Water is a laboratory
very much
Important but yet
easy
Neglected reagents. In the process of automatic biochemical analyzer detection, pure water is used as a carrier or medium for biochemical reactions, a diluent or solvent for samples or reagents, and a cleaning solution for the instrument.
as well as
Reaction participation
Reagent
Throughout the whole process of testing,
Purification quality
The level is directly related to the credibility of the test results. Currently
domestic
most
Laboratory of Laboratory
Use reverse osmosis central pure water system
. Ruifeng
Through the analysis of the workflow of the system and the actual situation encountered, we found and summarized several types of water purity.
the reason
And its impact on the detection of automatic biochemical analyzers.
1 Pure water system workflow and influencing factors
1.1 Raw water pretreatment
Raw water refers to tap water entering the laboratory. Pretreatment is to remove most of the impurities in tap water.
1.1.1 Method: Pretreatment is generally used
Pre-filter component package
,
Usually contains the following
:
1
Deep filtration
The filter element filters large particles such as sediment in the raw water;
2
Activated carbon filter removes most of the organic matter in water by adsorption
,
Especially the residual chlorine in tap water;
3 softener filter to reduce the concentration of calcium and magnesium ions in water, reducing the hardness of water. If the tap water hardness is low, the softener filter may not be installed.
1.1.2 Influencing factors:
1
Water quality of tap water: When the content of impurities in tap water is high, the service life of pretreatment parts will be shortened and the water quality will not reach the standard after treatment, and even the pipeline will be blocked. Generally, the solid dissolved content (TDS) in tap water is less than
10
00
Ppm
.
2
Pretreatment component life:
Deep filtration
Filter element, activated carbon filter,
Softener filter
Waiting for
use
Lifetime material,
they
The reverse osmosis membrane has a protective effect, and if they fail, the RO membrane load will be aggravated and the life will be shortened.
Specific service life
Should be based on the water quality of tap water
Reasonable setting
.
1.2 Reverse osmosis membrane (RO) treatment
Reverse osmosis membrane (RO)
Mass
Remove water
ion
with
Other impurities
.
The removal capacity can usually be greater than 95%.
1.2.1 Influencing factors
1
Inlet water pressure: general pure water system
Reverse osmosis membrane
It is necessary to use a high pressure pump to maintain a certain inlet pressure to maintain normal operation. When the pump pressure is insufficient, the water production will decrease.
2
Maintenance of pure water system: Pure water system generally has automatic backwashing function. When the setting is unreasonable or faulty and the manual maintenance is not proper, it will affect the normal operation of the pure water machine, resulting in purification efficiency and water quality.
1.
3
Preparation of deionized water
The water treated by the RO membrane can only reach the third grade pure water (resistivity >0. 2M
Ω·
Cm) standard. Third-grade pure water has removed most of it
Impurity
But among them
Impurity and other impurities
The concentration is still high, which will affect the micro-detection of the biochemical analyzer. Therefore, the third-stage pure water must be further deionized to reach the first-order pure water (resistivity ≥lOMΩ).
·
The standard of cm) can be used for biochemical testing.
1.
3
.1 method: ion exchange resin method is
pure
A common method for water preparation, the components used are ion exchange purification columns (tanks), including anion exchange column, cation exchange column and mixing column, etc., and the reagent is an anion exchange resin. The anion-cation exchange resin is generally a polymer formed by polymerizing styrene and then crosslinking the divinylbenzene to obtain a porous network skeleton structure, and then connecting the active group to the skeleton. The reactive group to which the ion exchange resin is attached can be classified into two major types of an acidic group and a basic group. The ion exchange resin to which the acidic group is attached is referred to as a cation exchange resin, and the resin to which the basic group is attached is referred to as an anion exchange resin.
1.2.2 Principle:
1
The principle of cation exchange column is the principle of hard water softening: the acidic group in the cation exchange resin has a sulfonic acid group (-S0)
3
H), carboxyl (a COOH) and phenol (-C
6
H
4
0H) An acidic group in which a hydrogen ion can be exchanged with a metal ion or other cation in a solution.
