Benzalkonium Chloride Solution Research Articles

Shelf life of cefuroxime eye-drops when dispensed in artificial tear preparations

Abstract There has recently been a clinical demand for cefuroxime formulated as an eyedrop. Cefuroxime exhibits a broad spectrum of activity against most common ocular infections and is considered to be less toxic to the compromised epithelium than some other topical antibiotics. A formulation in an artificial tear solution would be expected to enhance drug penetration by prolonging pre-corneal drug retention, and the presence of a preservative might enable a suitable formulation to be given a shelf life of more than 24 hours. This paper reports studies on the stability of cefuroxime 50mg/ml (5 per cent) in artificial tear solutions, sodium chloride eye-drops and in solutions of benzalkonium chloride, hypromellose or water for injections. Cefuroxime was assayed by high performance liquid chromatography. The method had a coefficient of variation of 0.23 per cent at the concentration investigated and recovery of added cefuroxime was 100 per cent. The preparation of cefuroxime in artificial tear solutions which were preservative free or contained benzalkonium chloride less than 0.002 per cent appeared to be physically stable. Preparation of cefuroxime in Sno Tears also produced a stable solution. This preparation can be given a shelf life of 28 days at 4C, 24 hours at 25C and 14 days if stored in a domestic refrigerator, enabling a full course of treatment to be given on a single visit to the pharmacy.

Preparation and evaluation of a kind of bacterial cellulose dry films with antibacterial properties

A kind of antibacterial bacterial cellulose (BC) dry film was developed and characterized as a potential functional wound dressing for acute traumas treatment. To achieve this, a freeze-dried BC film was immersed in a benzalkonium chloride solution, which belongs to cationic surfactant type antimicrobial agent, followed by another freeze-drying step. Some physical and antimicrobial properties of the prepared BC films were investigated and the results showed that the drug-loading capacity of the BC dry film was about 0.116mg/cm2 when soaked in 0.102% benzalkonium chloride solution. High water absorbing capacity, an important quality for wound dressings was also achieved with a swelling ratio of 26.2 in deionized water and of 37.3 in saline solution. With respect to the antimicrobial effect, a stable and prolonged antimicrobial activity for at least 24h was obtained especially against Staphylococcus aureus and Bacillus subtilis, which were general Gram-positive bacteria that found on the contaminated wound.

Disinfection of Contaminated Equipment: Evaluation of Benzalkonium Chloride Exposure Time and Solution Age and the Ability of Air‐Drying to Eliminate Flavobacterium psychrophilum

Disinfection of equipment that comes in contact with fish can help to minimize the spread of Flavobacterium psychrophilum (the etiological agent of bacterial coldwater disease) within and among fish culture facilities. We present the results of three studies that evaluated the potential use of benzalkonium chloride and air-drying to kill surface-attached F. psychrophilum. In the first study, we established a vat with a 600-mg/L benzalkonium chloride solution and sampled this solution 0, 14, 35, 56, 70, and 84 d after creation. The solution was kept outdoors and subjected to typical hatchery use. Plastic test strips were dipped in a solution containing F. psychrophilum and were then immersed in benzalkonium chloride for 0, 1, 10, 30, or 60 min. The strips were then rinsed with sterile water and streaked across a plate containing tryptone yeast extract salts (TYES) medium. No culturable bacteria were detected from any strips immersed for 10, 30, or 60 min. Bacteria were detected on 17% of the strips that were immersed for 1 min. The age of the benzalkonium chloride solution had no effect on disinfection ability. In the second study, plastic strips were immersed in a solution containing F. psychrophilum and then were dipped in a 600-mg/L benzalkonium chloride solution for 10 s. The strips were then air-dried for 1 h and were streaked onto TYES medium. No bacterial growth was observed from any strips in the second experiment. The third study determined whether air-drying alone was sufficient to kill F. psychrophilum. Plastic strips were dipped in a solution containing F. psychrophilum; were allowed to dry at room temperature for 0, 24, 48, or 96 h; and were then streaked across TYES medium. Bacteria were cultured from strips representing each drying interval, indicating that air-drying times of 96 h or less are insufficient to kill F. psychrophilum.

