Tests with Platinum Salts

Simulated occupational exposure tests to the dust from mixtures of low concentrations of platinum salts in lactose (Pepys et al. 1972 b), decanted repeatedly from one receptacle to another, show the degree of reactivity to different salts with (NH4)2[PtCl6] and (NH4)2[PtCl4] being of similar potency and both more potent than Na2[PtCl6] (Table 3) and the reproducibility of reactions to the test procedure 

Most subjects give immediate asthmatic reactions some give non-immediate reactions and some give both. There is suggestive evidence of the presence of antibodies in other immunoglobulin classes which might be responsible for type III reactions such as the serum-sickness-like reactions induced by repeated injections of platinum salts (Levene and Calnan 1971). 

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R. Merget, G. S. Weminghaus, F. Bode, E. M. Bergmann, W. Zachgo, J. Meier-Sydow, Quantitative skin prick and bronchial provocation tests with platinum salt, Br. J. Indust. Med., 48 (1991), 830D837. 

Deposition of platinum metal In the case of platinum no solid product was found. The ionic liquid darkened more and faster the smaller the distance between the surface of the ionic liquid [EMIM][TfO] containing tetrabutylammonium hexachloro-platinate ([n-Bu4N]2[PtCl6]) and the Ar/H2-plasma (3 1, overall pressure 100 Pa) was chosen. So far no other ionic liquid has been tested. The rate constant for the reduction of the tetrabutylammonium ion with a hydrated electron is only 1.4 x 106 LmoH1 s 1, hence the main rival pathway for reduction of platinum(IV) is the reduction of the imidazolium ion of the ionic liquid. As in the case of copper, a suitable platinum salt - maybe made by electro-oxidation of metallic platinum in a suitable ionic liquid - has to be found. 

Figure 4.1. Probability of platinum refinery workers remaining skin prick test negative to complex platinum salts, by smoking and exposure categories (reproduced from Calverley et a., 1995, with permission).

The presence of potash in any solution is best ascertained by the action of bichloride of platinum in solution, which, if any notable quantity of potash be present, forms with it a pale yellow precipitate of the double chloride of platinum and potassium. If the proportion of potash be very small, no precipitate may appear in this case, the liquid to be tested may be first concentrated by evaporation, and then again tested with the platinum salt, when the precipitate will in all probability appear or alcohol may be added to the first mixture, in which the double chloride is quite insoluble. The only uncertainty in this test is, that ammonia gives a similar precipitate so that we must first ascertain if ammonia be present and if so, expel it by a red-heat, before testing for potassium. 

Table 3. Comparison of inhalation tests with complex platinum salts...

Passive transfer tests with the sera of six sensitive refinery workers were made with unheated serum for IgE, long-term sensitising antibody and with heated serum for short-term sensitising, presumably IgG antibody to prick tests (Pepys et al. 1979). Table 5 shows positive reactions with all of the unheated sera in one or more of the three human Prausnitz-Kiistner recipients and with two and probably three of the sera in Prausnitz-Kiistner tests in the monkey. These findings support the possibility of specific IgE antibodies to the platinum salts. 

These findings confirm the suggestion that immediate reactions to appropriate concentrations of platinum complex salts are mediated by specific IgE antibody, possibly with a contribution by STS-IgG antibody in some cases. They also illustrate some of the problems of serological tests with highly reactive small molecular chemical compounds. 

Tolyl-specific IgE antibodies have now however also been demonstrated in exposed sensitive workers by Karol et al. (1978 a Karol and Alarie 1980). p-Tolyl(mono)isocyanate was coupled with human serum albumin for the paper (disc) radioimmunosorbent test (PRIST). There was no correlation between high titres of tolyl-specific IgE antibodies and levels of total serum IgE, in contrast to the findings with the platinum salts described earlier in which non-specific uptake of IgE could occur. The level of tolyl-specific antibodies decreased with cessation of exposure, as was the case with the platinum salts. The use of the monofunctional isocyanate prevented cross-linking of the carrier proteins which usually occurs with TDI, and ensured that the tolyl group was sterically exposed. The tolyl specificity... 

Pickering CAC (1972) Inhalation tests with chemical allergens complex salts of platinum. Proc R Soc Med 65 272... 

Dioxane solutions of mercuric iodide react also with Ag+ and Au+ ions. If the quantity of palladium is not too small, these interferences can be avoided by throwing down silver chloride, or by precipitating metallic gold with oxalic acid, before making the test for palladium. Platinum salts do not react with mercuric iodide. 

When hydrochloric acid solutions of noble metal salts are being tested, the presence of silver salts need not be considered. Gold chloride can be removed by shaking the strong hydrochloric acid solution with ether or ethyl acetate. The gold-free aqueous solution should be taken to dryness to remove the excess hydrochloric acid before the test with / -nitroso-diphenylamine is tried. There is as yet no method for the removal of platinum which is suitable for the spot test technique. Since the identification limit of the platinum reaction with />-nitrosodiphenylamine is 10 y, the palladium test just given is not impaired by small amounts of platinum. 

Self-Test 4A Write the diagram for a cell with a hydrogen electrode on the left and an irnn(III)/irnn(lI) electrode on the right. The two electrode compartments are connected by a salt bridge and platinum is used as the conductor at each electrode. 

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