Determination of Multiple Elements in Foods using Automated Fast Sequential-Flame AAS Analysis

Importance of the Topic

Multi‐element analysis of food matrices is essential for nutritional labeling, quality control, and regulatory compliance. Traditional flame atomic absorption spectrometry (FAAS) provides robust performance but can be slow when measuring multiple elements sequentially. Advances in automation and fast sequential analysis address throughput bottlenecks and reduce error sources, enabling high‐volume laboratories to meet growing sample loads with improved precision and efficiency.

Objectives and Study Overview

This application note evaluates the performance of the Agilent 280FS flame AAS equipped with Fast Sequential (FS) mode and the SIPS 20 sample introduction and preparation system. The study aims to demonstrate:

• Accurate determination of nine elements (K, Na, Ca, Cu, Mg, Mn, Fe, Ni, Zn) in a certified reference material (ORCHARD LEAVES CRM).
• Instrument detection limits (IDLs) and method detection limits (MDLs) for each element.
• Long‐term stability over multiple food sample digests.
• Productivity gains achieved via PROMT precision control, FS mode, and automated calibration with SIPS 20.

Methodology and Instrumentation

The analytical setup included an Agilent 280FS AAS with Mark 7 flame atomization (air‐acetylene), multi‐element hollow cathode lamps, and Agilent SpectrAA software. Key features:

• Fast Sequential mode: simultaneous lamp operation with motorized mirror for rapid wavelength switching (2 025 nm/min) and sub-30 ms gas flow adjustments via the hammer gas box.
• PRecision Optimized Measurement Time (PROMT): adaptive read times targeting a 1% RSD, shortening measurement of higher concentration samples.
• SIPS 20 accessory: automated bulk‐standard calibration, matrix modifier addition (Cs/Sr buffer for EIEs, Ca releasing agent), overrange dilution, and extended working range.

Sample preparation involved microwave digestion of food samples (0.5 g in 10 mL HNO₃) using a closed‐vessel program (210 °C ramp 15 min, hold 15 min), followed by dilution to 50 mL with deionized water. Calibration employed three automatic standards spanning expected concentration ranges.

Key Results and Discussion

Instrument detection limits ranged from 0.0031 mg/L (Mg) to 1.45 mg/L (K). MDLs were confirmed by repeated blank analyses and spiking experiments. Certified reference recoveries for the Orchard Leaves CRM were all within ±10%, with nickel spiked due to low native concentration. Long‐term stability was assessed over 12 QC checks during 4 h 19 min of analysis, yielding recoveries of 97–107% and RSDs below 5%.

Productivity gains relative to conventional FAAS (three 3 s replicates per element):

• PROMT reduced sample‐to‐sample read time by 8%.
• FS mode halved analysis time for nine elements.
• Combined FS and PROMT saved an additional 44 s per sample.
• Incorporating SIPS 20 further cut time by 66%, boosting throughput from 6.8 to 20 samples per hour.

Benefits and Practical Applications

The integrated system automates calibration, matrix modification, and overrange dilution, minimizing manual steps, contamination risk, and user intervention. Laboratories can achieve high sample throughput without sacrificing precision or accuracy, making this approach ideal for food testing, environmental monitoring, and industrial QA/QC.

Future Trends and Opportunities

Ongoing developments may include:

• Integration of additional auto‐dilution schemes and on‐line sample preconcentration.
• Extended multi‐element lamp technology for trace and ultra‐trace analysis.
• Enhanced software algorithms leveraging machine learning for real‐time method optimization.
• Coupling with complementary techniques (e.g., hydride generation, graphite furnace) for enhanced sensitivity and speciation studies.

Conclusion

The Agilent 280FS AAS with SIPS 20 delivers fast, accurate, and reliable multi‐element analysis in food matrices. Combined features—FS mode, PROMT, and automated sample introduction—achieve high throughput, stable performance, and robust detection limits, streamlining workflows and reducing cost per sample.

References

1. Agilent Technologies. Increasing Productivity and Simplifying Sample Preparation with the SIPS Accessory. Publication 5991-6613EN.