In daily work, many people refer to pure standard products as “fixed standards”. This designation can help us identify the standard as a pure type, and can also distinguish the physical state of the standard. But it is also easy for us to fall into a small “misunderstanding”, thinking that all pure-type standards are solid.
In the field of food and drug safety testing, most of the pure standard products we use are in solid form, but not all pure products are solid. In the fields of environment and chemical industry, there are more types of liquid pure products.
We cannot fully judge the state of matter of a pure product from its specifications. When the specification of a pure product is expressed in volume units (μL/mL, etc.), it is usually a liquid pure product; while the specifications expressed in mass units (μg/mg/g, etc.) are not necessarily all solid pure products. the physical properties of the compound itself. Below, I use Welch’s unique French A2S standard as an example for everyone.
Detailed example
1. Benzoic acid standard (00826-B054P01G)
Specifications are expressed in mass units, and are actually solid pure products.
The image on the left shows the basic information part of the certificate.
The image on the right shows the chemical information of the compound (benzoic acid).
This product is solid under recommended storage conditions.
In Figure 1, we can see from the left picture that this product is pure, the specification is expressed in mass unit (g), the detailed parameter is 1.02g ± 0.02% (uncertainty), and its characteristic value is expressed in purity. The parameters are 99.9±1%.
In the picture on the right, we can see that the melting point of benzoic acid is 121-125°C, and the physical state indicated on the certificate is solid. The recommended storage conditions for the certificate are (4±4°C, protected from light). Store in accordance with the recommended storage conditions of the certificate. The normal physical state of this product is a solid state.
2. Acrylonitrile Standard (00826-A016P05L)
Specifications are expressed in volume units, which are actually pure liquids
The image on the left shows the basic information part of the certificate.
The image on the right shows the chemical information of the compound (acrylonitrile).
This product is liquid under recommended storage conditions.
In Figure 2, we can see from the left picture that this product is pure, the specifications are expressed in volume units (mL), the detailed parameters are 5mL ± 0.04% (uncertainty), and its characteristic values are expressed in purity. is 99.0±1%.
In the picture on the right, we can see that the melting point of acrylonitrile is -83°C, and the physical state indicated on the certificate is liquid. The recommended storage conditions for the certificate are (4±4°C, protected from light). Store in accordance with the recommended storage conditions of the certificate. The normal physical state of this product is liquid.
3. Glutaraldehyde Standard (00826-G005P250)
Specifications are expressed in mass units, but they are actually pure liquids
The image on the left is the basic information part of the certificate
The image on the right shows the chemical information of the compound (glutaraldehyde).
This product is liquid under recommended storage conditions.
In Figure 3, we can see from the left picture that this product is pure, the specification is expressed in mass unit (mg), the detailed parameter is 253.81mg ± 0.02% (uncertainty), and its characteristic value is expressed in purity. The parameter is 94.5±1%.
In the picture on the right, we can see that the melting point of glutaraldehyde is -10°C, and the state of matter indicated on the certificate is liquid. The recommended storage conditions for the certificate are (4±4°C, protected from light). Store in accordance with the recommended storage conditions of the certificate. The normal physical state of this product is liquid.
In addition to solids and liquids, based on the physical properties of the compounds, some pure standards will also be in a semi-solid/semi-fluid state under normal circumstances.
So, don’t be surprised if the pure product you receive is not solid!
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