DETERMINATION OF LEAD , MERCURY AND ARSENIC IN FEEDING PHOSPHATES

Synek 0., S. Zima, M. Sucmanova, E. Sucman: Determination of Lead, Mercury and Arsenic in Feeding Phosphates. Acta vet. Bmo, 47, 1978: 153-158. Elaborated was the method of determination of lead, mercury and arsenic in feeding phosphates by means of atomic absorption spectrophotometry. Five different types of foreign and Czechoslovak phosphates commonly used for the preparation of feed mixtures were analyzed. The content of lead, mercury and arsenic ranged from 0.72 to 6.89 mg kg-I, 0.09 to 0.37 mg kg-l and from 0.75 to 69.77 mg kg-I, respectively. With regard to the content of all the three elements studies it was found that the relatively purest was dinatriumphosphate (Fosfa, n. p.), while the highest amount of admixtures was found in monocalciumphosphate (Reymeshoim) and dicalciumphosphate (CKF). Microelements, atomic absorption spectrophotometry, feed mixtures. The ever increasing industrialization and intensification of agricultural large-scale production necessitates investigations of new aspects in the nutrition of farm animals, aspects that had not been important before. One of the problems discussed has recently become the content of some microelements in feeds and feed mixtures; the intense development of instrumentation techniques over the past years has enabled these investigations to be carried out. The most important of these microelements are lead, cadmium, mercury and arsenic, indicated as "toxical civilization elements". The importance of uptake of these elements by farm animals should be judged from two aspects. i. e. from the point of view of the health condition of animals (possible intoxication, etc.), and because feed is the first link of the food chain which ends in man. Whereas the final links of this chain (raw materials for the preparation of foodstuffs, finished products, etc.) have already been studied, are being discussed, or there already exist standards for the admissible contents, in the field of feeds not many studies of this kind exist. These studies are aimed namely at lead of which namely the increased content in conventional feeds is closely associated with civilization. The intoxication of farm animals with lead in the industrial regions and in the vicinity of main roads with heavy traffic is becoming an ever increasing problem (Matyas 1975). The most important mineral components of feed mixtures include various types of phosphates, representing 1-10 % of the total composition of feed mixtures. With regard to the initial raw materials and the industrial character of the production of these substances the present study deals with the determination of lead, mercury and arsenic in the most frequently used types of feeding phosphates of both foreign and Czechoslovak origin. Materials and Methods Samples of dicalcium phosphate (DCP) and monocaIciumphosphate (MCP) imported to Czechoslovakia in 1975-1977 as mineral feed admixtures were analyzed as for the content of lead, mercury and arsenic. The other phosphates studied (dinatriumphosphate, pyrophosphate and hexametaphosphate) were produced in Fosfa n. p. in Postorna. Determination of the content of lead, mercury and arsenic in phosphates was performed using the method of atomic absorption spectrophotometry (AAS) with the Varian Techtron Model

The ever increasing industrialization and intensification of agricultural large-scale production necessitates investigations of new aspects in the nutrition of farm animals, aspects that had not been important before.One of the problems discussed has recently become the content of some microelements in feeds and feed mixtures; the intense development of instrumentation techniques over the past years has enabled these investigations to be carried out.The most important of these microelements are lead, cadmium, mercury and arsenic, indicated as "toxical civilization elements".The importance of uptake of these elements by farm animals should be judged from two aspects.i. e. from the point of view of the health condition of animals (possible intoxication, etc.), and because feed is the first link of the food chain which ends in man.Whereas the final links of this chain (raw materials for the preparation of foodstuffs, finished products, etc.) have already been studied, are being discussed, or there already exist standards for the admissible contents, in the field of feeds not many studies of this kind exist.These studies are aimed namely at lead of which namely the increased content in conventional feeds is closely associated with civilization.The intoxication of farm animals with lead in the industrial regions and in the vicinity of main roads with heavy traffic is becoming an ever increasing problem (Matyas 1975).
The most important mineral components of feed mixtures include various types of phosphates, representing 1-10 % of the total composition of feed mixtures.With regard to the initial raw materials and the industrial character of the production of these substances the present study deals with the determination of lead, mercury and arsenic in the most frequently used types of feeding phosphates of both foreign and Czechoslovak origin.

