A Survey of Selected Methods of Arsenic Analysis in Biological Materials and a Proposed Modification of the Evans-Bandemer Method

Arsenic (As) atomic number 33, atomic weight 74.91, is usually classed as a nonmetal or metalloid, although in the pure state it forms a steel grey metallic crystal and is referred to as metallic arsenic. Only one stable isotope is known at the present time, in spite of its fractional atomic weight. However, the number of allotropic forms and their properties seem to be undecided among many authors (1).“Arsenic” was known in the pre-Christian era, but as such was not the pure element. Instead it consisted of the sulfides of arsenic: realgar (As4S4) and orpiment (As2S3). These sulfides were encountered in the gold, silver, and tin mines of that time, accounting for the deaths of many of the miners. The early investigations of arsenic trioxide (As2O3) mentioned its medicinal values, but apparently the toxic effects were not discovered until around the first century A.D. (1,2). It is believed that elemental arsenic was obtained by Albertus Magnus in 1250 A.D., by heating As2S3 with soap (2). Perhaps the most important use of arsenic at that time was by the professional poisoners as a means of assassination (3). It is said that many a Roman wife dispatched her unworthy husband by this means. Today, the United States is the largest commercial producer of arsenic with respect to the ore processing method, and Mexico ranks second. Production was far in excess of demand, and for a time the arsenic produced from ore refining was sealed in cement blocks and dumped at sea. Due to the expense of disposal, however, storehouses were built with the hope of developing a future market for it. World production in 1943 was about 77,000 tons of white arsenic. In 1939 it sold for about three cents a pound, and by 1947 had doubled in price. In 1944 the United States produced about 36,000 tons and consumed about 43,000 tons (4). During the past twenty years there has been an increase in arsenic consumption. Insecticides and glass manufactures utilize about 80% and 5% respectively of the white arsenic produced today. In addition, a small percentage is used in metallurgy and drug preparations (4). The hazards of arsenic are many to the people producing or working with arsenical compounds. They, however, are aware of these dangers. Instead it is the unwary who are hurt by the substance, often through an indirect manner. The official food tolerance as established by the Federal Food and Drug Administration is 3.57 parts per million of As as As2O3, or 2.71 parts per million of As as As (5). This is the same as 2.71 micrograms or 0.00000271 gram of arsenic per gram of food. Consequently, there exists a need for a suitable method by which arsenic may be determined. Food products are often highly contaminated as the result of sprays or insecticides used on foods. Another source of arsenic poisoning is in the areas near ore processing plants. Mineral waters contain small quantities of arsenic due to leaching and weathering of mineral rocks. Perhaps the most important occurrence of arsenic to the average individual is in the form of foodstuffs and biological materials. A case of arsenic poisoning from beer was traced to the sulfuric acid used in processing the sugar (6). Wines as well contain traces of arsenic as the result of sprays used on the grapes (7). The problem is important from many standpoints, whether it be glassmaking, ore processing, pharmaceutical preparations, foodstuffs, or in the involvement of any of the hundreds of other occurrences of arsenic. It still must be sought out, separated, and determined quantitatively in a satisfactory fashion. The variety of its occurrences makes a universal method of analysis elusive. The objective of this investigation was to determine the best available chemical method for the determination of arsenic in micro quantities in biological materials, utilizing simple and readily available equipment. The author has attempted to make a survey of the most promising methods of arsenic analysis in biological materials and to improve or devise a better method in accordance with the objective of this problem