CHEMICAL PROPERTIES 607 



Determination 



The usual qualitative and quantitative methods for the detection and 

 analysis of inorganic arsenic (such as the Bettendorff, the Marsh, and the 

 Gutzeit tests), frequently used in commercial and forensic work, are de- 

 scribed in the standard texts, and it need only be mentioned that quanti- 

 ties as small as 0.1 //g of arsenic can be determined with considerable 

 accuracy by modifications of the Marsh test wherein the deposited arsenic 

 is titrated conductometrically. It is more pertinent for our present purposes 

 to mention the excellent analytical procedures developed by Crawford 

 in Edinburgh. Originally a technique was devised for the separation of 

 arsenite and arsenate in biological material using sodium ethylxanthate 

 and distribution in carbon tetrachloride (Crawford and Story, 1944). 

 However, it was found that sodium ethylxanthate is not suitable for the 

 aromatic arsinites and arsonates; for this purpose, ethane- 1,2-diol in carbon 

 tetrachloride proved to be satisfactory, the method being accurate for 

 2.//g arsenic (Crawford and Levvy, 1946). Thus it is possible to separate 

 and determine inorganic and organic trivalent and pentavalent arsenicals 

 in biological material and this has been of use in studying the distribution 

 and metabolism of such compounds (Crawford, 1947). A sensitive spectro- 

 photometric test for arsenic has recently been described by Dal Cortivo 

 et al. (1960) and is based on the evolution of arsine into a pyridine solution 

 of silver diethyldithiocarbamate. Arsenic in tissues can be determined 

 down to 1 //g% and in urine to 0.1 //g% by this method. It may be noted 

 that a specific color reaction between oxophenarsine and 1,2-naphthoqui- 

 none-4-sulfonate is often useful in detecting this arsenical in tissues (Ro- 

 senthal, 1932 a). Arsenite and arsenate can be separated and determined 

 by paper chromatography, and spot testing is available for the microde- 

 termination of arsenic. Organic arsenicals may be determined by a spot 

 test after conversion to arsenate by heating with lime and treatment with 

 stannous chloride in HCl solution, with a sensitivity of around 1.4 //g. 

 The most sensitive of all methods is based on activation analysis and quan- 

 tities down to 0.001-0.01 //g can be determined in biological material 

 (Christell and Sjostrand, 1962).* The method involves neutron bombard- 

 ment of the samples, separation of the As'^, and determination by /9-count- 

 ing or /-spectrometry. 



* This method allowed the determination of the arsenic content in the disinterred 

 fragments of the sixteenth century King Erik XIV of Sweden for the purpose of 

 providing evidence on the rumored poisoning by his brother. 



