Germicidal Quaternary Ammonium Salts in Dilute Solution A Colorimetric Assay Method

Quaternary Ammonium Compounds: A Chemical Class of Emerging Concern

Quaternary ammonium compounds (QACs), a large class of chemicals that includes high production volume substances, have been used for decades as antimicrobials, preservatives, and antistatic agents and for other functions in cleaning, disinfecting, personal care products, and durable consumer goods. QAC use has accelerated in response to the COVID-19 pandemic and the banning of 19 antimicrobials from several personal care products by the US Food and Drug Administration in 2016. Studies conducted before and after the onset of the pandemic indicate increased human exposure to QACs. Environmental releases of these chemicals have also increased. Emerging information on adverse environmental and human health impacts of QACs is motivating a reconsideration of the risks and benefits across the life cycle of their production, use, and disposal. This work presents a critical review of the literature and scientific perspective developed by a multidisciplinary, multi-institutional team of authors from academia, governmental, and nonprofit organizations. The review evaluates currently available information on the ecological and human health profile of QACs and identifies multiple areas of potential concern. Adverse ecological effects include acute and chronic toxicity to susceptible aquatic organisms, with concentrations of some QACs approaching levels of concern. Suspected or known adverse health outcomes include dermal and respiratory effects, developmental and reproductive toxicity, disruption of metabolic function such as lipid homeostasis, and impairment of mitochondrial function. QACs' role in antimicrobial resistance has also been demonstrated. In the US regulatory system, how a QAC is managed depends on how it is used, for example in pesticides or personal care products. This can result in the same QACs receiving different degrees of scrutiny depending on the use and the agency regulating it. Further, the US Environmental Protection Agency's current method of grouping QACs based on structure, first proposed in 1988, is insufficient to address the wide range of QAC chemistries, potential toxicities, and exposure scenarios. Consequently, exposures to common mixtures of QACs and from multiple sources remain largely unassessed. Some restrictions on the use of QACs have been implemented in the US and elsewhere, primarily focused on personal care products. Assessing the risks posed by QACs is hampered by their vast structural diversity and a lack of quantitative data on exposure and toxicity for the majority of these compounds. This review identifies important data gaps and provides research and policy recommendations for preserving the utility of QAC chemistries while also seeking to limit adverse environmental and human health effects.

Colorimetric detection of residual quaternary ammonium compounds on dry surfaces and prediction of antimicrobial activity using bromophenol blue

Controlling and monitoring the residual activity of quaternary ammonium compounds (QACs) are critical for maintaining safe yet effective levels of these agents in the environment. This study investigates the utility of bromophenol blue (BPB) as a safe, rapid and user-friendly indicator to detect in situ residual QACs dried on hard, non-porous surfaces, as well a means to assess their antimicrobial efficacy. At pH 7, BPB has a purple colour which turns blue upon its complexation with QACs such as didecyldimethylammonium chloride (DDAC). BPB itself has no antimicrobial properties up to 400 ppm. Within the range of 0-400 ppm, BPB colour change was tied to specific DDAC antimicrobial performances with a detection threshold of 100 ppm. BPB concentration and application volume could be adjusted such that a colour shift from purple to blue correlated with a set percent reduction (>99·9%) in test bacteria (Staphylococcus aureus and Klebsiella aerogenes). The BPB solutions developed in this study yielded similar colour shifts on polycarbonate and stainless steel surfaces and did not cross-react with chemical ingredients commonly found in sanitizers and disinfectant products. Overall, this study suggests that BPB provides a simple solution to safely monitor the post-application level and biocidal activity of residual dried QACs on surfaces.

A Specific Method of Assay of Strong Solutions of Benzalkonium Chloride and Other Quaternary Ammonium Germicides

A method of assay of quaternary ammonium germicides in strong solutions or concentrated solid form is described. It can be used for solutions down to about 1 per cent in content. A known excess of iodide is added to the sample solution and the quaternary ammonium iodide is removed by shaking with chloroform. The excess iodide is titrated by an iodate method. When the chloroform extraction is made from a slightly alkaline solution only quaternary ammonium compounds are measured; if it is made from a slightly acid solution, non-quaternary cationic amine impurities are also included. The difference between assay results obtained from acid and alkaline extractions represents the non-quaternary amine content.

