AQ2 Discrete Analyzer (Legacy System)

Succeeded by the AQ400, the AQ2 was our original discrete analyzer for automated, compact, benchtop colorimetric analysis. Renowned for its durability, ease-of-use, and flexibility for multiple analyses, the AQ2 built the trusted reputation SEAL Analytical has today.

The Original SEAL Discrete Analyzer

Released in 2002, the AQ2 was SEAL Analytical’s first discrete analyzer on the market—quickly becoming a reliable fixture in wastewater, municipal, industrial, soil, and private testing labs. Designed specifically for environmental applications, it brought a flexible approach to automated colorimetric nutrient analysis and helped countless laboratories achieve consistent, accurate results.

For over 20 years, the AQ2 proved its durability and performance by delivering exceptional detection limits and reliable data day after day. Its flow-through, 10 mm optical glass cuvette and thoughtfully-designed carryover elimination techniques enabled it to rival more complex flow injection analyzers for certain low-level colorimetric applications with increased automation and simplified day-to-day operation. Today, many of the original AQ2 units still operate seamlessly in labs worldwide, a testament to SEAL’s robust design philosophy.

Continued Support & Transition to Modern Systems

Your AQ2 is in Good Hands

Although some components can no longer be sourced and the AQ2 was pronounced obsolete in 2024, SEAL Analytical remains committed to supporting this legacy platform. We continue to offer consumables and spare parts (as available), as well as service and technical assistance from our support chemists and technicians. Our expert teams provide remote troubleshooting, on-site service visits, factory repairs, method guidance, and ongoing software compatibility with modern Windows® operating systems, including Windows 10 and Windows 11. The AQ2 might be a legacy product, but our dedication to your success is as strong as ever.

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Meet the AQ400: The Next Generation

Introduced in 2015 and manufactured side-by-side with the AQ2 until 2017, the AQ400 carries forward the AQ2’s legacy of reliability, ease-of-use, and robust performance—while delivering even greater throughput, capacity, and simplified maintenance. With software, maintenance procedures, operational knowledge, methodology, existing consumables, and some parts fully transferable from the AQ2 to the AQ400, environmental labs can seamlessly transition to this modern system or other SEAL discrete analyzers, benefiting from a new design, enhanced features, and access to an even broader range of approved methods.

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AQ2 Discrete Analyzer Methods

The methods refined and proven on the AQ2—ranging from ammonia and phosphate tests to nitrate+nitrite, chloride, and beyond—are compatible with SEAL’s modern analyzers. This ensures that laboratories migrating to the AQ400 or other SEAL instruments can retain their established workflows, QA/QC procedures, and application knowledge without disruption. Your investment in method development with the AQ2 continues to pay off, even as you upgrade to cutting-edge solutions.

Explore a wide range of our most common AQ2 methods for environmental, agricultural, industrial, and other markets. Don’t see what you’re looking for? Contact our team to review our full method options.

