[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Naturally new spe mate rials are being developed

Info icon This preview shows pages 628–630. Sign up to view the full content.

View Full Document Right Arrow Icon
greater use of solid-phase extraction (SPE) [281]. Naturally, new SPE mate- rials are being developed until now and it seems to be a never-ending story; however, present efforts are aimed mostly at finding an optimum material for a particular application rather than a universal sorbent suitable for every purpose. The analytical practice may be divided into two fields regarding specificity. A basic question of screening or specific target analysis demands for different approach and this point should be carefully defined at the outset of the work. 1 . 2 en. 3 sanitation health/dwq/guidelines/en.
Image of page 628

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
608 S. Kurunczi et al It has become apparent that any mistake occurring in collecting and processing a water sample or contamination during analysis could lead to a substantial error in the final result regardless of the performance of any state- of-the-art analytical technique applied subsequently. Therefore, it is important to emphasize the need for a clean environment during sample preparation and analysis [282]. In the case of TXRF a specimen is prepared on a flat carrier drying a liquid drop on it. The absolute amount of this film-like deposit is usually below 1 µ g and it is measured in the laboratory air. In the case of XRF, mainly thicker solid samples are prepared from the water sample, e.g., after preconcentration on ion-exchange resin. More strict rules of cleanliness are therefore required for the TXRF laboratory, applying Class-100 level or better air quality. 4 Conventional-XRF Applications Soon after the introduction of the energy dispersive (ED) spectrometers [283], several methods were explored for a suitable sample preparation. Various pre- concentration techniques were applied to wavelength dispersive spectrometers earlier, thus the idea of upgrading the sample preparation with the much ef- ficient ED detection system seemed promising. Luke’s paper [284] is based on measurements with a wavelength dispersive spectrometer and described a comprehensive view of precipitation methods mainly with carbamate, cup- ferrate, ammonia, and hydrogen sulfide. The paper discussed different copre- cipitating elements that were necessary to obtain quantitative recovery. The precipitates were filtered on a paper filter from aqueous solution and the cali- bration was established in the low µ g range. A selective preconcentration was developed using ammonium pyrrolidinedithiocarbamate and the subsequent liquid extraction of the organic complexes [285]. This method is based on the simple fact that organic reagents containing cyanide, heavy halides, and sulfur donors form much stable complexes with transition metals than with alkali or alkaline earths [286]. Seawater matrix (alkali metals, alkaline earth met- als, and halogens) do not form extractable complexes with dithiocarbamates.
Image of page 629
Image of page 630
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern