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L Saavedra

Publications and source records attributed to L Saavedra.

12 recordsLinked to original sources
PubMed2006

Chromatography-based on- and in-line pre-concentration methods in capillary electrophoresis.

Capillary electrophoresis (CE) poses unique challenges in many different analytical applications, mainly to biological and complex samples and when only small amounts of sample are available, due to its low sample consumption. As a consequence, poor limits of detection are usually observed with this technique, especially with UV photodetectors. Minimal or no sample treatment is desirable in any analytical method to avoid external sources of contamination or errors and to provide a high throughput. On- and in-capillary sample pre-concentration strategies, based on solid-phase extraction (SPE) technology can take advantage of both techniques (SPE and CE), while avoiding sample contamination and tedious manipulations when the sample amount is an issue. Moreover, the combination can provide two-dimensional separations. This review collects the most recent strategies that merge SPE technology built on- and in-capillary pre-concentration for increasing sensitivity and/or selectivity.

Chromatography↗
PubMed2004

Prevalence and risk factors for gallstone disease.

Gallstone disease is a main public health problem. The overall prevalence data range from 3.9% in the pre-echographic era to 13.7% when ultrasonography was used as a diagnostic tool. This study is aimed to determine the prevalence of gallstone disease in a medium income level population in Lima, as well as the relationship with some risk factors: age, sex, familiar history and obesity. A total of 534 adult men and women from a medium economic level underwent ultrasonographic examination of abdomen for detection of gallstone disease (July 2003). The echographic evaluation was performed by 10 general surgeons trained in ultrasonography. Likewise, 4 risk factors--age, gender, familial history, and obesity--were analyzed. Pearson chi2 test (2-sided) was used with a probability of <0.05 for statistical significance and logistic regression analyses for assessment of confounding factors. The prevalence founded was 15%. Eighty-one of 534 participants had lithiasis. Compared to the age group under 30, the odds ratio for the 31 to 50 years and >50 years of age group was 0.9 and 1.1, respectively. The female-male ratio was 1.07 and the odds ratio 0.8. The prevalence of gallstone disease in people reporting a first-degree relative with lithiasis was 21%, whereas in participants without such a condition, it was 13%. On the other hand, a familial history was present in 38% of the lithiasis group and in 25% of the nonlithiasis group. The odds ratio for familial history was 1.8 (P = 0.01, 95% confidence interval 1.1-2.9). The prevalence of the disease for body mass index <24, 25 to 29, and higher than 30 was 17%, 14% and 13%, respectively. Compared to the reference group (body mass index <24), the other 2 groups (body mass index 25-29 and >30) both had a similar odds ratio, 0.8. Logistic regression analyses showed an odds ratio of 1.9 for familiar history (95% confidence interval 1.1-3.2), whereas the odds ratio of the overweight (body mass index 25-29) and obese group (body mass index >30) when compared to the normal group, BMI <24, was 0.7 and 0.9, respectively. The prevalence data for gallstone disease remain slightly higher than those previously reported. Although the familiar history was the only characteristic with a statistically significant positive relationship with lithiasis, additional studies are needed because few biases could not be completely avoided and some confounding factors were not controlled.

Adult↗
PubMed2002

Urinary analysis of nephrolithiasis markers.

Renal stone disease is an ancient and common affliction, common in industrialised nations. The causes and incidence of nephrolithiasis are presented. Afterwards, the promoters and inhibitors of renal stone formation analysis in urine are described including enzymatic methods, chromatography, capillary electrophoresis and other techniques. Aspects such as sample collection and storage are also included. The review article includes referenced tables that provide summaries of methodology for the analysis of nephrolithiasis related compounds.

Biomarkers↗
PubMed2002

Optimization of the separation lactic acid enantiomers in body fluids by capillary electrophoresis.

