Flow analysis by using solenoid valves for As(III) determination in natural waters by an on-line separation and pre-concentration system coupled to a tungsten coil atomizer

A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS) was developed for As(III) determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC) as complexing agent, and by sorption of the As(III)-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent), followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL) and 4 s elution time (71 µL). The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP), an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L-1 (r = 0.9976), the retention efficiency was 94±1% (6.0 µg L-1), and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient) was 3.4% (n=5), the detection limit was 0.058 µg L-1 (4.1 pg in 71 µL of eluate injected into the coil), and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15). The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.

The value of adenosine deaminase (ADA) determination in the diagnosis of tuberculous ascites

In order to evaluate the role of the determination of adenosine deaminase activity (ADA) in ascitic fluid for the diagnosis of tuberculosis, 44 patients were studied. Based on biochemical, cytological, histopathological and microbiological tests, the patients were divided into 5 groups: G1 - tuberculous ascites (n = 8); G2 - malignant ascites (n = 13); G3 - spontaneous bacterial peritonitis (n = 6); G4 - pancreatic ascites (n = 2); G5 - miscelaneous ascites (n = 15). ADA concentration were significantly higher in G1 (133.50 ± 24.74 U/l) compared to the other groups (G2 = 41.85 ± 52.07 U/l; G3 = 10.63 ± 5.87 U/l; G4 = 18.00 ± 7.07 U/l; G5 = 11.23 ± 7.66 U/l). At a cut-off value of >31 U/l, the sensitivity, specificity and positive and negative preditive values were 100%, 92%, 72% and 100%, respectively. ADA concentrations as high as in tuberculous ascites were only found in two malignant ascites caused by lymphoma. We conclude that ADA determination in ascitic fluid is a useful and reliable screening test for diagnosing tuberculous ascites. Values of ADA higher than 31 U/l indicate more invasive methods to confirm the diagnosis of tuberculosis.

Serological diagnosis of toxoplasmosis: usefulness of IgA detection and IgG avidity determination in a patient with a persistent IgM antibody response to Toxoplasma gondii

We report the detection of specific IgA antibodies and the determination of IgG avidity in sequential serum samples from a patient exhibiting significant levels of Toxoplasma-specific IgM antibodies for seven years after the onset of the clinical symptoms of toxoplasmosis. IgM antibodies were detected by an indirect immunofluorescence test and by three commercial enzyme-linked immunosorbent assays (ELISA). Anti-T. gondii IgA was quantified by the a-capture ELISA technique using a commercial kit. As defined by the manufacturer of the IgA ELISA test used, most patients with acute toxoplasmosis have antibody levels > 40 arbitrary units per ml (AU/mL). At this cut-off level, the patient still had a positive ELISA result (45 AU/mL) in a serum sample taken one year after the beginning of clinical manifestations. The IgG avidity-ELISA test was performed with the Falcon assay screening test (F.A.S.T.®) - ELISA system. Avidity indices compatible with a recent Toxoplasma infection were found only in serum samples taken during the first 5 months after the onset of the clinical symptoms of toxoplasmosis. These results show that the interpretation of positive IgM results as indicative of recently acquired toxoplasmosis requires additional laboratory confirmation either by other tests or by the demonstration of a significant rise in the antibody titers in sequential serum samples.

Sex determination in the Giant fish of Amazon Basin, Arapaima gigas (Osteoglossiformes, Arapaimatidae), using laparoscopy

The Giant of Amazon basin, pirarucu, Arapaima gigas, is the largest scaled freshwater fish in the world. pirarucu cultivation has recently started, driven by the decline in natural populations and high market value. Currently, there are no reliable methods for sexual differentiation in this species other than direct examination of gonads, which requires dissection of specimens. A non-lethal and less invasive method for sexual identification is highly desirable in order to properly group broodstock for mating and offspring production. We utilized laparoscopic examination in anesthetized pirarucu to differentiate between male and female individuals. This method allowed for the observation and differentiation of the reproductive organs within an individual. Our results suggest that laparoscopy is an efficient method for sex differentiation in pirarucu causing minimal stress to the fish.

