Should LOQs be calculated?

Answer Explanations

• Expert 3
  Like in all analytical methods, LOQs should be claculated, as these ensures data reliability and comparability, and also help in distinguishing true signals. 
  For spectroscopic or chromatographic methods: LOQ=10×(S/σ), σ = standard deviation of the blank or low-concentration sample, S = slope of the calibration curve
  For repeated measurements of blanks or low-level spiked samples: LOQ= xblank +10×σblank, xblank = mean of blank measurements, σblank = standard deviation of blank 
  https://www.sciencedirect.com/science/article/pii/S0269749120365301
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• Yes (please explain and provide equations and citations)

  Expert 9
  If by LOQs, it is meant MDAs (minimum detectable amounts), then equations 1 and 2 as provided in the draft manuscript should be used, as these appear the current gold standard.
• Yes (please explain and provide equations and citations)

  Expert 2
  LOQ should be calculated very precise. This will help with the reliability of the studies making sure that the results even at low concentrations are reliable and reproducible.  Also, there is a need to calculate LOQ due to the fact that many standard such as FDA, EPA, ICH require that the LOQ to be reported for each study. Furthermore, LOQs play an important role in both the method validation as well as data interpretation.
• Yes (please explain and provide equations and citations)

  Expert 4
  Yes, assuming that the question is dealing with quantification of MNP levels in specific matrices. The calculations are needed for any matrix and any MNP type that is to be quantified.
  As a matter of course, this is not needed in case of qualitiative analysis.
• Yes (please explain and provide equations and citations)

  Expert 5
  LOQ is especially helpful in Py-GC/MS. If you can detect MNP below LOQ but above LOD, a determinations can be made such as, "present but below LOD", or, "let's alter our sample prep to allow signals above LOQ.
  Based on a calibration curve the LOD = 3.3σ / S, LOQ = 10σ / S.    σ is the standard deviation of the response and S is the slope of the calibration curve.
  Based on Signal/Noise "signal-to-noise ratio of 3:1 is generally considered acceptable for estimating the DL. For QL, a ratio of at least 10:1 is considered acceptable"
  LOQ and LOD calculations from: https://www.ema.europa.eu/en/documents/scientific-guideline/ich-q2r2-guideline-validation-analytical-procedures-step-5-revision-1_en.pdf
• Yes (please explain and provide equations and citations)

  Expert 6
  When researcher study biological tissues, the ultimate goal is to study the target impact on biological system or toxicity to biological system. When we talk about toxicity, we have to know and discuss the quantity or concentration. Thus, LOQ is also an important fact for an applied methodology. Using py-GC/MS technique as an example, it is an ongoing research field. Below are a few references for consideration. Traditional, the common practice is that the LOD is S/N ratio of 3 while LOQ is S/N ratio at 10. The practice has no issue when research and study is done in simple setting like water or simple environments samples. However, the py-GC/MS method is facing challenging and needs significant improvement when study certain polymer in human tissues, like discussed in ref 99 of current manuscript.   
  
  Quantification of microplastic targets in environmental matrices using pyrolysis-gas chromatography-mass spectrometry - Environmental Science: Advances (RSC Publishing) DOI:10.1039/D4VA00269E
  Progress in quantitative analysis of microplastics in the environment: A review - ScienceDirect
  Qualitative and quantitative analysis of mixtures of microplastics in the presence of calcium carbonate by pyrolysis-GC/MS - ScienceDirect
• Yes (please explain and provide equations and citations)

  Expert 8
  I would answer maybe if that was an option.  There's much debate and little standardization on LODs and LOQs.  I would want to refer to other standardized methods and would need time to look them up.  LOD is more important.
• Yes (please explain and provide equations and citations)

  Expert 7
   LOQ defines the lowest concentration of MNPs that can be reliably quantified with acceptable precision and accuracy, and maybe required by regulatory and scientific standards. It's also essential to confirm the accuracy of the low levels of MNPs.
  
  Signal-to-Noise Ratio (S/N): LOQ is often defined as the concentration that gives a signal 10 times the noise level.
  
  https://www.pharmacalculation.com/2023/01/signal-to-noise-ratio-calculation.html

  
  
  
• Yes (please explain and provide equations and citations)

  Expert 1
  Currently LOD/LOQ values in MNP research are based on levels found in blanks.  However, blank contamination varies from batch to batch and therefore LODs/LOQs vary periodically.  For this reason it is better to report LOQ and if possible for every batch of samples analyzed.
  
  Furthermore, the newly emerging methodologies such as pyrolysis gas chromatography mass spectrometry entail LOD/LOQ values based on instrument sensitivity, sample mass taken for analysis, in addition to levels found in blanks.  For such methods, reporting of LOD/LOQ is very important and is a part of guidelines for a good analytical method.
  
  Overall, considering the diverse array of methodologies, namely microscopy, vibrational and IR spectrometry, mass spectrometry used in MNP analysis, reporting of LOQ is required.  Each of these technologies have its own detection limits and without reporting LOQ, comparability of data between studies can be difficult.  LOQ should take into account of background levels of contamination present in blanks.
  
  In the discussions pertaining to LOD, the quantification is centered around reporting number of particles, not number of particles per unit volume or mass of samples.  A mere number of particles alone is not suitable for risk assessment.  It is the number per unit mass of sample makes the results more meaningful for risk assessment and comparison between studies.  In environmental monitoring studies, measurements are presented in the units of concentration (e.g., ng/g or ng/ml), which has a denominator.   Pyrolysis GCMS techniques are gaining popularity in recent years, for which detection limits are reported in the units of ng/g  or ug/g or mg/g tissue or sample.  Author may want to make some recommendations regarding normalizing of units per unit mass or per unit square area or per unit square volume of sample.  This is because LOQ can be affected by sample mass/volume and this is important in the analysis of biological samples.