Key Takeaways & Executive Findings
- •• • Achieved baseline separation of azide (N3−) from nitrate (NO3−) using a Dionex IonPac™ AS11-HC column with KOH gradient elution, with retention times of 13.67 min and 14.88 min, respectively, eliminating interference from common anions. • • The method provides a limit of quantification (LOQ) of 0.005 mg·L−1 for N3− in solution, translating to minimum quantifiable air concentrations of 0.00256 mg·m−3 for hydrazoic acid and 0.00387 mg·m−3 for sodium azide, enabling detection below the occupational exposure limit. • • Spiked recoveries ranged from 92.0% to 100.4% across low (0.005 mg·L−1), medium (0.010 mg·L−1), and high (0.050 mg·L−1) levels, with relative standard deviations (RSD, n=6) between 0.76% and 2.51%, demonstrating high accuracy and precision. • • The method uses a simple sampling approach: 40 mg·L−1 KOH as absorption solution for vapor/mist and microporous membrane for sol, followed by elution, making it practical for routine workplace air monitoring.
Abstract
A method for the determination of hydrazoic acid and sodium azide in workplace air was established using ion chromatography with suppressed conductivity detection. Vapor and mist states of hydrazoic acid were collected in 40 mg·L−1 KOH absorption solution, while sol states of hydrazoic acid or sodium azide were collected on microporous membranes and eluted with 40 mg·L−1 KOH. Separation was performed on a Dionex IonPac™ AS11-HC (250 mm × 4.0 mm) anion analytical column with KOH gradient elution, followed by suppressed conductivity detection. The azide ion (N3−) exhibited good linearity in the range of 0.005–0.5 mg·L−1, with a correlation coefficient (r) of 0.9997. The limit of detection (S/N=3) was 0.002 mg·L−1, and the limit of quantification (S/N=10) was 0.005 mg·L−1. The minimum quantifiable concentrations in air were 0.00256 mg·m−3 for hydrazoic acid and 0.00387 mg·m−3 for sodium azide, based on a 10.0 mL sample solution and a 20 L air sample. Spiked recoveries ranged from 92.0% to 100.4%, with relative standard deviations (RSD, n=6) between 0.76% and 2.51%. The method is efficient, accurate, and sensitive, suitable for monitoring and safety assessment of hydrazoic acid and sodium azide in workplace air.
1. Introduction
Hydrazoic acid and sodium azide are highly toxic industrial chemicals used in energetic materials and pharmaceuticals. Their toxicity parallels cyanide, causing rapid absorption via inhalation, skin contact, and ingestion, leading to mucosal irritation, hypotension, organ damage, and central nervous system effects. Accurate determination of airborne concentrations is critical for occupational exposure assessment and worker safety. The current national standard method (GBZ/T 300.43-2017) employs ferric chloride spectrophotometry, which suffers from poor sensitivity and interference, with a minimum quantifiable concentration equal to the maximum allowable concentration, resulting in a 'detectable equals exceedance' dilemma that fails to reflect low-level exposure risks.
To address this bottleneck, the authors developed an ion chromatography method with suppressed conductivity detection, leveraging the high selectivity and sensitivity of IC for anions. Using a high-capacity AS11-HC column and KOH gradient elution, they achieved baseline separation of azide from nitrate, a common interferent. The method achieves a limit of quantification of 0.005 mg·L−1 in solution, corresponding to air concentrations of 0.00256 mg·m−3 for hydrazoic acid and 0.00387 mg·m−3 for sodium azide, well below the occupational exposure limits. This provides a reliable tool for accurate monitoring and safety evaluation in workplaces.
Loading authentic research manuscript (Pages 1–5)...
ZHU Fuqiang, GANG Qiang, JIA Huimei, MENG Xianlong, LI Yuanyuan, CHEN Linlin (2026). Determination of Hydrazoic Acid and Sodium Azide in Workplace Air by Ion Chromatography with Suppressed Conductivity Detection. Environmental Chemistry. https://doi.org/10.0000/202605-1
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the basis for selecting the AS11-HC column over other anion exchange columns for azide determination?
The AS11-HC high-capacity column was chosen because AS19 and AS11 columns failed to resolve azide (N3−) from nitrate (NO3−), which have similar chromatographic behavior. With AS11-HC and gradient elution, baseline separation was achieved with retention times of 13.67 min for N3− and 14.88 min for NO3−, ensuring accurate quantification without interference.
How does the method's sensitivity compare to the existing spectrophotometric standard, and what are the implications for regulatory compliance?
The ion chromatography method achieves a limit of quantification (LOQ) of 0.005 mg·L−1 in solution, corresponding to air concentrations of 0.00256 mg·m−3 for hydrazoic acid and 0.00387 mg·m−3 for sodium azide. This is significantly lower than the spectrophotometric method's minimum quantifiable concentration, which equals the occupational exposure limit, thus allowing detection of sub-limit exposures and avoiding the 'detectable equals exceedance' issue.
What are the recovery and precision metrics, and how do they validate the method's reliability for routine monitoring?
