Investigation of Uncertainty Contributions for Elemental Analysis of Sesized Street Heroin by ICPMS

Abstract

The aim of the study was the identification and quantification of uncertainty sources associated with heroin elemental analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following sample dissolution through microwave assisted acid digestion. The percentage contribution of each source to the relative combined uncertainty was also calculated. The "bottom-up" approach The main objective of quantitative analysis is to obtain the most reliable analytical results, which must reflect unambiguously true and clear values of sample composition As measurement uncertainty estimation is considered an important part of the method validation procedure, the list of guidelines and works dedicated to this topic is getting longer every year. Previous studies about uncertainty determination in drugs of abuse analysis referred mostly to chromatographic techniques such as GC-FID [4], GC-MS [5,6] HPLC The level of inorganic impurities in seized drugs was also investigated In what method validation and, particularly, measurement uncertainty estimation are concerned, there is a gap in the area of illicit drug elemental analysis by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our study aimed to evaluate the uncertainty related to determination of metal content in seized heroin by ICP-MS. The contribution of each uncertainty source was investigated in order to identify solutions for the improvement of the combined measurement uncertainty. Experimental part Reagents and calibration standards Acid digestion of the samples was carried out with a mixture of nitric acid (60% volume concentration of HNO 3 * email: [email protected]; Tel.: +40742285994 ultrapure , Merck) and hydrogen peroxide (30% volume concentration of H 2 O 2 p.a., Fluka). Multi-element calibration Standard 3 (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, In, K, Li, Mg, Mn, Na, Ni, Pb, Rb, Se, Sr, Ti, V, U, Zn, for each 10 μg/mL) and Yttrium solution (1000 μg/mL) from Perkin Elmer were employed for calibration of the instrument and internal standardization respectively. Single element standard solutions (Al, Co, Cu, Mg, for each 1000 μg/mL) were used for the fortification of blank and sample solutions. All solutions were prepared or diluted with double deionized water (specific resistance 18.2 MΩcm -1 ) from a Milli-Q Millipore water purification system. Preparation of standard solutions Standard solutions were prepared just before analysis through a serial dilution method ( Sample preparation Heroin samples were weighed using a CP224S-0CE Sartorius electronic analytical balance and a microwave oven decomposition system (Multiwave 3000 with Rotor 8SXQ80, Anton Paar GmbH, Graz) was involved for samples microwave assisted acid digestion following a particular procedure described in our prior published work [16]