EPA Methods

Analyte	Method Detection Limit	Equivalence
Alkalinity	6.5 mg CaCO₃/L (Range: 10 to 100 mg CaCO3/L) 8.0 mg CaCO3/L (Range: 15 to 200 mg CaCO3/L) 16 mg CaCO3/L (Range: 50 to 500 mg CaCO3/L)	EPA 310.2 (1974)
Ammonia (phenate reagent)	0.004 mg N/L (Range: 0.02 - 2.0 mg N/L) 0.05 mg N/L (Range: 0.2 - 10 mg N/L)	EPA 350.1 (1993) SM 4500-NH3 F,G,H
Ammonia (phenate reagent, for brackish waters)	0.07 mg N/L (Range: 0.2 to 5.0 mg N/L)	EPA 350.1 (1993) SM 4500-NH3 F,G,H
Ammonia (salicylate reagent)	0.005 mg N/L (Range: 0.02 - 1.0 mg N/L) 0.016 mg N/L (Range: 0.1 - 5.0 mg N/L) 0.02 mg N/L (Range: 0.2 - 10 mg N/L) 0.18 mg N/L (Range: 1.0 - 100 mg N/L)	EPA 350.1 (1993) SM 4500-NH3 F,G,H
Chloride	0.3 mg N/L (Range: 2.0 - 100 mg Cl/L) 0.4 mg N/L (Range: 5.0 - 200 mg Cl/L)	SM 4500-Cl E
Chromium, Hexavalent	0.0005 mg Cr(VI)/L (Range: 0.01 - 0.5 mg Cr(VI)/L) 0.011 mg Cr(VI)/L (Range: 0.3 - 5.0 mg Cr(VI)/L)	SM 4500-Cr B
Color (480 nm)	2 Color Units (Range: 5 - 150 Color Units)	SM 2120 B,C
Cyanide, Total (Distillation Required)	1.0 μg CN/L (Range: 3.0 – 250 μg CN/L)	EPA 335.4, Rev 1 (1993)SM 4500-CN E,N
Hardness, Total	11 mg CaCO3 /L (Range: 25 – 400 mg CaCO3/L)	EPA 130.1 (1971)
Nitrogen, Total Kjeldahl (TKN, Hg Catalyst Kjeldahl Digestion Required)	0.03 mg N/L (Range: 0.1 – 4 mg N/L) 0.2 mg N/L (Range: 0.5 – 24 mg N/L)	EPA 351.2, Rev 2 (1993) SM 4500-N_org D
Nitrogen, Total Kjeldahl (TKN, Cu Catalyst Kjeldahl Digestion Required)	0.07 mg N/L (Range: 0.2 – 4 mg N/L) 0.12 mg N/L (Range: 0.5 – 25 mg N/L)	EPA 351.2, Rev 2 (1993) SM 4500-Norg D
Nitrate + Nitrite (Cadmium Reduction, Ammonium Chloride Buffer)	0.003 mg N/L (Range: 0.012 - 2.0 mg N/L) 0.01 mg N/L (Range: 0.06 - 5.0 mg N/L) 0.03 mg N/L (Range: 0.25 - 15 mg N/L)	EPA 353.2, Rev 2 (1993) SM 4500-NO3 E,F,I
Nitrate + Nitrite (Cadmium Reduction, Imidazole Buffer)	0.004 mg N/L (Range: 0.012 - 2.0 mg N/L)	EPA 353.2, Rev 2 (1993) SM 4500-NO3 E,F,I
Nitrate + Nitrite (Hydrazine Reduction)	0.005 mg N/L (Range: 0.02 - 1.5 mg N/L) 0.03 mg N/L (Range: 0.2 - 5.0 mg N/L)	EPA 353.1(1978) SM 4500-NO3 H
Nitrate + Nitrite (Vanadium (III) Chloride Reduction)	0.004 mg N/L (Range: 0.025 - 1.0 mg N/L)	Easy (1-Reagent) Nitrate Method (2011)
Nitrite (with Buffer Addition)	0.0001 mg N/L (Range: 0.0009 - 0.2 mg N/L) 0.0008 mg N/L (Range: 0.015 - 1.5 mg N/L)	EPA 353.2, Rev 2 (1993) SM 4500-NO3 E,F,I
Nitrite (no Buffer Addition)	0.0002 mg N/L (Range: 0.0009 - 0.2 mg N/L) 0.0006 mg N/L (Range: 0.015 - 1.5 mg N/L)	SM 4500-NO2 B
Phenolics (Distillation Required)	0.0025 mg Phenol/L (Range: 0.005 - 0.25 mg Phenol/L)	EPA 420.1 (1978) EPA 420.4, Rev 1 (1993) SM 5530 D
Phosphate, ortho	0.0006 mg P/L (Range: 0.003 - 0.3 mg P/L) 0.002 mg P/L (Range: 0.01 - 1.0 mg P/L) 0.005 mg P/L (Range: 0.05 - 5.0 mg P/L) 0.013 mg P/L (Range: 0.125 - 12.5 mg P/L)	EPA 365.1, Rev 2 (1993) EPA 365.3 (1978) SM 4500-P E,F,G,H
Phosphorus, Total (TP, Persulfate Digestion Required)	0.003 mg P/L (Range: 0.01 - 1.0 mg P/L) 0.006 mg P/L (Range: 0.05 - 5.0 mg P/L)	EPA 365.1, Rev 2 (1993) EPA 365.3 (1978) SM 4500-P E,F,G,H
Phosphorus, Total Kjeldahl (TKP, Hg Catalyst Kjeldahl Digestion Required)	0.007 mg P/L (Range: 0.04 - 3.2 mg P/L)	EPA 365.4 (1974)
Phosphorus, Total Kjeldahl (TKP, Cu Catalyst Kjeldahl Digestion Required)	0.009 mg P/L (Range: 0.04 - 3.2 mg P/L)	EPA 365.4 (1974)
Silica (No Reduction)	0.1 mg silica/L (Range: 0.25 - 25 mg silica/L)	SM 4500-SiO2 C
Silica (with ANSA Reduction)	0.018 mg silica/L (Range: 0.1 - 10 mg silica/L)	SM 4500-SiO2 D,E,F
Sulfate	1.0 mg/L (5.0 - 40 mg/L)	ASTM D516-02,07,11,16
Sulfate (use of gelatin as suspension agent)	0.09 mg/L (5.0 - 40 mg/L)	ASTM D516-02,07,11,16

