Purity Test - Carboxyl / Alfa Chemistry

Purity Grade

Most laboratory chemicals are labelled with a grade which generally indicates the purity of the chemical. There are many different standards used in grading. Common chemical grades in order of purity (highest to lowest) are listed below:

Purity Grade

In addition, chemical purity grades sorted by use are summarized as follow:

No.	Purity Grade	Abbr.	No.	Purity Grade	Abbr.
1	Guaranteed reagent	GR	28	For scintillation	Scint
2	Analytical reagent	AR	29	For electrophoresis use
3	Chemical pure	CP	30	For refractive index	RI
4	Laboratory reagent	LR	31	Developer
5	Pure	Pur	32	Indicator	Ind
6	Extra pure	EP	33	Complexon indicator	Complex ind
7	Purissimum	Puriss	34	Fluorescene indicator	Fluor ind
8	Ultra pure	UP	35	Redox indicator	Redox ind
9	Purified	Purif	36	Adsorption indicator	Adsorb ind
10	Ultra violet pure	UV	37	Primary reagent	PT
11	Spectrum pure	SP	38	Spectrographic standard substance	SSS
12	Scintillation pure		39	Atomic adsorption spectorm	AAS
13	Research grade		40	Infrared adsorption spectrum	IR
14	Biochemical	BC	41	Nuclear magnetic resonance spectrum	NMR
15	Biological reagent	BR	42	Organic analytical reagent	OAS
16	Biological stain	BS	43	Micro analytical reagent	MAR
17	For biological purpose	FBP	44	Micro analytical standard	MAS
18	For tissue medium purpose		45	Spot-test reagent	STR
19	For microbiological	FMB	46	Gas chromatography	GC
20	For microscopic purpose	FMP	47	Liquid chromatography	LC
21	For electron microscopy		48	High performance liquid chromatography	HPLC
22	For lens blooming	FLB	49	Gas liquid chromatography	GLC
23	Technical grade	Tech	50	Gas solid chromatography	GSC
24	Pratical use	Pract	51	Thin layer chromatography	TLC
25	Pro analysis	PA	52	Gel permeation chromatography	GPC
26	Super special grade	SSG	53	For chromatography purpose	FCP
27	For synthesis	FS

Test Methods and Equipment

According to customers’ requirements and relevant standards, Alfa Chemistry offers purity tests by various testing methods:

Chemical Testing Method

Potentiometric titration

Potentiometric titration belongs to chemical methods of analysis which is done via the usage of two electrodes – an indicator electrode and a reference electrode. One half-cell is formed with the indicator electrode and the ions of the analyte, which is generally an electrolyte solution. The other half-cell is formed by the reference electrode (see Fig.1).

Fig. 1 Potentiometric titrator

The course of the potentiometric titration curve provides information not only about the titration end point position, but also the position and shape of the curve may provide data about the processes accompanying the titration reaction. Another advantage is that the necessary apparatus is generally not expensive, reliable and readily available in the laboratories.

Chromatography

High performance liquid chromatography (HPLC)

HPLC is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pass a pressurized liquid solvent containing the sample mixture through a column filled with a solid adsorbent material. Each component in the sample interacts slightly differently with the adsorbent material, causing different flow rates for the different components and leading to the separation of the components as they flow out of the column.

The schematic of an HPLC instrument typically includes a degasser, sampler, pumps, and a detector. The sampler brings the sample mixture into the mobile phase stream which carries it into the column. The pumps deliver the desired flow and composition of the mobile phase through the column. The detector generates a signal proportional to the amount of sample component emerging from the column, hence allowing for quantitative analysis of the sample components (see Fig. 2).

HPLC Fig. 2 HPLC

Gas chromatography–mass spectrometry (GC-MS)

GC-MS is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample.

The GC-MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer (see Fig. 3). The gas chromatograph utilizes a capillary column whose properties regarding molecule separation depend on the column's dimensions (length, diameter, film thickness) as well as the phase properties. The mass spectrometer does this by breaking each molecule into ionized fragments and detecting these fragments using their mass-to-charge ratio.

GC-MS Fig. 3 GC-MS

Thin layer chromatography (TLC)

TLC is a chromatographic technique used to separate the components of a mixture using a thin stationary phase supported by an inert backing. TLC is an analytical tool widely used because of its simplicity, relative low cost, high sensitivity, and speed of separation. A few components involved in the TLC procedure are showed in Fig. 4.

Fig. 4 Diagram of Thin Layer Chromatography

Spectroscopy

Ultraviolet-visible spectroscopy (UV-Vis)

UV-Vis spectroscopy is based on the absorption of light by a sample. Depending on the amount of light and its wavelength absorbed by the sample, valuable information can be obtained, such as in analytical chemistry for the quantitative determination of different analytes. Spectroscopic analysis is commonly carried out in solutions, but solids and gases may also be studied. Fig. 5 is the UV-Vis spectrophotometer.

Fig. 5 UV-Vis spectrophotometer

Fourier transform infrared (FTIR) spectroscopy

FTIR spectroscopy is a technique that can be used mainly qualitatively, but occasionally quantitatively, for the identification of organic substances.

According to the reflection spectrum of the sample, we build the model through partial least squares regression (PLSR), and the spectral information can be extracted by the combination of derivative and standard normalization. Then the product purity information is obtained. Fig.6 is the FTIR.

Fig.6 Fourier transform infrared (FTIR) spectroscopy

Proton nuclear magnetic resonance (¹H-NMR)

¹H-NMR is the application of nuclear magnetic resonance in NMR spectroscopy with respect to hydrogen-1 nuclei within the molecules of a substance, in order to determine the structure and purity of the chemicals.

In general, the purity can be obtained by comparing the peak's area or peak's height caused by protons on a specified group of the measured chemical with that of the reference standard.

Fig. 7 NMR equipment

Chemists from Alfa Chemistry have a great deal of experience in the tests of chemicals. Our experienced chemists are pleased to work with you to solve your problems in scientific research and industrial applications. Please feel free to contact us for more details.

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