Microbial Contamination of Disinfectants Used for Intermittent Self-Catheterization

We investigated the microbial contamination of 0.02% benzalkonium chloride solution used in catheter kits for intermittent self-catheterization. Of 20 samples examined, 12 (60.0%) were contaminated with 8.8 x 10(2)-3.1 x 10(6) colony-forming units (cfu)/mL. The contaminants were Pseudomonas fluorescens, Burkholderia cepacia, and Aeromonas spp. These results showed that 0.02% benzalkonium chloride solution used for the lubrication/disinfection of catheters for self-catheterization is susceptible to contamination. Therefore, the lubricant/disinfectant for catheters for self-catheterization was changed from 0.02% benzalkonium chloride solution to 84-87% glycerin containing 0.02% benzalkonium chloride, and microbial contamination of the latter in catheter kits for self-catheterization was reinvestigated. Of 42 samples, 5 (11.9%) were contaminated with 20-2.0 x 10(4) cfu/mL. However, the rate of contamination of 84-87% glycerin containing 0.02% benzalkonium chloride was significantly lower than that of 0.02% benzalkonium chloride solution (P<0.0001). The contaminant of 84-87% glycerin containing 0.02% benzalkonium chloride was Bacillus spp. in all contaminated samples. In this survey, neither contaminants of 0.02% benzalkonium chloride solution nor the contaminant of 84-87% glycerin containing 0.02% benzalkonium chloride were the causative microbial species of urinary tract infection.

Influence of Benzalkonium Chloride on Langerhans Cells in Corneal Epithelium and Development of Dry Eye in Healthy Volunteers

Purpose: To investigate the influence of benzalkonium chloride (BAC) on corneal Langerhans cells (LCs) and on the development of dry eye.Methods: A randomized double-blind clinical trial was performed in 20 healthy volunteers. One eye of each subject was treated with a 0.01% BAC solution (and the fellow eye with a placebo solution) three times daily for 12 weeks. The distribution and density of LCs in the central and peripheral corneal epithelium were evaluated by in-vivo confocal laser-scanning microscopy (CLSM). The subjects were monitored for dry eye (subjective discomfort, slit-lamp biomicroscopy, tear film break-up time, Schirmer’s test).Results: In the BAC group, compared with placebo, a marked increase in LC density was found in the central cornea at Week 6 and in the central and peripheral cornea at Week 12. LC density then decreased again in both zones after the end of treatment, falling toward (or even below) baseline levels. Significant changes in the LC count relative to baseline were found at Week 12 in the central and peripheral cornea in the BAC group as well as in the peripheral cornea in the placebo group. LC density in the BAC group increased more rapidly in the central than in the peripheral cornea. During therapy the BAC group showed no signs of dry eye.Conclusion: 12-week application of a 0.01% BAC solution in healthy volunteers induces a significant increase in LCs in the central cornea at Week 12 without dry-eye changes. The return of LC counts toward (or even below) baseline levels just four weeks after the end of BAC administration demonstrates the rapid normalization of the inflammatory environment.

Microbial Contamination of Cotton Soaked in 0.025% Benzalkonium Chloride Solution and its Preventive Measure

Microbial Contamination of Cotton Soaked in 0.025% Benzalkonium Chloride Solution and its Preventive Measure

Effects of benzalkonium chloride on MUC1 in human conjunctival epithelial cells

To investigate the effects of benzalkonium chloride (BAC), a preservative used in many ophthalmic topical solutions, on mucin1 (MUC1) in human conjunctival epithelial cells in vitro. Cultured epithelial cells obtained from human conjunctiva were exposed to medium containing BAC solutions at 0.0100%, 0.0050%, 0.0010%, 0.0005% and 0.0001% concentrations for a period of 15 min. Cells were examined after treatment and 6, 12, 24, 48 and 72 h later. The relative expression of the MUC1 mucin gene was determined by conventional reverse transcription-polymerase chain reaction (RT-PCR). Monoclonal antibody for MUC1 was used in Western blot analysis to detect MUC1. Cell exposure to 0.0100% and 0.0050% BAC decreased the expression of MUC1 at gene level between 12 and 72 h after treatment. Cells treated with 0.0010% and 0.0005% BAC decreased the expression of MUC1 between 24 and 48 h after treatment, recovered 72 h after treatment. At protein level, cells exposed to 0.0100% BAC decreased MUC1 between 24 and 72 h, 0.0050% BAC between 12 and 72 h, 0.0010% BAC 72 h later. These results suggest that BAC induces decreased expression of MUC1 at both gene and protein levels. The mode of BAC-induced decreased expression of MUC1 is dose-dependent.

