Retraction notice to “Solid phase extraction method for the determination of lead, nickel, copper and manganese by flame atomic absorption spectrometry using sodium bispiperdine-1,1′-carbotetrathioate (Na-BPCTT) in water samples” [J. Hazard. Mater. 146 (1–2) (2007) 131–136] - Retraction Notice | RetractBase