The present work aims the determination of As, Co, Cr, Cu, Mn and Pb in seawater samples using coprecipitation extraction procedure before standard mode inductively coupled plasma mass spectrometry (ICP-MS) (no collision/reaction cell). The coprecipitation procedure is based on the precipitation of Mg(OH)2 from the reaction of the Mg2+ ions (present into the seawater) with ammonia added to the sample. Central composite design, desirability function, and response surface methodology were used to optimize the coprecipitation procedure. The optimum values obtained were 1200 µL of aqueous ammonia, 30 min of centrifugation time and 400 µL of nitric acid. The procedure obtained showed low limits of detection since good preconcentration factors were obtained. Good accuracy was also obtained when the reference material Trace Metals 1 in seawater was evaluated. Thus, the proposed procedure can be considered a good strategy for the determination of As, Co, Cr, Cu, Mn and Pb in seawater by ICP-MS, due to its simplicity, low cost, high analytical frequency, besides the good sensitivity and accuracy achieved.

Cocaine is usually seized mixed with a wide variety of adulterants such as benzocaine, lidocaine, caffeine, and procaine. The forensic identification of cocaine in these street drug mixtures is normally performed using colorimetric testing kits, but these tests may suffer from interferences, producing false-positive results. Here, we describe the use of analytical techniques including attenuated total reflection Fourier transform infrared (ATR-FTIR) and ultraviolet-visible (UV-VIS) spectroscopies to distinguish between cocaine and other adulterants (lidocaine, promethazine, powdered milk and yeast) that yield positive results on the Scott test using the thiocyanate cobalt reagent. A further 13 substances were also analyzed using the Scott test.