Trace-metal distribution of cigarette ashes as marker of tobacco brands.

The trace-metal distribution of cigarette ashes offers a potential interest from the point of view of forensics and criminology dealing with the determination and classification of tobacco brands. There is a vast bibliography related to the determination of different metals in tobacco leaves. Nevertheless, none of them are directly linked to this matter. Therefore, in this work we present a methodology to assess the viability of discriminating between different tobacco brands by analysing the ashes after smoking. This methodology encompasses the data analysis by atomic techniques (inductively coupled plasma) and further data analysis by principal component analysis and partial least squares-discriminant analysis. The metal distribution (Zn, B, Mn, Fe, Mg, Cu, Ti, Al, Sr, Ca, Ba, Na, Li, and K) of cigarette ashes of different tobacco brands was determined in 149 samples obtained from local stores, representing the most common brands of cigarettes readily available to consumers in Spain. Further analysis of the data with PCA denoted significant differences between different brands of tobacco in their metallic content. In that sense, blond tobaccos were found to contain different patterns in metallic content than black tobaccos. Intrinsic differences were found between different brands, being possible to study the relationship between each brand and its metallic concentration and compare this relationship with other brands. Moreover the possibility of developing classification models to be able to discriminate between different brands was also introduced.

Application of enzymatic probe sonication extraction for the determination of selected veterinary antibiotics and their main metabolites in fish and mussel samples.

A new method based on enzymatic probe sonication extraction prior to high-performance liquid chromatography (HPLC) has been developed for the determination of 11 antibiotics (drugs) and the main metabolites of five of them in fish tissue and mussel samples. The analytes belong to four different classes of antibiotics (sulfonamides, tetracyclines, penicillins and amphenicols). The analysed compounds were sulfadiazine (SDI) and N(4)-acetylsulfadiazine (NDI) metabolite, sulfamethazine (SMZ) and N(4)-acetylsulfamethazine (NMZ), sulfamerazine (SMR) and N(4)-acetylsulfamerazine (NMR), sulfamethoxazole (SMX), trimetroprim (TMP), amoxicillin (AMX) and its main metabolite amoxicilloic acid (AMA), ampicillin (AMP) and its main metabolite ampicilloic acid (APA), chloramphenicol (CLF), thiamphenicol (TIF), oxytetracycline (OXT) and chlortetracycline (CLT). The main factors affecting the extraction efficiency (type of enzyme, type and volume of extractant, ultrasounds power and extraction time) were optimised in tissue of hake (Merluccius merluccius), anchovy (Engraulis encrasicolus), mussel (Mytilus sp.) and wedge sole (Solea solea). The extraction was carried out using an extraction time of 5 min with 5 mL of water and subsequent clean-up with dichloromethane. High-performance liquid chromatography (HPLC) with diode array (DAD) and fluorescence (FLD) detectors was used for the determination of the antibiotics. The separation of the analysed compounds was conducted by means of a Phenomenex Gemini C(18) (150 mm x 4.6 mm I.D., particle size 5 microm) analytical column with LiChroCART LiChrospher C(18) (4 mm x 4 mm, particle size 5 microm) guard-column. Analysed drugs were determined using formic acid 0.1% (v/v) in water and acetonitrile in gradient elution mode as mobile phase. The proposed method was also evaluated by a laboratory assay consisting of the determination of the targeted analytes in samples of Cyprinus carpio which had previously administered the antibiotics.

Urea as new stabilizing agent for imipenem determination: electrochemical study and determination of imipenem and its primary metabolite in human urine.

