Multi-Element Hydride Generation AAS

What is the Multi-Element Hydride Generation AAS?

A multi-element hydride generation AAS measures several hydride-forming elements in one run using multiple lamps and detection channels. It is chosen when panels of arsenic, selenium and antimony must be measured quickly.

Overview

This configuration uses several hollow-cathode lamps, each modulated or time-sequenced, with either separate detectors or a polychromator to measure more than one element from the same hydride stream. Because all hydride-forming elements are generated under broadly similar acid and reductant conditions, one reaction can serve several elements, which saves time and reagents. Calibration and QC are applied to each element channel, and the software deconvolutes overlapping signals. Detection limits may be slightly higher than dedicated single-element methods because conditions are a compromise and light is shared, but for routine panels such as arsenic, selenium and antimony in water or food the throughput gain is substantial. The approach is well suited to compliance laboratories with fixed element lists.

How does it work?

The sample is mixed with acid and sodium borohydride, which reduces the analyte to a volatile covalent hydride such as arsine or selenide. A carrier gas sweeps the hydride into a heated quartz tube or a small flame, where it decomposes into free atoms. The atoms absorb light from an element-specific hollow-cathode lamp, and absorbance follows the Beer-Lambert law. Because the hydride is separated from the liquid matrix before atomization, most interferents remain behind, which gives high sensitivity and low background. Mercury can be determined by cold vapor generation without heating because it is already volatile. Reaction conditions such as acid type and concentration, borohydride concentration, flow rates and reaction temperature must be tightly controlled, and interfering ions such as copper and nickel are masked or removed. Calibration uses aqueous standards treated in the same way as samples.

What are the key features?

• Multiple modulated hollow-cathode lamps
• Separate detectors or polychromator channels
• One reaction serves several hydride elements
• Per-element calibration and quality control
• Software deconvolution of overlapping signals
• Suited to fixed routine element panels

What are the technical specifications?

A typical multi-element hydride generation aas configuration offers simultaneous elements of 2–4, elements of As, Se, Sb, Bi, Sn, detection limit of 0.1–1 µg/L typical, carrier gas of argon, 200–400 mL/min, quartz cell temperature of 800–900 °C and reductant of 0.5–2% sodium borohydride. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Multi-Element Hydride Generation AAS is used in arsenic, selenium and antimony in water, multi-element food safety screening, geological exploration sample panels and contract laboratory trace element panels. Across the wider Hydride Generation AAS class, laboratories also deploy it for arsenic and selenium in drinking water, arsenic and mercury in rice, fish and seafood and antimony and tin in packaging material migration.

Which standards and certifications apply?

Relevant standards and methods include Ph. Eur. 2.2.22 Atomic absorption spectrometry, USP <852> Atomic Absorption Spectroscopy, ISO 11969 Water quality — Determination of arsenic by AAS, US EPA Method 7062 Arsenic by hydride generation, US EPA Method 7473 Mercury in solids and solutions and IEC 61010-1. Certification candidates for this model are CE, ISO 9001 manufacturing and 21 CFR Part 11 software compliance; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Hydride generation uses sodium borohydride solutions that must be prepared fresh or kept cooled, and reactions can release hydrogen gas, so ventilation is required. Acid and reductant concentrations, tubing lengths and gas flows affect the yield and must be fixed in the method. Interfering elements are controlled with masking agents such as thiourea or by separation. Quartz cells cloud with use and need periodic cleaning or replacement, and their temperature affects atomization efficiency. Because the technique measures a transient or steady signal from a gas, blank contamination from reagents is a common problem; ultrapure reagents and method blanks are essential. Install the system on the flame or furnace instrument with the correct gas supply and waste handling.

How do I select the right Multi-Element Hydride Generation AAS?

Select the multi-element variant when a fixed set of hydride-forming elements is measured in high numbers and time per sample matters. Confirm that the shared reaction conditions give acceptable limits and precision for every element, and validate each channel. If the panel varies widely, single-element continuous flow may be more flexible.

How does it compare with other Hydride Generation AAS variants?

Choose a hydride generation system when the target elements are arsenic, selenium, antimony, bismuth, tin, tellurium or mercury and detection limits around 0.01 to 0.5 micrograms per litre are required at moderate cost. Continuous-flow designs offer stable signals and good throughput, flow-injection designs use less reagent and allow fast transient measurements, and batch systems are cheapest but slowest. If mercury is also required, add a cold vapor module or select an instrument with both modes. Multi-element configurations reduce time when several hydride-forming elements are measured together. For very low detection limits on arsenic and selenium, compare with ICP-MS, which may offer lower limits at higher cost.