Indirect voltammetric determination of thiomersal in influenza vaccine using photo-degradation and graphene quantum dots modified glassy carbon electrode.

Thiomersal is an organomercury derivative that degrades producing thiosalicylic acid, dithiobenzoic acid and ethylmercury. It is widely used in topical pharmaceutical preparations and as preservative in vaccines and cosmetics. In this work, an electro-analytical method for thiomersal was developed using graphene quantum dots (GQDs) as a surface modifier of a glassy carbon electrode. The method rely on using square-wave voltammetry and exploring the synergistic effect between GQDs, visible radiation and the applied potential in producing very intense Hg oxidation peak during the anodic scan. A linear voltammetric response was obtained for the analyte in the concentration range from 3.0 µmol L-1 (1.2 µg mL-1) to 32 µmol L-1 (12 µg mL-1), with a detection limit of 0.9 µmol L-1 (0.34 µg mL-1). The proposed method was successfully applied for thiomersal determination in influenza vaccine.

Liquid chromatography coupled to molecular fluorescence with postcolumn UV sensitization for thimerosal and derivative compounds monitoring in environmental samples.

A HPLC coupled with molecular fluorescence (MF) spectrometry method for determination of thimerosal (THM, sodium ethylmercurythiosalicylate, C9 H9 HgNaO2 S), and derivatives is proposed. A sensitization of MF was provoked by UV irradiation of analytes in a home-made photoreactor that served as interface between the LC column and MF spectrometer. This method is applied to determination of THM, ethyl mercury, and thiosalicylic acid in samples of pharmaceutical industry effluents, and waters of La Carolina and Jáchal rivers situated in the center-west side of San Luis city and in the east of San Juan city (Middle West, Argentine) where the effluents are dumped. The LODs calculated on basis of 3σ criterion were 1.8, 5, and 0.05 µmol/L for THM, ethyl mercury, and for thiosalicylic acid, respectively.

Sociological Environmental Causes are Insufficient to Explain Autism Changepoints of Incidence.

The Environmental Protection Agency (EPA) recently published a study analyzing time trends in the cumulative incidence of autistic disorder (AD) in the U.S., Denmark, and worldwide. A birth year changepoint (CP) around 1988 was identified. It has been argued that the epidemic rise in autism over the past three decades is partly due to a combination of sociologic factors along with the potential contribution of thimerosal containing vaccines. Our work conducted an expanded analysis of AD changepoints in CA and U.S., and determined whether changepoints in time trends of AD rates temporally coincide with changepoints for the proposed causative sociologic and environmental factors. Birth year changepoints were identified for 1980.9 [95% CI, 1978.6-1983.1], 1988.4 [95% CI, 1987.8-1989.0] and 1995.6 [95% CI, 1994.6-1996.6] for CA and U.S. data, confirming and expanding the EPA results. AD birth year changepoints significantly precede the changepoints calculated for indicators of increased social awareness of AD. Furthermore, the 1981 and 1996 AD birth year changepoints don't coincide with any predicted changepoints based on altered thimerosal content in vaccines nor on revised editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM).

Determination of thimerosal in pharmaceutical industry effluents and river waters by HPLC coupled to atomic fluorescence spectrometry through post-column UV-assisted vapor generation.

A high performance liquid chromatography coupled with atomic fluorescence spectrometry method for the determination of thimerosal (sodium ethylmercury thiosalicylate, C9H9HgNaO2S), ethylmercury, and inorganic mercury is proposed. Mercury vapor is generated by the post-column reduction of mercury species in formic acid media using UV-radiation. Thimerosal is quantitatively converted to Hg(II) followed by the reduction of Hg(II) to Hg(0). This method is applied to the determination of thimerosal (THM), ethylmercury (EtHg) and inorganic Hg in samples of a pharmaceutical industry effluent, and in waters of the San Luis River situated in the west side of San Luis city (Middle West, Argentine) where the effluents are dumped. The limit of detections, calculated on the basis of the 3σ criterion, where 0.09, 0.09 and 0.07 µg L(-1) for THM, EtHg(II) and for Hg(II), respectively. Linearity was attained from levels close to the detection limit up to at least 100 µg L(-1).

Thimerosal: current sources of contact in Brazil.

Thimerosal is an organic mercury derivative found in ophthalmic solutions and certain vaccines in Brazil. Although most studies suggest the prevalence of thimerosal sensitivity to be quite high, this condition does not currently have any clinical relevance. The present article surveyed 184 Brazilian products (151 topical medications and 33 vaccines) and found that thimerosal was only present in 3 ophthalmic solutions and 5 vaccines.

On-line species-unspecific isotope dilution analysis in the picomolar range reveals the time- and species-depending mercury uptake in human astrocytes.