Spiked recoveries ranged from 92.0% to 100.4% across low, medium, and high concentration levels (0.005, 0.010, and 0.050 mg·L−1), with relative standard deviations (RSD, n=6) between 0.76% and 2.51%. These metrics demonstrate high accuracy and reproducibility, meeting the requirements for occupational exposure assessment.
How is the sampling procedure designed to capture different physical states of hydrazoic acid and sodium azide?
Vapor and mist states of hydrazoic acid are collected using 40 mg·L−1 KOH as an absorption solution in a multi-hole glass absorption tube. Sol states (aerosols) of hydrazoic acid or sodium azide are collected on a microporous membrane (0.80 μm pore size, 40 mm diameter) and subsequently eluted with 40 mg·L−1 KOH. This dual approach ensures comprehensive capture of both gaseous and particulate forms.
What is the total analysis time and throughput for routine monitoring?
The chromatographic run includes gradient elution with a final high-concentration step (35 mmol·L−1 KOH) to wash strongly retained components. The retention times for N3− and NO3− are 13.67 and 14.88 minutes, respectively, with additional time for column re-equilibration. The method is suitable for routine monitoring with a typical run time of approximately 20-25 minutes per sample, allowing efficient processing of multiple samples per day.
Related Chinese Research & Cross-Citations
Exploring the Potential Molecular Mechanisms of Eight Environmental Pollutants in Lung Adenocarcinoma through Network Toxicology, Machine Learning, and Multi-Omics Analysis
Epidemiological studies have established a significant association between exposure to environmental pollutants (EP) and the risk of lung adenocarcinoma (LUAD). This study integrates network toxicology and multi-omics analysis to elucidate the EP-LUAD molecular regulatory network and identify key regulatory genes, thereby revealing novel mechanisms of environmental carcinogenesis. Transcriptomic data from GEO and TCGA databases yielded 4,971 and 4,488 disease-related targets, respectively. Integration of toxicology databases (TargetNet, Swiss Target Prediction, CTD, SEA) identified 24,860 potential targets for eight common pollutants (SO2, NO, CO, NO2, O3, benzene, toluene, and polycyclic aromatic hydrocarbons). Intersection of these datasets produced 1,536 EP-LUAD common target genes. Protein-protein interaction network analysis identified 247 core targets. Machine learning selected five key genes: AGER, CAV1, CD44, CEP55, and GNB3, which demonstrated robust diagnostic and prognostic efficacy. Their expression correlated with immune cell infiltration, including CD4+ memory T cells and macrophages. Single-cell RNA sequencing revealed epithelial cell-specific expression patterns. Molecular docking confirmed stable pollutant-target binding, with PAH showing highest affinity for CD44 (binding energy −9.32 kcal·mol−1) and GNB3 (−8.32 kcal·mol−1). These findings establish AGER, CAV1, CD44, CEP55, and GNB3 as core molecular mediators of pollution-related LUAD. The high-affinity binding of PAH to CD44 and GNB3 underscores its carcinogenic potential. This study constructs a multi-level regulatory network for EP-LUAD, revealing underlying molecular mechanisms and providing novel potential targets and theoretical basis for early warning and intervention.
Effects of Different Functionalized Nanoplastics on the Transformation of Extracellular Antibiotic Resistance Genes in Aquatic Environments
The rapid dissemination of antibiotic resistance genes (ARGs) in aquatic environments poses serious threats to public health and environmental safety under the 'One Health' framework. Nanoplastics (NPs), as co-occurring pollutants, can exacerbate ARG risks by promoting horizontal gene transfer (HGT), yet the influence of different functional groups on extracellular ARG (eARG) transformation remains unclear. This study investigated the effects of carboxy-modified polystyrene NPs (PS-COOH) and amino-functionalized polystyrene NPs (PS-NH2) compared to unmodified polystyrene NPs (PS) on the transformation of the extracellular resistance plasmid IE-V1955 (carrying an ampicillin resistance gene) into Escherichia coli DH5α. Results showed that PS-COOH exposure promoted plasmid transformation similarly to PS, with effects increasing over 0.1–20 mg·L−1. Low concentrations (0.1–0.5 mg·L−1) of PS-NH2 also enhanced transformation, with stronger effects than PS-COOH at equal doses, whereas high concentrations (1–20 mg·L−1) inhibited it. Mechanistically, PS-COOH (0.1–20 mg·L−1) and low PS-NH2 induced intracellular reactive oxygen species (ROS), increased cell membrane permeability, elevated the protein-to-polysaccharide ratio in extracellular polymeric substances (EPS), and promoted biofilm formation, thereby facilitating transformation. High PS-NH2 concentrations caused excessive ROS leading to cell lysis and formed aggregates with plasmids larger than membrane pores, blocking uptake. These findings provide a theoretical basis for assessing the combined environmental health risks of NPs and ARGs.
