Matrix interferences in flame atomic absorption spectrophotometry Prof

Matrix interferences in flame atomic absorption spectrophotometry Prof. Dr Snežana Maletić, Prof. Dr Ivana Ivančev Tumbas Technical assistance: Dr Malcolm Watson, Dr Anita Leovac Maćerak Course: Environmental Quality Control (Advanced Course) – lab exercise University of Novi Sad, Faculty of Sciences, Trg Dositeja Obradovića 3, 21000 Novi Sad, Republic of Serbia _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Objectives • To equip the students with the knowledge of: • (1) proper preparation of complex matrix for metal analysis; • (2) optimization of instrument operation conditions; • (3) different matrix influences on absorbance signals and subsequently on the resulting metal concentration; • (4) dealing with complex matrices such as sediment samples. _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Outcomes This laboratory excercise is designed to help students achieve the following outcomes: ü Ability to properly prepare a complex matrix for metal analysis. ü Ability to optimize instrument conditions. ü Awareness of the effects of different matrix on absorbance signals and their effects on the results. ü Ability to deal with complex matrices such as sediment samples. _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Background • Matrix interferences are physical interferences. • They either suppress or enhance absorbance signal of the analyte. • They occur when components of the sample matrix, other than the analyte, react to form molecular species and give sample background. • The detector picks up unspecified signals from the sample matrix that do not match the absorbance line of the analyte. • This can affect the quantitative and qualitative analysis. _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Causes of matrix interferences: • Sample and standards differ in viscosity and surface tension. • Sample and standards are prepared in different solvents. • Sample and standards are measured at different temperatures. • The sample contains a high concentration of dissolved salts or acids. • Presence of organics in the sample matrix. • Sample and standards differ in aspiration and atomization rates in the flame. _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Brief description • Sediment certified reference material as an example of a complex matrix will be prepared by acid microwave digestion according to the EPA 3051 a standard method. • In brief: • weight 0. 5 -1 g of sediment certified material, • add 6 cm 3 of cc HNO 3 and 3 cm 3 of cc HCl • digest the sample in the microwave digestion unit, temperature program: Time (min) Temperature (o. C) 5 10 175± 5 _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. MW power (Wat) Do 1200

Brief description • In order to demonstrate the matrix interferences, the concentration of the Cu in the sediment certified material will be determined by: • traditional calibration curve approach using calibration standards prepared in: 10% HNO 3 10% H 2 SO 4 Mixture HCl+HNO 3 – in the same quantity used for the sediment sample preparation • standard addition method in the acid digestate of the sediment certified reference material _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Brief description • In the digested sediment certified reference material Cu will be analyzed by the AAS. • The Cu concentration in the sediment will be calculated by using different calibration curves. • Results will be compared to the certified value given in the sediment certificate of analysis (146 mg Cu/kg). • The bias of the Cu concentration in the sediment sample will be compared to the acceptance criteria according to: • EPA 7000 b method (± 25%), • the prediction interval given in the certificate of analysis (133 -158 mg Cu/kg). _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Material and reagents • cc. H 2 SO 4 (http: //www. sciencelab. com/msds. php? msds. Id=9925146) • cc. HNO 3 (http: //www. sciencelab. com/msds. php? msds. Id=9926241) • cc. HCl (http: //www. sciencelab. com/msds. php? msds. Id=9924285) • Cu stock standard solution 1 g/dm 3. (https: //www. msdsdigital. com/aa-standard-cu-coppermsds) • Please refer to given link of MSD for the health and safety information of the used chemicals. _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Materials and reagents • Aquatic sediment Certified reference material _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Equipment • Analytical balance • Microwave digestion unit - MILESTONE START E • Atomic Absorption Spectrometer - AAnalyst 700 Perkin. Elmer precisely • Please refer to the instrument guideline manual for the operation and safety information. • (printed version available in the laboratory for the AAS analysis upon request) • Milestone Start. E Users manual • AAnalyst 700 Atomic Absorption Spectrometer • Analytical Methods for Atomic Absorption Spectrometer – User Guide • Burner System Atomic Absorption Spectrometer – User Guide _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

Content ü Certified sediment reference material preparation by microwave digestion. ü Part 1 – Sample preparation for MW digestion ü Part 2 – MW digestion setup ü Part 3 – MW digestion control ü Part 4 – Sample processing after MW digestion ü Preparing and analyzing the calibration standards in several different matrices. ü Part 5 – Preparation of the calibration standards in different matrices ü AAS instrument start up and optimization of operation conditions. ü Part 6 – Instrument optimization operation ü Analyzing samples by AAS. ü Part 7 – Sample analysis ü Data processing in the AAS software ü Part 8 - Data processing in the AAS software ü Data processing - calculation and comparison. ü Part 9 – Data processing _____________________________________________ This project has been funded with support from the European Commission. This publication reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.