The OI DA3500 Batch Selective, Random Access, Simultaneous - Multi-chemistry Discrete Analyzer

The DA3500 is capable of performing almost every colorimetric or turbidimetric test in aqueous solution.

The DA3500 is a true discrete analyzer. All samples are “blanked”, mixed, reacted, and measured in individual optical cuvettes without the use of pump tubes. There are no baselines to stabilize, no hardware to change, and no washing stations that add instrument complexity or introduce potential doubt as to reagent carryover between measurements. Reagents are only used per test, which minimizes waste.

“True Discrete Analyzer”

TheDA3500 is a true discrete analyzer. All readings, reactions, mixing, and / or dilutions are contained in individual optical cuvettes.

The DA3500 uses two computer controlled, high precision displacement pumps to accurately dispense sample and reagents at volumes from 2 ul to 900 ul.

The DA3500 uses individual disposable cuvettes per sample. The DA3500 does not wash these disposable cuvettes. This is because the DA3500 analyzes trace environmental contaminants and operates as a random selective analyzer. Cleaning a cuvette from one test runs the risk of cross contamination from the high level of analyte that exists in the reagents from previous tests. For example, the nitrate test uses ammonium chloride and phosphoric acid as reagents for the test. If a nitrate test is followed immediately by either a phosphate test or ammonia test there will always be a risk that some of the previously used reagents will remain in the washed cuvette. Simply checking the optical purity of a washed cuvette does not guarantee that it is chemically clean.

The DA3500 measures absorbance throughsamples contained in individual optical cuvettes. The light travels horizontally through the sample solution. There is neither flow cell, nor are there any air – liquid or liquid – liquid interfaces. The analyzer does not measure through a noise-producing meniscus, so therefore, does not require “careful stabilization” prior to absorbance measurement.

The DA3500 automatically “blanks” every sample obtaining a sample zero prior to measurement of the final sample absorbance. All results are calculated from this “delta OD”. Sample blanking compensates for any absorbance that may occur due to turbidity, refractive index, or color in the un-color developed sample solution.

“Select Methods by Software”

The DA3500 users select methodology strictly by software. There are no other hardware configurations necessary. Calibrations are also stored by method ensuring that when analysts select methods, they are selecting properly calibrated ones as well.

The DA3500 continuously monitors reagent volumes and the amounts required for specified tests, sample volumes and the amounts required for specified tests, and guarantees that all tests selected will have enough sample and reagent before the analysis is begun. The system monitors and displays status of which samples are currently being measured, and which reagents and/or replicate is currently being dispensed. Messages, such as over range readings are displayed “real time” as well as the results for tests already finished.

The DA3500 has 24 numbered locations specifically for reagent placement negating the need to color code. Since the DA3500 is a multi-chemistry batch analyzer and may be analyzing a single sample for several tests simultaneously it does not color code sample status.

“No Additional Hardware Required”

TheDA3500is a complete unit with no additional hardware requirements for operation.

The DA3500 is capable of running almost any wet chemical analysis, as received, and does not utilize pump tubes, coils, or injection loops. All method settings are defined by software.

The DA3500 is an open chemistry analyzer and gives the operator/user complete control over methodology. The DA3500 is capable of running almost any wet chemistry analysis.

The DA3500 is a complete system as purchased. The only configuration decision required at purchase is whether a nitrate module for use in measuring nitrate nitrogen by cadmium reduction need be installed. There are no other configuration requirements.

The DA3500 is a batch wet chemistry analyzer designed to bracket samples for analysis surrounded by quality control then check those results against accepted ranges prior to continuing analysis. The DA3500 is also multi-chemistry analyzer intended to analyze multiple chemistries at a time. The DA3500 maintains 140 heated reaction segments that allow one batch of ten samples plus quality control samples to be analyzed for up to 8 chemistries, or one batch of twenty samples plus quality control samples to be analyzed for up to 5 chemistries, all in one sample schedule in completely unattended operation. If operated according to these conditions, samples are loaded at no more than 20 at a time.

The DA3500 comes standard with a 42-position sample tray.

“A Single Piece, Ergonomic Design”

The DA3500 does not require a “reagent rack” as the single piece integrated instrument design incorporates positions made specifically to hold reagents.

The DA3500 holds up to 24 reagents in standard reagent positions plus an extra 18 position on the sample tray can be used for reagents if needed. Standardized reagent volumes are 2 ml, 5 ml, 25 ml, and 160 ml.

The DA3500 was designed specifically for high precision trace analysis of environmental contaminants in aqueous solutions. High precision sacrifices speed.

While the DA3500 is capable of sampling rates at 140 tests per hour (discrete analyzer throughput is measured in tests per hour, not samples per hour), these rates imply single reagent, non – environmental, high analyte concentration tests. Also, the sampling rate of discrete analyzers is a function of the number of reagents per test; the more reagents per test the slower the throughput.

Since the DA3500 is a multi-chemistry selective analyzerit is capable of analyzing multiple tests all concurrently within a single run. This speeds throughput because the analyzer does not wait for one test to finish before continuing with the next. An accurate estimate of throughput, for most environmental tests, would be 40 – 60 tests per hour.

The DA3500blanks all samples. There is no value in not performing this very important function.

The DA3500 introduces the precisely measured sample aliquot into the cuvette without additional chemicals or deionized water.

