Test for Heavy Metals

Active compounds often form a chelate with heavy metal ions, and elution from a column containing heavy metal ions is poor.3,4 The existence of heavy metals 

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The ash may be used for the determination of the sodium chloride and for testing for heavy metals (especially copper and lead), barium and talc with soft cheeses, the two latter may arise by infiltration from the artificial layer coating the rind. 

This sample should be examined visually for colour and the presence of tablet residues or excipients (often maize starch). The odour should be noted as tiiis may indicate the presence of alcohols, aldehydes, ketones, phenols, cyanide, ethchlorvynol, nicotine, etc. The following tests, details of which are given on p. 5, should be performed Trinder s test for salicylates, cresol-ammonia test for paracetamol, FPN reagent for phenothiazines, Fujiwara test for trichloro-compounds, and the diphenyl- nine test for oxidising agents. In addition, tiie Reinsch Test for heavy metals (p. 57) should be carried out, and a diluted, filtered extract examined by direct ultraviolet spectrophotometry for drugs with highyl values. 

Of 260 Asian patent medicines available in California, 7 % contained undeclared pharmaceuticals. When 251 samples were tested for heavy metals, 24 products contained at least 10 parts per million of lead, 36 contained arsenic, and 35 contained mercury (149). 

For medium-chain triglycerides intended for use in parenteral nutrition, the test for heavy metals is replaced by the tests for chromium, copper, lead, nickel, and tin. 

Aqueous parenteral preparations can contain trace amounts of heavy metal ions in concentrations sufficient to catalyze oxidative reactions. Aqueous parenterals are produced with the use of Water for injection, which complies with the limit test for heavy metals (European Pharmacopoeia, 2002). This is, however, no guarantee for exclusion of metal ions. Heavy metal contamination brought into the formulation by excipients is also a problem, especially for sugars, phosphate, and citrate (Nema et al., 2002). Heavy metals may also be extracted from the container by the preparation (European Pharmacopoeia, 2002 see Section 14.3). Moreover, trace elements like zinc, copper, manganese, and chromium constitute important components in several parenteral nutrition formulas (Trissel, 2001). 

This limit test for heavy metals is one of the most widely used and is being referenced in many monographs. The methods most often referenced are method (a) and method (c). 

Comprehensive chemical analysis. In addition to all quantitative measurements necessary to evaluate a water, this water analysis should also include tests for heavy metals, in particular toxic heavy metals, and where necessary quantitative measurements of these substances. Furthermore, tests should be conducted for indicators of organic contamination, such as... 

Table 6.6 Bench-scale test for heavy metal removal (based on [10]).

United States Pharmacopeia (USP) A federal agency who is responsible for all standards, limits, methods, and guidelines for aU pharmaceutical products made in the United States. After a 4-year review and approval process, it has just published Chapters <232>, <233>, and <2232> for the determination of elemental impurities in pharmaceutical products and dietary supplements, as a replacement for Chapter <231>, a 100-year-old colorimetric test for heavy metals. 

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