Bromomethylaniline Testing

Bromomethylaniline testing mainly conducts scientific testing and analysis on the bromomethylaniline isomer testing, content and purity testing, related impurity testing, moisture testing, residual solvent testing, heavy metal element testing and other items, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for the production enterprise quality control and downstream user product acceptance.

Testing items

Bromomethylaniline isomer testing: The bromomethylaniline has three isomers of the ortho-, meta- and para-positions, with the different chemical properties and toxicities. The testing needs to clearly distinguish the target isomers, usually focusing on the para-bromomethylaniline (CAS 7745-89-3) and ortho-bromomethylaniline (CAS 583-68-6), and they are the important intermediates and potential impurities in the pharmaceutical syntheses and organic syntheses.

Content and purity testing: The precise determination of the target bromomethylaniline contents in the samples is the core testing item. Through the quantitative methods such as the chromatography, determine the purities of its main components, evaluate whether they conform to the specification requirements as the chemical raw materials or intermediates, usually requiring the main component contents not lower than 98.0%.

Related impurity testing: The bromomethylaniline may introduce or generate various impurities in the synthesis or storage processes, such as the unreacted raw material anilines, brominating reagents, polybrominated by-products, oxidation products (such as the imines) as well as the isomer impurities. The controls of these impurities directly affect the qualities and safeties of the downstream reactions.

Moisture testing: The bromomethylaniline compounds are sensitive to the moisture, and the side reactions such as the hydrolyses may occur. Through the Karl Fischer coulometric method or volumetric method determine the moisture contents, and are the key indicators of the evaluation of its chemical stabilities and the compliance of the storage conditions, usually requiring the moisture lower than 0.5%.

Residual solvent testing: The organic solvents used in the synthesis processes (such as the dichloromethane, ethyl acetate, methanol and toluene, etc.) may remain in the final products. Need to according to the ICH Q3C guideline, adopt the headspace gas chromatography for the testing and control of the residual solvent levels, ensuring the product safeties.

Heavy metal element testing: Test the contents of the harmful heavy metal elements such as the lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) in the samples. Usually adopt the inductively coupled plasma mass spectrometry (ICP-MS) or atomic absorption spectrometry (AAS), to meet the strict restrictions of the pharmaceutical or fine chemical products on the impurity metals.

Solution colour and clarity testing: For the specific uses (such as the pharmaceutical intermediates), need to according to the pharmacopoeia general chapter methods test the clarity and colours of its solutions. This can intuitively reflect whether the insoluble particles or coloured impurities exist in the products, and is the auxiliary means of the rapid evaluation of its purities.

Testing scope

Pharmaceutical APIs and intermediates: The bromomethylaniline is the key building block of the synthesis of the various drugs (such as the certain antibacterial drugs and antihypertensive drugs). In this field, the testing scope covers from the process impurity research in the research and development stages to the quality control (QC) release testing in the production stages, ensuring that it conforms to the strict pharmaceutical standards.

Pesticide and fine chemical intermediates: This compound can be used for the synthesis of the pesticide molecules with the biological activities or the high-performance material monomers. The testing serves the quality controls in the production processes, the competitor product analyses as well as the impurity profile evaluations of the new process routes, to optimise the synthesis paths.

Scientific research reagents: For the reagent-grade bromomethylaniline purchased by the universities, research institutes and enterprise research and development departments, need to test its labelled purities, isomer compositions and main impurities, to ensure the accuracies and repeatabilities of the experimental results, avoiding the research deviations caused by the reagent quality problems.

Import and export commodity inspections: As the regulated chemicals, often need to accept the inspections of the customs or third-party testing institutions in the cross-border trades. The testing is based on the technical indicators agreed in the contracts of the buyers and sellers or the related international standards, issuing the compliance reports, to meet the regulatory and commercial requirements.

Environmental and occupational safety monitoring: The bromomethylaniline has the certain toxicities and irritancies. The testing scope extends to the monitoring of the occupational exposure concentrations in the workshop air, as well as the residual testing of this substance and its degradation products in the factory discharge wastewaters, to evaluate the environmental risks and occupational health and safeties.

Reference substance/control substance calibrations: For the bromomethylaniline reference substances or control substances used for the chromatographic analyses or content determinations, need to carry out the value assignments and uncertainty evaluations through the high-precision absolute quantitative methods (such as the mass balance method and quantitative nuclear magnetic resonance method), ensuring the accurate and reliable values.

Stability research samples: In the drug developments, need to carry out the stability research of the bromomethylaniline intermediates (such as the stress tests, accelerated tests and long-term tests). Regularly sample and test the changes of its contents, impurity profiles and physical properties, to determine the reasonable storage conditions and shelf lives.

Testing methods

Gas chromatography (GC): Applicable to the separations and testing of the bromomethylaniline and its volatile impurities (such as the residual solvents and low boiling point by-products). Usually equipped with the flame ionisation detectors (FID) or mass spectrometry detectors (MS), and the method developments need to optimise the chromatographic columns (such as the weak-polar to medium-polar capillary columns), temperature programmes and injection modes.

