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Testing dissolved oxygen (DO) in water is either measured via chemical analysis such as a titrimetric method, electroanalytical (using galvanic & polarographic probes), optical dissolved oxygen, and colorimetric methods. However, modern techniques mainly use electrochemical or optical sensor methods.
测试水中的溶解氧 (DO) 可以通过化学分析（例如滴定法）、电分析（使用原电池和极谱探针）、光学溶解氧和比色法来测量。然而，现代技术主要使用电化学或光学传感器方法。
Oxygen is not only important in the air we breathe, but it is also an essential element in liquids like water which is why it is important to test dissolved oxygen (DO).
氧气不仅在我们呼吸的空气中很重要，而且也是水等液体中的重要元素，因此测试溶解氧 (DO) 很重要。
DO is the measurement of the number of free oxygen molecules in water. Measuring DO levels is an important indicator in industries such as water quality systems and aquatic ecosystems as oxygen is an essential chemical element for most forms of life.
DO 是水中游离氧分子数量的测量值。测量溶解氧水平是水质系统和水生生态系统等行业的重要指标，因为氧气是大多数生命形式的重要化学元素。
In this article we will look at why testing DO is so important and the best ways to measure DO levels in water.
在本文中，我们将探讨为什么测试溶解氧如此重要以及测量水中溶解氧水平的最佳方法。
DO is measured using a Dissolved Oxygen meter. The best time to measure DO in water is the same time every day, as concentrations can fluctuate throughout the day. DO is usually measured in milligrams per liter (mg/L) or percentage saturation (% sat), but sometimes it can be measured in parts per million (ppm), which allows measurement comparisons between sites that have different salinity and temperature values.
DO 使用溶解氧计测量。测量水中溶解氧的最佳时间是每天的同一时间，因为浓度可能会在一天中波动。 DO 通常以毫克每升 (mg/L) 或饱和度百分比 (% sat) 为单位进行测量，但有时也可以以百万分之一 (ppm) 为单位进行测量，这样可以在具有不同盐度和温度值的地点之间进行测量比较。
We can test DO in water through the following methods: titrimetric, electroanalytical (galvanic & polarographic probes), optical dissolved oxygen, and colorimetric.
我们可以通过以下方法测试水中的溶解氧：滴定法、电分析（原电池和极谱探针）、光学溶解氧和比色法。
Titrations use one liquid where the concentration is already determined (titrant), to identify the concentration of another (your sample).
滴定使用浓度已确定的一种液体（滴定剂）来确定另一种液体（您的样品）的浓度。
Iodemtry titrations use iodine as an indicator; the iodine indicator will either appear or disappear at the end of the titration. Titrations for testing DO in water are known as the “Winkler Method”. The Winkler Method gives you a “one-time measurement” of the sample being tested.
碘滴定法使用碘作为指示剂；滴定结束时碘指示剂会出现或消失。测试水中溶解氧的滴定法称为“Winkler 方法”。温克勒方法为您提供被测样品的“一次性测量”。
When using the Winkler Method, water samples are collected, fixed, and titrated in the field or a laboratory setting. As atmospheric contact and agitation can shift DO levels, you must fix the sample with the reagents immediately. Titration methods use a specialized bottle (BOD bottle) that seals without trapping air inside. Usually, all reagents come pre-measured to make it easier and increase accuracy in testing DO in water. To get an accurate DO reading, ensure the titrant solution is proportional to the sample you are testing.
使用温克勒方法时，需要在现场或实验室环境中收集、固定和滴定水样。由于大气接触和搅拌可能会改变溶解氧水平，因此您必须立即用试剂固定样品。滴定方法使用特殊的瓶子（BOD 瓶），该瓶子密封且内部不会残留空气。通常，所有试剂都会预先测量，以便更轻松地测试水中的溶解氧并提高其准确性。为了获得准确的 DO 读数，请确保滴定剂溶液与您正在测试的样品成比例。
The Winkler Method is still commonly used to test DO in water, however, there are some concerns with inaccuracies, possible sample contaminants/interferences, and human error. That is why new technologies have created easier and more accurate ways to test DO in water.
温克勒方法仍然常用于测试水中的溶解氧，但是，存在一些关于不准确、可能的样品污染物/干扰以及人为错误的担忧。这就是为什么新技术创造了更简单、更准确的方法来测试水中的溶解氧。
If you are testing in the lab or the field, this is probably the easiest way to test DO in water. Electroanalytical or electrochemical dissolved oxygen sensors are also known as amperometric or Clark-type Sensors.