Cardiovascular Toxicity Induced by Micro/Nano-Plastics and Its Mechanisms
Micro/nano-plastics (MNPs) are emerging contaminants widely detected in human circulatory systems, including blood, heart, and vascular endothelium, raising concerns about cardiovascular health risks. This systematic review analyzed 61 peer-reviewed studies (2008–2024) to elucidate the cardiotoxic effects and molecular mechanisms of MNPs. Evidence indicates that MNPs exposure elevates risks of atherosclerosis, thrombosis, and arrhythmias through oxidative stress, inflammatory cascades, endothelial dysfunction, and metabolic dysregulation. Notably, co-exposure with persistent organic pollutants (POPs) or heavy metals may produce synergistic or antagonistic effects. Current research relies predominantly on animal and cell models, with critical gaps in low-dose, long-term exposure data and epidemiological evidence. Future studies should optimize experimental designs, integrate metabolomics and epigenetics, and explore transgenerational effects and combined toxicity mechanisms to inform pollution control policies and mitigate cardiovascular risks.
Body Burden of Polybrominated Diphenyl Ethers and Joint Effects on Thyroid Function in a Physical Examination Population in Shenzhen
This study characterized the body burden of polybrominated diphenyl ethers (PBDEs) in a physical examination population in Shenzhen and evaluated its impact on thyroid function. Serum samples from 368 residents were analyzed for eight PBDE congeners using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS). The median concentration of ∑8PBDEs was 10.2 ng·g⁻¹ lipid weight (lw), ranging from 0.13 to 2089.4 ng·g⁻¹ lw, with BDE-209 predominating (59.7% of total). Multiple linear regression revealed that a 1.7-fold increase in serum BDE-153 was associated with a 0.4% increase in free triiodothyronine (FT3) (P<0.05), while a 1.7-fold increase in BDE-183 was associated with a 0.9% decrease in total triiodothyronine (T3) and a 0.7% decrease in FT3 (P<0.05). Bayesian kernel machine regression (BKMR) indicated a negative correlation between mixed PBDE exposure and thyroid-stimulating hormone (TSH) at high exposure levels. Weighted quantile sum (WQS) regression showed that mixed exposure was associated with decreased T3 levels and T3/FT3 ratio, with BDE-153 and BDE-183 as the primary contributors. These findings suggest that PBDE exposure may adversely affect thyroid function and disrupt thyroid hormone homeostasis, with BDE-183 and BDE-153 playing key roles. This study provides a scientific basis for PBDE health risk assessment and thyroid protection.
Mechanisms of Natural Organic Matter in Regulating Microplastic Aggregation and Transport in Soil-Groundwater Systems: A Review
Microplastics (MPs) are persistent emerging contaminants ubiquitously distributed in soil-groundwater environments, where their aggregation and transport critically govern pollutant fate and ecological risks. Natural organic matter (NOM), a complex assemblage of organic compounds, interacts with MPs and porous media via hydrogen bonding, π-π interactions, hydrophobic effects, and electrostatic binding, thereby modulating MP surface properties and environmental behavior. This review systematically synthesizes the mechanisms by which NOM influences MP aggregation and transport, with emphasis on the distinct roles of humic substances, proteins, and extracellular polymeric substances (EPS), and their synergistic modulation with solution chemistry (pH, ionic strength, ion type). Additionally, NOM accelerates MP aging and alters surface characteristics, consequently impacting transport capacity. Current research limitations are identified, and future directions are proposed to inform MP pollution risk assessment and management strategies. Key findings indicate that NOM generally enhances MP stability and mobility at low ionic strengths, while high ionic strengths may induce aggregation depending on NOM type and ion valence. Humic substances predominantly increase electrostatic repulsion, whereas proteins and EPS can bridge particles, promoting aggregation. Aging processes, accelerated by NOM photochemical activity, increase surface oxygen functionality and hydrophilicity, further altering transport. The review underscores the need for systematic studies under environmentally relevant conditions to predict MP fate accurately.
Neurotoxicity of Carboxyl-Modified Polystyrene Microplastics on Zebrafish at Early Developmental Stage
Carboxyl-modified polystyrene microplastics (PS-COOH) are negatively charged particles formed by surface oxidation and functional group modification of polystyrene microplastics (PS), widely used in biomedical and analytical chemistry. However, studies on their neurotoxic effects on aquatic organisms are scarce. This study employed zebrafish (Danio rerio) as a model organism, exposing embryos to environmentally relevant concentrations (0.1, 1, 10, 100 μg·L−1) of PS and PS-COOH. Neurotoxic effects were assessed by measuring tail coiling frequency at 24 hpf and swimming velocity under alternating light/dark cycles at 120 hpf. Results demonstrated that both PS and PS-COOH induced neurotoxicity, with PS-COOH significantly reducing tail coiling frequency and average swimming speed compared to PS (P<0.05). Exposure to 10 μg·L−1 PS-COOH disrupted neurotransmitter homeostasis, altering levels of acetylcholine (ACh), serotonin (5-HT), and γ-aminobutyric acid (GABA). Transgenic zebrafish Tg(huc:EGFP) fluorescence assays revealed that PS-COOH (0.1–100 μg·L−1) caused damage to central neurons. These findings indicate that PS-COOH exposure impairs cholinergic, serotonergic, and GABAergic neurotransmission, induces neuronal damage, and exerts neurotoxic effects on zebrafish larvae. This study provides a theoretical basis for assessing the ecological and health risks of modified microplastics.