Analytical methods applied to the determination of heterocyclic aromatic amines in foods.

Analytical aspects concerning the heterocyclic aromatic amines (HAAs) determination in foods are reviewed. Sample pre-treatment procedures such as liquid-liquid extraction (LLE), supercritical fluid extraction, solid-phase extraction (SPE), solid-phase microextraction (SPME), and the mainly used LLE-SPE tandem extraction are discussed. The analytical methods used for the identification and quantification are HPLC, HPLC combined with single or tandem MS detection (HPLC-MS, HPLC-MS/MS), GC-MS and capillary electrophoresis. Advantages and figures of merit for each technique are discussed.

Estudio de correlación y análisis factorial aplicado a la excreción urinaria de selenio / Study of correlation and factor analysis applied to the excretion urinary of selenium

Objetivo. En este trabajo se ha evaluado la influencia del sexo, edad, peso y talla sobre distintas formas de expresión de la excreción urinaria de selenio (Se) correspondientes a un grupo de personas sanas. Diseño experimental. Se analizaron 97 muestras de orina de 24 h (46 hombres y 51 mujeres) pertenecientes a la población sana de la isla de Tenerife. La determinación de los niveles de Se se realizó por un método espectrof luorimétrico, y la creatinina (CT) por el método modificado de Jaffé. Los análisis estadísticos han sido realizados usando el programa SPSS versión 10.0 para Windows. Resultados. Se obtuvieron numerosas correlaciones significativas entre las variables analizadas, destacando la existente entre la concentración urinaria de Se y de creatinina. En cuanto al análisis factorial, se seleccionaron cuatro factores, los cuales presentaron autovalores mayores que 1. Estos factores explicaron el 83 por ciento de la varianza total del sistema. Se constata que el primer factor estaba relacionado con parámetros antropométricos; el segundo y el tercer factor estaban influenciados principalmente por parámetros relacionados con la excreción de Se y de creatinina; respectivamente; en el cuarto factor las variables más influyentes fueron las concentraciones de Se y de creatinina. Conclusiones. El estudio de correlación puso de manifiesto la relación existente entre la concentración urinaria de Se y de creatinina. Además, se comprobó que la concentración de Se expresada como microg Se/g CT representa mejor la excreción urinaria de Se que la concentración expresada como microg Se/l (AU)

Concentraciones de calcio, magnesio, sodio y potasio en leche materna y fórmulas de inicio / Concentrations of calcium, magnesium, sodium and potassium in human milk and infant formulas

Concentrations of calcium, magnesium, sodium and potassium were determined in 55 samples of mature human milk from Canary women and 5 samples of powdered infant formula. According to the literature our data fell within the normal intervals described for each kind of milk. The mean concentration of Ca, Mg, Na y K of powdered infant formula was higher than those concentrations found in the human milks. Significant differences among the concentrations of Ca, Mg and Na for the milks of the considered mothers were observed. Only the Ca intakes for infants fed with human milk were lower than those requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had an adequate intake of all the studied metals. A progressive decrease of the Na, K and Ca concentrations with the lactation stage was observed. Maternal age, parity and sex of the newborns did not affect the metal concentrations significantly.

[Concentrations of calcium, magnesium, sodium and potassium in human milk and infant formulas]. / Concentraciones de calcio, magnesio, sodio y potasio en leche materna y fórmulas de inicio.

Concentrations of calcium, magnesium, sodium and potassium were determined in 55 samples of mature human milk from Canary women and 5 samples of powdered infant formula. According to the literature our data fell within the normal intervals described for each kind of milk. The mean concentration of Ca, Mg, Na y K of powdered infant formula was higher than those concentrations found in the human milks. Significant differences among the concentrations of Ca, Mg and Na for the milks of the considered mothers were observed. Only the Ca intakes for infants fed with human milk were lower than those requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had an adequate intake of all the studied metals. A progressive decrease of the Na, K and Ca concentrations with the lactation stage was observed. Maternal age, parity and sex of the newborns did not affect the metal concentrations significantly.

Concentrations of iron, copper and zinc in human milk and powdered infant formula.

Concentrations of iron, copper and zinc were determined in 56 samples of mature human milk from Canarian women and 5 samples of powdered infant formula. According to the literature our data fall within the normal limits in each kind of milk. The mean concentration of Fe, Cu and Zn of powdered infant formula was significantly higher than those concentrations found in the human milks. Significant differences among the concentrations of the studied metals for the milks of considered mothers were observed. The Fe, Cu and Zn intakes of infants fed with human milk are lower than the requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had consumed an adequate intake of Fe and Cu. A progressive decrease of the metal concentrations with the lactation stage was observed. The human milk obtained in spring presented Fe and Zn concentrations lower than in autumn, which could be due to changes in nutritional habits of the mothers. Age of mother and number of previous children seem to influence the Zn and Cu concentrations of human milk.