如果您在实验室或现场进行测试，这可能是测试水中溶解氧的最简单方法。电分析或电化学溶解氧传感器也称为电流传感器或克拉克型传感器。
There are two types of electroanalytical sensors: galvanic and polarographic probes. The probes work off redox (oxidation-reduction) reactions, providing continuous and live measurements. As both probes have an applied voltage, they require a “warm-up time” before use to polarize the electrodes before measuring the DO in water.
电分析传感器有两种类型：原电池探针和极谱探针。探头通过氧化还原反应进行工作，提供连续、实时的测量。由于两个探头都有外加电压，因此在使用前需要一段“预热时间”来极化电极，然后再测量水中的溶解氧。
Galvanic Probes/Sensors 电流探头/传感器
These are membrane probes that have two parts that produce a voltage, acting as a battery (the metals have different electrode potentials). A thin semi-permeable membrane inside the cap of the electrode allows gasses to pass through and block anything else. When oxygen diffuses across the membrane, it dissolves into the probe cap that contains a buffered electrolyte. This allows the oxygen to react with the cathode (usually silver) in the electrode, gaining an electron. The electron given to the oxygen molecule comes from the anode (usually zinc or lead) in the electrode, creating a voltage between the anode and cathode in the probe. It is when this current is formed the meter can convert the reading taken from the probe into a DO concentration value.
这些是膜探针，有两个产生电压的部分，充当电池（金属具有不同的电极电位）。电极帽内的薄半透膜允许气体通过并阻挡其他任何物质。当氧气扩散穿过膜时，它会溶解到含有缓冲电解质的探头帽中。这使得氧气与电极中的阴极（通常是银）发生反应，获得电子。给予氧分子的电子来自电极中的阳极（通常是锌或铅），在探针的阳极和阴极之间产生电压。当该电流形成时，仪表可以将从探头获取的读数转换为溶解氧浓度值。
Because of self-polarization, these sensors do not require a warm-up time.
由于自极化，这些传感器不需要预热时间。
Polarographic Probes/Sensors
极谱探头/传感器
These work slightly differently from galvanic probes, but, polarographic probes also contain a thin semi-permeable membrane allowing oxygen into an unbuffered electrolyte. However, instead of acting like a battery, a voltage is applied between the silver anode and gold cathode in the probe. The voltage acts as a catalyst driving an oxygen reaction. When oxygen hits the cathode, an electron is added creating a current, determining the DO concentration.
它们的工作原理与原电池探针略有不同，但是极谱探针还包含一层薄的半透膜，允许氧气进入未缓冲的电解质。然而，它的作用并不像电池，而是在探针的银阳极和金阴极之间施加电压。电压充当驱动氧反应的催化剂。当氧气撞击阴极时，会添加一个电子，产生电流，从而确定溶解氧浓度。
Polarographic probes can be separated further into steady-state and rapid-pulsing sensors.
极谱探针可以进一步分为稳态传感器和快速脉冲传感器。
Steady-state sensors allow you to measure DO in water without having to stir the sample. When using a Rapid-pulsing sensor, there is also no need to stir the sample, but it contains a third silver electrode as these sensors turn on and off every few seconds to allow the DO to replenish on the cathode surface when it reaches the membrane. Both still utilize a cathode and anode and measure DO by creating a constant voltage to polarize the electrons.
稳态传感器使您无需搅拌样品即可测量水中的溶解氧。使用快速脉冲传感器时，也无需搅拌样品，但它包含第三个银电极，因为这些传感器每隔几秒就会打开和关闭，以便 DO 在到达膜时在阴极表面补充。两者仍然使用阴极和阳极，并通过产生恒定电压使电子极化来测量溶解氧。
This method also uses a probe with a semi-permeable membrane to test DO in water, but the probe and meter monitor luminescence instead of monitoring a reaction. Sometimes these DO meters are called fluorescent sensors. However, this is technically incorrect as the probes emit blue light not UV (ultraviolet) light.
该方法还使用带有半透膜的探针来测试水中的溶解氧，但探针和仪表监测发光而不是监测反应。有时这些溶解氧测量仪被称为荧光传感器。然而，这在技术上是不正确的，因为探头发射蓝光而不是紫外光。
The probe emits the blue light that excites (electrons gain energy) light-sensitive material inside the probe cap. When it becomes relaxed (reaches its normal energy state) it emits a red light that is measured as it hits the light sensor inside the probe; the red light is reflected by the dye. If DO is present in water, it suppresses the red light as wavelengths are limited/altered. The frequency, intensity, and decay of the red light are dependent on the amount of DO in the water.