Temperature-sex determination in Podocnemis expansa (Testudines, Podocnemididae)

This study has been carried out at the central region of the Araguaia river on the border between the states of Goiás and Mato Grosso in the Brazilian Amazon Basin from September to December 2000. We recorded temperature fluctuation, clutch-size, incubation period and hatching success rate and hatchlings' sex ratio of five nests of Podocnemis expansa (Schweigger, 1812). Despite the relatively small sample size we infer that: a) nests of P. expansa in the central Araguaia river have a lower incubation temperature than nests located further south; however, incubation period is shorter, hatching success rate is lower and clutch-size is larger; b) Podocnemis expansa may present a female-male-female (FMF) pattern of temperature sex-determination (TSD); c) thermosensitive period of sex determination apparently occur at the last third of the incubation period; and, d) future studies should prioritize the relationship between temperature variation (i.e., range and cycle) and embryos development, survivorship and sex determination.

Enzyme-linked immunosorbent assay and Western blot antibody determination in sera from patients diagnosed with different helminthic infections with Anisakis simplex antigen purified by affinity chromatography

An evaluation of the sensitivity and the specificity of the Anisakis simplex antigens purified by affinity chromatography was performed using sera from patients diagnosed with Anisakis sensitisation and sera from patients previously diagnosed with different helminthic infections. Only the sera of the patients diagnosed with Schistosoma mansoni or Onchocerca volvulus parasitic infections were negative against the A. simplex antigen and its purified fractions (PAK antigen: A. simplex antigen purified using columns prepared with anti-A. simplex rabbit IgG and PAS antigen: PAK antigen purified using columns prepared with anti-Ascaris suum rabbit IgG). However all the sera were positive against the A. suum antigen. In all the sera from the patients diagnosed with Anisakis sensitisation, the antibody levels detected using the purified antigens (PAK and PAS antigens) were lower than the observed using the A. simplex crude extract with the highest diminution in the case of the IgG. When these same sera were tested against the A. simplex crude extract by Western blot, several bands of high molecular masses were observed as well as, intense bands at 60 and/or 40 kDa. A concentration of these last proteins was observed in the PAK and the PAS antigens. When the sensitivity and the specificity determinations were performed, only seven of the 38 patients diagnosed of Anisakis sensitisation were positive, as well as, the sera from the patients diagnosed with parasitisms by Echinococcus granulosus or Fasciola hepatica.

Evaluation of sample preparation methods and optimization of nickel determination in vegetable tissues

Nickel, although essential to plants, may be toxic to plants and animals. It is mainly assimilated by food ingestion. However, information about the average levels of elements (including Ni) in edible vegetables from different regions is still scarce in Brazil. The objectives of this study were to: (a) evaluate and optimize a method for preparation of vegetable tissue samples for Ni determination; (b) optimize the analytical procedures for determination by Flame Atomic Absorption Spectrometry (FAAS) and by Electrothermal Atomic Absorption (ETAAS) in vegetable samples and (c) determine the Ni concentration in vegetables consumed in the cities of Lorena and Taubaté in the Vale do Paraíba, State of São Paulo, Brazil. By means of the analytical technique for determination by ETAAS or FAAS, the results were validated by the test of analyte addition and recovery. The most viable method tested for quantification of this element was HClO4-HNO3 wet digestion. All samples but carrot tissue collected in Lorena contained Ni levels above the permitted by the Brazilian Ministry of Health. The most disturbing results, requiring more detailed studies, were the Ni concentrations measured in carrot samples from Taubaté, where levels were five times higher than permitted by Brazilian regulations.

Analytical methods for vancomycin determination in biological fluids and in pharmaceuticals

Vancomycin is a glycopeptide antibiotic employed in the treatment of infections caused by certain methicillin-resistant staphylococci. It is indicated also for patients allergic to penicillin or when there is no response to penicillins or cephalosporins. The adequate vancomycin concentration levels in blood serum lies between 5 and 10 mg/L. Higher values are toxic, causing mainly nephrotoxicity and ototoxicity. Various analytical methods are described in the literature: spectrophotometric, immunologic, biologic and chromatographic methods. This paper reviews the main analytical methods for vancomycin determination in biological fluids and in pharmaceutical preparations.

Moisture sorption isotherms and isosteric heat determination in Chilean papaya (Vasconcellea pubescens)

The moisture sorption isotherms of Chilean papaya were determined at 5, 20, and 45 ºC, over a relative humidity range of 10-95%. The GAB, BET, Oswin, Halsey, Henderson, Smith, Caurie and Iglesias-Chirife models were applied to the sorption experimental data. The goodness of fit of the mathematical models was statistically evaluated by means of the determination coefficient, mean relative percentage deviation, sum square error, root-mean-square error, and chi-square values. The GAB, Oswin and Halsey models were found to be the most suitable for the description of the sorption data. The sorption heats calculated using the Clausius-Clapeyron equation were 57.35 and 59.98 kJ·mol-1, for adsorption and desorption isotherms, respectively.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg-1 was found for organic Hg by CVAAS.