Chemometric studies of several minerals in milks.

A statistical study of correlation, factorial, and discriminant analysis on the metal composition (Se, Fe, Cu, Zn, Na, K, Ca, Mg) of different types of milks (human, cow, goat, pasteurized, and powdered infant formula) was carried out to establish the relationships between the metal concentrations and, therefore, differentiate the samples according to the type of milk. A large number of significant intermetallic correlations were found in all samples, which could be due to biological relationships between the metals studied. After the factorial analysis, the dimension space was reduced from eight variables to two factors, accounting for approximately 71.4% of the total variance. After an orthogonal rotation, the first factor was positively correlated with Ca and the second factor with Fe. The representation of the scores makes it possible to separate not only human milk from powdered infant formula but also to separate both of these from the other milks. In the discriminant analysis, four discriminant functions were obtained, which are linear combinations of the quantitative variables that best explain the differences among the different milks analyzed. These functions make it possible to classify 98% of the samples analyzed within each type of milk correctly. Therefore, discriminant functions obtained here can be used to identify the origin of any milk sample.

Selenium in human lactation.

The primary factor determining selenium concentration in human milk is the maternal selenium intake. A significant correlation between selenium in human milk and maternal selenium intake has been reviewed in papers from different regions of the world. Infants fed human milk have higher selenium intake than those fed commercially available formula milk or baby foods. Selenium compounds found in breast milk seem to be more biologically available for infant nutrition than those in formulas. Increased requirements of selenium have been observed in pregnant and lactating women. Supplementation of lactating and pregnant women with different selenium compounds has been assayed, and selenium supplementation of soil and cows has been used to increase the selenium status of children fed infant formula made from cow's milk.

Urinary selenium status of healthy people.

Urinary selenium (Se) concentrations (microgram/l of urine and microgram/g of creatinine) and urinary Se excretions (microgram/d and microgram/d.kg of body weight) have been determined in healthy Canarian people. Urinary Se status was relatively low and similar to those data published from European regions. Females excreted daily significantly (P = 0.005) higher amounts of Se per kg of body weight in urine than males. An increase of daily urinary Se excretion was observed up to 30 years of age. Children (< 10 years old) had daily urinary Se excretion per kg of body weight higher than persons with age > 10 years old. Both units of Se excretion, microgram/d and microgram/d.kg, increased or decreased respectively with weight and height of the individuals. Food habits such as consumption of rich protein or rich fibre food, and drinking alcohol or coffee as well as smoking do not seem to influence the urinary Se status. Depletion of daily urinary Se excretion was observed with the increase of physical exercise. Unit of concentration (microgram/g of creatinine) is a more adequate indicator of the urinary Se excretion than the unit microgram/l.

Urinary selenium concentrations in heroin abusers.

Urinary selenium (Se) concentrations (micrograms Se/l and microgram Se/g creatinine) have been determined in heroin abusers and in healthy controls. Heroin abusers showed significantly (P < 0.050) lower urinary Se concentrations (microgram Se/l and microgram Se/g creatinine) than healthy controls. The decrease of the urinary Se concentration (microgram Se/g creatinine) observed with the increase in age of heroin abusers may be due to the higher exposure to heroin with increased age. No significant differences (P > 0.100) of urinary Se concentrations (both as microgram Se/l and microgram Se/g creatinine) are observed between heroin abusers during methadone treatment and heroin abusers who have stopped taking the drug, with respect to healthy controls.

Urinary selenium concentrations.

Urinary selenium concentrations are used as an indicator of selenium status. A strong correlation has been established between dietary selenium and daily urinary selenium excretion in a wide range of populations from all over the world with different dietary selenium intake. Data on urinary selenium concentrations in healthy individuals and patients with different pathological conditions are reviewed. Selenium excretion rates of 20-200 micrograms/day are not associated with deficiency or toxicity problems. Urinary Se excretion is decreased in children, elderly people, and pregnant women. Workers exposed to heavy metals, and cancer patients, have higher and lower urinary Se concentrations, respectively, than control groups. The trimethylselenonium ion, a minor metabolite of Se in urine, assumes a significant role only in the detoxification of excess Se intake. Studies of bioavailability and balance show the important role of the kidneys in homeostatic regulation of Se.