Proficiency Tests Conducted by Soil and Plant Analysis Laboratories in Mexico

Abstract

Measurement is the comparison of a quantity against a certain standard. Measurements conducted in chemistry are usually compared against certified reference material (CRM). When a laboratory makes proper measurements, the results obtained have a low level of uncertainty; they are reliable, traceable in accordance with the International System of Units, and comparable to those made in any laboratory in the world. The purpose of this article was to determine the performance of the analytical measurements carried out by Mexico's soil and plant analysis laboratories through a proficiency testing program. The materials used for this program came from three sample batches of corn leaves, which were certified by Centro Nacional de Metrologìa of Mexico (CENAM). The critical mean quadratic error (MQEc) was used as the evaluation criterion. Although the percentage of acceptable results reported by laboratories has risen only slightly as a consequence of the proficiency testing program, it is worth mentioning that laboratory managers in Mexico are becoming more aware of the importance of quality control and the use of CRM.

Keywords:

• Certified reference materials
• metrology
• uncertainty

Acknowledgments

Appreciation is expressed to M. Sc. Laureano Pastrana and his team, Yoshito Mitani and his staff from CENAM for contributing to the success of this project, the Mexican Society of Soil Science, and all the participants in the Interlaboratory Comparison Program: Agro Ambiental, S. A. de C. V., Ensenada; UNIFRUT, Cd. Cuauhtemoc; Lab. de Edafología Ambiental, Instituto de Geología–UNAM; Lab. de la UAE, Toluca; Lab. de Alta Tecnología de Orizaba; ITA No. 33, Celaya; INIFAP–Celaya; Análisis Técnicos, S. A de C. V., Pachuca; INIFAP–Santiago Ixcuintla; Lab. de la Fac. Ciencias Forestales, UAN; Centro de investigación en Alimentación y Desarrollo A. C., Culiacán; CIIDIR–Sinaloa; ITA No. 23, Oaxaca; Universidad Autónoma de Chiapas, Huehuetan; Fac. de Ciencias Agrícolas y Forestales, UAC, Cd. Delicias; Centro de Investigación en Ciencias Agropecuarias, UAE, Toluca; Lab. de Inv. Agrícola de Casa Cuervo, Zapopan; Lab. de Suelos del Valle de Apatzingán; LASPA, CP–Campus Tabasco; LAFER, CP–Campus Montecillo; Lab. del Centro de Investigación en Ciencias Agropecuarias, Villahermosa; Lab. del INIFAP–Huimanguillo; Lab. de Análisis Quí. de Suelos, Aguas y Plantas; Instituto de Ecología, A. C., Jalapa; Lab. de Nutrición Vegetal del CIICA, Tapachula; INIFAP–Gómez Palacio; and Tabacos Desvenados, Tepic.