“High Precision Analyzer”

The DA3500 makes all measurements within the optical cuvette. There are 140 optical heated reaction cuvettes for use in a single batch analysis. Sample blanking is performed on all samples and does not require “extra” time. These “blank” corrections are usually made after the addition of pH adjusting or complexing reagents to compensate for potential changes in color or turbidity that often occurs after the addition of these reagents.

The DA3500 uses two high precision displacement pumps to accurately measure and dispense sample and/or reagents at volumes between 2 and 900 micro-liters. The single arm/probe is heated internally to “speed” reactions and the probe is rinsed internally and externally after every liquid contact to eliminate cross contamination. A level detect mechanism built into the sample probe/arm indicates liquid level to the software that keeps track of sample and reagents volumes plus guarantees that the sampling probe does not immerse into solutions at depths too high to prevent adequate rinsing at the wash station. Optional sensors enable alarms that halt instrument operation if wash water becomes too low, or before waste solutions can over flow.

The DA3500 automatically goes into “standby” after a user-defined period of non – use conserving lamp life and saving power. The high quality optical detector measures within 1% accuracy.

The DA3500 uses individual disposable cuvettes per sample. The DA3500 does not wash these disposable cuvettes. This is because the DA3500 analyzes trace environmental contaminants and operates as a random selective analyzer. Cleaning a cuvette from one test runs the risk of cross contamination from the high level of analyte that exists in the reagentsfrom previous tests. For example, the nitrate test uses ammonium chloride and phosphoric acid as reagents for the test. If a nitrate test is followed immediately by either a phosphate test or ammonia test there will always be a risk that some of the previously used reagents will remain in the washed cuvette. Simply checking the optical purity of a washed cuvette does not guarantee that it is chemically clean.

“No Contamination or Carryover”

The following table illustrates the possibility of contamination that can occur if a previously used cuvette is used for other tests. Remember that the major components in the reagent will be present in large excess compared to the trace amounts sought in subsequent samples.

Also, remember that the following tests are often analyzed from the same sample solutions:

Chloride and Sulfate

Nitrite and Phosphate

Ammonia and Nitrate + Nitrite

TKN and Total Phosphate

Similar to the use of disposable Petri dishes in microbiology, it is safer and more cost effective to use disposable lab ware.

The DA3500 software evaluates each cuvette for optical defects and existing sample solutions from previous tests prior to each use. Optical purity is not equivalent to chemically clean; therefore, the DA3500 does not automatically wash cuvettes and recommends single use.

The DA3500 contains positions for 140 heated reaction cuvettes. Eight tests in a single batch of 10 samples with QC are possible with the 140 positions with enough places to spare for potential automated dilutions. Five tests in a single batch of 20 samples plus QC is possible with the 140 positions leaving enough places to spare for potential automated dilutions.

The DA3500 maintains heated reaction cuvettes at fixed user defined temperatures ranging from ambient to 50º C. The default temperature is 37º C and stability is +/- 0.2º C.

The DA3500 utilizes a diode array spectrophotometer with a fixed holographic grating. Use of a diode array ensures no movable parts (such as a filter wheel), there are no optical filters that can degrade over time, and there are 27 total wavelengthsso that the hardware always exists if future methods are added. A shutter (not a dark filter) provides the means for a “dark” reading. The linear range is limited to 2.0 AUFS to prevent users from making measurements on extremely dark sample solutions.

The minimum volume required is 180 micro-liters of combined sample and reagent. The maximum volume allowed is 900 micro-liters.

Detection modes are endpoint, differential, bichromatic, and kinetic. Calibration modes are single point, first, second, and third order fits, and weighted linear. ISE is optional.

The DA3500 verifies the optical integrity of all reaction segments prior to use. The software also includes the capability of detecting cuvettes that contain solution from preceding tests. Any cuvette that does not pass acceptance criteria will be automatically skipped. Operator intervention is required to replace cuvettes between batches. It is recommended the operator use this time to verify that wash reservoirs are full, waste containers are empty, and that analysis reagents are fresh. Overnight operation is of no difficulty. For example, a batch of 20 samples plus QC being analyzed for 5 tests each will consume just over 100 cuvettes and, depending on methods, could take up to 5 hours to complete. Once completed, the instrument will turn off the lamp to preserve its life. All of the reaction chemistry occurs in the reaction cuvettes where final absorbance measurement also is done. There are no flow cells. Calibration stability of the diode array along with the electronic detector and lamp control provided in the operating software guarantees calibrations stability over long periods of time. The fixed path length, absence of peristaltic pump tubing, and “through the side” absorbance reading in individual disposable cuvettes guarantees no baseline drift or reagent carryover.

Similar to disposable Petri dishes for microbiology analysis, it is more economical to use disposable sample cuvettes. Use of disposable cuvettes guarantees no carryover contamination from preceding tests.

“Open Chemistry Analyzer”

The DA3500 is an open chemistry multi-chemistry batch analyzer capable of analyzing aqueous solutions for just about any colorimetric or turbidimetric test.

The DA3500 operating software allows true unattended operation with minimal maintenance. The instrument can do pre run auto diagnostics, all method changeover, standard preparation, and dilutions automatically. Once a run is completed the power to the lamp is shut off conserving its life. Daily operation is limited to verification that wash bottles are full, placing samples and reagents, and cuvettes on the trays, preparing an analytical schedule and starting testing.