探头发出蓝光，激发（电子获得能量）探头帽内的光敏材料。当它变得放松（达到正常能量状态）时，它会发出红光，当它撞击探头内部的光传感器时，就会测量到红光；红光被染料反射。如果水中存在溶解氧，它会因为波长受到限制/改变而抑制红光。红光的频率、强度和衰减取决于水中溶解氧的量。
While optical dissolved oxygen probes provide a continuous measurement of DO, they can be affected by humidity.
虽然光学溶解氧探头可以连续测量溶解氧，但它们可能会受到湿度的影响。
This method measures color and comes in two variations: Indigo Carmine and the Rhodazine D method. Chemical reagents are added that react with DO in the sample to display a particular color. The chemical reagents used are similar to the modern Winkler Method. How intense the color is, is proportional to how much DO is in the sample.
该方法测量颜色并有两种变体：靛蓝胭脂红和罗达嗪 D 方法。添加的化学试剂与样品中的 DO 发生反应，显示特定的颜色。使用的化学试剂与现代温克勒方法类似。颜色的深浅与样品中溶解氧的含量成正比。
Indigo Carmine is used for measuring DO concentrations between 0.2 and 15 ppm, whereas Rhodazine D is used to measure much lower DO concentrations (ppb).
靛蓝胭脂红用于测量 0.2 至 15 ppm 之间的 DO 浓度，而罗达嗪 D 用于测量低得多的 DO 浓度 (ppb)。
Indigo Carmine produces a blue color where the intensity is proportional to the DO concentration. If using this method, keep reagents away from bright lighting, as this can deteriorate the Indigo Carmine. This method is not affected by salinity, temperature, or dissolved gases, but ferric iron, and nitrate and sodium sulfate can. Results are obtained between 30 seconds (low-range tests) and 2-minutes (high-range tests).
靛蓝胭脂红产生蓝色，其强度与溶解氧浓度成正比。如果使用此方法，请将试剂远离强光，因为这可能会使靛蓝胭脂红变质。该方法不受盐度、温度或溶解气体的影响，但三价铁、硝酸盐和硫酸钠可以。结果在 30 秒（低范围测试）和 2 分钟（高范围测试）之间获得。
Rhodazine D reagents react with DO, producing a rose-colored or pink solution. Oxidizing agents (chlorine, cupric copper, and ferric iron) can interfere with results creating higher DO readings, however, this method is not affected by salinity or sulfide that are usually present in water samples. As this method is time-dependent, ensure you analyze the water sample within 30 seconds of adding the reagent.
Rhodazine D试剂与 DO 反应，产生玫瑰色或粉红色溶液。氧化剂（氯、铜和三价铁）可能会干扰产生较高 DO 读数的结果，但是，该方法不受水样中通常存在的盐度或硫化物的影响。由于该方法具有时间依赖性，因此请确保在添加试剂后 30 秒内分析水样。
Either a spectrophotometer, colorimeter, or simple comparator can be used to measure DO in water using the colorimetric method.
分光光度计、比色计或简单的比较器都可用于使用比色法测量水中的溶解氧。
Testing DO in water depends on the industry. For example, you may need to test DO when brewing beer or measure the dissolved oxygen in wastewater.
水中溶解氧的测试取决于行业。例如，您可能需要在酿造啤酒时测试 DO或测量废水中的溶解氧。
Dissolved oxygen is an essential parameter in monitoring water quality and a key indicator of healthy aquatic ecosystems. Low DO levels in water are problematic for most aquatic life, often creating dead zones where aquatic life dies off.
溶解氧是监测水质的重要参数，也是健康水生生态系统的关键指标。水中溶解氧含量低对大多数水生生物来说都是一个问题，通常会产生导致水生生物死亡的死区。
In wastewater treatments, testing DO levels in water helps us understand the biodegradable organic matter and the biological oxygen demand (BOD). Both these tests indicate general water quality.
在废水处理中，测试水中的溶解氧水平有助于我们了解可生物降解的有机物和生物需氧量 (BOD)。这两项测试都表明了一般水质。
Alternatively, too much oxygen in water can also be harmful, this is known as supersaturated oxygen. DO in water originates from the atmosphere and photosynthesis, which can be affected by temperature, salinity, and atmospheric pressure.
