Table 3.

Summary of advantages and limitations of methodology applied in the sample matrices

Laboratory equipment and instrumentation	Type of sample	Advantages	Limitations
Sample pre-treatment
10–30% KOH	Blood thrombi [18], heart [20], colectomy tissues [21], placenta [22], breastmilk [32], semen [33], stool [34,35], urine [41]	Cheap and effective that allows the isolation of microplastics from the sample. Efficiency of KOH may increase when incorporated with higher temperature at 60–70°C	Higher percentage may influence the degradation of microplastics. Time-consuming
10% KOH + CHKO2	Placenta [25]	CHKO2 increased the efficiency of the digestion process	Newly developed method is considered risky to use due to a lack of substantial supporting studies
10M KOH + sodium hypochlorite	Liver, kidney, spleen [22]	Sodium hypochlorite acts as a catalyst in increasing the efficiency of the digestion process	Sodium hypochlorite is expensive
30% H2O2	Vein [19], lung ground nodules [29], lung tissue [30], stool [39]	Readily available and relatively inexpensive. Effectively digest organic matter	Requires PPE as H2O2 is a strong oxidising agent. H2O2 may lead to formation of by-products that can interfere with the analysis of microplastics
30% H2O2 + 0.05M NaOH	Placenta [24], meconium [24]	Readily available and relatively inexpensive. Effectively digest organic matter. NaOH is cheap and can enhance the efficiency of the digestion process.	Higher percentage may influence the degradation of microplastics
30% H2O2 + 0.05M Fenton reagent	Urine [42]	Effectively digest organic matter. Fenton reagent acts as a catalyst	Expensive reagent
35% H2O2 + ZnCl2	Hand, hair, faces [27]	Effectively digest organic matter	ZnCl2 is highly toxic to the environment
HNO3	Placenta, infant faeces, meconium [26], stool [37,38]	Effectively digest organic matter	Highly corrosive. Can be hazardous to handle.
ZnCl2	Sputum [40]	Efficiency of ZnCl2 remains above 95% after five filtrations. Can be reused	Highly corrosive. Can be hazardous to handle. Highly toxic to the environment.
TRIS HCl buffer	Blood [17]	Works in denaturing proteins for blood sample	Newly developed method is considered risky to use due to a lack of substantial supporting studies
0.05% SDS solution +5 mM CaCl2 + 1 M TRIS HCl	Testis [31], semen [31]	SDS (sodium dodecyl sulfate) is a surfactant that can solubilise proteins and lipids, and it can also solubilise microplastics. The addition of CaCl2 can enhance the efficiency of the digestion process.	Newly developed method is considered risky to use due to a lack of substantial supporting studies.
NaOH + HNO3 + Protease	Lung tissues [28]	The addition of HNO3 and protease can enhance the efficiency of the digestion process	Newly developed method is considered risky to use due to a lack of substantial supporting studies
Physical characterisation
Microscopic observation	Blood [17], thrombi [18], vein [19], colectomy [21], placenta [23,25,26], meconium [24], infant faeces [26], breastmilk [26,32], hand, hair, faces [27], lung ground nodules [29], lung tissue [30], testis [31], semen [31,33], stool [35,39], urine [41,42]	Obtain clear view of microplastic particles including their shape, size and colour. Easy to use. Non-destructive	Unable to detect the polymer type of microplastic. Prone to significant human error. Labour intensive.
Nile Red fluorescence microscopy	Liver, kidney, spleen [22]	Rapidly estimate microplastic count under the microscope. Easy to use.	Does not specify polymer composition of microplastics. Staining can conceal the original colour and surface morphology of microplastics.
SEM-EDX	Colectomy [21], lung ground nodules [29]	Able to observe any adherence of foreign particles on the microplastic sample. High resolution imaging machine that can provide detailed images of microplastics	Destructive to the sample. Time consuming and expensive.
Chemical characterisation
Raman/μRaman	Thrombi [8], liver, kidney, spleen [22], placenta [23], hand, hair, faces [27], lung tissues [28], lung ground nodules [29], breastmilk [32], semen [33], stool [35,37,38], urine [41,42]	Offer precise and reliable results. Non-destructive to the microplastic particles.	Requires meticulous sample preparation. Prolonged processing time.
FTIR/μFTIR	Vein [19], colectomy tissues [21], placenta [24], meconium [24], lung ground, nodules [29], lung tissue [30], stool [34,39], sputum [40], urine [42]	Common method for analysing microplastic polymers. Offer precise and reliable results. Can detect up to 10 μm in size (for μFTIR).	Can be affected by the presence of other materials adhered on the microplastic particles. ATR-FTIR may be destructive to the surface morphology of the sample
Py-GC/MS	Blood [17], testis [31], semen [31]	Utilises various types of microplastic polymers. Offer both accuracy and high sensitivity in obtaining results. Efficient and effective approach for analysis.	Prolonged processing times. Requires high count of microplastics particles especially fibre shaped due to their low weight.
LDIR	Placenta [25,26], infant faeces [26], breastmilk [26]	Can detect up to 10 μm in size. High automation and integration	Extensive sample pre-treatment.

ATR-FTIR – Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy, CaCl₂ – Calcium Chloride, CHKO₂ – Potassium Formate, HNO₃ – Nitric Acid, H₂O₂ – Hydrogen peroxide, KOH – Potassium Hydroxide, LD-IR – Laser Direct Infrared Spectrometry, NaOH – Sodium Hydroxide, M – molar, TRIS HCl – Tris (Hydroxymethyl) Aminomethane, mM – millimolar, PPE – Personal Protective Equipment, PY-GC/MS – Pyrolysis–Gas Chromatography Tandem Mass Spectrometry, SDS – Solution Sodium Dodecyl Sulfate Solution, SEM-EDX – Scanning Electron Microscopy/Energy Dispersive Spectroscopy, ZnCl₂ – Zinc Chloride, μFTIR – microFourier Transform Infrared Spectrometry, μm – micrometre, μRaman – microRaman