Write down the approaches of determination of trace elements in environmental sample. What are their limitations？ How to reduce or eliminate these problems？

A、The main analytical techniques used for determination of trace elements in environmental samples include:

B、Atomic absorption spectrometry (flame or electrothermal) (AAS, ET-AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma optical (or atomic) emission spectrometry (ICP-OES or ICP-AES), neutron activation analysis (NAA), X-ray fluorescence (XRF), proton-induced X-ray emission (PIXE), spark source or isotope dilution mass spectrometry (SSMS, IDMS), electrochemical (anodic stripping voltammetry and polarography) or inductively coupled plasma-mass spectrometry (ICP-MS).

C、The main limitations for most of these analytical methods are sensitivity or precision problems due to interferences and sample matrix effects.

D、In some cases these problems have been reduced or eliminated by the use of pre-analysis separation schemes, matrix-matching of reagent blanks, calibration standards and samples; the inclusion of instrument background correction (AAS) or the coupling of hydride generation (HG), electro thermal vaporization (ETV), cold vapor (CV), flow injection (FI), ultrasonic nebulisation (USN) or laser ablation (LA) devices to the trace element detector.