Method for the extraction and the determination of microplastics in samples with organic and inorganic matrices, including the fundamental stages of: a) sampling and pre-treatment, b) acid digestion of the sample, c) extraction of microplastics during the liquid phase, d) identification and quantification of the microplastics, in which said acid digestion is conducted with strong acid, in a ratio of 1:1 m/v or v/v with the abovementioned sample, for a duration of at least 24 hours at a temperature of 60 °C, and in which said extraction stage of the microplastics in liquid phase includes the following phases: 1. mix an aliquot of ultra-pure water with said sample treated with strong acid, in a ratio of 1:3 m/v or v/v, to obtain a liquid mixture; 2. mix a first aliquot of non-polar halogenated solvent with said liquid mixture in a ratio of 1:3 m/v or v/v, to obtain a heterogeneous liquid mixture; 3. agitate said heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two fractions: A and B, in which fraction A is watery and fraction B is organic; 4. separate the watery fraction A from the organic fraction B; 5. add a second aliquot of non-polar halogenated solvent to the watery fraction A to obtain a second heterogeneous mixture; 6. agitate said second heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two liquid phases: C and D, in which fraction C is watery and fraction D is organic; 7. recombine the organic fractions B and D and then evaporate to dryness at a temperature of 70 °C, to obtain an extract of microplastics; 8. suspend said extract of microplastics in acetonitrile with a volume between 100 and 500 microliters, and in which the stage of the identification and quantification of the microplastics involves the transfer of said extract suspended in acetonitrile on metallic support and its successive metallization with gold, and measuring the dimension and counting a plurality of microplastics, as the reading area measures 1 mm 2, by means of electronic microscope coupled with energy dispersive X-ray analysis. a) sampling and pre-treatment, b) acid digestion of the sample, c) extraction of microplastics during the liquid phase, d) identification and quantification of the microplastics, and in which said extraction stage of the microplastics in liquid phase includes the following phases: 1. mix an aliquot of ultra-pure water with said sample treated with strong acid, in a ratio of 1:3 m/v or v/v, to obtain a liquid mixture; 2. mix a first aliquot of non-polar halogenated solvent with said liquid mixture in a ratio of 1:3 m/v or v/v, to obtain a heterogeneous liquid mixture; 3. agitate said heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two fractions: A and B, in which fraction A is watery and fraction B is organic; 4. separate the watery fraction A from the organic fraction B; 5. add a second aliquot of non-polar halogenated solvent to the watery fraction A to obtain a second heterogeneous mixture; 6. agitate said second heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two liquid phases: C and D, in which fraction C is watery and fraction D is organic; 7. recombine the organic fractions B and D and then evaporate to dryness at a temperature of 70 °C, to obtain an extract of microplastics; 8. suspend said extract of microplastics in acetonitrile with a volume between 100 and 500 microliters, 1. mix an aliquot of ultra-pure water with said sample treated with strong acid, in a ratio of 1:3 m/v or v/v, to obtain a liquid mixture; 2. mix a first aliquot of non-polar halogenated solvent with said liquid mixture in a ratio of 1:3 m/v or v/v, to obtain a heterogeneous liquid mixture; 3. agitate said heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two fractions: A and B, in which fraction A is watery and fraction B is organic; 4. separate the watery fraction A from the organic fraction B; 5. add a second aliquot of non-polar halogenated solvent to the watery fraction A to obtain a second heterogeneous mixture; 6. agitate said second heterogeneous liquid mixture for 30 s and centrifuge it at 4000 rpm for 15 minutes to obtain two liquid phases: C and D, in which fraction C is watery and fraction D is organic; 7. recombine the organic fractions B and D and then evaporate to dryness at a temperature of 70 °C, to obtain an extract of microplastics; 8. suspend said extract of microplastics in acetonitrile with a volume between 100 and 500 microliters, and in which the stage of the identification and quantification of the microplastics involves the transfer of said extract suspended in acetonitrile on metallic support and its successive metallization with gold, and measuring the dimension and counting a plurality of microplastics, as the reading area measures 1 mm 2, by means of electronic microscope coupled with energy dispersive X-ray analysis.