Validación de una metodología analítica para determinar bifenilos policlorados en muestras de plasma sanguíneo / Validation of an analytical methodology to determine polychlorinated biphenyls in samples from blood plasma

Resumen Introducción. Los bifenilos policlorados se encuentran entre los cinco contaminantes orgánicos persistentes más tóxicos para los organismos vivos, según la Agency for Toxic Substances and Disease Registry (ATSDR) de los Estados Unidos. Objetivo. Estandarizar y validar un método analítico para la determinación y cuantificación de los bifenilos policlorados indicadores en muestras de plasma sanguíneo, mediante cromatografía de gases acoplada a espectrometría de masas. Materiales y métodos. Se fortificó un pool de plasma para hacer los ensayos en la matriz. Además, se utilizó el material de referencia NIST SRM ® 1958 (Organic Contaminants in Fortified Human Serum, Freeze-Dried) para los ensayos de veracidad y precisión intermedia. Resultados. Los porcentajes de recuperación obtenidos con la metodología estuvieron entre 88,4 y 97,5 %, y el sesgo fue menor del 20 %. Los límites de detección y cuantificación de los bifenilos policlorados indicadores policlorados fueron de 0,04 µg/L y 0,10 µg/L, respectivamente. La linealidad representada por el coeficiente de determinación (R2) varió entre 0,9866 y 0,9886. La precisión expresada como desviación estándar relativa fue menor del 20 % en todo el rango lineal de trabajo (0,5-500 µg/L). Por último, se analizaron 115 muestras de población colombiana de diferentes zonas del país y se encontraron 65 muestras positivas, de las cuales dos estuvieron por encima de los valores de control biológico en humanos (Human Biomonitoring Values, HBM- II): 7,0 µg/L, 2XΣPCB 138, 153, 180 , y otras dos, por encima del HBM-I: 3,5 µg/L, 2XΣPCB 138, 153, 180. Conclusión. El método desarrollado resultó ser preciso para el análisis de los bifenilos policlorados en muestras de plasma sanguíneo y se puede utilizar para el control biológico de estos contaminantes en población colombiana.

Abstract Introduction: Polychlorinated biphenyls are among the five most toxic persistent contaminants for living organisms according to the Agency for Toxic Substances and Disease Registry (ATSDR). Objective: To standardize and validate an analytical method to determine and quantify polychlorinated biphenyl indicators in samples from blood plasma by means of gas chromatography-mass spectrometry. Materials and methods: We fortified a plasma pool to do the matrix assays. Additionally, we used the NIST SRM® 1958 reference material for the veracity and intermediate accuracy assays. Results: Methodology recovery percentages ranged between 88.4 and 97.5%, and the bias was less than 20%. Detection and quantification limits were 0.04 µg/L and 0.10 µg/L, respectively, for all polychlorinated biphenyl indicators. The linearity represented by the determination coefficient (R2 ) varied between 0.9866 and 0.9886. Accuracy, expressed as relative standard deviation was less than 20% in all the linear work range (0.5-500 µg/L). Finally, we analyzed 115 samples from Colombian population in various zones of the country and we found 65 positive samples, from which two samples were above HBM-II (7.0 µg/L, 2XΣPCB 138, 153, 180), and two, above HBM-I (3.5 µg/L, 2XΣPCB 138, 153, 180 ). Conclusion: The method we developed is accurate for PCB analysis in blood plasma samples and could be used for biological surveillance of these contaminants in the Colombian population.

Lipophilic metabolite profiling of maize and sorghum seeds and seedlings, and their pest spotted stem borer larvae: A standardized GC-MS based approach.

In order to better understand the biochemical interactions and to identify new biomarkers for plant resistance against insects, we proposed a suitable lipophilic profiling method for insects and their host plants. The critical components of GC-MS based analysis are: sample amount, extraction, derivatization, temperature gradient, run time, and identification of peaks. For lipophilic metabolite profiling of maize and sorghum, and their insect pest, spotted stem borer larvae, we recommend 100 mg sample weight for seeds and insect samples (whole insect body), and 200 mg for seedlings. Maize and sorghum seeds required less time for fat extraction in comparison to their seedlings and the pest fed on these seedlings. GC-MS was standardized for better separation and intensity of peaks using different temperature gradients in the range of 180-300 C. A total of 48 lipophilic compounds encompassing various classes based on their functional groups such as fatty acids, fatty alcohols, hydrocarbons, sterols and terpenoids, vitamin derivative, etc. were separated in the seedlings (30), seeds (14), and the pest (26) in the retention time range of 3.22 to 29.41 min. This method could be useful to study nutritional aspects of different field crops in relation to various stresses apart from the analysis of lipophilic compounds for better understanding of insect-plant interactions.