Solubilization of drugs by cationic surfactants micelles: Conductivity and 1H NMR experiments

Taking into account the advantages of surfactant micelles as drugs carriers, the solubilization of two model drugs, sulfamethoxazole and metronidazole, has been studied in aqueous solutions of benzalkonium chloride, which is a cationic surfactant safe for human use. The combination of conductivity and 1H NMR experiments led to the conclusion that the less soluble drug, sulfamethoxazole, was solubilized in the interior of the surfactant micelles. In the case of metronidazole the 1H NMR results showed that it interacted to some extent with the polar headgroup of the surfactant. However, this interaction was weak since no change in the micellization phenomenon was observed, at least under the experimental conditions used.

Tensioactive-mediated Transepithelial Corneal Cross-linking – First Laboratory Report

Purpose:The aim of this study was to investigate the possibility of delivering riboflavin into the corneal stroma for cross-linking with the aid of a tensioactive substance (benzalkonium chloride), without removing the epithelium, in order to make corneal cross-linking (CXL) a less invasive technique.Methods:Rabbit corneas were cross-linkedin vivowithout removal of the epithelium, using riboflavin solution 0.1% to which benzalkonium chloride solution was added. The corneas were then examined by light and electron microscopy for evidence of collagen cross-linking. Control non-treated eyes were compared with treated ones.Results:The treated corneas were stiff and yellow in colour, and on light microscope examination they showed straight compact collagen fibres in comparison with control corneas in approximately 50% of the corneal thickness. Electron microscopy revealed regular arrangement of fibres in the outer 200μm with reduced inter-fibre distances in the treated corneas, but with no noticeable differences between control and treated corneas in the inner 100μm.Conclusion:The addition of benzalkonium chloride to the riboflavin solution facilitated its entry to the corneal stroma through the epithelium, and CXL occurred without epithelium removal.

Comparison of Irrigation Solutions and Devices in a Contaminated Musculoskeletal Wound Survival Model

There is much to learn about the effectiveness of different methods currently used for the irrigation of open wounds. The purpose of this study was to compare various approaches in a survival animal model. We used an established goat model involving the creation of a reproducible complex musculoskeletal wound followed by inoculation with Pseudomonas aeruginosa (lux) bacteria. This genetically altered luminescent bacterium provides the ability for quantitative analysis with a photon-counting camera system. For Study 1, wound irrigation was performed six hours after the injury and inoculation; the goats were assigned to four treatment groups: normal saline solution, bacitracin solution, castile soap, and benzalkonium chloride. All wounds received sharp débridement and irrigation with use of a pulsatile lavage device (19 psi). Images and photon counts were obtained prior to irrigation, after irrigation, and forty-eight hours after injury and inoculation. For Study 2, we used the same animal model and compared bulb syringe and pulsatile lavage irrigation with saline solution. In Study 1, the irrigation treatment lowered the bacterial counts in all treatment groups. The greatest reduction was seen with castile soap, which lowered the photon count to 13% of the pretreatment level. This was followed by benzalkonium chloride, bacitracin, and saline solution at 18%, 22%, and 29%, respectively. At forty-eight hours, imaging showed a rebound in bacterial counts in every group. The highest rebound was measured in the castile soap group, which rebounded to 120% of the pretreatment level. The benzalkonium chloride group experienced a rebound to 94% of the pretreatment level. These were followed by bacitracin solution (89%) and normal saline solution (68%). In Study 2, both treatment methods were effective in removing 75% of the bacteria initially. At forty-eight hours, the bacterial levels in the pulsed lavage group rebounded to 94% of the original levels (compared with 48% in the bulb syringe group). The difference in the mean photon count ratios at forty-eight hours was significant (p = 0.048). Approaches used to remove bacteria from wounds, such as irrigants other than saline solution or high-pressure devices, may not have the best clinical outcome.

Benzalkonium Chloride Intoxication Mimicking Herpes Zoster Encephalitis.

Benzalkonium chloride (BAC) is a frequently used disinfectant and its most well-known side effect is contact dermatitis. In this report, two children who had vesicular dermatitis, headache, lethargy, fever and encephalopathy mimicking Herpes zoster encephalitis were presented. Their consciousness level improved on the second day. From the medical history it was understood that the mother had applied 20% BAC solution to the scalps of two children. The aim of the presentation of this report is to draw attention to the fact that BAC application to the scalp for treating pediculosis capitis may resemble the herpes encephalitis clinical picture.