ISO Methods

Analyte	Method Detection Limit	Equivalence
Ammonia	0.003 mg N/L (Range: 0.01 to 1.0 mg N/L)	ISO 7150-1
Chloride	1.4 mg Cl/L (Range: 5 - 400 mg Cl/L)	ISO 15682
Colour	1 mg Pt/L (Range: 1 - 100 mg Pt/L)	ISO 7887:2011(E)
Nitrate + Nitrite (Hydrazine Reduction)	0.008 mg N/L (Range: 0.1 - 6.0 mg N/L	ISO/DIS 15923-1
Nitrite	0.0003 mg N/L (Range: 0.02 - 1.0 mg N/L)	ISO/DIS 15923-1
Phosphate	0.002 mg P/L (Range: 0.006 - 1.0 mg P/L)	ISO 6878
Silicate	0.016 mg Si/L (Range: 0.05 - 6.0 mg Si/L)	ISO/DIS 15923-1
Sulfate	0.42 mg/L (Range: 4.0 - 200 mg/L)	ISO/DIS 15923-1

Agricultural Methods

Analyte	Extract	Method Detection Limit
Ammonia	2 M KCl	0.04 mg N/L (Range: 0.2 - 10 mg N/L)
Nitrate + Nitrite (Cadmium Reduction)	2 M KCl	0.015 mg N/L (Range: 0.06 - 5.0 mg N/L)
Nitrate + Nitrite (Cadmium Reduction)	0.1 M K₂SO₄	0.01 mg N/L (Range: 0.05 - 5.0 mg N/L)
Phosphate, ortho	Bray's P1 or P2, or similar extract	0.015 mg P/L (Range: 0.05 - 5.0 mg P/L)
Phosphate, ortho	DI Water	0.13 mg P₂O₅/L (Range: 7 - 350 mg P₂O₅)
Phosphate, ortho	Modified Morgan's or similar acetate/acetic acid extract	0.01 mg P/L (Range: 0.2 - 8.0 mg P/L)
Phosphate, ortho	Olsen 0.5 M sodium bicarbonate extract	0.01 mg P/L (Range: 0.1 - 5.0 mg P/L)
Phosphate, ortho	2 M KCl	0.04 mg P/L (Range: 0.1 - 5.0 mg P/L)
Sulfate	KH₂PO₄, or similar extraction	0.75 mg SO₄/L (Range: 5.0 - 40 mg SO₄/L)

Other models

AQ300 Discrete Analyzer

Featuring a minimal and compact design, the SEAL AQ300 discrete analyzer offers the same benefits as the AQ400 discrete analyzer at a lower throughput rate, making it the ideal solution for laboratories with limited space and smaller workloads.

