0,450
0,465
Contoh 2
0,450
0,408
Sampel yang Ditambahkan 1
0,571
Sampel yang Ditambahkan 2
0,5144Tingkat Pemulihan (%) = (Nilai Terukur Setelah Peningkatan - Konten Asli) / Jumlah Peningkatan × 100%3Batas Standar Nasional untuk Arsenik dan Merkuri dalam Produk Susu3Serial3Kategori2Kontaminan0Batas (mg/kg)
Susu mentah, susu pasteurisasi, susu steril, susu formula, susu fermentasi
Merkuri (Hg)
0,01
Arsenik (As)
0.1
Susu bubuk
Merkuri (Hg)
Dikendalikan melalui sumber susu mentahArsenik (As)0,5
2. Reagent: Hydrochloric acid (GR grade), Nitric acid (GR grade), Standard solutions for each element, Acetylene gas (99.0%).
1. Instrument: HKL-AFS for Determination of heavy metal element in goat milk (equipped with hollow cathode lamps for As, Hg, Pb, Sb, Se, etc., as required)
2. Reagent: Nitric acid (GR grade), Hydrochloric acid (GR grade), Potassium borohydride (GR grade), Sodium hydroxide (GR grade), Thiourea (AR grade), Potassium dichromate (AR grade), Hydroxylamine hydrochloride (AR grade), Potassium permanganate (AR grade), Standard solutions for each element, High-purity argon gas (99.99%).
Pretreatment
1. Sample
Weigh 1.0 g to 4.0 g (accurate to 0.001 g) of milk or dairy product into a conical flask of the digestion apparatus. Add several glass beads and 30 ml of nitric acid. For milk, add 10 ml of sulfuric acid; for dairy products, add 5 ml of sulfuric acid. Swirl the flask to prevent localized charring. Attach a condenser and heat gently while conducting a blank test in parallel.
After pretreatment, in an acidic medium, arsenic (As) and mercury (Hg) in the sample are reduced by potassium borohydride (KBH4) to their volatile species, which are then carried by the carrier gas (argon) into the atomizer. In the hydrogen flame, the elements are atomized. Under irradiation from a specially designed hollow cathode lamp, ground-state atoms are excited to higher energy states. Upon returning to the ground state, they emit fluorescence at characteristic wavelengths. The fluorescence intensity is proportional to the elemental concentration and is quantified by comparison with a standard series.
2. Instrument Setup
Adjust the instrument to optimal working conditions according to the user manual. Key parameters:
Photomultiplier tube voltage: 240 V
Mercury hollow cathode lamp current: 30 mA
Atomizer temperature: 300 °C
Carrier gas flow rate: 500 ml/min
Shield gas flow rate: 1000 ml/min
Interference and Elimination
In acidic media, elements capable of reacting with potassium borohydride (KBH4) to form hydrides may interfere with each other. The addition of a thiourea-ascorbic acid mixed solution can effectively eliminate such interference. Additionally, transition metals such as copper (Cu) at concentrations above a certain threshold may also cause interference. However, the thiourea-ascorbic acid solution can remove the majority of these interferences.
To mitigate physical interference, a double-layered quartz tube atomizer is utilized. Both the inner and outer layers are purged with argon (Ar), creating a protective shield that isolates the sample from atmospheric oxygen (O2) and nitrogen (N2). This prevents collisions between ground-state atoms of the target elements and air molecules, thereby reducing fluorescence quenching and improving measurement accuracy.
Test Result
|
Standard Solution Concentration: 100 μg/ml Final Volume: 100 ml |
||||
|
Serial |
Volume of Standard Added (ml) |
Calibration Standard Concentration (μg/L) |
Fluorescence Intensity (IF) |
Remarks |
|
Original Record of Calibration Curve Preparation |
||||
|
1 |
0.000 |
0.000 |
||
|
2 |
0.200 |
350.419 |
||
|
3 |
0.400 |
642.898 |
||
|
4 |
0.600 |
949.686 |
||
|
5 |
0.800 |
1233.224 |
||
|
6 |
1.000 |
1543.116 |
||
|
a=24.358 b= 1524.398 r=0.9996 |
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|
Detection Limit Record Sheet |
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|
Analysis Date: 2020.03.09 |
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|
Serial |
Blank Fluorescence Value (IF) |
Slope (b) |
Instrument Detection Limit (μg/L) |
Method Detection Limit (μg/L) |
|
1 |
17.393 |
1524.398 |
0.0076ug/L |
0.012ug/L |
|
2 |
11.379 |
|||
|
3 |
11.325 |
|||
|
4 |
13.718 |
|||
|
5 |
14.473 |
|||
|
6 |
13.348 |
|||
|
7 |
12.993 |
|||
|
8 |
3.698 |
|||
|
9 |
11.536 |
|||
|
10 |
8.570 |
|||
|
11 |
6.421 |
|||
|
Recovery Rate Record Sheet |
||||
|
Serial |
Concentration (μg/L) |
Final Volume (ml) |
Measured Value (μg/L) |
Recovery Rate (%) |
|
Sample 1 |
0.450 |
100 |
0.465 |
|
|
Sample 2 |
0.450 |
100 |
0.408 |
|
|
Spiked Sample 1 |
100 |
0.571 |
106 |
|
|
Spiked Sample 2 |
100 |
0.514 |
106 |
|
|
Recovery Rate (%)= (Measured Value After Spiking - Original Content)/ Spiked Amount×100% |
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|
National Standard Limits for Arsenic and Mercury in Dairy Products |
|||
|
Serial |
Category |
Contaminant |
Limit (mg/kg) |
|
1 |
Raw milk, pasteurized milk, sterilized milk, formulated milk, fermented milk |
Mercury (Hg) |
0.01 |
|
2 |
Arsenic (As) |
0.1 |
|
|
3 |
Milk powder |
Mercury (Hg) |
Controlled via raw milk sources |
|
4 |
Arsenic (As) |
0.5 |
|