In Vitro Effects of Preservatives in Nasal Sprays on Human Nasal Epithelial Cells

The preservatives benzalkonium chloride and potassium sorbate are widely used in nasal drops and sprays. Recently, side effects resulting from mucosal damage caused by benzalkonium chloride and potassium sorbate were reported. We investigated the toxicity of benzalkonium chloride and potassium sorbate on human nasal epithelial cells in vitro. Using primary human nasal epithelial cells, different concentrations of benzalkonium chloride, potassium sorbate, or phosphate-buffered saline (PBS; control group) solutions were cocultured with nasal epithelial cells for 15 minutes. Then, the viability of the cells and the cell morphology were assessed. Nasal epithelial cells were more severely damaged with use of clinical preparations or higher concentrations of benzalkonium chloride than in the control group. In addition, nasal epithelial cell membrane lysis was seen on electronic microscopy in the benzalkonium chloride groups. In contrast, there was no significant cell damage seen in the potassium sorbate groups compared with the control group, even with higher concentrations than clinically used. Potassium sorbate appears to be a relatively safer preservative than benzalkonium chloride for use in nasal sprays and drops in vitro study.

Very-High-Frequency Ultrasound Corneal Imaging as a New Tool for Early Diagnosis of Ocular Surface Toxicity in Rabbits Treated with a Preserved Glaucoma Drug

Aim: To evaluate very-high-frequency (VHF) ultrasound imaging as a new method to detect and quantify early corneal epithelium changes induced by chronic exposure to a benzalkonium-chloride-containing antiglaucoma drug. Methods: Timolol preserved with 0.01% benzalkonium chloride solution was applied b.i.d. in 1 eye of 10 rabbits for 56 days. Unpreserved timolol solution was used as control. Ocular surface changes were assessed weekly combining clinical examinations, in vivo 60-MHz ultrasound imaging and ex vivo histological analysis. Results: VHF ultrasound imaging allowed quantitative measurement of corneal epithelium thickness and qualitative imaging of toxic epithelial damage. It revealed significantly decreased epithelial thickness in vivo as early as the 21st day of treatment (40.75 ± 1.72 µm at D0 vs. 39 ± 2 at D21, vs. 31.9 ± 2.98 at D56; p = 0.017 and p = 0.005, respectively). The first clinical changes appeared from the 42nd day of treatment (conjunctival redness, conjunctival staining and corneal staining; D56 compared to D0: p = 0.005, 0.01 and 0.004, respectively) and then correlated with VHF ultrasound data. Epithelial thickness measured with VHF ultrasound was correlated with histological epithelial pachymetry (p < 0.001) and with the corneal damage score assessed with scanning electron microscopy (p = 0.038). Conclusion: VHF ultrasound imaging provided an early in vivo diagnosis of corneal epithelium pathology induced by chronic exposure to a preserved glaucoma drug, before the first clinical evidence of ocular toxicity. It could be a new reproducible method to detect the toxicity of glaucoma medication so that therapy can then be adapted.

Stability of an extemporaneously prepared recombinant human interferon alfa-2b eye drop formulation

The stability of an extemporaneously prepared recombinant human interferon alfa-2b (rh-IFN-alpha2b) eye drop formulation was studied. A volume of 3 x 10(6) International Units (IU) of rh-IFN-alpha2b formulated in solution was diluted with 5 mL of a 0.01% benzalkonium chloride solution. The stability of the extemporaneous formulation was evaluated for 30 days at room temperature (5 +/- 3 degrees C) and at 28 +/- 2 degrees C. Solutions were periodically subjected to bioactivity assay (antiviral titration), enzyme-linked immunosorbent assay, preservative-efficacy and sterility testing, organoleptic evaluation, and pH testing. Preservative efficacy was tested against five microorganisms. The organoleptic characteristics were verified by checking for the transparency and absence of suspended solids against light and dark backgrounds. Statistical significance was determined using analysis of variance after a comparison of the homogeneity of variance (Bartlett's test). Results from this evaluation indicated that the formulation was stable for 15 days at 5 +/- 3 C. During this storage period, the biological activity varied between 80 and 125% of the nominal value (0.5 x 10(6) IU/mL). The formulation was sterile and organoleptically acceptable. The pH ranged from 6.7 to 7.3, and the preservative was effective. The formulation was stable for 7 days when stored at 28 +/- 2 degrees C. The formulation remained sterile, colorless, and without suspended solids. The pH range was 6.7-7.3. An extemporaneously pre -pared rh-IFN-alpha2b eye drop formulation was stable at 5 +/- 3 degrees C for 15 days and at 28 +/- 2 degrees C for 7 days.