2
Principle of anion exchange column: the basic group in the anion exchange resin has a season
ammonia
Base [-N (CH
3
)
3
0H],
ammonia
Base (-NH
2
) and Asia
ammonia
base(
=
NH) and so on. They produce OH- ions in water and can exchange with various anions.
3
Mixing column: when the two are used in series or in combination, the product is only water
.
1.2.3 Influencing factors:
1
Quality of ion exchange resin: ion exchange resin is available
use
Life limit, when the ion exchange reaches a certain amount, it reaches saturation and needs to be regenerated. Therefore, the better the quality, the longer the service life is.
2
The connection mode of anion-cation exchange resin: double bed type: several cation exchange columns and several anion exchange columns are connected in series, and the yang is in the front yin, the advantage is that the regeneration is convenient, and the disadvantage is that the effluent quality is not high (single-stage complex) Bed type water discharge resistivity is only 0.5 MΩ
·
Cm, two-stage double bed type water resistivity 2 M
Ω
· cm). Mixed bed type: The cationic resin and the anion resin are uniformly mixed into the same exchange column at a volume ratio of 1:2. The advantage is that the purity of the effluent is high (resistivity ≥1 OMΩ.cm), and the disadvantage is that regeneration is difficult. Combined type: the combination of the double bed type and the mixed bed type is completed, and the water quality is high (the resistivity is up to 18.3 MΩ.cm, that is, ultrapure water), and the service life is long.
3
Purity of tertiary pure water: When the quality of the third-grade pure water is unqualified, some of the non-ionic impurities will pass through the ion exchange column, which will affect the service life of the ion exchange column and cause the water quality to decrease. Some open pure water systems store the third-grade pure water in the water tank for other purposes. The storage time is too long or the secondary pollution caused by other reasons will also reduce the water purity.
2.1 Impurity components in unqualified pure water
The failure of pure water quality means the failure of pure water system purification, which may occur in the raw water pretreatment process.
Reverse osmosis process,
Ion exchange process
with
Any step in pure water storage. No matter which step fails, the source of impurities is nothing more than the pollutants in the water channel of the tap water and the pure water machine. The main ones are:
1
ion
Commonly there are H+, Na+, K+, NH
4
+,Mg
2
+,Ca
2
+,Fe
3
+,Cu
2
+, Mn
2
+,Zn
2
+,Al
3
+etc.cation and F-,CI-,N0
3
-, HC0
3
-,S0
4
2
-, P0
4
3
-, H
2
P0
4
-,HSi0
3
- anion;
2
Organic substances such as pesticides, hydrocarbons, alcohols and esters;
3
particulates
Such as rust and sediment in the water pipe
;
4
microorganism;
5
Dissolved gas (Nz, 02, C1
2
, H
2
S, CO, CO
2
, CH4, etc.)
.
2.2 Influence of different impurity components on biochemical analyzer and test results
2.2.1
ion
High content impact:
1
The most direct effect is the increase in the determination of the same ion in serum (slurry), such as the determination of Mg2+, Ca2+, Fe3+, Cu2+, Zn2+, etc., and also affect the calibration of these items.
;
2
Because many metal ions are supplemented by enzymes
Enzyme
Factor, so when the metal ion content is high, it often affects the detection of enzyme activity (such as Mg2+ is an activator of various phosphorylation kinases, when the water content exceeds the standard, it will lead to the increase of these enzyme activity values; and many heavy metal ions are for the enzyme Inhibition, resulting in decreased enzyme activity)
;
3
Many anions also act as cofactors for enzymes, affecting the determination of enzyme activity (eg CI-pair)
α
-Amylase has an activation effect)
;
4
ion
High-content water is more likely to form crystals and cause organic matter such as proteins to be denatured and attached to the piping system, which makes the biochemical analyzer piping system more likely to clog, eventually causing distortion or failure of the measurement; at the same time, it is difficult to clean the reaction cup when using it. Cleaning it will accelerate the aging and damage of the cuvette and increase the blank of the cup.
2.2.2 Effects of organic substances: The influence of organic substances mainly lies in the increase of the results of the determination of similar substances when measuring similar substances. At the same time, an increase in the organic content will also accelerate the cleaning and aging of the piping system and the reaction cup.
