Environmental Science

You line up your samples in a row. You then add a reagent and somehow mix the reagent and sample. You do this for each sample.

Is there color or turbidity in the samples? Instead of lining up samples, you are pouring aliquots into sample cups that are placed on an auto sampler tray. Instead of transferring a known amount of sample to a cuvette, the discrete analyzer does. Instead of adding reagents and mixing, the discrete analyzer does. Instead of starting a timer, the discrete analyzer does.

The discrete analyzer pipettes, dilutes, adds reagents, mixes, calibrates, measures, calculates, and reports all for you. Drift is common in flow analyzers because the peristaltic pump tubing delivers reagents by proportion. The discrete analyzer delivers the exact amount of sample and reagent every time. The discrete analyzer has a fixed path length if the discrete analyzer does not transfer color-developed sample to another cuvette, or flow cell, for measurement.

As mentioned previously, daily calibration is required for continuous flow methods because flow methods proportion the reagents and sample using a peristaltic pump. Those pump tubes are changing with time changing the relative proportion of sample and reagents. Many methods written for manual spectrometers merely say, “analyze a check standard with each sample set”.

A manual method uses more reagent and sample volume because we, as humans, cannot work easily with small volumes. A flow system uses more reagent than a discrete analyzer because a flow instrument is continuously pumping reagent through the system.

Discrete analyzers that measure the sample absorbance within the same container that the reaction occurred generate less waste than instruments that wash the vessel, or use a flow cell. In fact, adequately rinsing a flow cell requires significant rinsing between samples making the waste volume generated essentially equivalent to that of a micro-flow Segmented Flow Analyzer, or Low Flow Flow Injection Analyzer.

The discrete analyzer uses significantly less reagent, and generates significantly less waste than manual methods.

The discrete analyzer measuring the absorbance of a color reacted sample contained in individual cuvettes.

A discrete analyzer dispenses, reacts, incubates, and measures all within the reaction cuvette without transferring to a flow cell. Analyzers that transfer to a flow cell are not “true” discrete analyzers, but instead, are hybrids between flow and discrete.

All discrete analyzers have reaction segments. Some analyzers do chemical reactions in a cuvette segment and then transfer the reacted sample to a flow cell. This type of analyzer is a hybrid of discrete and flow, and not a true discrete analyzer. A true discrete analyzer reacts and measures the sample within the optical cuvette. Some analyzers wash the optical cuvette between tests. Other discrete analyzers utilize disposable optical quality cuvettes.

This residual contamination can come from preceding samples, or more likely, from the reagents used in processing the preceding samples.

Analyzers that use a flow cell still react samples in some sort of cuvette. If the discrete analyzer has 100 sample positions and 200 reaction cuvettes, then the analyzer can run 100 samples for 2 tests each. The discrete analyzer with the flow cell must rinse the flow cell between each sample, and rinse vigorously between each test. Consider that a two-channel flow analyzer can analyze 100 samples for two tests each in less than half the time as a discrete analyzer with a flow cell. Also, consider that the flow analyzer generates no more waste than the discrete analyzer with a flow cell. If the required testing is a lot of samples for one or two tests it makes more sense to use a flow analyzer.

Reagents can interfere as cross contamination between samples. The discrete analyzer easily and rapidly analyzes multiple tests on single sample solutions. Only disposable individually contained reactions ensure that there is no interaction between samples or tests.

If not, you will at least rinse it in between samples, and possibly with sample prior to transferring your sample aliquot to the sample container. This is to avoid carryover between samples. A flow analyzer uses an auto sampler.

A discrete analyzer also uses a probe; however, it operates differently than flow analyzers. A discrete analyzer’s level detect mechanism ensures that the probe immerses into the sample or reagents no further than necessary to withdraw the required sample aliquot. The probe then washes itself on the outside at the wash station and pushes the sample or reagent out into the sample cuvette. A flow analyzer does not know. A flow analyzer could end up aspirating from empty sample cups or empty reagent bottles all night long and think it is still running samples. A discrete analyzer with level detection prevents this. The discrete software calculates the volume of reagents and samples based on the height of liquid. The software continuously monitors sample and reagent volumes and will not continue the test when it detects that reagents or samples have “run out”.

The sampling depth on a flow analyzer is usually adjustable by the user and is usually towards the bottom of the sample vial. On a discrete analyzer, the depth the probe immerses in a sample solution is a result of programming or instrument design. The depth sampled on the OI Discrete analyzer is determined by the level detect mechanism and the sample aliquot required for the test. A flow analyzer would not as readily detect this loss or gain because it samples from the bottom of the sample cup.

A discrete analyzer reacts sample in a heated cup that is open to allow the probe to dispense samples and reagents. Since discrete analyzer reactions are occurring in individually contained cuvettes, the time delay between reagent additions on discrete analyzers is limited only by software. Unless you have an added auto-dilutor attached to your flow analyzer, you will still be diluting standards and over calibration samples. Auto-dilution is an integral function of a discrete analyzer. The dilutions can be preset during sample table entry if you know that the samples need to be diluted.

The discrete analyzer method is selected by mouse click when scheduling analyses on the sample tray.

Think of those short holding time samples.

If everything is to run on the discrete analyzer, then collect your samples in a vial that fits on the discrete analyzer. Discrete analyzers are very simple to use requiring minimal software training.

Discrete Analyzers in the Environmental Laboratory

What China can learn from Switzerland’s political situation

While Switzerland may not be perfect in this area, China could emulate the Swiss government’s commitment to fighting corruption. This regime is still currently running the government. Many individuals in China are suffering as the country has been marred by protests against the government. The Chinese government needs to change the way they operate by instituting true democracy.

• Swiss people’s party
• Christian Democratic people’s party
• Social Democratic party
• Free Democratic party

In relation to the Tibetan crisis, the Chinese government could borrow a leaf from Switzerland.

What China can learn from Switzerland’s economic situation

The reason why these inequalities arose was that unlike the Swiss government, the Chinese governed has a direct approach to controlling the country’s economy. China can adopt the Swiss government’s approach to economic governance. (Economy watch, 2008) The Swiss government rarely makes abrupt policy changes that would destabilize the entire macro-economic system.

What China can learn from Switzerland’s social situation

In terms of China’s social system, there are a number of pointers that China could borrow from Switzerland. For instance, they ought to relax government control in religion.; Time and time again, the Chinese government has been accused by international media and local critics of its excessive religious control. The Chinese government seems to be operating in fear of religious leaders claiming that these leaders can destabilize the government or even overthrow it. This example illustrates just how much the Swiss government is committed to religious freedom.

The Chinese government can also learn from such an experience by creating systems that enhance racial or religious accountability.

What China can learn from Switzerland’s environmental situation

China could learn from the Swiss environmental laws because the latter government has carbon limits for various emitting sources. The Swiss government has been very keen on this and their approach could serve as lesson to the Chinese government in the future. Socially, China can learn from Switzerland by curbing religious discrimination. Economically, China can learn from Switzerland by separating politics from the economy as is the case today in China. Lastly, the Chinese government ought to be more vigilant about its environmental polices like their counterparts in Switzerland.