Hydride Generation (HG-AAS)
Definition
Sensitivity booster for As, Sb and Se. Sample plus NaBH4 in acid liberates AsH3 / SbH3 / SeH2 gas, which is swept into a heated quartz cell on an AAS for atomisation. Detection limits drop to sub-ppb levels, well below BIS drinking-water thresholds.
- Full name
- Hydride generation atomic absorption spectroscopy
- Target elements
- Arsenic, antimony, selenium
- Reagent
- Sodium borohydride (NaBH4) in acid
- Sensitivity
- Detection limits down to sub-ppb levels
Common questions
Why is hydride generation needed instead of running these elements through standard flame AAS?+
Arsenic, antimony and selenium have relatively poor sensitivity in conventional flame atomisation, so converting them into volatile hydride gases that are swept directly into a heated quartz cell concentrates and atomises the element far more efficiently, achieving the sub-ppb sensitivity needed for trace poisoning cases.
What forensic toxicology scenario relies on this level of sensitivity?+
Suspected chronic low-dose arsenic or antimony poisoning, or environmental exposure cases, require detecting concentrations far below what would produce acute symptoms, and HG-AAS's sub-ppb detection limits make it suited to confirming exposure at trace levels in blood, urine or tissue.
Can HG-AAS distinguish different chemical forms of arsenic, such as organic versus inorganic?+
Basic HG-AAS measures total hydride-forming arsenic species and does not on its own distinguish organic from inorganic forms; speciation typically requires coupling with a chromatographic separation step beforehand to resolve which arsenic species are present.
Related terms
- Arsenic (As)
- Metalloid; trivalent arsenite (As III) is 60 times more toxic than pentavalent arsenate (As V). Thiol-group blocker that poisons mitochondrial enzymes (pyruvate...
- Dry Ashing
- Viscera or hair is dried and incinerated in a muffle furnace at 450 to 550 degrees Celsius. Inorganic ash is dissolved in...
- Lead (Pb)
- Cumulative neurotoxin from chronic occupational exposure (battery recycling, smelter work), leaded paint, contaminated cosmetics (low-grade sindoor, surma, kohl), and adulterated Ayurvedic preparations....
- Marsh Test (1836)
- Confirmatory test for arsenic devised by James Marsh after the Bodle case (1832), in which Marsh was unable to convince a jury...
- Mercury (Hg)
- Three toxic forms: elemental (vapour from broken thermometers, dental amalgam), inorganic salts (mercuric chloride, corrosive sublimate), and organic (methylmercury from biomagnification, ethylmercury...
- Reinsch Test
- Classical screen for arsenic, antimony, mercury and bismuth. A clean copper strip is immersed in the acidified sample (concentrated HCl, near-boiling) for...
- Thallium (Tl)
- The 'poisoner's poison' because thallium sulphate is tasteless, odourless and colourless. Substitutes for potassium in cellular transport. Alopecia at 2 to 3...
- Wet Digestion
- Viscera is digested with HNO3 + H2SO4 + HClO4 (or HNO3 + H2O2) at controlled temperature. Closed-vessel microwave-assisted digestion in Teflon bombs...