Angka Penting (Significant Figures) Limit Deteksi (Limit of Detection)

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Penting (Significant Figures) Deteksi (Limit of Detection)/ kuantifikasi (Limit of Quantifi ifitas (Sensitivity)

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Angka Penting (Significant Figures) Limit Deteksi (Limit of Detection)/ Limit kuantifikasi (Limit of Quantification) Sensitifitas (Sensitivity). Significant Figures. What is a significant figure?. - PowerPoint PPT Presentation

Transcript of Angka Penting (Significant Figures) Limit Deteksi (Limit of Detection)

Page 1: Angka Penting (Significant Figures) Limit Deteksi (Limit of Detection)

Angka Penting (Significant Figures)Limit Deteksi (Limit of Detection)/Limit kuantifikasi (Limit of Quantification)Sensitifitas (Sensitivity)

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Significant Figures

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Angka penting adalah semua angka yang diperoleh dari hasil pengukuran, yang terdiri dari angka eksak dan satu angka terakhir yang ditaksir (approximate).

What is a significant figure?

Bilangan penting diperoleh dari kegiatan mengukur, sedangkan bilangan eksak diperoleh dari kegiatan membilang.

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What is a significant figure?

There are 2 kinds of There are 2 kinds of numbers:numbers:Exact: Exact: the amount of the amount of

money in your account. money in your account. Known with certainty.Known with certainty.

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What is a significant figure?

ApproximateApproximate: weight, : weight, height—anything height—anything MEASURED. MEASURED.

No measurement is perfectNo measurement is perfect..

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When to use Significant figures

If you measured the If you measured the width of a paper with width of a paper with your ruler you might your ruler you might record 21.7cm.record 21.7cm.

To a mathematician 21.70, To a mathematician 21.70, or 21.700 is the same.or 21.700 is the same.

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But, to a scientist 21.7 cm and 21.700 cm is NOT the same

21.700 cm to a scientist 21.700 cm to a scientist means the measurement means the measurement is accurate to within one is accurate to within one thousandth of a cm.thousandth of a cm.

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But, to a scientist 21.7cm and 21.700 cm is NOT the same

If you used an ordinary If you used an ordinary ruler, the smallest ruler, the smallest marking is the mm, so marking is the mm, so your measurement has your measurement has to be recorded as to be recorded as 21.7cm.21.7cm.

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How do I know how many Significant Figures?

Rule: All digits are Rule: All digits are significant starting with significant starting with the the first non-zerofirst non-zero digit digit on the left.on the left.

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Exception to rule:Exception to rule: In In whole numbers that end whole numbers that end in zero, the zeros at the in zero, the zeros at the end are not significant.end are not significant.

How do I know how many Significant Figures?

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How many significant figures?

7740400.50.50.000030.000037 x 107 x 1055

7,000,0007,000,000

111111111111

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How do I know how many Significant Figures?

22ndnd Exception to rule: Exception to rule: If If zeros are sandwiched zeros are sandwiched between non-zero digits, between non-zero digits, the zeros become the zeros become significant.significant.

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How do I know how many Significant Figures?

3rd Exception to rule:3rd Exception to rule: If If zeros are at the end of a zeros are at the end of a number that has a number that has a decimal, the zeros are decimal, the zeros are significant. significant.

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How do I know how many Sig Figs?

3rd Exception to rule:3rd Exception to rule: These zeros are showing These zeros are showing how accurate the how accurate the measurement or measurement or calculation are.calculation are.

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How many sig figs here? 1.21.2 21002100 56.7656.76 4.004.00 0.07920.0792 7,083,000,0007,083,000,000

22 22 44 33 33 44

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How many sig figs here? 34013401 21002100 2100.02100.0 5.005.00 0.004120.00412 8,000,050,0008,000,050,000

44 22 55 33 33 66

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What about calculations with sig figs?

Rule: When Rule: When adding or adding or subtractingsubtracting measured measured numbers, the answer can have numbers, the answer can have no more places after the no more places after the decimal than the LEAST of decimal than the LEAST of the measured numbers.the measured numbers.

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Add/Subtract examples2.45cm + 1.2cm = 3.65cm, 2.45cm + 1.2cm = 3.65cm, Round off to Round off to = 3.7cm= 3.7cm

7.432cm + 2cm = 9.432 7.432cm + 2cm = 9.432 round to round to 9cm9cm

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Multiplication and Division

Rule: When Rule: When multiplying multiplying or dividingor dividing, the result , the result can have no more can have no more significant figures than significant figures than the least reliable the least reliable measurement.measurement.

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A couple of examples56.78 cm x 2.45cm = 139.111 cm56.78 cm x 2.45cm = 139.111 cm22

Round to Round to 139cm139cm22

75.8cm x 9.6cm = ?75.8cm x 9.6cm = ?

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(104.250 x 2.26) / 15.553 = ?