Performance characteristics of high performance liquid chromatography, first order derivative UV spectrophotometry and bioassay for fluconazole determination in capsules

The bioassay, first order derivative UV spectrophotometry and chromatographic methods for assaying fluconazole capsules were compared. They have shown great advantages over the earlier published methods. Using the first order derivative, the UV spectrophotometry method does not suffer interference of excipients. Validation parameters such as linearity, precision, accuracy, limit of detection and limit of quantitation were determined. All methods were linear and reliable within acceptable limits for antibiotic pharmaceutical preparations being accurate, precise and reproducible. The application of each method as a routine analysis should be investigated considering cost, simplicity, equipment, solvents, speed, and application to large or small workloads.

Certified reference material to water content determination in bioethanol fuel

Bioethanol is a strategic biofuel in Brazil. Thus, a strong metrological basis for its measurements is required to ensure the quality and promote its exportation. Recently, Inmetro certified a reference material for water content in bioethanol. This paper presents the results of these studies. The characterization, homogeneity, short-term stability and long-term stability uncertainty contributions values were 0.00500, 0.0166, 0.0355 and 0.0391 mg g-1, respectively. The certificated value for water content of bioethanol fuel was (3.65 ± 0.11) mg g-1. This CRM is the first and up to now the unique in the world.

DEVELOPMENT AND VALIDATION OF ANALYTICAL METHOD FOR PALM OIL DETERMINATION IN MICROCAPSULES PRODUCED BY COMPLEX COACERVATION

The microencapsulation of palm oil may be a mechanism for protecting and promoting the controlled release of its bioactive compounds. To optimize the microencapsulation process, it is necessary to accurately quantify the palm oil present both external and internal to the microcapsules. In this study, we developed and validated a spectrophotometric method to determine the microencapsulation efficiency of palm oil by complex coacervation. We used gelatin and gum arabic (1:1) as wall material in a 5% concentration (w/v) and palm oil in the same concentration. The coacervates were obtained at pH 4.0 ± 0.01, decanted for 24 h, frozen (−40 ºC), and lyophilized for 72 h. Morphological analyzes were then performed. We standardized the extraction of the external palm oil through five successive washes with an organic solvent. We then explored the best method for rupturing the microcapsules. After successive extractions with hexane, we determined the amount of palm oil contained in the microcapsules using a spectrophotometer. The proposed method was shown to be of low cost, fast, and easy to implement. In addition, in the validation step, we confirmed the method to be safe and reliable, as it proved to be specific, accurate, precise, and robust.

Interaction study of moxifloxacin with Cu(II) ion using square-wave voltammetry and its application in the determination in tablets

This work presents an electroanalytical method for the determination of moxifloxacin (MOXI) in tablets by its interaction with Cu(II) ion and subsequent electrochemical reduction at hanging mercury drop electrode (HMDE). A well-defined reduction peak at -0.21 V vs. Ag/AgCl in Phosphate buffer 0.04 mol L-1 pH 8.0 was observed for the complex reduction MOXI-Cu(II), using square-wave voltammetry (SWV). Using a 10 s of accumulation time at -0.40 V was found a limit detection of 3.60x10-8 mol l-1. The obtained results have shown good agreement with those obtained by spectrophotometric method.

A decision support system for cost determination in grain storage facility operations

Many research works have being carried out on analyzing grain storage facility costs; however a few of them had taken into account the analysis of factors associated to all pre-processing and storage steps. The objective of this work was to develop a decision support system for determining the grain storage facility costs and utilization fees in grain storage facilities. The data of a CONAB storage facility located in Ponta Grossa - PR, Brazil, was used as input of the system developed to analyze its specific characteristics, such as amount of product received and stored throughout the year, hourly capacity of drying, cleaning, and receiving, and dispatch. By applying the decision support system, it was observed that the reception and expedition costs were exponentially reduced as the turnover rate of the storage increased. The cleaning and drying costs increased linearly with grain initial moisture. The storage cost increased exponentially as the occupancy rate of the storage facility decreased.