Electron capture detector (ECD). Electron capture detectors (ECD) are typically used in environmental testing for detecting PCBâs, organochlorine pesticides, herbicides and various halogenated hydrocarbons. With an electron capture detector, a beta emitter such as radioactive tritium or 63Ni is used to ionize the carrier gas.
Las Piedras: Las Piedras, city, southern Uruguay. It is situated in a wine-growing district just north of Montevideo. It was the site of a decisive battle (1811) in Uruguayâs struggle for independence, in which the revolutionaries defeated Spanish forces. Las Piedras is among the largest cities in Uruguay. It is known for its ostrich farming and horse racing. Las Piedras is on the main highway and railroad linking Montevideo with TacuarembÃ³ and Rivera. Pop.
San Cristobal de las Casas is situated in a fertile valley surrounded by mountains in the southern state of Chiapas, Mexico. Chiapas is home to several indigenous groups descended from the Maya, two of the largest being the Tzotzils and Tzeltals who inhabit highland villages surrounding San Cristobal.an Cristobal, designated as one of Mexico's Magic Towns, is a classic Spanish colonial-style wonder. San Cristobal de las Casas was the capital of Chiapas until 1892 and is still considered the cultural capital of the state.