Materials and Methods
Samples of dicalcium phosphate (DCP) and monocaIciumphosphate (MCP) imported to Czechoslovakia in 1975Czechoslovakia in -1977 as mineral feed admixtures were analyzed as for the content of lead, mercury and arsenic.The other phosphates studied (dinatriumphosphate, pyrophosphate and hexametaphosphate) were produced in Fosfa n. p. in Postorna.
Determination of the content of lead, mercury and arsenic in phosphates was performed using the method of atomic absorption spectrophotometry (AAS) with the Varian Techtron Model 1000 apparatus.Absorbance signals were recorded using a Varian-Aerograph A-25 recorder.
Samples to be used for the determinations were dissolved in the following way: for arsenic determination a phosphate sample (1-2 g) was shaken for 3 hours with 25 ml of concentrated Hel.Next, about 30 ml of deionized water was added and the solution was heated (one hour) so that its temperature would not exceed 80 o e.After cooling down to room temperature the volume was refilled in a volumetric flask to 100 ml.For the determination of lead and mercury the method was the same, only that a mixture of 10 ml of concentrated HNOa and 15 ml of concentrated HCl was used.By an optimation of analytical conditions the methods were elaborated of determinations of the elements given in a certain material.Tab. 1 gives the basic parametres of the apparatus for the individual elements.
The content of lead was determined using flameless atomization; for this purpose the basic apparatus was supplied with the eRA device, Model 63, of the firm Varian.For the dosing of the samples analyzed we used an Eppendorf micropipette of a volume of 5,d.Mercury was determined using the cold vapour technique after reduction with tin dichloride in the equipment ofthe firm Varian, Model 64 (Han:h, Ott 1968;Hoower et a1.1971;Sucmanova et al. 1976).A constant volUme (20 ml) ofthe standard solution or sample was dosed into the reaction vessel.After adding 1 ml of 20 % SnCl. in concentrated Hel the solution was intensively mixed with an electromagnetic stirer and after 90 s the mercury vapours wl!l"e carried into an absorption measuring cell with a stream of argon.For the determination of arsenic we used the method of hydride development after reduction with sodium borohydride (5 ml of 5 % NaBH4) in the Model 64 device of the firm Varian.A nitrogen-entrained air-h)drogen flame served as absorption medium.A constant volume (20 ml) of standard solution or sample was dosed into the reaction vessel.
Tab. 2 shows the analytical characteristics of processes elaborated for the determination of the individual elements.The results measured were statistically elaborated in the common way.

Results
Tables 3, 4 and 5 give the contents of lead, mercury and arsenic found in the feeding phosphates analyzed.
The minimum content of lead determined in dinatriumphosphate was 0.72 mg kg-I.Of the DCP imported the lowest content (1.12 mg kg-I) was found in the sample of the firm Windmill, whilst the maximum content (6.89 mg kg-I) was found in DCP of the firm CKF.In total, the contents of lead in the samples analyzed ranged within one order.
The amounts of mercury found in phosphates were relatively low.The content of mercury did not exceed 0.5 mg kg-I in any of the samples analyzed.
However, the arsenic contents ranged within two orders.The highest content of arsenic was found in DCP of the firm CKF and the lowest in dinatriumphosphate, i. e. 69.77 mg kg-I and 0.75 mg kg-I, resp.From the point of view of all the elements studied the relatively purest was considered to be dinatriumphosphate, the impurest were DCP of the firm CKF and MCP of the firm Reymesholm.

Discusion
It was Lebeda and PHkrylova (1976) who drew attention to the importance of investigating the content of microelements in feeds as well as in commercially produced feed mixtures.Also Matyas (1976) considers investigations of microelements in feeds to be an important aspect in the prevention of intoxication and also of the good quality of foodstuffs.
The ever more frequent cases of intoxication of farm animals with lead necessitated investigations of the content of lead in feeds.Oelschlager (1974) determined that the content of lead in green fodder from different regions without developed industry and traffic ranged from 0.6 to 3.9 mg kg-I.Many authors (Hapke 1975;Horak et a1. 1977;Auermann et a1. 1976) dealt with determinations of the lead content in plants near to roads with heavy traffic; the results acquired are in accordance and range from 10 to 300 mg kg-I (in extreme cases even more) with regard to the distance of the place of sampling from the road and to some other factors.Mineral feeding phosphates can be considered to be a further potential source of lead with regard to the initial raw materials and technology of production.However, data on the content of lead are not very frequent in literature.Oelschlager (1974) found an average of 6.8 mg kg-I in the mineral additive for cattle and 11.0 mg kg -1 in the mineral additive for pigs which was ofthe same order as our results.Fox et a1. (1978) analyzed the commercially prepared mineral additives of feed mixtures for laboratory animals and found that the lead content ranged from 0.1 to 3,600 mg kg-I.The value for monocalciumphosphate was 23.2 mg kg-I.Crossmann (1977) determined that the average lead content in a number of various types of commercial feed mixtures for cattle, pigs, horses and poultry ranged from 0.65 to 7.77 mg kg-I.He stated that the content of lead in the mineral feeding additives themselves (not specified in greater detail) ranged from 0.42 to 21.7 mg kg-I.
Very dangerous for farm animals are -from the point of view of mercury poisoning -especially fungicides on the basis of mercury compounds, to a lesser extent water.The contents of mercury in feeding phosphates analyzed found by the authors of this study are relatively low.This fact is in accordance with data of Cross mann (1977) who found that the content of mercury in mineral feeding additives ranged from 0.01 to 0.36 mg kg-I.The average mercury contents in the finished feed mixtures were always found to be lower than O.1mg kg-I; in about 69 % its content was below the limit of detection, i. e. lower than 0.01 mg kg-I.
The common source of arsenic are mostly pesticides on the basis of arsenic (III) compounds.Arsenic in low concentrations is considered to be essential (Schwarz 1977).Arsenic poisoning is not very frequent and as stated by Selby et al. (1977) it afflicts mostly cattle and also dogs.Recently, investigations of the content of arsenic in foodstuffs have been carried out.Jelinek and Corneliussen (1977) state that in meat and fish the range was 0.020 to 0.180 mg kg-I.The values of arsenic contents in feeding phosphates' given in the present study are relatively high, especially for DCP of the firm CKF (69.77 mg kg-I) and for MCP (20.70 mg kg-I).This fact could playa certain role in long-term feeding with regard to the cummulative properties of arsenic in the animal organism.