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AQ400 Discrete Analyzer

Our flagship discrete analyzer, the AQ400 is designed for mid-sized laboratories looking to increase their testing capacity and throughputs. Leveraging advanced robotics for fast sample preparation, the AQ400 is ideal for applications where multiple varied tests are needed on different samples in a short period of time.

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AQ700 Discrete Analyzer

The AQ700 is the highest throughput and highest capacity discrete analyzer offered by Seal Analytical. The system has four robotic arms and four sample trays which allow for a long walkaway time and unattended operation for laboratories with the highest testing demands.

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Frequently Asked Questions

Below, we’ve listed a few frequently asked questions that will help you better understand our Discrete Analyzers. If you don’t find the answer you're looking for, please don't hesitate to contact our support team for further assistance.

Why do SEAL discrete analyzers use a dedicated quartz cuvette rather than individual styrene cuvettes?

SEAL Analytical’s AQ analyzers come standard with a 10 mm quartz flow-through cuvette used for all readings on the system. This material ensures the highest optical purity at detection. As the detector is entirely stationary rather than rotating to different wells, there is no added variance from changes in detector alignment. Additionally, each sample is analyzed in the same cuvette rather than individual wells, eliminating a critical variable in analysis conditions.

What benefits does a probe washer bring to a discrete analyzer?

The traveling probe washer, unique to all SEAL discrete analyzers, ensures the sample probe is wiped clean and free of droplets before each sample probe movement. This ensures droplets are not falling off the sample probe into reaction wells, sample cups, reagent containers, etc as the sample probe moves to different locations. Additionally, it provides extra cleaning to the outside of the probe to further eliminate cross-contamination. The traveling probe washer is accompanied by a stationary wash bath for additional sample probe cleaning between crucial reaction steps.

How do SEAL Discrete Analyzers prevent carryover while using the same cuvette for each analysis?

Most carryover in discrete analysis happens during reaction preparation, but SEAL’s dual washing system described above eliminates this risk. At detection, high-speed water flushes alternating with air thoroughly clean the quartz cuvette, inspired by the proven rinsing method of our continuous flow analyzers.

Can AQ discrete analyzers run multiple parameters in a single run?

Yes. Multiple parameters can be defined on the same samples, or different samples during the same run. This is all defined in the accompanying software that allows the analyst to define which parameters are analyzed on which samples.

What is the capacity of your discrete analyzers?

AQ300: up to 97 sample positions; 18 reagent positions; 180 reaction positions

AQ400: up to 120 sample positions; 26 reagent positions; 216 reaction positions

AQ700: up to 424 sample positions, 24 reagent positions; 848 reaction positions

Do AQ discrete analyzers have hardware integrated to analyze for Nitrate+Nitrite by cadmium reduction?

Yes, all AQ discrete analyzers are equipped with the ability to run Nitrate+Nitrite by cadmium reduction, in addition to other common reduction pathways including hydrazine sulfate, vanadium (III) chloride, and enzymatic reduction. A tubular cadmium coil is fitted in a dedicated loop so only sample and buffer pass through the cadmium coil during the reduction step of a Nitrate+Nitrite test. All other tests bypass the cadmium coil so that the cadmium coil can always be installed on the system.

Do AQ Discrete Analyzer offer in-line pre- and post-dilutions?

Yes, all SEAL discrete analyzers offer auto-dilution capabilities. Dilutions can be assigned to samples before the run for the analyzer to dilute the samples immediately before analysis. As an additional option, over-range samples can be flagged by the software for auto-dilution at the end of the run. The software allows for dilution factors and post-run quality control bracketing for dilutions to be customizable by test, ensuring you meet your compliance requirements.