Acute Corneal Epithelial Change after Instillation of Benzalkonium Chloride Evaluated Using a Newly Developed in vivo Corneal Transepithelial Electric Resistance Measurement Method

Objective: Acute corneal permeability change after instillation of benzalkonium chloride (BAC) was evaluated using a newly developed in vivo corneal transepithelial electric resistance (TER) measurement method. Method: Corneal TER was measured by Ag/AgCl electrodes placed in the anterior aqueous chamber and on the cornea of live rabbit eyes. TER was measured and TER change after instillation of 0.05% BAC solution was monitored. After TER measurement, cornea was excised and fixed for transmission and scanning electron microscopy. For the control study, physiologic saline was used instead of BAC. Results: The TER of normal rabbit cornea was 602.3 ± 195.0 Ωcm². TER decreased instantly after instillation of 0.05% BAC. In 5 s, TER decreased to 58.3 ± 5.2%. In 60 s, TER decreased to 18.5 ± 3.2%. At all time points, TER after instillation of 0.05% BAC was significantly lower than that of the control (p < 0.0001). Dissociation of tight junctions and the destruction of superficial cell membranes were observed under electron microscopy. Conclusion: Corneal epithelial change with increased permeability is rapid and intense after the instillation of highly concentrated BAC solution, accompanied by disorder of tight junctions and cell membranes of superficial cells. The newly developed in vivo corneal TER measurement method is suitable for assessing acute corneal change after drug instillation.

Comparison of Toxicological Profiles of Benzalkonium Chloride and Polyquaternium-1: An Experimental Study

The aim of this study was to compare, in vivo on a rat model, two different preservatives- benzalkonium chloride (BAC) and polyquaternium-1 (PQ-1)-using new experimental approaches. Thirty (30) eyes of 15 male Lewis rats were used in this study. Rats were randomly divided into five groups instilled twice a day for 11 days with eye drops containing different concentrations of preservatives, 0.1% BAC, 0.5% BAC, 0.1% PQ-1, 0.5% PQ-1, and balanced salt solution (BSS) as a control. The ocular surface toxicity of these two preservatives was investigated using new in vivo experimental approaches. Slit-lamp examination, the fluorescein test, the red phenol test, impression cytology, and in vivo corneal confocal microscopy were used to evaluate the rat ocular surface after preservative instillation. Histology sections and immunohistochemistry were also examined to confirm these results. Compared to PQ-1, BAC consistently and dramatically altered the corneoconjunctival surface as evaluated by slit-lamp examination, the fluorescein test, impression cytology, in vivo confocal microscopy, and histology. The 0.5% BAC solution also significantly decreased tear production compared to the control. Although 0.5% PQ-1 significantly decreased goblet cell density in comparison to the control, and some abnormalities were observed with in vivo confocal microscopy, no statistically significant differences were observed between these two groups using the tear production test, slit-lamp and fluorescein evaluation, or histology. Using an acute rat model of ocular toxicity by comparing preservatives at high concentrations, we demonstrated in vivo that high doses of PQ-1 were much less toxic than BAC. In vivo confocal microscopy and impression cytology are new promising experimental approaches to studying the rat corneoconjunctival surface, particularly in the field of ocular surface toxicity.

Study of Eye Drops Dispensing and Dose Variability by Using Plastic Dropper Tips

ABSTRACTThe application of eye drops from flexible dropper bottles fitted with different types of dropper tips is associated with the high variability of eye drop weights. The aim of this report was to investigate the simultaneous effect of three factors influencing the mean weight of drops dispensing from two plastic dropper tips. Using a designed experiment (Box-Behnken), the effect of the concentration of benzalkonium chloride solutions (BAC) in the range of 0–0.02%, the dispensing angle from 90° to 30° from horizontal, and the residual volume of liquid in the dropper bottle from 4 to 10 mL on the mean drop weights were examined. The significant effect of the increase in BAC concentration resulted in a linear decrease in drop weights for both of the dropper tips investigated. The significant effect of the dispensing angle was influenced by the dropper tip design. For the dropper tip A, the effect of the dropper tip tilt was described by the quadratic equation with a minimum, which corresponded to the dispensing angle equal to that of 48° from horizontal. Below this angle, the increase in drop weights occurred due to the drop formation from the wetted external surface of the tip orifice. The linear decrease in drop weights in response to the decrease in dispensing angle was detected for the dropper tip B. The regression equations and the contour line plots obtained allowed the drop weights to be estimated for the actual combinations of both the BAC concentration and the dispensing angle. The effect of the residual volume was found to be non-significant. Based on the formula of Tate's law, the direct proportion between surface tension of a solution and the radius of the effective perimeter of a dropper tip can be used to estimate the theoretical maximal weight of drops at the dispensing angle of 90°. Using the stalagmometric values of surface tension of the BAC solutions, the maximal drop weights were estimated for both of the dropper tips investigated. A comparison between the theoretical and the experimentally measured drop weights enabled the dropper tips behavior to be discussed by using Harkins and Brown correction factor F. The F-value of 0.74 noted for the dropper tip A differed from that of stalagmometer F-value (0.61) indicating a deviation from the simple drop formation process in answer to more complicated design of the dropper tip A. On the other hand, the F-value of 0.6 observed for the dropper tip B demonstrated the better consistency with stalagmometry. As a result, the dropper tip B with the linear decrease of drop weights in response to the increased concentration of BAC and the decreased dispensing angle without the adverse external drop formation could be recommended in real drop dispensing.

