the Beutler and West (1984) spectrophotometric method, optimized in our laboratory. In all the samples, analyses of some biochemical and hematological parameters were made to evaluate the health condition of a population of 200 volunteer non-smokers occupationally not exposed to CO. Each individual answered a questionnaire to obtain data pertinent to the interpretation of the results. The reference values were expressed as mean values +/- standard deviation, with a 95% confidence interval, and an upper reference value. The statistical distribution of the results was made so as to enable comparisons between the results of groups of workers, rather than individual evaluations, to be made. RESULTS AND CONCLUSIONS The mean value +/- standard deviation was 1.0% +/- 0.75; the 95% confidence interval was 0.9-1.1% and the upper reference value was 2.5%. By the t Student test (p < or = 0.05), no difference was detected between the values related to sex, age or ingestion of alcoholic beverages. The reference values obtained were close to those reported for others countries.

Influência do hábito de fumar na excreção urinária do ácido trans, trans-mucônico

Tobacco smoking is the major individual benzene source for no occupationally exposed subjects. This solvent is a volatile carcinogen and can induce serious health problems. Several biomarkers for benzene have been proposed, the most used is its metabolite trans,trans-muconic acid (ttMA) in urine, a suitable indicator since it reflects the internal dose of low benzene exposure. The present study aimed to evaluate the influence of smoking on urinary ttMA excretion. The analysis was performed by High Pressure Liquid Chromatography in a reversed-phase column and UV detection, after extraction of ttAM from urine using SAX cartridges. The method was validated, showing linearity between 0.006 to 10 µg mL-1 (r= 0.996), detection and quantification limits of 1.41 x 10-3 µg mL-1 and 6.0 x 10-3 µg mL-1 respectively, CVs from 1.79 to 2.91% (intra assay precision) and 3.53 to 18.37% (interassay precision). A significant positive correlation was observed between ttMA excretion and smoking (p= 0.005388). However, the cigarette number smoked by day seems have no influence on the urinary ttMA excretion.

UPLC-MS/MS method for simultaneous determination of cyclophosphamide, docetaxel, doxorubicin and 5-fluorouracil in surface samples

INTRODUCTION There is certainly a great benefit to treatment with antineoplastic drugs for cancer patients with a life-threatening disease. However, for the workers who are exposed to these agents as part of their work practice, precautions should be taken to eliminate or reduce exposure as much as possible. OBJECTIVE The aim of this study is to develop and validate a wipe sampling procedure followed by liquid chromatographic separation with electrospray ionization and a tandem mass spectrometric detection method for the simultaneous determination of cyclophosphamide (CP), docetaxel (DOC), doxorubicin (DOXO) and 5-fluorouracil (5-FU). METHOD The chromatographic separation was carried out in 15min by applying a gradient elution of 0.1% formic acid and acetonitrile. MS/MS was performed on a triple quadrupole instrument in the multiple reaction monitoring (MRM) mode. RESULTS The analytical range was linear between 3.5 to 300ng/mL for CP, 4 to 300ng/mL for DOC and DOXO and 2 to 300ng/mL for 5-FU. The present method offers a high sensitivity, with detection limits of 1.0ng/mL for CP, DOXO and DOC and 0.5ng/mL for 5-FU. The selectivity, accuracy (relative standard error between 82.3 and 113.9%) and precision (relative standard deviation between 1.2 and 14.2%) make the method suitable for the routine determination of these drugs to estimate the occupational exposure of personnel handling. CONCLUSIONS The developed method allows a reliable assessment of exposure, which is one of the steps for evaluation the risk inherent to workers in contact with antineoplastic drugs.

Simultaneous detection of three antineoplastic drugs on gloves by liquid chromatography with diode array detector

The aim of this study was to develop a method for simultaneous detection of antineoplastic drugs on gloves since, in occupational exposure, the main contamination route is through dermal contact, which may occur via prolonged contact with contaminated surfaces or materials. The assay was performed by liquid chromatography using the following conditions for the detection of 5-fluorouracil (5-FU), methotrexate (MTX) and paclitaxel (TAX): diode array detection and UV quantification at 195 nm for TAX, at 265 nm for 5-FU and at 302 nm for MTX; ODS column (250 x 4 mm, 5 μm) with a similar guard column; mobile phase consisted of water (pH 4)-methanol-acetonitrile (35:15:50, v/v/v) with a flow rate of 1 mL min-1. The method presented a linear range from 0.25 to 20 μg mL-1 with r2 higher than 0.99. Repeatability was 0.25 μg mL-1 in samples, although detection was possible in samples that presented values of around 0.1 μg mL-1. The results obtained suggest that the method developed can be applied for the simultaneous determination of the drugs studied and can be considered useful in exposure assessment for health care workers.

Headspace solid-phase microextraction procedure for gas-chromatography analysis of toluene in urine

Toluene is widely used in industrial and laboratory applications and in many countries is related with social problems of abuse. Unaltered urinary toluene was introduced as a bioindicator of occupational exposure to the solvent, but its analysis presents difficulties due to the low levels of the compound excreted in urine. A gas-chromatography/flame ionization method for toluene in urine is described using headspace solid-phase microextraction and establishing the better conditions for two different extracting phases: polydimethylsiloxane (PDMS) and carboxen-PDMS. The carboxen-PDMS fiber showed lower quantifying limit (12.5 ng mL-1), better extraction efficiency (up to 28.1%) and repeatability (CV < 4.9%) than PDMS coating. The method was applied to analysis of toluene in urine of workers from car repair shops exposed to low solvent levels.