The purpose of this proposed USP general chapter is to limit the amounts of elemental contaminants in dietary supplements. USP <2232> along with USP <232> Elemental Impurities – Limits and USP <233> Elemental Impurities – Procedures, have been proposed, with USP <232> and USP <233> already published and promulgated as of January 18, 2018. These general chapters are to replace the long standing general chapter USP <231> Heavy Metals Test procedure. The USP <231>  has been in existence for over a hundred years. It is not specific in the determination of a individual elements, has a very high limit of detection and is very undefined when looking for a visual colorimetric change. The USP <2232>, are more technically advanced allowing for the introduction of inductively coupled plasma – optical emission (ICP-OES) and inductively coupled plasma – mass spectrometry (ICP-MS) as the techniques to determine the elemental contaminants. These more advanced techniques are far more accurate, precise and quicker in rendering sound quality scientific data.

The USP <2232> general chapter is not intended to set limits for dietary ingredients, because the limits are set in the individual monographs. This proposed general chapter is focused on the four elements of concern for toxicological reasons. Those four elements being, arsenic, cadmium, lead, and mercury. Manufacturers should consider the presence of unexpected elemental contaminants to determine compliance.

Limits of Elemental Contaminants

The levels of elemental contaminants should be restricted as shown in Table 1 unless stated in the individual monograph. Specific monographs may provide different limits for articles that need to be consumed in large quantities.

Element PDE (ug/day)*
Arsenic (inorganic) 15
Cadmium 5
Lead 10
Mercury (total) 15
Methylmercury (as Hg) 2
*Permissible Daily Exposure

Arsenic may be measured using a nonspeciation procedure under the assumption that all arsenic contained in the supplement is in the inorganic form. Where the limit is exceeded using a nonspeciation procedure, compliance with the limit for inorganic arsenic shall be demonstrated on the basis of a speciation procedure. Methylmercury determination is not necessary when the content for total mercury is less than the limit for methylmercury.

The USP revision for elemental impurities in dietary supplements will be published in the PF 38(3) for comment. An update will appear separately in the “Hot Topics” page of the USP web site.

Chemical Solutions Ltd. (CSL) has been providing trace elemental analyses for nearly 16 years. You can count on CSL to provide you with accurate, precise, and on-time data. Contact CSL for further information regarding this new proposed change to the USP regulations.