Influence of various anions on intestinal disappearance of hexamethonium chloride and pralidoxime chloride in rats

The intestinal transfer of two poorly absorbed quaternary ammonium drugs, hexamethonium chloride (I) and pralidoxime chloride (II), in the presence of various organic and inorganic anions was investigated in the rat using a modified in situ gut technique. The results were in agreement with those of the conventional in situ loop and plasms drug level techniques. Of the anions investigated, cholate, desoxycholate, taurocholate, phoscholate, dehydrocholate, and hyodesoxycholate had the greatest effect on increasing the amount and rate of disappearance of I. Similarly, the amount and rate of disappearance of II were enhanced markedly in the presence of phoscholate and trichloroacetate. The effect of cholate and phoscholate was investigated in detail. The membrane permeability and histological studies indicated that these anions may compromise the structural integrity of the membrane tissue, thus enhancing drug transfer.

Direct spectrophotometric determination of thebaine in Arya II population capsules of Papaver bracteatum Lindl

A simple spectrophotometric determination of thebaine based on the complexation reaction with bromcresol green was developed. The yellow complex was extracted with chloroform over the pH 1.5--4.5 range. The solution of the complex in chloroform showed the maximum absorption at 415 nm and obeyed Beer's law over the concentration range of 4.0--14.0 microgram/ml. The molar absorptivity of the complex was 1.9460 X 10(4). The ratio of thebaine to bromcresol green in the complex was 1:1. The method was applied successfully to the direct determination of thebaine in the Arya II population capsules of Papaver bracteatum Lindl. The thebaine content of the dried capsules was 3.14%.

The biological activity of phenolic compounds; the effect of surface active substances upon the penetration of hexyl resorcinol into Ascaris lumbricoides var. suls

The effect of surface active substances (sodium cholate, sodium oleate and cetyl trimethyl ammonium bromide (C. T. A. B.)), upon the penetration of hexyl resorcinol into the pig round-worm ( Ascaris lumbricoides var. suis ) has been measured quantitatively, and parallel mea­surements carried out upon the interfacial activity of these solutions again staninert mineral oil. In all three cases a marked similarity of action, differing only in degree, was observed. Using a fixed hexyl resorcinol concentration (0∙025%) the soap in dilute solution accelerated the penetration of this drug, the maximum accelerations being in the order sodium cholate sodium oleate < C. T. A. B., but when present in high concentration the penetration was com­pletely inhibited. The soaps alone were found to penetrate Ascaris very slowly, if at all, the amounts taken up being reasonably explained on the basis of surface adsorption only. Measurement of interfacial tensions showed that the soap and hexyl resorcinol molecules associate at an interface, forming a labile complex of increased surface activity. Using a fixed drug concentration (0∙025% as above), the interfacial tension went through a minimum as the soap concentration was increased, ultimately rising to the value for the soap alone. Maximum interfacial activity (i. e. minimum interfacial tension), was found in all cases to occur at that soap concentration giving maximum hexyl resorcinol penetration into Ascaris , and was in the same order, viz. cholate ≪ oleate < C. T. A. B. The interfacial tension measurements also showed that this particular soap concentration corresponded to the onset of micellar aggregation of the soap molecules. From the interfacial tension data a simple explanation for the biological measurements can be suggested, which at the same time appears to explain a number of observations upon other biological systems, in particular the effect of soaps upon the bactericidal activity of phenols. This explanation suggests that the biological activity of hexyl resorcinol (as measured by its rate of penetration) is determined by the interfacial activity of the mixture, and that when soap micelles are present the drug distributes itself between the micelles and any other interface present (e. g. oil/water or Ascaris /water). The maximum biological activity thus occurs at the critical concentration for micelle formation, since this has maximum interfacial activity. At high soap concentrations the hexyl resorcinol is mainly held by the soap micelles, so that the biological activity is thereby diminished, ultimately to zero since the soaps alone penetrate so extremely slowly. In the case of C. T. A. B./hexyl resorcinol mixtures it has been possible, from physical data only, to calculate a theoretical curve for the biological activity which is in good agreement with experiment. The possible bearings of these conclusions upon in vivo activity of hexyl resorcinol as an anthelmintic, and upon drug action in general, are briefly mentioned.