High performance liquid chromatography (HPLC): This is the most common method for the determination of the bromomethylaniline contents and related impurities. Adopt the reversed-phase C18 chromatographic columns, with the methanol-water or acetonitrile-water (often added with the buffer salts to adjust the pH) as the mobile phases, combined with the ultraviolet detectors (UV, with the detection wavelengths at about 254 nm) for the quantifications and impurity limit inspections.

Gas chromatography-mass spectrometry (GC-MS): The powerful tool for the unknown impurity identifications and structure confirmations. Through the electron impact ionisation sources (EI) obtain the fragment ion mass spectra, compare with the standard spectrum libraries such as the NIST, can rapidly identify the by-products, degradation products or isomers generated in the syntheses.

High performance liquid chromatography-mass spectrometry (HPLC-MS/MS): Especially applicable to the testing of the trace bromomethylaniline in the complex matrices, such as the environmental water samples or biological samples. Adopt the electrospray ionisation sources (ESI) and multiple reaction monitoring (MRM) modes, can provide the extremely high selectivities and sensitivities, used for the pharmacokinetic or environmental migration research.

Titration analysis method: For the industrial-grade products with the relatively high purities, can adopt the acid-base titration methods for the determination of its amine group contents, thereby convert to the main component contents. For example, carry out the non-aqueous titrations with the perchloric acid glacial acetic acid standard solutions, judge the end points by the potentiometric methods or indicators, with the rapid operations and relatively low costs.

Nuclear magnetic resonance spectroscopy (NMR): As the method of the structure confirmations and quantitative analyses. The proton spectra (1H NMR) and carbon spectra (13C NMR) can be used for the confirmation of the molecular structures of the bromomethylaniline and the distinction of the isomers. The quantitative nuclear magnetic resonance (qNMR) can precisely determine its absolute contents with the internal standards of the known purities.

Ultraviolet-visible spectrophotometric method (UV-Vis): Based on the characteristic absorptions of the aniline derivatives at the specific wavelengths, can be used for the rapid quantitative screenings of the bromomethylaniline. This method is simple, but the specificities are relatively poor, easily interfered by the coexisting impurities, usually served as the auxiliary or preliminary screening means.

Testing standards

Domestic standards:

1. GB/T 602, Chemical reagent — Preparations of standard solutions for impurity determination

2. GB/T 603, Chemical reagent — Preparations of reagent solutions for use in test methods

International standards:

1. ICH Q3C, Impurities: Guideline for residual solvents

2. ISO 3696, Water for analytical laboratory use — Specification and test methods

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Gas chromatographs (GC): The core components include the autosamplers, capillary injection ports, chromatographic column ovens and detectors (FID/MS). Used for the purity analyses, residual solvent testing and volatile impurity profile research of the bromomethylaniline, requiring the instruments to have the good split/splitless injection repeatabilities and stable column temperature controls.

High performance liquid chromatographs (HPLC): The systems are composed of the online degassers, high pressure infusion pumps, autosamplers, column ovens and ultraviolet/diode array detectors (DAD). Are the main equipment of the content determinations and related substance inspections, requiring the high pump flow rate precisions and low detector base-line noises.

Gas chromatography-mass spectrometry instruments (GC-MS): Tandem the mass spectrometry detectors on the basis of the GC, including the ion sources, mass analysers (often the quadrupoles) and detectors. Are the indispensable equipment of the impurity identifications, requiring the stable vacuum systems, with the full scan (Scan) and selected ion monitoring (SIM) functions.

Liquid chromatography-mass spectrometry instruments (LC-MS/MS): Usually are the triple quadrupole mass spectrometers, equipped with the electrospray (ESI) or atmospheric pressure chemical ionisation (APCI) ion sources. Used for the trace and ultra-trace analyses and the complex matrix testing, requiring the mass spectrometry to have the high sensitivities and low cross-contaminations.

Karl Fischer moisture analysers: Specially used for the precise determination of the moisture contents in the samples. Divided into the volumetric method and coulometric method, and the coulometric method has the greater advantages for the determination of the trace moisture (ppm level). The instruments need to be regularly calibrated with the standard water solutions, ensuring the good sealing of the titration cells and the stable electrolysis efficiencies.

Ultraviolet-visible spectrophotometers: Used for the ultraviolet absorption scans and the quantitative analyses at the specific wavelengths of the bromomethylaniline. The instruments should have the wavelength accuracies and photometric repeatabilities, and be equipped with the quartz cuvettes. The modern instruments are usually connected with the computer software, convenient for the data processing and method storages.

Analytical balances and precision pH meters: The analytical balances (precisions of 0.1 mg or 0.01 mg) are used for the precise weighing of the samples and reference substances, and are the basis of all the quantitative analyses. The precision pH meters are used for the preparation of the buffer solutions, ensuring the repeatabilities of the liquid chromatography methods, and need to be regularly calibrated with the standard buffer solutions.