Analysis of perfluorinated acids at parts-per-quadrillion levels in seawater using liquid chromatography-tandem mass spectrometry - Gamo, Toshitaka.; Horii, Yuichi.; Kannan, Kurunthachalam.; Okazawa, Tsuyoshi.; Petrick, Gert.; Taniyasu, Sachi.; Yamashita, Nobuyoshi.