Evaluation of Antiseptic Use in Plastic and Hand Surgery

Despite the growing complexity of plastic surgical cases, antiseptics available for preoperative preparation do not always prove effective. In addition to the varied sites of plastic surgery, there is a likelihood of considerable contamination with microorganisms since surgical gloves are frequently punctured during surgical procedures. With an aim to find a solution to all of these problems, a study was conducted in 2 stages. First, antimicrobial effects on the normal flora of hands of 4 different surgical handwashing procedures, which consist of scrubbing with 7.5% povidone-iodine (PI) scrub by using the sponge/brush, 7.5% PI scrub alone, 0.5% benzalkonium chloride (BC) solution, and 0.1% BC solution, were compared. In the second stage, bacteriological samplings were obtained from fingertips of the operating team during the surgical procedure. At the end of the study, the following results were obtained: (1) scrubbing with 7.5% PI detergent by using a scrub sponge was significantly more effective than without using a scrub sponge (P < 0.05). (2) There was no statistically significant difference in scrubbing when povidone-iodine detergent and 0.5% benzalkonium chloride solution (P > 0.05) were compared. (3) At the end of the surgery lasting 1-5 hours, hands were found to be cleaner than previously washed hands for preoperative preparation, which was considered a consequence of the sustained effect of PI. (4) There was a statistically significant difference between the cultures taken from the gloves at the end of the operation and from the hands after the gloves were taken off (P < 0.01). At the end of the operation, the gloves themselves were found to be extremely dirtier than the hands inside them. As a conclusion, bacterial escape due to glove perforation occurs from outside of the glove to the inside, contrary to the generally accepted concept.

The effect of benzalkonium chloride on rabbit nasal mucosa in vivo: an electron microscopy study.

In this study we investigated the histopathological changes of nasal mucosa after the use of topical benzalkonium-chloride solution. In the study, 28 male New Zealand white rabbits were used. The animals were divided into two groups. In the first group, 50 micro l of 0.001% benzalkonium-chloride solution was sprayed into the right nostril and 50 micro l of 0.9% saline into the left twice daily for 14 days. In the second group, the same solutions were applied twice daily for 28 days. All of the biopsies from each nasal cavity were processed for electron microscopy. In the nostrils treated with 0.001% benzalkonium chloride, there were areas with obvious squamous cell metaplasia. Some cells showed broken cristae of the mitochondria. Degenerative changes in the supportive and olfactory cells, deformation of nuclei and the increase of heterochromatin were observed. The present investigation has shown that the application of topical benzalkonium chloride does induce degenerative morphologic changes in the nasal mucosa in rabbits in vivo.

Sensitized spectrophotometric determination of trace Hg(II) in benzalkonium chloride media

A sensitized and convenient determination of trace Hg(II) with HgI 4 2− complex in benzalkonium chloride media has been studied. The UV–VIS spectrum of HgI 4 2− complex in benzalkonium chloride solution had higher sensitivity and reproducibility than that in aqueous solution. The HgI 4 2− complex in benzalkonium chloride media was very stable at pH 10.0 and could be quantitatively complexed if I − was added to the sample solution more than 17 times the moles of Hg(II). The optimum concentration of benzalkonium chloride was 0.07%. The calibration curve of HgI 4 2− complex with good linearity ( R 2=0.9963) was obtained in 0.07% benzalkonium chloride media. The detection limit was 1.8×10 −8 M. Recovery yields of Hg(II) in spiked real and synthetic samples were mostly above 95%. Based on the experimental results, this proposed technique could be applied to the rapid and simple determination of trace Hg(II) in real samples.