Imipenem shows a fast chemical conversion to a more stable imin form (identical to that of biochemical dehydropeptidase degradation) in aqueous solutions and stabilizing agents used avoid its electrochemical study and determination. The aim of this work is the proposal of urea as stabilizing agent which allows the electrochemical study of imipenem and the proposal of electrochemical methods for the determination of imipenem and its primary metabolite (M1) in human urine samples. Electrochemical studies were realized in phosphate buffer solutions over pH range 1.5-8.0 using differential-pulse polarography, DC-tast polarography, cyclic voltammetry and adsorptive stripping voltammetry. In acidic media, a non-reversible diffusion-controlled reduction involving a two steps mechanism which involves one electron and one proton in the first step and two electrons and two protons in the second step occurs and the mechanism for the reduction was suggested. A differential-pulse polarographic method for the determination of imipenem in the concentration range 3.2x10(-6) to 2x10(-5)M (0.95-3.4 mg/L) and its primary metabolite in the concentration range 1.4x10(-6) to 10(-4)M (0.43-26.1 mg/L) with detection limits of 9.6x10(-7)M (0.28 microg/L imipenem) and 4.3x10(-7)M (0.14 microg/L M1) was proposed. Also, a method based on controlled adsorptive pre-concentration of imipenem on the hanging mercury drop electrode followed by voltammetric measure, allows imipenem determination in the concentration range 1.8x10(-8) to 1.2x10(-6)M (5.42-347 microg/L) with a detection limit of 5.4x10(-9)M (1.63 microg/L). The proposed methods have been used for the direct determination of the analytes in a pharmaceutical formulation and human urine.

Determination of imipenem and rifampicin in mouse plasma by high performance liquid chromatography-diode array detection.

A high performance liquid chromatographic (HPLC) method for the determination of imipenem and rifampicin was developed and validated. The method involves plasma deproteinisation with methanol, gradient elution on a RP-18 column and diode array detection. Separation was carried out in 8 min using a mobile phase composed of methanol and 0.2M borate buffer (pH 7.2). Imipenem and rifampicin were detected at 300 nm and 255 nm, respectively. A linear response was observed at plasma levels ranged between 0.3 and 30 microgmL(-1) for imipenem and 1.5 and 20 microgmL(-1) for rifampicin. The detection limits were 0.07 microgmL(-1) and 0.47 microgmL(-1) for imipenem and rifampicin, respectively. The method was applied to the determination of both compounds in mouse plasma samples.

Simultaneous determination of cefepime and grepafloxacin in human urine by high-performance liquid chromatography.

A liquid chromatographic method with UV detection for simultaneous determination of cefepime and grepafloxacin has been developed. The method uses a C18 column, equipped with a pre-column of the same material, and acetonitrile-0.1 M phosphoric acid/sodium hydroxide buffer (pH 3.0)-0.01 M n-octylamine (pH 3.0) as mobile phase in gradient mode. Mobile flow rate and sample volume injected were 1.3 mL min(-1) and 20 microL, respectively. Detection wavelengths were 259 nm for cefepime and 278 nm for grepafloxacin. The retention times were 4.03 min for cefepime and 8.85 min for grepafloxacin, with detection limits of 1.0 and 1.1 microg mL(-1), respectively. The method was applied to the determination of both antibiotics in spiked samples of human urine.

Electrochemical behaviour and determination of acrivastine in pharmaceuticals and human urine.

The differential pulse polarography, DC-tast polarography and cyclic voltammetry behaviour of acrivastine was studied in Britton-Robinson buffer solutions (pH 2-11.7). In acidic media, a non-reversible diffusion controlled reduction process involving four electrons takes place. Two reduction waves appear at a E(1/2)=-0.6 and -0.99 V. The reduction mechanism is discussed. The linear relationship between peak current height and acrivastine concentration allowed the differential pulse polarographic determination of acrivastine over a wide concentration range, from 0.35 to 26.1 mg l(-1)at pH 2.5. The procedure was applied to determination of the drug in pharmaceutical formulations and human urine samples.

Spectrofluorimetric determination of levofloxacin in tablets, human urine and serum.

A spectrofluorimetric method to determine levofloxacin is proposed and applied to determine the substance in tablets and spiked human urine and serum. The fluorimetric method allow the determination of 20-3000 ng ml(-1) of levofloxacin in aqueous solution containing acetic acid-sodium acetate buffer (pH 4) with lambda(exc)=292 and lambda(em)=494 nm, respectively. Micelle enhanced fluorescence improves the sensibility and allows levofloxacin direct measurement in spiked Human serum (5 mug ml(-1)) and urine (420 mug ml(-1)), in 8 mM sodium dodecyl sulphate solutions at pH 5.

Differential-pulse polarographic determination of iron in acids, waters, fruit juices and wines.

A method for the determination of iron by differential-pulse polarography, based on the formation of a 5,5-dimethylcyclohexane-1,2,3-trione 1,2-dioxime 3-thiosemicarbazone-iron(II) complex, is proposed. The method was applied to the determination of iron in acids, waters, wines and fruit juices.