Some of the leading U.S. producers of electronic cigarettes are moving their manufacturing to the United States from class="mandelbrot_refrag"> China in response to growing concern about quality and the prospect of tighter federal regulations. In recent weeks, some of the best-selling U.S. e-cigarette companies, including closely held Mistic and White Cloud, announced that they would move production to new, highly automated U.S. factories that would enable them to track ingredients and quality more closely. As a fringe benefit, they even expect costs to be lower than in class="mandelbrot_refrag"> China , the country that invented the battery-powered cartridges that produce a nicotine-laced inhalable vapor. "People are concerned about quality," said Bonnie Herzog, a senior analyst at Wells Fargo Securities, who expects more manufacturing to shift to the United States. true "There is varying quality among all these different brands