另外，水中过多的氧气也可能有害，这被称为过饱和氧。水中的溶解氧来源于大气和光合作用，受温度、盐度和大气压力的影响。
DO concentrations are affected by temperature, salinity, pressure, and humidity, so you will need to take this into account when testing DO.
DO 浓度受温度、盐度、压力和湿度的影响，因此在测试 DO 时需要考虑到这一点。
Temperature is one of the biggest, if not the most, common factors that directly affects DO in water. Colder water contains more oxygen than warmer water, as particle motion decreases. As particles get more excited and bounce around more, they collide and break the bonds that hold them together.
温度是直接影响水中溶解氧的最大（即使不是最常见的）因素之一。由于粒子运动减少，较冷的水比较热的水含有更多的氧气。随着粒子变得更加兴奋并反弹得更多，它们会发生碰撞并破坏将它们结合在一起的键。
Therefore, the lower the DO, the higher the temperature, and inversely the DO concentration increases as temperature decreases.
因此，DO越低，温度越高，并且相反，DO浓度随着温度降低而增加。
Salinity can also affect how much DO is in water. Freshwater contains more oxygen than saltwater because of the charge a salt molecule carries. Salt molecules are attracted to water molecules and easily dissolved in water. If salt is present, oxygen cannot attract to water molecules, therefore as salinity levels increase in a solution, DO decreases.
盐度也会影响水中溶解氧的含量。由于盐分子带有电荷，淡水比盐水含有更多的氧气。盐分子被水分子吸引，很容易溶解在水中。如果存在盐，氧气无法吸引水分子，因此随着溶液中盐度水平的增加，溶解氧会减少。
When we talk about pressure and DO, we are referring to atmospheric pressure. As atmospheric pressure decreases, the partial pressure of oxygen also decreases, therefore, the concentration of DO increases. So, as altitude or atmospheric pressure increases, the number of DO molecules absorbed in water decreases as there is less pressure forcing the oxygen to be diffused in the water, increasing the partial pressure of oxygen.
当我们谈论压力和溶解氧时，我们指的是大气压力。随着大气压力降低，氧分压也降低，因此，DO的浓度增加。因此，随着海拔或大气压力的增加，水中吸收的 DO 分子数量会减少，因为压力较小，迫使氧气在水中扩散，从而增加了氧分压。
Water vapor or humidity is another factor that is often not thought about, yet it has major implications for DO concentrations, and can also affect the calibration of some DO meters.
水蒸气或湿度是另一个经常被忽视的因素，但它对溶解氧浓度有重大影响，并且还会影响某些溶解氧测量仪的校准。
When humidity levels increase, the partial pressure of oxygen increases, which also increases the level of DO.
Now that you have an understanding of testing DO in water and why it is important, you may be thinking which equipment is best for testing. First, you need to think about accessibility, will you need a portable meter or will a bench top meter work better for you?
Depending on where you wish to test DO in water, there are two types used: portable meters or benchtop meters.
Portable meters provide flexibility to test wherever you want while still receiving high-level accurate readings.
They either use the colorimetric method, optical DO probe, or the electroanalytical method using galvanic or polarographic probes. Choosing which portable meter you need depends on the sample being measured, the level of accuracy you require, and your personal preference. Some portable meters can test more water parameters than DO so always do your research beforehand to get the right meter for you.
When it comes to electrochemical sensing and measuring DO in water, it can get confusing, which is why we offer a variety of meters to meet your testing needs. Whether you are measuring a simple sample or are working with a PLC, we have you covered when it comes to dissolved oxygen probes. All our portable meters allow you to take highly accurate and interference-free readings of DO in water.
Benchtop meters also come in a variety of types meeting your testing requirements. One thing you need to consider with benchtop meters is space. Some benchtop meters can take up more space than electroanalytical probes. However, there are some benchtop meters that have a “zero-footprint” allowing you to mount them to a wall.
Dissolved oxygen is an important characteristic of water quality in many industries (hydroponics, food and beverage industries, aquariums, environmental sampling, wastewater, etc.).
Testing dissolved oxygen in water is either measured via chemical analysis such as a titrimetric method, electroanalytical (using galvanic & polarographic probes), optical dissolved oxygen, and colorimetric methods. However, modern techniques mainly use electrochemical probes.
If you would like to learn more about other water quality measurements, characteristics, or applications for DO, do not hesitate to contact our world-class team at Atlas Scientific.
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