In order to reveal the time-depending mercury species uptake by human astrocytes, a novel approach for total mercury analysis is presented, which uses an accelerated sample introduction system combined on-line with an inductively coupled plasma mass spectrometer equipped with a collision/reaction cell. Human astrocyte samples were incubated with inorganic mercury (HgCl2), methylmercury chloride (MeHgCl), and thimerosal. After 1-h incubation with Hg(2+), cellular concentrations of 3 µM were obtained, whereas for organic species, concentrations of 14-18 µM could be found. After 24 h, a cellular accumulation factor of 0.3 was observed for the cells incubated with Hg(2+), whereas the organic species both showed values of about 5. Due to the obtained steady-state signals, reliable results with relative standard deviations of well below 5 % and limits of detection in the concentration range of 1 ng L(-1) were obtained using external calibration and species-unspecific isotope dilution analysis approaches. The results were further validated using atomic fluorescence spectrometry.

A comparative pharmacokinetic estimate of mercury in U.S. Infants following yearly exposures to inactivated influenza vaccines containing thimerosal.

The use of thimerosal preservative in childhood vaccines has been largely eliminated over the past decade in the United States because vaccines have been reformulated in single-dose vials that do not require preservative. An exception is the inactivated influenza vaccines, which are formulated in both multidose vials requiring preservative and preservative-free single-dose vials. As part of an ongoing evaluation by USFDA of the safety of biologics throughout their lifecycle, the infant body burden of mercury following scheduled exposures to thimerosal preservative in inactivated influenza vaccines in the United States was estimated and compared to the infant body burden of mercury following daily exposures to dietary methylmercury at the reference dose established by the USEPA. Body burdens were estimated using kinetic parameters derived from experiments conducted in infant monkeys that were exposed episodically to thimerosal or MeHg at identical doses. We found that the body burden of mercury (AUC) in infants (including low birth weight) over the first 4.5 years of life following yearly exposures to thimerosal was two orders of magnitude lower than that estimated for exposures to the lowest regulatory threshold for MeHg over the same time period. In addition, peak body burdens of mercury following episodic exposures to thimerosal in this worst-case analysis did not exceed the corresponding safe body burden of mercury from methylmercury at any time, even for low-birth-weight infants. Our pharmacokinetic analysis supports the acknowledged safety of thimerosal when used as a preservative at current levels in certain multidose infant vaccines in the United States.

Determination of thiomersal by flow injection coupled with microwave-assisted photochemical online oxidative decomposition of organic mercury and cold vapor atomic fluorescence spectroscopy.

We developed a flow injection (FI) method for the determination of thiomersal (sodium ethylmercurithiosalicylate, C9H9HgNaO2S) based on the UV/microwave (MW) photochemical, online oxidation of organic mercury, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. Thiomersal was quantitatively converted in the MW/UV process to Hg(II), with a yield of 97±3%. This reaction was followed by the reduction of Hg(II) to Hg(0) performed in a knotted reaction coil with NaBH4 solution, and AFS detection in an Ar/H2 miniaturized flame. The method was linear in the 0.01-2 µg mL(-1) range, with a LOD of 0.003 µg mL(-1). This method has been applied to the determination of thiomersal in ophthalmic solutions, with recoveries ranging between 97% and 101%. We found a mercury concentration in commercial ophthalmic solutions ranging between 7.5 and 59.0 µg mL(-1).

Gas diffusion flow injection determination of thiomersal in vaccines.

A new simple gas diffusion flow injection method has been developed for the determination of thiomersal in biological samples. The method is based on cold vapor generation of monoatomic mercury from thiomersal reaction with acidic stannous chloride solution (0.6%) acting as reducing agent. The evolved mercury partially diffuses through a Teflon membrane into an acidic permanganate (2.25 × 10(-4) mol L(-1)) acceptor stream, where it is oxidized and re-converted to Hg(II). The resulting decrease in acceptor stream absorbance is sensitively monitored at 528 nm. Flow injection variable parameters such as reagents concentrations, injected volume, reactor length, temperature and flow rate were carefully investigated and optimized. The concentration-response relationship was linear over a concentration range of 1-30 mg L(-1) with a correlation coefficient greater than 0.99 and a good reproducibility (RSD<1.42%, n=6) at 10 mg L(-1). A detection limit of 0.07 mg L(-1) (S/N=3) and a sampling frequency of 5 samples h(-1) were obtained. The method was successfully applied for the determination of thiomersal in different types of vaccines and gave results in close agreement with those found by previously established HPLC method with no significant interference from vaccines matrices.

Speciation of methyl- and ethyl-mercury in hair of breastfed infants acutely exposed to thimerosal-containing vaccines.

