That's why good internal assays are done from randomly chosen batches or, if ordered by the end-user, from randomly chosen packaged product.
Even better is to order multiple units of product and mix them thoroughly. This averages out any differences intentional or not and provides a 'big picture' view. Such a 'big picture' view is especially relevant for a customer who takes the material on a daily basis over long periods of time, because their body will 'see' the average.
If and when I submit SP's material to one of my local analysis firms, I'll mix the powders from several containers thoroughly, then submit a sample. It's not a top priority though, because synthesis-derived contaminants are likely below their relevant safety-thresholds.
Without even paying for a test, a simple way to measure the risk is to look at the top synthesis methods for the product in question, and check the contamination rates for the ingredients and intermediates including solvents. Also valuable is the speciation. For example, there's no worry about inorganic metals in organic solvents - they simply aren't co-soluble. For organic solvents, halogenated organics (ex. PCBs, PBBs), organo-heavy metals such as dimethylmercury and functionalized hydrocarbons (usually carcinogenic ie. PAHs) are the most likely contaminants.
Organic solvents are made from hydrocarbon feedstocks, often hydrogenated with the aid of light hydrocarbon fractions from one to six carbons long (methane - hexane range). These have a high mercury contamination rate due to natural copresence in the source deposit. High-grade oil refineries usually specifically remove mercury from natural gas - because it poisons their own hydrogenation catalysts and corrodes metal piping by amalgamation (especially aluminium). Mercury literally dissolves into most metals except iron. That doesn't mean that all refineries do so, and like most products both natural gas feedstock and light solvents made with its inclusion are available in a variety of purities.
The real nasty one is syntheses that directly use heavy metals. In those cases secondary purification and testing are
mandatory. Years ago I read this horror story while looking up MDMA synthesis. It's an underground recipe that involves the use of aluminium foil and mercury rubbed into it (amalgam). Realizing that underground chemists wouldn't have the facilities, money or care to test the product, never mind even purify it to remove the inevitable contamination, I decided right then to never buy anything from such suppliers.
For those that don't believe, here's the relevant part of
that MDMA synthesis story:
Shulgin's choices of synthesis procedures in the second half of the book are themselves perhaps a small act of subversion: While the reactions are beyond the ability of people with no chemistry education, they tend to emphasize techniques that do not require difficult to obtain chemicals. Notable among these are the use of mercury-aluminum amalgam.
Mercury-aluminum amalgam: Aluminium amalgam is a solution of aluminium in mercury. Aluminium amalgam may be prepared by either grinding aluminium pellets or wire in mercury, or by allowing aluminium wire to react with a solution of mercury chloride in water.
I won't go any further with that sordid story {check out
Discussions on the Aminomercuration of Safrole for the ugly details}, except to note that as a person of supposedly high intelligence, Shulgin showed a remarkable lack of concern for both the environment and the obvious implications of creating such recipes for underground chemists to carry out in their pursuit of profits. Without the equipment, government regulation and mandated testing of end-product that legal pharmaceutical corporations are burdened with, the obvious result is an epidemic of mercury-contaminated MDMA on the black market.
In the case of inorganic heavy metals, the most likely source is cheap catalysts which are themselves metals. Though decent catalysts are usually clean of them - because heavy metals often poison catalysts - it may still be economic to use lower-purity versions and throw them out more often. Like Chinese manual labor whose wages are still low enough to warrant their use over machines in such industries as garment manufacture, the low price of contaminated catalysts may warrant their use despite significantly faster decline of catalytic activity.
One disadvantage of a mixing procedure is if it's done excessively it can dilute a single highly-contaminated batch or container with many that are not contaminated, producing a correct but misleading average. A person who consumed the single contaminated container might get sick, while if all containers were premixed to dilute the toxin(s) and consumed over a longer time, no illness might result.
However, the likelyhood of the second case being more frequent than the first is lower, usually by an amount that warrants a certain range of reasonable mix-ratios for analytical submission.
Edited by Isochroma, 06 September 2009 - 06:47 AM.