(0.002450 x 0.1478) / 0.120 =

Hitung :

4.0 x 10^4/ 1.15 x 10^4 =

2.0 x 307 =

50 / 3.0069 =

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Sensitivity

The sensitivity of a measuring instrument is its The sensitivity of a measuring instrument is its ability to ability to detect quickly a small changedetect quickly a small change in the value of a in the value of a measurement.measurement.

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A measuring instrument that has a scale with A measuring instrument that has a scale with smaller divisionssmaller divisions is more sensitive.is more sensitive.

Sensitivity

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As an example, the length of a piece of wire is measured As an example, the length of a piece of wire is measured with rulers A and B which have scales graduated in with rulers A and B which have scales graduated in intervals of intervals of 0.1 cm 0.1 cm and and 0.5 cm 0.5 cm respectively, as shown in respectively, as shown in Figure below. Which of the rulers is more sensitive?Figure below. Which of the rulers is more sensitive?

Sensitivity

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Results:Results: Ruler A: Length = 4.8 cmRuler A: Length = 4.8 cm Ruler B: Length = 4.5 cmRuler B: Length = 4.5 cm Ruler A is more sensitive as it can measure to an accuracy Ruler A is more sensitive as it can measure to an accuracy

of 0.1 cm compared to 0.5 cm for ruler Bof 0.1 cm compared to 0.5 cm for ruler B

Sensitivity

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44 In addition to the size of the divisions on the scale In addition to the size of the divisions on the scale of the instrument, the of the instrument, the designdesign of the instrument has an of the instrument has an effect on the sensitivity of the instrument. For example, a effect on the sensitivity of the instrument. For example, a thermometer has a higher sensitivity if it can detect small thermometer has a higher sensitivity if it can detect small temperature variations. A thermometer with a temperature variations. A thermometer with a narrow narrow capillarycapillary and a thin-walled bulb has a higher sensitivity. and a thin-walled bulb has a higher sensitivity.

Sensitivity

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The slope of the calibration curve at the concentration The slope of the calibration curve at the concentration of interest is known as of interest is known as calibration sensitivitycalibration sensitivity..

S = mc + SS = mc + Sblbl

S = measured signal; c= analyte concentration; S = measured signal; c= analyte concentration;

SSbl bl = blank signal; m = sensitivity (Slope of line)= blank signal; m = sensitivity (Slope of line)

Analytical sensitivity (Analytical sensitivity ())

= m/s= m/sss

m = slope of the calibration curvem = slope of the calibration curve

sss s = standard deviation of the measurement= standard deviation of the measurement

Y = ax + b

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LOD: The smallest amount or concentration of analyte that can be detected statistically

IUPAC:

Limit of Detection (LOD)

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LOD: the smallest concentrationor absolute amount of analyte that has a signal significantly larger than the signal arising from a reagent blank

IUPAC:

Limit of Detection (LOD)

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Limit of Detection (LOD)

LOD is the lowest amount of analyte in a sample which can be detected but not necessarily quantitated as an exact value.

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Limit of Detection (LOD)

there may be a gray area where the analyte is sometimes detected and sometimes not detected.

LOD Implies that

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Calculation of LOD (1)

The analyte’s signal at the detection limit, (SA)LOD

(SA)LOD = Sreag + zreag

Sreag : the signal for a reagent blankreag : the known standard deviation for the reagent blank’s signalz : factor accounting for the desired confidence level

(typically, z is set to 3)

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Calculation of LOD (1)LOD is calculated based on (SA)LOD divided with slope of calibration graph (a)

y = ax + b(SA)LOD = a * LOD + b

x

ya

b

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(SA)LOQ = Sreag + 10reag

Limit of Quantification (LOQ)LOQ: The smallest concentration or absolute amount of analyte that can be reliably determined (American Chemical Society)

y = ax + b(SA)LOQ = a * LOQ + b

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Calculation of LOD (2)

Signal to Noise Ratio (S/N) is a dimensionless measure of the relative strength of an analytical signal (S) to the average strength of the background instrumental noise (N)

Signal to Noise Ratio (S/N) method

S/N = 3

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Calculation of LOD (2)Signal to Noise Ratio (S/N) method

Noi

se

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Calculation of LOD (2)Signal to Noise Ratio (S/N) method

y = ax + b3N = a * LOD + b

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  Ion Count (CPS)

  Ga Ge In

blank 1 29.78 9.08 18.67

blank 2 30.53 9.50 23.34

blank 3 25.91 10.79 28.41

blank 4 27.73 10.16 20.025

blank 5 29.82 9.78 23.49

blank 6 29.11 10.09 31.93

blank 7 25.31 12.52 23.80

blank 8 28.63 11.188 24.72

blank 9 26.21 13.22 17.21

blank 10 30.04 12.56 23.86

Std 1 (1 ppb) 250.87 43.07 60.56

Std 2 (2 ppb ) 499.68 77.36 108.95

Std 3 (3 ppb ) 773.46 109.43 151.83

Calculate LOD of Ga, Ge, and In