BACKGROUND: Different chemical forms of mercury occur naturally in human milk. The most controversial aspect of early post-natal exposure to organic mercury is ethylmercury (EtHg) in thimerosal-containing vaccines (TCV) still being used in many countries. Thus exclusively breastfed infants can be exposed to both, fish derived methylmercury (MeHg) in maternal diets and to EtHg from TCV. The aim of the study is to evaluate a new analytical method for ethyl and methyl mercury in hair samples of breastfed infants who had received the recommended schedule of TCV. METHODS: The hair of infants (<12 months) that had been exposed to TCV (Hepatitis B and DTaP) was analysed. A method coupling isothermal gas chromatography with cold-vapor atomic fluorescence spectrometry was used for MeHg which can also speciate EtHg in biological matrices. RESULTS: In 20 samples of infants' hair, all but two samples showed variable amounts of MeHg (10.3 to 668 ng/g), while precise and reliable concentrations of EtHg (3.7 to 65.0 ng/g) were found in 15 of the 20 samples. A statistically significant inverse association (r=-05572; p=0.0384) was found between hair-EtHg concentrations and the time elapsed after the last TCV shot. CONCLUSIONS: The analytical method proved sensitive enough to quantify EtHg in babies' hair after acute exposure to thimerosal in vaccine shots. Provided that the mass of hair was above 10mg, organic-mercury exposure during early life can be speciated, and quantified in babies' first hair, thus opening opportunities for clinical and forensic studies.

Thimerosal exposure (from tetanus-diphtheria vaccine) during pregnancy and neurodevelopment of breastfed infants at 6 months.

AIM: We studied the effect on neurodevelopment of infants who are exposed to thimerosal in tetanus-diphtheria (Td) vaccines during pregnancy. METHODS: We compared Gesell Developmental Schedules (GDS) of exclusive breastfed infants at 6 months born to mothers who received Td (1 to 3 doses) against those who were born to mothers who did not take such vaccines. RESULTS: Compared with the group of infants not exposed to ethylmercury in utero, the infants of exposed mothers showed no significant difference in neurodevelopment delays. Although there was a significant correlation between hair-Hg of mothers and hair-Hg of neonates (Spearman r = 0.353; p = 0.0011), there was no significant correlation between the level of in utero exposure to ethylmercury in Td vaccines and neonate's hair-Hg concentrations (Spearman r = 0.060; p = 0.5922). However, regression analysis showed that GDS at 6 months was significantly associated with total mercury concentration of neonate's hair but was not sensitive to the number of vaccines taken by the mother. CONCLUSION: Early neurodevelopment of exclusively breastfed infants is sensitive to in utero exposure to mercury, but maternal thimerosal exposure in tetanus-diphtheria vaccines per se cannot portend clinical neurodevelopment delays measured by GDS at 6 months.

Measurement and decomposition kinetics of residual hydrogen peroxide in the presence of commonly used excipients and preservatives.

Quantitation of residual hydrogen peroxide (H(2)O(2)) and evaluation of the impact on product stability is necessary as unwanted H(2)O(2) can potentially be introduced during the manufacturing of pharmaceuticals, biologics, and vaccines. A sensitive and convenient microplate-based method with fluorescence detection for H(2)O(2) quantitation was recently reported (Towne et al., 2004, Anal Biochem 334: 290-296). This method was found to be highly robust and reproducible, with a level of detection of 0.015 ppm and a level of quantitation of 0.025 ppm (in water). The relatively small sample requirements and amenability for automation make this assay an attractive tool for detecting residual H(2)O(2) levels. Without additional manipulation, the assay can be conducted on heterogeneous solutions with significant degree of turbidity, such as the presence of suspensions or aluminum-containing adjuvants. The quantitation of H(2)O(2) and its decomposition kinetics was also studied in presence of two common vaccine preservatives (thimerosal and phenol) and eight commonly used excipients (polyols). Over time, there is a distinct, temperature dependent decrease in H(2)O(2) recovered in thimerosal and phenol containing samples versus non-preservative containing controls. Based on the half-life of spiked H(2)O(2), the decay rates in eight polyols tested were found to be: ribose > sucrose > (glycerol, glucose, lactose, mannitol, sorbitol, and xylose).

A simple flow-injection spectrofluorimetric method for the determination of mercury.

A highly sensitive flow-injection spectrofluorimetric method is presented for the rapid and simple determination of Hg (II) in environmental and pharmaceutical samples. Murexide (ammonium purpurate) was used as the fluorescence reagent in the carrier stream. An emission peak of murexide, which is decreased linearly by addition of Hg (II), occurs at 435 nm in aqueous solution with excitation at 335 nm. A linear calibration was obtained for 5-200 ng ml(-1) Hg (II) with the relative standard deviation 2.5% (n = 5) for a 20 microl injection volume Hg (II). The limit of the detection was 1 ng ml(-1) and the sampling rate was 80 h(-1). No significant interference was found by the ions commonly found in the most environmental samples. The proposed method was successfully applied for the determination of trace mercury in real samples and the validation of the proposed methodology is provided.