Identifying the constituents of an ink

An ink can be a solution, a suspension or a colored paste that will be used for writing, drawing or printing.

There are two main categories of ink:

  • Dye inks whose coloring substance is dissolved in an organic solvent or water and whose origin is either of synthetic origin (most of it) or of natural origin (natural dye obtained from plants, animals …).
    They are liquid and are mainly used in printing (flexography, heliography), in inkjet printers, fountain or ballpoint pens and certain types of markers.
  • Pigment inks in which the coloring substance is a pigment which is dispersed in a binder in which it is insoluble. These are inorganic compounds or molecules of organic origin, encapsulated in a synthetic resin and then placed in suspension in a liquid.
    They are oily and mainly found in printing inks (offset, typography) and in certain types of markers.
Constituants d'une encre

Study of the composition of an ink

In general, an ink is made up of several constituents:

  • A dye: substance that is often solid, in solution or in suspension (in the case of pigments) and which gives it its color. They can be of inorganic nature (carbon black, iron trioxide Fe2O3 as red pigment, titanium or aluminum oxide for white pigments, etc.) or organic of natural (animal, plant, etc.) or industrial origin (synthesis and artificial: nitro derivatives, triphenylmethane derivatives, xanthenics, acridine, quinoline, anthraquinonics, indigoids, phthlocyanins, oxidation bases and azo).
  • A solvent that will dissolve or suspend the dye. Most of the time, these are so-called petroleum solvents (non-aromatic), but also alcohols, esters, glycols, water, etc.
  • A binder : natural or synthetic polymer matrix which makes it possible to keep the pigment in suspension and / or to give the ink a certain viscosity, as well as to allow the pigment to be fixed on the support. Some examples of binders that can be analyzed (identification and sometimes quantification) in a matrix by Pyrolysis / GCMS: Polyurethane, Polyacrylic, Polyvinyl, Epoxy, Phenoplast, Vegetable oil, Natural resin, etc.
  • Various additives to give shine, accelerate drying, allow crosslinking under UV, etc…. Some examples of additives that can be analyzed (identification and quantification) in a matrix by GCMS, Pyrolysis / GCMS, UPLC / TOF-MS, MEB / EDX: animal (Bee), vegetable (Carnauba, Jojoba, Candelilla ...) or mineral (PE) waxes or PTFE), plasticizers, antioxidants, anti-staining agents (silica, starch, cellulose…), drying agents, photo-initiators, fungicides, thickeners, flavorings, adhesion promoters…

Some examples of colorants that can be analyzed (identification and quantification) in a matrix by UPLC / TOF-MS:

Acid Black 1 - CAS 1064-48-8

Acid black 2 (Nigrosine) - CAS 8005-03-6

Acid blue 258 (Tectilon Blue 6G) - CAS 61847-68-5

Acid Green 16 - CAS 12768-78-4

Acid Red 26 - CAS 3761-53-3

Acid red 42 (Rouge Tectilon 4B) - CAS 6245-60-9

Acid Violet 17 - CAS 4129-84-4

Acid Violet 49 - CAS 1694-09-3

Acid Yellow 36 - CAS 587-98-4

Acid yellow 169 (Jaune Tectilon 2G) - CAS 12220-88-1

Basic Blue 7 - CAS 2390-60-5

Basic Green 1 (brilliant green) - CAS 633-03-4

Basic Red 1 - CAS 989-38-8

Basic Red 9 - CAS 569-61-9

Basic Violet 1 - CAS 8004-87-3

Azorubine Red / Carmoisine (E122) - CAS 3567-69-9

Ponceau 4R or Cochineal Red A (E124) - CAS 2611-82-7

Basic Violet 10 (rhodamine b) - CAS 81-88-9

Basic Violet 3 - CAS 548-62-9

Disperse Blue 1 - CAS 2475-45-8

Disperse Blue 106 - CAS 12223-01-7

Disperse Blue 124 - CAS 61951-51-7

Disperse Blue 3 - CAS 2475-46-9

Disperse Blue 35 - CAS 12222-75-2

Disperse Orange 3 - CAS 730-40-5

Disperse Orange 37 - CAS 12223-33-5

Disperse Red 1 - CAS 2872-52-8

Disperse Red 17 - CAS 3179-89-3

Disperse Yellow 3 - CAS 2832-40-8

Disperse Yellow 9 - CAS 6373-73-5

Pigment Orange 5 - CAS 3468-63-1

Pigment Red 53 - CAS 2092-56-0

Red Allura AC (E 129) - CAS 25956-17-6

Brilliant blue FCF (Xylene blue VSG or Erioglaucine or E 133)
CAS 2650-18-2; 3844-45-9

Pigment Red 57-1 (Lithol rubine BK) - CAS 5281-04-9

Pigment red 122 - CAS 980-26-7

Pigment red 170 - CAS 2786-76-7

Pigment Violet 3 - CAS 1325-82-2

Pigment Yellow 13 - CAS 5102-83-0; 6358-85-6

Pigment Yellow 83 - CAS 5567-15-7

Solvent black 5 (Nigrosine) - CAS 11099-03-9

Solvent Blue 35 (Sudan blue 2) - CAS 17354-14-2

Solvent Orange 7 (Sudan II) - CAS 3118-97-6

Solvent Red 24 (Sudan IV) - CAS 85-83-6

Solvent Red 49 - CAS 509-34-2

Solvent Violet 9 - CAS 467-63-0

Solvent Yellow 2 (butter yellow, dimethyl yellow) - CAS 60-11-7

Tartrazine yellow (E 102) - CAS 1934-21-0; 12225-21-7

Quinoline yellow (E 104) - CAS 8004-92-0

Orange yellow (E110) - CAS 2783-94-0

Patent blue V (E 131) - CAS 3536-49-0

Food brown 3 (E 155) - CAS 4553-89-3

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Identifying the constituents of an ink
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Identifying the constituents of an ink