The optimization of the separation conditions of the two optical isomers of lactic acid by a factorial design is reported. Initially, different chiral selectors were systematically investigated and then a experimental design with three quantitative factors (cyclodextrin concentration and background buffer pH and concentration) were evaluated. Optimal conditions for obtaining a resolution higher than 1.5 were: phosphate buffer 200 mM at pH=6.0 with 413 mM 2-hydroxypropyl-beta-cyclodextrin added (HP-beta-CD), 20 degrees C, -20 kV of applied potential and polyacrylamide-coated capillary. The method was validated for the measurement in plasma and it was applied to the identification of both isomers in body fluids such as urine, amniotic fluid and cerebrospinal fluid. Samples were centrifuged and diluted (1:4) prior to the analysis.

Body Fluids↗
PubMed2001

Capillary electrophoresis for evaluating orange juice authenticity: a study on Spanish oranges.

Fruit juices have very distinct organic acid profiles that can be used as fingerprints for establishing possible adulteration. Recently, our group developed and validated a capillary electrophoresis method using UV detection for determining citric, isocitric, tartaric, and malic acids in natural and commercial orange juices. Sample treatment consisted of only dilution and centrifugation or filtration. This method has been applied to evaluate these acids and their ratios in 63 samples of Navelina, the most common variety of Spanish oranges, over a three month period. This evaluation has been conducted to establish ranges of acid concentrations and to compare them with those found in commercial juices. The more reliable parameter, because of the lower variability in fresh samples, was found to be the citrate/isocitrate ratio with a value of 113 (RSD = 10%). Only one of nine ramdonly selected commercial juices presented values within the range of those of the population of just-pressed Navelina orange juice. Moreover, three of them had measurable tartrate values, which is not a natural component of orange juice, showing mixtures with cheaper fruits.

Beverages↗
PubMed2000

Development and validation of a capillary electrophoresis method for direct measurement of isocitric, citric, tartaric and malic acids as adulteration markers in orange juice.

Fruit juices each have very distinct organic acids profiles that can be used as fingerprints for establishing authenticity. A method has been developed, optimised and validated for measuring by capillary electrophoresis citric, isocitric, malic and tartaric acids as authenticity markers in orange juices, without any sample treatment other than dilution and filtration. Final conditions were phosphate buffer 200 mM, pH 7.50, -14 kV as applied potential, and 57 cm length neutral capillary. Detection was direct UV at 200 nm. Different kinds and marks of orange juice, chosen from the great variety existent in the market, were analysed and clear differences could be found between them and just pressed orange juice.

Beverages↗
PubMed2000

Optimization and validation of a method for the determination of caffeine, 8-chlorotheophylline and diphenhydramine by isocratic high-performance liquid chromatography. Stress test for stability evaluation.

The optimization of a HPLC method for caffeine, 8-chlorotheophylline and diphenhydramine separation with UV detection at 229 nm is described. The conditions studied included: stationary phase, compositions of mobile phases with pH modulators. Optimal conditions were: SymmetryShield RP8 column and acetonitrile-(0.01 M H3PO4-triethylamine, pH 2.8) (22:78, v/v). Validation was performed using standards and a pharmaceutical preparation containing the compounds described above. Results from both standards and samples show suitable validation parameters. The pharmaceutical grade substances were tested by factors that could influence the chemical stability. These reaction mixtures were analyzed to evaluate the capability of the method to separate degradation products. Degradation products did not interfere with the determination of the substances tested by the assay.

Caffeine↗
PubMed2000

Vaginal bacterial microflora modifications during the growth of healthy cows.

The aim of this work was first, to determine the predominant groups capable of colonizing the vagina and maintaining high numbers with time. The normal microbial flora of the cow's vagina and its evolution from weaning to service was then studied using standard microbiological methods. The results show that the most dominant bacteria belong to the streptococci, followed by the staphylococci, with similar levels during the whole study period. Enterobacteriaceae and lactobacilli were present at very low levels, the latter increasing during the cow's growth, suggesting some kind of hormonal influence. The results will allow the selection of micro-organisms with probiotic characteristics, classified as GRAS (Generally Regarded as Safe), to be used in the prevention of infections in the vaginal tract of cows, such as metritis, which produces delayed periods between partum and conception, and consequent economic losses.

Animals↗