2.2.3 Effects of particulate matter: It is generally difficult for particulate matter to enter the biochemical analyzer pipeline and reaction system through the pure water system. The source is generally secondary pollution of the storage tank, but it is easy to increase the absorbance once it enters. Block the pipe and damage the reaction cup.
2.2.4 Effects of microorganisms: The removal of microorganisms mainly depends on the pretreatment of raw water. Some pure water systems also add ultraviolet sterilization or microfiltration and ultrafiltration devices to the ultrapure water to further remove residual bacteria, particles and heat sources in the water. Wait. However, once the pretreatment fails or the pure water storage tank is re-contaminated, the microorganisms and their products can enter the biochemical analyzer piping system and the reaction system. There are two possible situations:
1
Microorganisms in the pipeline and reaction system, causing blockage of the pipeline, while increasing the absorbance and cup blank;
2
Microbial production of specific enzymes has an impact on the biochemical analyzer enzyme assay, and the specific effect depends on the type of contaminating bacteria.
2.2.5 Dissolved gases: The effects of increased dissolved gases are:
1
The effect on the determination of the same gas;
2
Also affects the pH of the water, such as C0
2
,Cl
2
, H
2
The increase in S and other dissolution leads to a decrease in the pH of the water, and also affects the determination of biochemical items with a strong pH dependence;
3
Certain gases such as C1
2
Increased, due to its strong oxidative properties, will affect the biochemical measurement items related to redox reactions, such as the determination of ALT, AST, BUN, etc. based on the absorption peaks of NADH and NADPH at 340 nm, Lead to an increase in the measured value.
2.2.6 Impact of other impurities: Some pure water systems also store the ultra-pure water or the first-stage pure water finally produced in the water tank. When the water tank is rusted, the iron is not measured properly.
, usually in the pressure tank
There is also an increase in the TG measurement result when the oil leakage caused by the mechanical device is not tightly sealed. Although these conditions are rare, they are also the most easily overlooked.
3 Discussion
3.1 There are two types of automated pure water systems commonly used in laboratories:
1
Large distiller system, the sunrise water volume is about 100 L, the raw water utilization rate is 10%-15%, the energy consumption is large, the degree of automation is low, the purity of the prepared distilled water is generally low, and the scope of application is narrow, and now it has been basically eliminated.
.
2
Reverse osmosis central pure water system consisting of mechanical filtration, activated carbon adsorption, reverse osmosis membrane and ion exchange resin, etc.
5
00 L or so, raw water utilization rate of 30% -40%, high degree of automation, low energy consumption, the main components can be used repeatedly, the purity of the effluent is high, and it is widely used at present. In addition, some laboratories directly purchase commercial purified water due to limited conditions, but commercial purified water is mostly drinking water, and its standards are different from laboratory water standards.
Very easy
Influencing the detection.
3.2 Common indicators for evaluating water quality
1
Resistivity is a measure of the conductivity of laboratory water. It increases with the decrease of inorganic ions in water. However, due to the dissociation of water itself, the resistivity can only reach 18.
2
MΩ.cm or so is the main indicator for detecting the ion concentration in water;
2
Total organic carbon refers to the concentration of carbon in water, reflecting the content of organic compounds in water;
3 particles, reflecting the concentration of particulate matter in the water;
4 pyrogen
,
Usually
Cell wall of Gram-negative bacteria
metabolite
.
3.3
Suggest
1
Strictly standard quality control of laboratory ultrapure water, regular measurement of pure water resistivity and other indicators,
Print water quality reports regularly
.
2
Enhance laboratory water quality awareness and actively prevent the impact and loss caused by water use.
3
The water for the open water storage tank should be strictly controlled to prevent secondary pollution caused by this.
4
It is necessary to master the service life and maintenance methods of the components of the pure water machine, and actively prevent various water quality changes caused by the failure of the pure water machine components, and at the same time extend or guarantee the life of the RO membrane and the ion exchange resin.
5
To understand the water quality of the region and assess its impact on pure water machines
The life can be increased by installing a large pretreatment device.
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