Method Validation Analysis of Toxic Elements As, Cd, Pb and Hg in Cannabidiol (CBD)-rich Oil by Inductively Coupled Plasma Mass Spectrometry

Santos, Eder José dos; Herrmann, Amanda Beatriz

doi:10.1590/1678-4324-2024230455

Article - Engineering, Technology and Techniques • Braz. arch. biol. technol. 67 • 2024 • https://doi.org/10.1590/1678-4324-2024230455 linkcopy

Method Validation Analysis of Toxic Elements As, Cd, Pb and Hg in Cannabidiol (CBD)-rich Oil by Inductively Coupled Plasma Mass Spectrometry

Authorship SCIMAGO INSTITUTIONS RANKINGS

The development of a method and its validation for determination of toxic elements As, Cd, Pb and Hg in Cannabidiol-rich oil is presented. The samples, 500 mg, were initially treated with 5 mL HNO₃ and 4 mL H₂O₂ followed by digestion in a microwave system. The clean solutions were subsequently diluted with deionized water and the analytes quantitated by inductively coupled plasma mass spectrometry (ICP-MS). Instrumental conditions were carefully evaluated, including the use of correction equations and He collisional gas (KED) to avoid/correct for possible interferences such as ⁴⁰Ar³⁵Cl affecting ⁷⁵As. Limits of quantitation (LOQs, calculated from replicate measurements of method blanks) were: 0.01 µg g^-1 (As), 0.001 µg g^-1 (Cd and Pb), and 0.0005 µg g^-1 (Hg) based on processing 500 mg subsamples/50 mL. The accuracy of the method was confirmed by spiking the Cannabidiol-rich oil sample at different concentration levels and determining recoveries with acceptable results under repeatability and intermediate precision conditions. Eight commercially available formulations were analyzed and only one showed 0.14 µg g^-1 Pb. The present fit-for-purpose analytical method is robust and precise and was adopted for use by the Tecpar`s laboratory of the Parana Institute of Technology (Curitiba, Brazil).

Keywords:
Cannabidiol oil; toxic elements; ICP-MS; As, Cd, Pb and Hg

A robust method was developed for detection of As, Cd, Pb and Hg in Cannabidiol (CBD)-rich oil.

Instrumental conditions were investigated by ICP-MS to selectively determine the toxic elements in Cannabidiol (CBD)-rich oil.

Method validation demonstrated accuracy and precision.

Parameters	Specifications
Radiofrequency	24 MHz
Radiofrequency power	1600 W
Plasma gas flow rate	15.0 L min^-1
Auxiliary gas flow rate	1.2 L min^-1
Nebulizer gas flow rate	0.94 L min^-1
Nebulizer type	Meinhard® glass concentric nebulizer
Spray chamber	Glass cyclonic
Peltier temperature (spray chamber)	3°C
Replicates	5
Torch type	Standard NexION quartz torch with 2.0 mm i.d. injector
Sample introduction system	PerkinElmer® HTS with autosampler S20 series
Collision Helium cell gas flow (KED)	3.5 mL min^-1
Cell entrance voltage (KED)	-8 V
Cell exit voltage (KED)	-25 V
Isotopes of the monitored analytes	⁷⁵As, ¹¹¹Cd, ^206,207,208Pb, ^200,201,202Hg
Internal standard Isotope	¹¹⁵In (95.7 % abundance )

Step	Ramp (min)	Target Temp (ºC)	Hold (min)	Power (W)
1	20	200	--	1800
2	--	200	30	1800
3	--	cooling	10	--

Analyte	Standard 1 (µg L^-1)	Standard 2 (µg L^-1)	Standard 3 (µg L^-1)	Standard 4 (µg L^-1)	Standard 5 (µg L^-1)
As	0.50	1.0	2.0	5.0	10.0
Cd	0.50	1.0	2.0	5.0	10.0
Pb	0.50	1.0	2.0	5.0	10.0
Hg	0.050	0.10	0.20	0.50	1.0

Analyte	Polyatomic ion interferences
⁷⁵As	⁴⁰Ar³⁵Cl, ³⁸Ar³⁷Cl, ³⁶Ar³⁹K ,³⁶Ar³⁸ArH, ⁴⁰Ar³⁴SH, ⁴⁰Ca³⁵Cl, ³⁷Cl₂H, ⁵⁹Co¹⁶O,
¹¹¹Cd	⁹⁵Mo¹⁶O, ⁹⁴Zr¹⁶OH, ³⁹K₂¹⁶O₂H
^206,207,208Pb	¹⁹⁰Pt¹⁶O, ¹⁹¹Ir¹⁶O, ¹⁹²Pt¹⁶O
^200,201,202Hg	---------------

Analyte	Linear regression coefficients	Slope (µg g^-1)^-1 cps^-1	Limit of detection* µg g^-1	Limit of quantification* µg g^-1
⁷⁵As	1.000	3023	0.003	0.01
¹¹¹Cd	0.999	4134	0.0002	0.001
^206,207,208Pb**	1.000	56517	0.0005	0.001
^200,201,202Hg***	0.999	9232	0.0001	0.0005

Analyte	Nominal Spiked Conc. µg g^-1	Conc. Obtained * µg g^-1	RSD, %	Recovery, %	Limits from EU Pharm** µg g^-1 maximum
⁷⁵As	0.02	0.022 ± 0.001	5.1	110	0.2
¹¹¹Cd	0.005	0.0051 ± 0.0001	2.7	102	0.3
^206,207,208Pb	0.02	0.021 ± (0.0004)	1.9	105	0.5
^200,201,202Hg	0.002	0.0021 ± (0.0001)	6.1	105	0.1

	Repeatability conditions (n=7)			Intermediate precision conditions (n=14)*
Analyte	0.050 μg g^-1 0.0050 μg g^-1(Hg)	0.50 μg g^-1 0.050 μg g^-1(Hg)	1.00 μg g^-1 0.10 μg g^-1(Hg)	0.050 μg g^-1 0.0050 μg g^-1(Hg)	0.50 μg g^-1 0.050 μg g^-1(Hg)	1.00 μg g^-1 0.10 μg g^-1(Hg)
As	0.053 ± 0.004	0.51 ± 0.03	1.10 ± 0.06	0.057 ± 0.004	0.52 ± 0.02	1.15 ± 0.07
Cd	0.047 ± 0.001	0.48 ± 0.02	0.96 ± 0.03	0.047 ± 0.001	0.48 ± 0.01	0.94 ± 0.03
Pb	0.055 ± 0.005	0.46 ± 0.01	0.92 ± 0.03	0.048 ± 0.008	0.47 ± 0.02	0.96 ± 0.05
Hg	0.0046 ± 0.0003	0.051±0.001	0.096 ± 0.006	0.0041 ± 0.0005	0.046 ± 0.006	0.089 ± 0.009
**RSD %	2.1 - 9.1	2.0 - 5.9	3.1 - 6.3	2.1 - 16.6	2.1 - 13.0	3.2 - 10.1
**Rec %	92-110	92-102	92-110	93-113	90-108	94-115

location_on

Instituto de Tecnologia do Paraná - Tecpar Rua Prof. Algacyr Munhoz Mader, 3775 - CIC, 81350-010 , Tel: +55 41 3316-3054 - Curitiba - PR - Brazil
E-mail: babt@tecpar.br

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[TFN1] * accounting for sample preparation 500 mg / 50 mL.

[TFN2] ** Pb results were based on the sum of the signals measured at mass 206, 207, and 208

[TFN3] *** Hg results were based on the sum of the signals measured at mass 200, 201, and 202